What affects the desiccation tolerance threshold of Brazilian Eugenia (Myrtaceae) seeds?

Desiccation sensitive (DS) seeds are shed at high water contents (WC) and metabolically active, but WC thresholds vary broadly among species even in the same genus. Eugenia is an important ecological genus that has high occurrence in several Brazilian morphoclimatic domains. In this study, we assessed seed desiccation tolerance of five Eugenia species collected in specific meteorological conditions. We reported the species geographical ranges and verified the rainfall and temperature of species sites in the year prior to seed collection. We also assessed initial WC, seed germination and vigor and seedling growth upon desiccation. Eugenia uniflora was the widest spread among the five species, while E. astringens was the most restricted. In this specific study, widespread species showed a higher WC threshold than restricted species. In the same way, the WC of fresh seeds was not correlated to the desiccation tolerance threshold. Seed desiccation tolerance was species dependent and correlated with the environmental status of seed collection sites. Wetter and warmer conditions were correlated to the E. uniflora higher DS threshold. Low rainfall and temperature corresponded to a lower desiccation sensitivity of E. astringens seeds. Seeds of the five species lost half viability between 0.44 and 0.25 g H2O g DW- 1 and after 65-270 h of desiccation. Our results indicate that abiotic factors impact plant populations during the seed production season and can drive seed desiccation tolerance threshold and physiological behavior. These results should be taken into account in ex-situ plant conservation programs and tropical species management.

Respiratory rates of Eugenia brasiliensis Lam. (Myrtaceae) seeds at modified atmospheres / Taxas respiratórias de sementes de Eugenia brasiliensis Lam. (Myrtaceae) sob atmosferas modificadas

Successful seed conservation depends on reducing the metabolism of both the seeds and other associated organisms. The metabolic activity can be analyzed by the respiratory rates but it depends on the developing of methodological protocols. In addition, modified atmosphere has shown some control in respiration when O2 and CO2 concentrations are changed. This work evaluated the effect of changes in O2 and CO2 concentrations on the inhibition of the respiratory metabolism of Eugenia brasiliensis Lam seeds. The results showed that in atmospheres with CO2 concentration between 1.9% and 3.7% it is possible to decrease the metabolism of these seeds. In addition, a model that allows controlling the factors involved in the analysis of respiratory rates in seeds is presented.

O sucesso da conservação de sementes se resume à redução tanto do seu metabolismo quanto de outros organismos associados a elas. Uma das formas de se avaliar a intensidade metabólica é analisando-se as taxas respiratórias, mas há necessidade de se desenvolver protocolos metodológicos para isso. Além disso, atmosfera modificada tem demonstrado algum controle na respiração quando as concentrações de O2 e CO2 são alteradas. Neste trabalho, avaliou-se o efeito da alteração das concentrações de O2 e CO2 do ambiente em que sementes foram armazenadas de maneira a inibir o metabolismo respiratório das sementes de Eugenia brasiliensis Lam. Os resultados demonstraram que em atmosferas com concentração de CO2 entre 1,9% e 3,7% é possível diminuir o metabolismo respiratório dessas sementes. Além disso, é apresentado um modelo que permite controlar os fatores envolvidos na análise das taxas respiratórias em sementes.

Transcriptome analysis in osmo-primed tomato seeds with enhanced longevity by heat shock treatment.

Seed priming is widely used in commercial seeds and its main function is to accelerate and synchronize seed germination. Undesirably, primed seeds show reduced longevity and treatments like heat shock have been shown to improve longevity in primed seeds. Nonetheless, the effect of heat shock treatment on primed seeds at the mRNA level is not known. Thus, the aim of this work was to investigate the effect of heat shock treatment on the longevity of primed tomato (Solanum lycopersicum) seeds at the physiological and transcriptome levels. Tomato seeds were primed and dried (control). Alternatively, primed seeds were subjected to heat shock treatment (38 °C/32 % relative humidity) before drying. Germination, vigor and longevity were evaluated. Transcriptome analysis was performed by RNA sequencing (RNA-seq) from biological samples collected immediately after priming and another samples collected from primed seeds followed by the heat shock treatments. The gene expression was validated by quantitative real time PCR (RT-qPCR). We showed that applying heat shock treatment after priming increased germination speed, enhanced seed longevity and preserved the vigor during storage of primed tomato seeds. Through transcriptome analysis, 368 differentially expressed genes were identified, from which 298 genes were up-regulated and 70 were down-regulated. We showed the increase of mRNA levels of HEAT SHOCK FACTOR-like and HEAT SHOCK PROTEIN-like chaperone genes, suggesting the involvement of the proteins coded by these transcripts in the enhancement of longevity in primed tomato seeds. The heat shock treatment after priming enhances and preserves the vigor of tomato primed seeds during storage. In addition, improves seed longevity through the increase in the expression of transcripts related to protection by response to stress.

Challenges for Ex Situ Conservation of Wild Bananas: Seeds Collected in Papua New Guinea Have Variable Levels of Desiccation Tolerance.

Ex situ seed conservation of banana crop wild relatives (Musa spp. L.), is constrained by critical knowledge gaps in their storage and germination behaviour. Additionally, challenges in collecting seeds from wild populations impact the quality of seed collections. It is, therefore, crucial to evaluate the viability of seeds from such collecting missions in order to improve the value of future seed collections. We evaluate the seed viability of 37 accessions of seven Musa species, collected from wild populations in Papua New Guinea, during two collecting missions. Seeds from one mission had already been stored in conventional storage (dried for four months at 15% relative humidity, 20 °C and stored for two months at 15% relative humdity, -20 °C), so a post-storage test was carried out. Seeds from the second mission were assessed freshly extracted and following desiccation. We used embryo rescue techniques to overcome the barrier of germinating in vivo Musa seeds. Seeds from the first mission had low viability (19 ± 27% mean and standard deviation) after storage for two months at 15% relative humidity and -20 °C. Musa balbisiana Colla seeds had significantly higher post-storage germination than other species (p < 0.01). Desiccation reduced germination of the seeds from the second collecting mission, from 84 ± 22% (at 16.7 ± 2.4% moisture content) to 36 ± 30% (at 2.4 ± 0.8% moisture content). There was considerable variation between and (to a lesser extent) within accessions, a proportion of individual seeds of all but one species (Musa ingens N.W.Simmonds) survived desiccation and sub-zero temperature storage. We identified that seeds from the basal end of the infructescence were less likely to be viable after storage (p < 0.001); and made morphological observations that identify seeds and infructescences with higher viability in relation to their developmental maturity. We highlight the need for research into seed eco-physiology of crop wild relatives in order to improve future collecting missions.

Seed freeze sensitivity and ex situ longevity of 295 species in the native Hawaiian flora.

PREMISE: Ex situ seed banking is critical for plant conservation globally, especially for threatened floras in tropical ecosystems like Hawai'i. Seed bank managers must maximize longevity, and species managers must plan restoration before seeds lose viability. Previous observations suggested some native Hawaiian seeds lost viability in frozen storage (-18°C). We investigated seed storage behavior in the Hawaiian flora to optimize storage conditions and recommend re-collection intervals (RCI) to maximize viability of stored seeds. METHODS: Using 20+ years of real-time seed storage viability data, we tested freeze sensitivity for 197 species and calculated RCIs for 295 species. Using paired tests of accessions stored >2 yr at 5°C and -18°C, we developed an index of relative performance to determine freeze sensitivity. We calculated RCIs at 70% of highest germination (P70). RESULTS: We identified four families (Campanulaceae, Cyperaceae, Rubiaceae, and Urticaceae) and four genera with seed freeze sensitivity and six additional genera with likely freeze sensitivity. Storage longevity was variable, but 195 species had viability >70% at the most recent tests (1 to 20+ yr), 123 species had RCIs >10 yr, and 45 species had RCIs <5 yr. CONCLUSIONS: Freeze sensitive storage behavior is more widely observed in Hawai'i than any other regional flora, perhaps due to insufficient testing elsewhere. We present a new protocol to test seed freeze sensitivity, which is often not evident until 2-5 years of storage. Re-collection intervals will guide restoration practices in Hawai'i, and results inform seed conservation efforts globally, especially tropical and subtropical regions.

Patents for the Physiological Quality in Seeds of Peach Rootstock Classified by Weight and Stored for Different Periods.

BACKGROUND: Among stone fruit, the peach (Prunus persica (L) Batsch) is one of the most widely grown species in Brazil, in both area cultivated and in production. OBJECTIVE: The aim of this study was to evaluate the physiological quality of heavy and light seeds of four cultivars of Prunus persica for two storage periods, from tests of electrical conductivity, germination, and an analysis of initial plantlets growth. METHODS: The Electrical Conductivity test (EC) was conducted in a Completely Randomised Design (CRD), in a 4 x 2 x 5 factorial scheme with five replications. The germination test was carried out in CRD, in a 4 x 2 factorial scheme with eight replications. The physiological quality of the seeds was determined at zero and twelve month's storage. For the growth analysis, the experimental design was in CRD, in a 4 x 2 factorial scheme with four replications. RESULTS: Under the conditions of the present study, it was found that the tests of germination and electrical conductivity were complementary in evaluating physiological quality in seeds of Prunus persica rootstock, suggesting that independent of the weight of the seeds, in 'Capdeboscq', 'Aldrighi', 'Okinawa' and 'Okinawa Roxo', there is a loss of quality and viability when the seeds are stored for a period of 12 months. CONCLUSION: Under the experimental conditions of the present study, it was concluded that storage for a period of 12 months in Recent patents is not rather recommendable for maintaining quality and viability in seeds of Prunus persica of the Capdeboscq, Aldrighi, Okinawa and Okinawa Roxo cultivars.

Rethinking the approach to viability monitoring in seed genebanks.

Seed viability monitoring, usually through a germination test, is a key aspect of genebank management; a low viability result triggers the regeneration of an accession in order to ensure that the genetic diversity of the accession is conserved and available for distribution. However, regular viability monitoring of large collections is costly in terms of seeds, labour and other resources. Genebanks differ in how they conduct their viability monitoring and how they collect, manage and store the data that are generated. In this article, we propose alternatives to the current norm of conducting an initial germination test soon after arrival at the genebank and then testing after regular, set storage intervals, as recommended in the Food and Agriculture Organization's Genebank Standards for Plant Genetic Resources for Food and Agriculture. We use real data from the International Rice Genebank (held at the International Rice Research Institute) to illustrate some of the issues regarding the accuracy and reliability of germination test results, in particular when they are used to predict the longevity of a seed lot in storage and to set viability monitoring intervals. We suggest the use of seed storage experiments on samples of seeds to identify which seed lots from a particular crop season to test first. We also give advice on the use of sequential testing schemes potentially to reduce the number of seeds used for viability testing; the use of tolerance tables to identify unlikely results when samples are subdivided into replicates; and what data to include in a genebank management database to improve the management of seed collections.

Barley Seed Aging: Genetics behind the Dry Elevated Pressure of Oxygen Aging and Moist Controlled Deterioration.

Experimental seed aging approaches intend to mimic seed deterioration processes to achieve a storage interval reduction. Common methods apply higher seed moisture levels and temperatures. In contrast, the "elevated partial pressure of oxygen" (EPPO) approach treats dry seed stored at ambient temperatures with high oxygen pressure. To analyse the genetic background of seed longevity and the effects of seed aging under dry conditions, the EPPO approach was applied to the progeny of the Oregon Wolfe Barley (OWB) mapping population. In comparison to a non-treated control and a control high-pressure nitrogen treatment, EPPO stored seeds showed typical symptoms of aging with a significant reduction of normal seedlings, slower germination, and less total germination. Thereby, the parent Dom ("OWB-D"), carrying dominant alleles, is more sensitive to aging in comparison to the population mean and in most cases to the parent Rec ("OWB-R"), carrying recessive alleles. Quantitative trait locus (QTL) analyses using 2832 markers revealed 65 QTLs, including two major loci for seed vigor on 2H and 7H. QTLs for EPPO tolerance were detected on 3H, 4H, and 5H. An applied controlled deterioration (CD) treatment (aged at higher moisture level and temperature) revealed a tolerance QTL on 5H, indicating that the mechanism of seed deterioration differs in part between EPPO or CD conditions.

Germinação de sementes de dalbergia nigra (Vell.) Allemao ex Benth. (Fabaceae-Papilionoideae) no armazenamento / Germination of Dalbergia nigra (Vell.) Allemao ex Benth. (Fabaceae-Papilionoideae) during storage

Dalbergia nigra (Vell.) Allemao ex Benth. (jacarandá-da-bahia), espécie de alto valor econômico pela qualidade da madeira e potencial ornamental em razão da copa bem formada e à delicadeza da folhagem, está na lista de espécies ameaçadas de extinção. Em função disso, conduziu-se este trabalho, visando à avaliação da qualidade de suas sementes, submetidas a períodos crescentes de armazenamento. Os frutos foram coletados em outubro de 2003, e as sementes armazenadas em geladeira a 6º C ± 2, em sacos de plástico transparente fechados. Mensalmente, durante 690 dias, foram retiradas 200 sementes, sendo que 100 foram utilizadas nos ensaios de germinação (quatro repetições de 25 sementes) e 100 para a determinação do teor de água. Os ensaios germinativos foram conduzidos em estufa tipo B.O.D., a 25º C e com fotoperíodo de 12 horas. As variáveis analisadas foram a porcentagem de germinação, índice de velocidade de germinação e massa seca das plântulas originadas. Os resultados indicaram que, até 360 dias de armazenamento, as sementes apresentaram porcentagem de germinação próxima de 50 por cento, com redução de cerca da metade do índice de velocidade de germinação, porém, com maior comprometimento do acúmulo da massa seca das plântulas. A porcentagem de germinação inicial e final foram de 87 por cento e 36 por cento, respectivamente. As sementes de D. nigra têm comportamento ortodoxo e podem ser armazenadas por um período de até dois anos em sacos de plástico a baixa temperatura, com redução em cerca de 50 por cento de sua capacidade.

Dalbergia nigra (Vell.) Allemao ex Benth. (Brazilian rosewood) is a highly economically valuable species because of its wood quality and ornamental potential, mainly due to its well formed canopy and the delicacy of its foliage. Unfortunately, these features contributed to list it as an endangered Brazilian species (IBAMA Regulation number 06/92). This work had as its objective to study the quality of Dalbergia nigra seeds submitted to increasing storage periods. Fruits from trees located at the Botanical Institute of Sao Paulo were collected in October 2003. After harvested, the fruits were sun dried and the seeds manually separated. The seeds were stored in closed transparent plastic bags under refrigeration (6º C ± 2). Monthly, during 690 days, 200 seeds were removed from the refrigerator. One hundred (100) seeds were used in germination tests, which consisted of four repetitions with 25 seeds each; and the other 100 were used in the determination of water content. The germination tests were conducted in a B.O.D. chamber at 25º C under a 12 hour photoperiod. The analyzed variables were; the germination percentage, germination velocity index, and dry mass of the seedlings. The results indicated that after 360 days of storage, the seeds showed germination percentage close to 50 percent and reduction of the germination velocity index to half, whereas the dry mass accumulation was the most compromised. The initial and final germination percentages were 87 percent and 36 percent, respectively. We concluded that Dalbergia nigra seeds present orthodox behavior and can be stored for a period of approximately two years in plastic bags at low temperature, compromising 50 percent of their germination capacity.

Evaluation of substrate type and storage period for the germination of Cordia glabrata (Mart.) DC seeds - DOI: 10.4025/actascibiolsci.v31i3.1013 / Avaliação do tipo de substrato e do período de armazenamento para a germinação de sementes de Cordia glabrata (Mart.) DC. - DOI: 10.4025/actascibiolsci.v31i3.1013

Information about the feasibility and adequate substrates for the germination of seeds from native arboreous species are scarce. Cordia glabrata (louro preto), a pioneering species with wide distribution, is included among these species. Its characteristics allow its use in ornamentation, apiculture and popular medicine. Considering its potential of utilization, this work had as objective to evaluate the germination rates, in different substrates, of recently reaped seeds stored for up to 120 days in laboratory, which were collected in Pantanal of the Rio Negro, Mato Grosso do Sul State. Tests were done with recently reaped seeds and after 30, 60, 90 and 120 days of storage, in three kinds of substrate (paper filter, sandy soil and sandy soil + organic matter). The results revealed that C. glabrata has a small percentage of water (1.55%) in the seeds, which decreases with the storage period. Its feasibility period is short (90 days) and the best results were obtained with recently reaped seeds germinated in paper filter (34%), with a germination speed rate of 10.

Informações sobre a viabilidade e substratos adequados para a germinação de sementes de espécies arbóreas nativas são escassas. Cordia glabrata (louro-preto), espécie pioneira e de ampla distribuição, está incluída entre essas espécies. Suas características permitem a utilização em ornamentação, na prática apícola e na medicina popular. Levando em conta seu potencial de utilização, este trabalho teve por objetivo avaliar as taxas de germinação, em diferentes substratos, de sementes recém-colhidas e armazenadas até 120 dias em laboratório, as quais foram coletadas no Pantanal do Rio Negro, Estado do Mato Grosso do Sul. Foram realizados testes com sementes recém-colhidas e após 30, 60, 90 e 120 dias de armazenamento, em três tipos de substrato (papel-filtro, solo arenoso e solo arenoso + matéria orgânica). Os resultados revelaram que C. glabrata possui pequena porcentagem de água (1,55%) nas sementes, que decai com o período de armazenamento. Seu período de viabilidade é curto (90 dias) e os melhores resultados foram obtidos com sementes recém-colhidas germinadas em papel-filtro (34%), com índice de velocidade de germinação de 10.