Biological and molecular characterization of a resistance-breaking isolate of citrus tristeza virus from Uruguay and its effects on Poncirus trifoliata growth performance.

Resistance-breaking (RB) isolates of citrus tristeza virus (CTV) can replicate and move systemically in Poncirus trifoliata, a rootstock widely used for management of decline caused by CTV and other purposes. In Uruguay, severe CTV isolates are prevalent, and an RB isolate (designated as RB-UY1) was identified. In order to predict the implications of this genotype circulating in citrus crops grafted on trifoliate rootstocks, the aim of this work was to determine the biological and molecular characteristics of this isolate, the efficiency of its transmission by Toxoptera citricida, and its effects on plant growth performance of P. trifoliata. Our results show that RB-UY1 can be classified as a mild isolate, that it is phylogenetically associated with the RB1 group, and that it is efficiently transmitted by T. citrida. They also suggest that the RB-UY1 isolate should not affect the performance of citrus crops grafted on trifoliate rootstocks, although some growth parameters of P. trifoliata seedlings were affected four years after inoculation.

Vigor and mortality of citrus progenies with potential use as rootstocks / 10.1590/1678-992x-2016-0455

Rootstocks influence certain characteristics of the scion, such as vigor, fruit yield and quality, and tolerance to biotic and abiotic factors. In conventional citrus breeding programs, hybridization is the main method used for obtaining rootstock varieties. Between Sept and Oct 2006, controlled pollinations were carried out resulting in nine progenies, totaling 461 hybrid seedlings. The female parents were the ‘Santa Cruz Rangpur lime (SCRL) and the ‘Sunki of Florida mandarin (SFM), while the male parents, in addition to this mandarin, were the ‘Indio and ‘Riverside citrandarins, the ‘Thomasville citrangequat (THOM), the ‘Swingle citrumelo, the ‘Argentina citrange (AGC) and the ‘Benecke trifoliate orange (BKTO). Fruit setting rates of these crosses were measured and the hybrids generated were planted in the field in 2008 and evaluated from 2010 to 2014, for the variables of plant mortality, visual vigor, plant height and trunk diameter. The descriptive statistics mean, variation range, coefficient of variation and Pearson skewness coefficient were calculated. Data were submitted to analysis of variance and the means of the treatments were grouped by the Scott-Knott test, both at 5 % significance. The progenies, having the ‘Sunki mandarin as the female parent, presented higher fruit setting rates and lower plant mortality rates than those obtained from the female parent ‘Rangpur lime, while zero plant mortality was observed in the SFM × BKTO cross. The crosses SCRL × SFM, SFM × BKTO, SFM × AGC and SFM × THOM have the potential to generate vigorous hybrids, resulting in rootstock varieties adapted to the landscape unit of Coastal Tableland.(AU)

QTLs and eQTLs mapping related to citrandarins' resistance to citrus gummosis disease.

BACKGROUND: Phytophthora nicotianae Breda de Haan (Phytophthora parasitica Dastur) causes severe damage to citrus crops worldwide. A population of citrandarins was created from the cross between the susceptible parent Citrus sunki Hort. Ex Tan. and the resistant parent Poncirus trifoliata (L.) Raf. cv. Rubidoux, both parents and two reference rootstocks (Rangpur lime and Swingle citrumelo) were grafted in a greenhouse on Rangpur lime. Inoculations were performed at 10 cm and 15 cm above the grafting region and the resulting lesions were evaluated by measuring the lesion length 60 days after inoculation. As control, non-inoculated plants of each genotype were used. In addition, we evaluated the expression of 19 candidate genes involved in citrus defense response 48 h after pathogen infection by quantitative Real-Time PCR (qPCR). We mapped genomic regions of Quantitative Trait Loci (QTLs) and Expression Quantitative Trait Loci (eQTLs) associated with resistance to P. parasitica in the linkage groups (LGs) of the previously constructed maps of C. sunki and P. trifoliata. RESULTS: We found disease severity differences among the generated hybrids, with lesion lengths varying from 1.15 to 11.13 mm. The heritability of the character was 65%. These results indicate that there is a great possibility of success in the selection of resistant hybrids within this experiment. The analysis of gene expression profile demonstrated a great variation of responses regarding the activation of plant defense pathways, indicating that citrandarins have several defense strategies to control oomycete infection. The information of the phenotypic and gene expression data made possible to detect genomic regions associated with resistance. Three QTLs and 84 eQTLs were detected in the linkage map of P. trifoliata, while one QTL and 110 eQTLs were detected in C. sunki. CONCLUSIONS: This is the first study to use eQTLs mapping in the Phytophthora-citrus interaction. Our results from the QTLs and eQTLs mapping allow us to conclude that the resistance of some citrandarins to the infection by P. parasitica is due to a favorable combination of QTLs and eQTLs transmitted by both parents.

Vigor and mortality of citrus progenies with potential use as rootstocks / 10.1590/1678-992x-2016-0455

Rootstocks influence certain characteristics of the scion, such as vigor, fruit yield and quality, and tolerance to biotic and abiotic factors. In conventional citrus breeding programs, hybridization is the main method used for obtaining rootstock varieties. Between Sept and Oct 2006, controlled pollinations were carried out resulting in nine progenies, totaling 461 hybrid seedlings. The female parents were the ‘Santa Cruz Rangpur’ lime (SCRL) and the ‘Sunki of Florida’ mandarin (SFM), while the male parents, in addition to this mandarin, were the ‘Indio’ and ‘Riverside’ citrandarins, the ‘Thomasville’ citrangequat (THOM), the ‘Swingle’ citrumelo, the ‘Argentina’ citrange (AGC) and the ‘Benecke’ trifoliate orange (BKTO). Fruit setting rates of these crosses were measured and the hybrids generated were planted in the field in 2008 and evaluated from 2010 to 2014, for the variables of plant mortality, visual vigor, plant height and trunk diameter. The descriptive statistics mean, variation range, coefficient of variation and Pearson skewness coefficient were calculated. Data were submitted to analysis of variance and the means of the treatments were grouped by the Scott-Knott test, both at 5 % significance. The progenies, having the ‘Sunki’ mandarin as the female parent, presented higher fruit setting rates and lower plant mortality rates than those obtained from the female parent ‘Rangpur’ lime, while zero plant mortality was observed in the SFM × BKTO cross. The crosses SCRL × SFM, SFM × BKTO, SFM × AGC and SFM × THOM have the potential to generate vigorous hybrids, resulting in rootstock varieties adapted to the landscape unit of Coastal Tableland.

Vigor and mortality of citrus progenies with potential use as rootstocks

ABSTRACT: Rootstocks influence certain characteristics of the scion, such as vigor, fruit yield and quality, and tolerance to biotic and abiotic factors. In conventional citrus breeding programs, hybridization is the main method used for obtaining rootstock varieties. Between Sept and Oct 2006, controlled pollinations were carried out resulting in nine progenies, totaling 461 hybrid seedlings. The female parents were the Santa Cruz Rangpur lime (SCRL) and the Sunki of Florida mandarin (SFM), while the male parents, in addition to this mandarin, were the Indio and Riverside citrandarins, the Thomasville citrangequat (THOM), the Swingle citrumelo, the Argentina citrange (AGC) and the Benecke trifoliate orange (BKTO). Fruit setting rates of these crosses were measured and the hybrids generated were planted in the field in 2008 and evaluated from 2010 to 2014, for the variables of plant mortality, visual vigor, plant height and trunk diameter. The descriptive statistics mean, variation range, coefficient of variation and Pearson skewness coefficient were calculated. Data were submitted to analysis of variance and the means of the treatments were grouped by the Scott-Knott test, both at 5 % significance. The progenies, having the Sunki mandarin as the female parent, presented higher fruit setting rates and lower plant mortality rates than those obtained from the female parent Rangpur lime, while zero plant mortality was observed in the SFM × BKTO cross. The crosses SCRL × SFM, SFM × BKTO, SFM × AGC and SFM × THOM have the potential to generate vigorous hybrids, resulting in rootstock varieties adapted to the landscape unit of Coastal Tableland.

Produção de mudas de laranjeira Pêra por meio do método de interenxertia / Production of nursery trees of Pera sweet orange by the interstock method

A interenxertia é uma prática que é usada, quando se deseja unir duas plantas que, sabidamente, são incompatíveis, ou quando se pretende diminuir o vigor da cultivar copa. Neste trabalho, avaliou-se uma metodologia alternativa para a produção de mudas de laranjeira Pêra interenxertadas, usando a subenxertia como técnica auxiliar na formação de um interenxerto de limoeiro Cravo. Foram avaliados os seguintes tratamentos: T1 - porta-enxerto trifoliata Flying Dragon (FD) e interenxerto de laranjeira Bahia; T2 - porta-enxerto Citrumeleiro Swingle (CS) e interenxerto de laranjeira Bahia; T3 - porta-enxerto limoeiro Cravo (LC); T4 - porta-enxerto FD e interenxerto de LC; T5 - Porta-enxerto CS e interenxerto de LC. As mudas produzidas no tratamento 4 (Pêra / LC / FD) se aproximaram em vigor das mudas produzidas sem filtro (Pêra / LC). A produção de mudas de laranjeira Pêra interenxertadas pelo sistema tradicional, tendo como porta-enxerto CS ou FD e interenxerto de laranjeira Bahia, não foi possível, em virtude da baixa viabilidade e vigor das brotações.

The interstock is a practice used when to merge two plants that are known to be incompatible or when it is intended to low vigor of the scion. In this study we evaluated an alternative method for the production of Pêra sweet orange nursery trees interstocked, using the technique as inarching assist in forming a interstock of Rangpur Lime (RL). The treatments were: T1 - rootstock trifoliate Flying Dragon (FD) and interstock of sweet orange Bahia, T2 - rootstock Citrumelo Swingle (CS) and interstock of sweet orange Bahia, T3 - rootstock Rangpur Lime (RL); T4 - rootstock FD and interstock RL; T5 - rootstock CS and interstock RL. The sweet orange nursery trees produced in treatment 4 (Pêra / RL / FD) had vigor nearest sweet orange nursery trees produced with interstock (Pêra / RL). The production Pera sweet orange nursery trees interstocked for traditional system, with the rootstock CS or FD and interstock sweet orange Bahia was not possible because of the low viability and vigor of the shoots.

Produção de mudas de laranjeira Pêra por meio do método de interenxertia / Production of nursery trees of Pera sweet orange by the interstock method

A interenxertia é uma prática que é usada, quando se deseja unir duas plantas que, sabidamente, são incompatíveis, ou quando se pretende diminuir o vigor da cultivar copa. Neste trabalho, avaliou-se uma metodologia alternativa para a produção de mudas de laranjeira Pêra interenxertadas, usando a subenxertia como técnica auxiliar na formação de um interenxerto de limoeiro Cravo. Foram avaliados os seguintes tratamentos: T1 - porta-enxerto trifoliata Flying Dragon (FD) e interenxerto de laranjeira Bahia; T2 - porta-enxerto Citrumeleiro Swingle (CS) e interenxerto de laranjeira Bahia; T3 - porta-enxerto limoeiro Cravo (LC); T4 - porta-enxerto FD e interenxerto de LC; T5 - Porta-enxerto CS e interenxerto de LC. As mudas produzidas no tratamento 4 (Pêra / LC / FD) se aproximaram em vigor das mudas produzidas sem filtro (Pêra / LC). A produção de mudas de laranjeira Pêra interenxertadas pelo sistema tradicional, tendo como porta-enxerto CS ou FD e interenxerto de laranjeira Bahia, não foi possível, em virtude da baixa viabilidade e vigor das brotações.(AU)

The interstock is a practice used when to merge two plants that are known to be incompatible or when it is intended to low vigor of the scion. In this study we evaluated an alternative method for the production of Pêra sweet orange nursery trees interstocked, using the technique as inarching assist in forming a interstock of Rangpur Lime (RL). The treatments were: T1 - rootstock trifoliate Flying Dragon (FD) and interstock of sweet orange Bahia, T2 - rootstock Citrumelo Swingle (CS) and interstock of sweet orange Bahia, T3 - rootstock Rangpur Lime (RL); T4 - rootstock FD and interstock RL; T5 - rootstock CS and interstock RL. The sweet orange nursery trees produced in treatment 4 (Pêra / RL / FD) had vigor nearest sweet orange nursery trees produced with interstock (Pêra / RL). The production Pera sweet orange nursery trees interstocked for traditional system, with the rootstock CS or FD and interstock sweet orange Bahia was not possible because of the low viability and vigor of the shoots.(AU)

Aproveitamento de plântulas de porta-enxertos cítrico oriundas do desbaste e seu desenvolvimento vegetativo inicial / Utilization of rootstock citrus seedlings deriving of thinning and its initial vegetative development

Avaliou-se o desenvolvimento vegetativo inicial de porta-enxertos cítricos cultivados em casa de vegetação, por meio de semeadura e de repicagem de raiz nua. O experimento foi conduzido em casa de vegetação, na Estação Experimental Agronômica da UFRGS, em Eldorado do Sul, RS, a partir do mês de setembro de 2003, afim de testar a viabilidade de aproveitamento de plântulas oriundas do desbaste. O delineamento experimental adotado foi o de blocos casualizados, com quatro repetições, em esquema de parcela subdividida e cada subparcela constituída por 22 tubetes. Nas parcelas principais foram testados dois sistemas de propagação: semeadura e repicagem no momento do desbaste. Nas subparcelas foram testados três porta-enxertos cítricos: Trifoliata (Poncirus trifoliata [L.] Raf.), citrangeiro "C37" (P. trifoliata x Citrus sinensis [L.] Osbeck.) e limoeiro "Cravo" (C. limonia Osbeck.). A semeadura foi realizada em tubetes cônicos de polietileno preto (capacidade de 120cm³), com duas a três sementes por tubete. A repicagem foi feita no momento do desbaste da bandeja semeada quando as plântulas estavam, em média, com duas a quatro folhas. Os resultados demonstraram que há viabilidade de aproveitamento das plântulas resultantes do desbaste, sem que ocorra diferenças no desenvolvimento vegetativo. Além disso, foi observado que o porta-enxerto "C37" apresentou um vigor inicial maior que o Trifoliata e o limoeiro "Cravo".

The initial vegetative growth of citrus seedling rootstocks was evaluated by means of sowing and transplantation of bare-root seedling. The experiment was conduced in September 2003 in greenhouse conditions in the Estação Experimental Agronômica/UFRGS in Eldorado do Sul, Brazil. The objective of this study was to test the viability of use of seedlings deriving from thinning. The experiment was in randomized blocks with four replications in a split plot design and each sub-plot consisted of 22 tubs. In the main plot were tested two propagation systems: sowing and transplantation at the thinning moment. In sub-plots were tested three citrus rootstocks: Trifoliate orange (Poncirus trifoliata [ L. ] Raf.); 'C37' citrange (P. trifoliata x Citrus sinensis [ L. ] Osbeck.), and 'Rangpur' lime (C. limonia Osbeck.). The sowing was carried in conical tubs of black polyethylene (capacity of 120cm³) with two to three seeds in each tub. Transplantation was made at the thinning moment, when the seedlings had, in average, two to four leaves. The results demonstrate that it is possible to use seedlings resulting from thinning, without differences in the vegetative development comparatively to sowing. The 'C37' citrus rootstock presents a larger initial vigor when compared to the other citrus rootstocks tested.

Aproveitamento de plântulas de porta-enxertos cítrico oriundas do desbaste e seu desenvolvimento vegetativo inicial

The initial vegetative growth of citrus seedling rootstocks was evaluated by means of sowing and transplantation of bare-root seedling. The experiment was conduced in September 2003 in greenhouse conditions in the Estação Experimental Agronômica/UFRGS in Eldorado do Sul, Brazil. The objective of this study was to test the viability of use of seedlings deriving from thinning. The experiment was in randomized blocks with four replications in a split plot design and each sub-plot consisted of 22 tubs. In the main plot were tested two propagation systems: sowing and transplantation at the thinning moment. In sub-plots were tested three citrus rootstocks: Trifoliate orange (Poncirus trifoliata [ L. ] Raf.); 'C37' citrange (P. trifoliata x Citrus sinensis [ L. ] Osbeck.), and 'Rangpur' lime (C. limonia Osbeck.). The sowing was carried in conical tubs of black polyethylene (capacity of 120cm³) with two to three seeds in each tub. Transplantation was made at the thinning moment, when the seedlings had, in average, two to four leaves. The results demonstrate that it is possible to use seedlings resulting from thinning, without differences in the vegetative development comparatively to sowing. The 'C37' citrus rootstock presents a larger initial vigor when compared to the other citrus rootstocks tested.

Avaliou-se o desenvolvimento vegetativo inicial de porta-enxertos cítricos cultivados em casa de vegetação, por meio de semeadura e de repicagem de raiz nua. O experimento foi conduzido em casa de vegetação, na Estação Experimental Agronômica da UFRGS, em Eldorado do Sul, RS, a partir do mês de setembro de 2003, afim de testar a viabilidade de aproveitamento de plântulas oriundas do desbaste. O delineamento experimental adotado foi o de blocos casualizados, com quatro repetições, em esquema de parcela subdividida e cada subparcela constituída por 22 tubetes. Nas parcelas principais foram testados dois sistemas de propagação: semeadura e repicagem no momento do desbaste. Nas subparcelas foram testados três porta-enxertos cítricos: Trifoliata (Poncirus trifoliata [L.] Raf.), citrangeiro "C37" (P. trifoliata x Citrus sinensis [L.] Osbeck.) e limoeiro "Cravo" (C. limonia Osbeck.). A semeadura foi realizada em tubetes cônicos de polietileno preto (capacidade de 120cm³), com duas a três sementes por tubete. A repicagem foi feita no momento do desbaste da bandeja semeada quando as plântulas estavam, em média, com duas a quatro folhas. Os resultados demonstraram que há viabilidade de aproveitamento das plântulas resultantes do desbaste, sem que ocorra diferenças no desenvolvimento vegetativo. Além disso, foi observado que o porta-enxerto "C37" apresentou um vigor inicial maior que o Trifoliata e o limoeiro "Cravo".

Aproveitamento de plântulas de porta-enxertos cítrico oriundas do desbaste e seu desenvolvimento vegetativo inicial

The initial vegetative growth of citrus seedling rootstocks was evaluated by means of sowing and transplantation of bare-root seedling. The experiment was conduced in September 2003 in greenhouse conditions in the Estação Experimental Agronômica/UFRGS in Eldorado do Sul, Brazil. The objective of this study was to test the viability of use of seedlings deriving from thinning. The experiment was in randomized blocks with four replications in a split plot design and each sub-plot consisted of 22 tubs. In the main plot were tested two propagation systems: sowing and transplantation at the thinning moment. In sub-plots were tested three citrus rootstocks: Trifoliate orange (Poncirus trifoliata [ L. ] Raf.); 'C37' citrange (P. trifoliata x Citrus sinensis [ L. ] Osbeck.), and 'Rangpur' lime (C. limonia Osbeck.). The sowing was carried in conical tubs of black polyethylene (capacity of 120cm³) with two to three seeds in each tub. Transplantation was made at the thinning moment, when the seedlings had, in average, two to four leaves. The results demonstrate that it is possible to use seedlings resulting from thinning, without differences in the vegetative development comparatively to sowing. The 'C37' citrus rootstock presents a larger initial vigor when compared to the other citrus rootstocks tested.

Avaliou-se o desenvolvimento vegetativo inicial de porta-enxertos cítricos cultivados em casa de vegetação, por meio de semeadura e de repicagem de raiz nua. O experimento foi conduzido em casa de vegetação, na Estação Experimental Agronômica da UFRGS, em Eldorado do Sul, RS, a partir do mês de setembro de 2003, afim de testar a viabilidade de aproveitamento de plântulas oriundas do desbaste. O delineamento experimental adotado foi o de blocos casualizados, com quatro repetições, em esquema de parcela subdividida e cada subparcela constituída por 22 tubetes. Nas parcelas principais foram testados dois sistemas de propagação: semeadura e repicagem no momento do desbaste. Nas subparcelas foram testados três porta-enxertos cítricos: Trifoliata (Poncirus trifoliata [L.] Raf.), citrangeiro "C37" (P. trifoliata x Citrus sinensis [L.] Osbeck.) e limoeiro "Cravo" (C. limonia Osbeck.). A semeadura foi realizada em tubetes cônicos de polietileno preto (capacidade de 120cm³), com duas a três sementes por tubete. A repicagem foi feita no momento do desbaste da bandeja semeada quando as plântulas estavam, em média, com duas a quatro folhas. Os resultados demonstraram que há viabilidade de aproveitamento das plântulas resultantes do desbaste, sem que ocorra diferenças no desenvolvimento vegetativo. Além disso, foi observado que o porta-enxerto "C37" apresentou um vigor inicial maior que o Trifoliata e o limoeiro "Cravo".

Formação do porta-enxerto Trifoliata: época de semeadura e tegumento na emergência de plântulas

This study was aimed at evaluating the effect of the time of sowing and the seedcoat in seedling emergency and production of Trifoliata rootstock. The experiment was carried out in a glasshouse, in Pelotas-RS. Sowing was performed in dibble tubes of 50cm3, containing commercial substrate. Two sowing plates (winter and spring) and three seedcoat treatments (integral tegument, with a hole in the endosperm and without tegument) were studied. The experimental design was a randomized complete block, in a factorial schedule, with four replications and experimental units composed by 42 dibble tubes with one seed each. The rootstocks were considered adequate for the transplant when they reached 15cm height. The speed and final germination percentage of Trifoliata rootstocks were significantly higher in the spring (95.6%) compared to the winter (83.6%). Regardless of the season of the year, the removal of the seedcoat improved the germination (96.9%) compared with the use of seed with integral tegument (84.8%). The period necessary for rootstock formation in dibble tubes was 70 days in the spring and 130 days in the winter.

O objetivo deste trabalho foi avaliar o efeito da época de semeadura e do tegumento da semente na emergência de plântulas e o tempo necessário para formação do porta-enxerto Trifoliata. O experimento foi realizado em casa de vegetação, em Pelotas-RS. A semeadura foi realizada em tubetes de 50cm3, contendo substrato comercial. Os tratamentos compreenderam duas épocas de semeadura (inverno e primavera) e três tratamentos do tegumento das sementes (tegumento íntegro, com furo no endosperma, e sem tegumento). Esses foram dispostos em delineamento de blocos ao acaso, em esquema fatorial, com quatro repetições, sendo as unidades experimentais constituídas por 42 tubetes com uma semente cada. Os porta-enxertos foram considerados aptos para o transplantio quando atingiram 15cm de altura. A velocidade e a porcentagem final de germinação de Trifoliata foi significativamente superior na primavera (95,6%) em relação ao inverno (83,6%). Independentemente da época do ano, a remoção do tegumento favoreceu a germinação (96,9%) em relação ao uso de semente com tegumento íntegro (84,8%). O período necessário para a formação dos porta-enxertos nos tubetes foi de 70 dias na primavera e de 130 dias no inverno.

Formação do porta-enxerto Trifoliata: época de semeadura e tegumento na emergência de plântulas

This study was aimed at evaluating the effect of the time of sowing and the seedcoat in seedling emergency and production of Trifoliata rootstock. The experiment was carried out in a glasshouse, in Pelotas-RS. Sowing was performed in dibble tubes of 50cm3, containing commercial substrate. Two sowing plates (winter and spring) and three seedcoat treatments (integral tegument, with a hole in the endosperm and without tegument) were studied. The experimental design was a randomized complete block, in a factorial schedule, with four replications and experimental units composed by 42 dibble tubes with one seed each. The rootstocks were considered adequate for the transplant when they reached 15cm height. The speed and final germination percentage of Trifoliata rootstocks were significantly higher in the spring (95.6%) compared to the winter (83.6%). Regardless of the season of the year, the removal of the seedcoat improved the germination (96.9%) compared with the use of seed with integral tegument (84.8%). The period necessary for rootstock formation in dibble tubes was 70 days in the spring and 130 days in the winter.

O objetivo deste trabalho foi avaliar o efeito da época de semeadura e do tegumento da semente na emergência de plântulas e o tempo necessário para formação do porta-enxerto Trifoliata. O experimento foi realizado em casa de vegetação, em Pelotas-RS. A semeadura foi realizada em tubetes de 50cm3, contendo substrato comercial. Os tratamentos compreenderam duas épocas de semeadura (inverno e primavera) e três tratamentos do tegumento das sementes (tegumento íntegro, com furo no endosperma, e sem tegumento). Esses foram dispostos em delineamento de blocos ao acaso, em esquema fatorial, com quatro repetições, sendo as unidades experimentais constituídas por 42 tubetes com uma semente cada. Os porta-enxertos foram considerados aptos para o transplantio quando atingiram 15cm de altura. A velocidade e a porcentagem final de germinação de Trifoliata foi significativamente superior na primavera (95,6%) em relação ao inverno (83,6%). Independentemente da época do ano, a remoção do tegumento favoreceu a germinação (96,9%) em relação ao uso de semente com tegumento íntegro (84,8%). O período necessário para a formação dos porta-enxertos nos tubetes foi de 70 dias na primavera e de 130 dias no inverno.

Frequency and distribution of microsatellites from ESTs of citrus

Nearly 65,000 citrus EST (Expressed Sequence Tags) have been investigated using the CitEST project database. Microsatellites were investigated in the unigene sequences from Citrus spp. and Poncirus trifoliata. From these sequences, approximately 35 percent of the non-redundant ESTs contained SSRs. The frequencies of different SSR motifs were similar between Citrus spp and trifoliate orange. In general, mononucleotide repeats appeared to be the most abundant SSRs in the CitEST database, but we also identify di-, tri-, tetra-, penta- and hexanucleotide repeats. The AG/CT and AAG/CTT were the most common dinucleotide and trinucleotide motifs, with frequencies of 54.4 percent and 25.2 percent, respectively. Primer sequences flanking SSR motifs were successfully designed and synthesized. After in silico polymorphism analysis, a subset of sixty-eight primers was validated in different Citrus spp. and Poncirus trifoliata. PCR-amplification revealed polymorphism in citrus with all tested primer pairs and showed the potential of these markers for linkage mapping. Our study showed that the CitEST database can be exploited for the development of SSR markers that can amplify Citrus spp. and related genus for comparative mapping and other genetic analyses.

Diversidade genética de porta-enxertos cítricos baseada em marcadores moleculares RAPD

This research intended to characterize the genetic diversity of citrus rootstocks from the Experimental Agronomic Station of the Rio Grande do Sul Federal University (EEA/UFRGS) and rootstocks collected in nurseries of the Cai River Valley - Rio Grande do Sul - Brazil. The method used was the Random Amplification of Polymorphic DNA (RAPD) markers. Leaves of nine citrus rootstocks from EEA/UFRGS and ten accesses of trifoliate orange (Poncirus trifoliata) from different nurseries were collected. With the use of nine random primers it was possible to separate the rootstocks in two main groups: one formed by ‘Rangpur’ lime (Citrus limonia) and the other by trifoliate orange and its hybrids of low genetic similarity. RAPD molecular marker was very efficient for the citrus rootstock characterization and for the trifoliate orange separation from its hybrids. The technique might be used to characterize cultivars, analysis of genetic variability among progenitors in improvement breeding programs of rootstock , and identify zygotic seedlings of trifoliate orange in commercial nurseries.

Este trabalho teve como objetivo caracterizar a diversidade genética, através do marcador molecular RAPD, dos porta-enxertos da Coleção de Citros da Estação Experimental Agronômica da Universidade Federal do Rio Grande do Sul (EEA/UFRGS) e acessos de porta-enxertos cítricos coletados em viveiristas da Região do Vale do Rio Caí do estado do Rio Grande do Sul. Para tanto, coletaram-se folhas de nove porta-enxertos cítricos da EEA/UFRGS e de dez acessos de trifoliata (Poncirus trifoliata) de viveiristas. Com o uso de nove seqüências inicializadoras, foi possível separar os porta-enxertos cítricos em dois grupos principais, um formado pelo limoeiro ‘Cravo’ e outro pelo trifoliata e seus híbridos, apresentando alta dissimilaridade genética entre os grupos. Marcadores moleculares RAPD foram eficientes para caracterizar variedades de porta-enxertos de citros e para separar o porta-enxerto P. trifoliata de seus híbridos podendo serem utilizados para caracterização de plantas matrizes, análise de variabilidade genética entre genitores em programas de melhoramento genético de porta-enxertos e para identificar a origem sexual ou nucelar de mudas de trifoliata em viveiros comerciais.

Diversidade genética de porta-enxertos cítricos baseada em marcadores moleculares RAPD

This research intended to characterize the genetic diversity of citrus rootstocks from the Experimental Agronomic Station of the Rio Grande do Sul Federal University (EEA/UFRGS) and rootstocks collected in nurseries of the Cai River Valley - Rio Grande do Sul - Brazil. The method used was the Random Amplification of Polymorphic DNA (RAPD) markers. Leaves of nine citrus rootstocks from EEA/UFRGS and ten accesses of trifoliate orange (Poncirus trifoliata) from different nurseries were collected. With the use of nine random primers it was possible to separate the rootstocks in two main groups: one formed by ‘Rangpur lime (Citrus limonia) and the other by trifoliate orange and its hybrids of low genetic similarity. RAPD molecular marker was very efficient for the citrus rootstock characterization and for the trifoliate orange separation from its hybrids. The technique might be used to characterize cultivars, analysis of genetic variability among progenitors in improvement breeding programs of rootstock , and identify zygotic seedlings of trifoliate orange in commercial nurseries.

Este trabalho teve como objetivo caracterizar a diversidade genética, através do marcador molecular RAPD, dos porta-enxertos da Coleção de Citros da Estação Experimental Agronômica da Universidade Federal do Rio Grande do Sul (EEA/UFRGS) e acessos de porta-enxertos cítricos coletados em viveiristas da Região do Vale do Rio Caí do estado do Rio Grande do Sul. Para tanto, coletaram-se folhas de nove porta-enxertos cítricos da EEA/UFRGS e de dez acessos de trifoliata (Poncirus trifoliata) de viveiristas. Com o uso de nove seqüências inicializadoras, foi possível separar os porta-enxertos cítricos em dois grupos principais, um formado pelo limoeiro ‘Cravo e outro pelo trifoliata e seus híbridos, apresentando alta dissimilaridade genética entre os grupos. Marcadores moleculares RAPD foram eficientes para caracterizar variedades de porta-enxertos de citros e para separar o porta-enxerto P. trifoliata de seus híbridos podendo serem utilizados para caracterização de plantas matrizes, análise de variabilidade genética entre genitores em programas de melhoramento genético de porta-enxertos e para identificar a origem sexual ou nucelar de mudas de trifoliata em viveiros comerciais.

Produção de mudas cítricas no Rio Grande do Sul: diagnóstico da região produtora

A questionnaire was applied in the principal nursery citrus production área in Rio Grande do Sul State, Brasil, to characterize that área, in relation to rootstock and scion utilization. The nurseries researched belong to lhe 'Avimuda' and 'Avimaffo' producer associations m the 'Caí' river valley. The questionnaire was applied to 35% of the nurseries registered in the associations, from May to June 1998. The principal results show that the most used rootstock is the Poncirus trifoliata, and that the scion is obtained from material with non-controiled origin.

Com o objetivo de caracterizar a produção de mudas cítricas, principalmente quanto ao uso de porta-enxertos e à origem do material propagativo utilizado, aplicou-se um questionário aos viveiristas da principal zona de produção de mudas do Estado do Rio Grande do Sul, pertencentes a duas associações de produtores de mudas do Vale do Rio Caí, a Avimuda e a Avimaffo. O questionário foi aplicado a um total de 35% dos viveiristas inscritos nas associações, sorteados ao acaso, durante os meses de maio a junho de 1998. Os principais resultados demonstram que a atividade de viveirista, nessa região, baseia-se, principalmente, na produção de mudas cítricas e já é desenvolvida há muitos anos; o porta-enxerto mais utilizado é o Poncirus trifoliata, sendo que a enxertia é realizada com borbulhas de origem não controlada.

Produção de mudas cítricas no Rio Grande do Sul: diagnóstico da região produtora

A questionnaire was applied in the principal nursery citrus production área in Rio Grande do Sul State, Brasil, to characterize that área, in relation to rootstock and scion utilization. The nurseries researched belong to lhe 'Avimuda' and 'Avimaffo' producer associations m the 'Caí' river valley. The questionnaire was applied to 35% of the nurseries registered in the associations, from May to June 1998. The principal results show that the most used rootstock is the Poncirus trifoliata, and that the scion is obtained from material with non-controiled origin.

Com o objetivo de caracterizar a produção de mudas cítricas, principalmente quanto ao uso de porta-enxertos e à origem do material propagativo utilizado, aplicou-se um questionário aos viveiristas da principal zona de produção de mudas do Estado do Rio Grande do Sul, pertencentes a duas associações de produtores de mudas do Vale do Rio Caí, a Avimuda e a Avimaffo. O questionário foi aplicado a um total de 35% dos viveiristas inscritos nas associações, sorteados ao acaso, durante os meses de maio a junho de 1998. Os principais resultados demonstram que a atividade de viveirista, nessa região, baseia-se, principalmente, na produção de mudas cítricas e já é desenvolvida há muitos anos; o porta-enxerto mais utilizado é o Poncirus trifoliata, sendo que a enxertia é realizada com borbulhas de origem não controlada.

Efeito da composição do substrato na formação de mudas de laranjeira `pera'

To verify the effect of five substrate mixtures on the development of young sweet orange trees (Citrus sinensis cv. `Pera'), this study used the rootstocks Ranpur lime (Citrus limonia L. Osbeck), Cleopatra mandarin (Citrus reticulata, Blanco), and Swingle citrumelo (Citrus paradisi x Poncirus trifoliata). The experimental design was in randomized blocks, 5 x 3 factorial (substrates x rootstocks). The different materials and their proportion studied were, respectively: 1) Soil (100%); 2) Soil (33%) + fine sand (33%) + manure (33%); 3) Soil (33%) + vermiculite (33%) + manure (33%); 4) Soil (33%) + wood chips (33%) + manure (33%); 5) Soil (25%) + wood chips (25%) + fine sand (25%) + manure (25%). Plants of Rangpur lime and Swingle citrumelo presented better growth rate as expresed in plant height and trunk diameter than those of Cleopatra mandarin on most substrates. `Pêra' sweet orange budded on those rootstocks also presented better fresh weight when compared to Cleopatra mandarin. All substrate mixtures were better than the control (100%) in inducing plant development. Different substrate mixtures affected each rootstock differently, but in general, the compositions with 1/3 soil and 1/3 manure in volume were the best to produce young sweet orange trees in containers.

O efeito de cinco composições de substratos na produção de mudas de laranjeira `Pêra' (Citrus sinensis, L. Osbeck) foi estudado sobre três porta-enxertos (limoeiro `Cravo', Citrus limonia, L. Osbeck; tangerineira `Cleópatra', Citrus reticulata, Blanco; e citrumeleiro `Swingle', Citrus paradisi x Poncirus trifoliata). O experimento obedeceu ao delineamento estatístico de blocos aleatorizados em esquema fatorial 5 x 3 (substratos x porta-enxertos). As composições de misturas utilizadas como substrato e respectivas combinações volumétricas foram: 1) Terra (100%); 2) Terra (33%) + areia fina (33%) + esterco bovino curtido (33%); 3) Terra (33%) + vermiculita (33%) + esterco bovino curtido (33%); 4) Terra (33%) + raspas de madeira (33%) + esterco bovino curtido (33%); 5) Terra (25%) + raspas de madeira (25%) + areia fina (25%) + esterco bovino curtido (25%). A análise dos resultados revelou que plantas de limoeiro `Cravo' e citrumeleiro `Swingle' apresentaram maior desenvolvimento do que as de tangerineira `Cleópatra'. A mistura de materiais com solo mostrou-se vantajosa e induziu à formação de plantas mais desenvolvidas do que aquelas em substrato constituído de terra exclusivamente. A composição do substrato influenciou diferentemente no desenvolvimento de cada porta-enxerto, mas de uma forma geral, composições contento 1/3 de volume de solo e 1/3 de volume de esterco bovino proporcionaram bons resultados para os três porta-enxertos estudados.

EFEITO DA COMPOSIÇÃO DO SUBSTRATO NA FORMAÇÃO DE MUDAS DE LARANJEIRA `PERA'

To verify the effect of five substrate mixtures on the development of young sweet orange trees (Citrus sinensis cv. `Pera'), this study used the rootstocks Ranpur lime (Citrus limonia L. Osbeck), Cleopatra mandarin (Citrus reticulata, Blanco), and Swingle citrumelo (Citrus paradisi x Poncirus trifoliata). The experimental design was in randomized blocks, 5 x 3 factorial (substrates x rootstocks). The different materials and their proportion studied were, respectively: 1) Soil (100%); 2) Soil (33%) + fine sand (33%) + manure (33%); 3) Soil (33%) + vermiculite (33%) + manure (33%); 4) Soil (33%) + wood chips (33%) + manure (33%); 5) Soil (25%) + wood chips (25%) + fine sand (25%) + manure (25%). Plants of Rangpur lime and Swingle citrumelo presented better growth rate as expresed in plant height and trunk diameter than those of Cleopatra mandarin on most substrates. `Pêra' sweet orange budded on those rootstocks also presented better fresh weight when compared to Cleopatra mandarin. All substrate mixtures were better than the control (100%) in inducing plant development. Different substrate mixtures affected each rootstock differently, but in general, the compositions with 1/3 soil and 1/3 manure in volume were the best to produce young sweet orange trees in containers.

O efeito de cinco composições de substratos na produção de mudas de laranjeira `Pêra' (Citrus sinensis, L. Osbeck) foi estudado sobre três porta-enxertos (limoeiro `Cravo', Citrus limonia, L. Osbeck; tangerineira `Cleópatra', Citrus reticulata, Blanco; e citrumeleiro `Swingle', Citrus paradisi x Poncirus trifoliata). O experimento obedeceu ao delineamento estatístico de blocos aleatorizados em esquema fatorial 5 x 3 (substratos x porta-enxertos). As composições de misturas utilizadas como substrato e respectivas combinações volumétricas foram: 1) Terra (100%); 2) Terra (33%) + areia fina (33%) + esterco bovino curtido (33%); 3) Terra (33%) + vermiculita (33%) + esterco bovino curtido (33%); 4) Terra (33%) + raspas de madeira (33%) + esterco bovino curtido (33%); 5) Terra (25%) + raspas de madeira (25%) + areia fina (25%) + esterco bovino curtido (25%). A análise dos resultados revelou que plantas de limoeiro `Cravo' e citrumeleiro `Swingle' apresentaram maior desenvolvimento do que as de tangerineira `Cleópatra'. A mistura de materiais com solo mostrou-se vantajosa e induziu à formação de plantas mais desenvolvidas do que aquelas em substrato constituído de terra exclusivamente. A composição do substrato influenciou diferentemente no desenvolvimento de cada porta-enxerto, mas de uma forma geral, composições contento 1/3 de volume de solo e 1/3 de volume de esterco bovino proporcionaram bons resultados para os três porta-enxertos estudados.

Effects of growth regulators on Poncirus trifoliata x Citrus paradisi seeds germination / Efeitos de fitorreguladores na germinação de sementes de citrumelo "swingle"

The objective of this research was study the effects of kinetin and gibberellins on Poncirus trifoliata x Citrus paradisi seed germination. The medium for seed germination was filter paper moisted with distilled water. The seeds were removed from ripe fruits, washed, dried and placed in refrigerator at 4-5C. After that, the seeds were treated with growth regulators during 24 hours. The treatments were H2O; 50 mg/l de GA3; 250 mg/l de GA3, 50 mg/l de GA4 + GA7 + phenylmethylaminepurine; 100 mg/l de GA4 + GA7 + phenylmethylaminepurine; 20 mg/l of phenylmethylaminepurine; 40 mg/l of phenylmethylaminepurine. The evaluations were accomplished every two days starting 10 days after seeding. The GA3 50 or 250 mg/l proved to be most beneficial in enhancing seed germination.

Foram estudados os efeitos de giberelinas e citocininas, na germinação de sementes de citrumelo "Swingle" (Poncirus trifoliata x Citrus paradisi). As sementes foram colocadas no germinador em gerbox contendo papel de filtro umedecido com água destilada. As sementes, retiradas de frutos maduros, foram lavadas, secadas à sombra e armazenadas em câmara fria; logo após, foram tratadas com os fitorreguladores por 24 horas, definindo os seguintes tratamentos: H2O; 50 mg/l de GA3; 250 mg/l de GA3, 50 mg/l de GA4 + GA7 + fenilmetilaminopurina; 100 mg/l de GA4 + GA7 + fenilmetilaminopurina; 20 mg/l de fenilmetilaminopurina e 40 mg/l de fenilmetilaminopurina. As avaliações foram realizadas depois de 10 dias de semeadura, num intervalo de 2 dias entre elas. Através da análise estatística dos resultados obtidos, foi possível concluir que, no tratamento com 50 ou 250 mg/l de GA3, houve a maior porcentagem de germinação de sementes, em menor tempo.