RESUMO
The rajado seeded Andean bean (Phaseolus vulgaris L.) cultivar BRSMG Realce (striped seed coat) developed by Embrapa expressed a high level of anthracnose resistance, caused by Colletotrichum lindemuthianum, in field and greenhouse screenings. The main goal of this study was to evaluate the inheritance of anthracnose resistance in BRSMG Realce, map the resistance locus or major gene cluster previously named as Co-Realce, identify resistance-related positional genes, and analyze potential markers linked to the resistance allele. F2 plants derived from the cross BRSMG Realce × BRS FC104 (Mesoamerican) and from the cross BRSMG Realce × BRS Notável (Mesoamerican) were inoculated with the C. lindemuthianum races 475 and 81, respectively. The BRSMG Realce × BRS FC104 F2 population was also genotyped using the DArTseq technology. Crosses between BRSMG Realce and BAT 93 (Mesoamerican) were also conducted and resulting F2 plants were inoculated with the C. lindemuthianum races 65 and 1609, individually. The results shown that anthracnose resistance in BRSMG Realce is controlled by a single locus with complete dominance. A genetic map including 1,118 SNP markers was built and shown 78% of the markers mapped at a distances less than 5.0 cM, with a total genetic length of 4,473.4 cM. A major locus (Co-Realce) explaining 54.6% of the phenotypic variation of symptoms caused by the race 475 was identified in Pv04, flanked by the markers snp1327 and snp12782 and 4.48 cM apart each other. These SNPs are useful for marker-assisted selection, due to an estimated selection efficiency of 99.2%. The identified resistance allele segregates independently of the resistance allele Co-33 (Pv04) present in BAT 93. The mapped genomic region with 704,867 bp comprising 63 putative genes, 44 of which were related to the pathogen-host interaction. Based on all these results and evidence, anthracnose resistance in BRSMG Realce should be considered as monogenic, useful for breeding purpose. It is proposed that locus Co-Realce is unique and be provisionally designated as CoPv04R until be officially nominated in accordance with the rules established by the Bean Improvement Cooperative Genetics Committee.
RESUMO
The use of fungicides to control powdery mildew in sweet pepper has been ineffective and genetic resistance is the best alternative. Resistance sources identified in Capsicum annuum L. are rare and unsatisfactory. The purpose of this work was to study the inheritance of C. annuum reaction to powdery mildew. Three homozygous powdery mildew resistant parents, HV-12, Chilli and /124 and three susceptible lines, 609, 442 and 428 were used to obtain seven F1's and respectively their generations F2: HV-12 x 609, 442 × HV-12, 428 × HV-12, Chilli × 609, /124 × 609, Chilli × HV-12 and /124 × HV-12. The powdery epidemic was natural using inoculum from highly sporulating susceptible pepper host. Powdery mildew host reaction evaluations were carried out during the fruit production using a rating system based on disease severity scales varying from 1 (resistant) to 5 (highly susceptible). The experimental design was completely randomized. The following genetic parameters were estimated: locus numbers, gene action, heritability coefficient, expected selection gain and observed progress in F3 generation, and possibly allelic relationship among resistance genes of different resistance sources. The HV-12×609 cross was the only one that showed absence of dominance. Other genetically analyzed crossings showed dominant and epistatic effects. Resistance was characterized as being due to at least four pairs of genes. The heritability and selection gains estimates were high. The resistance mechanisms of /124, Chilli and HV-12 showed differences in their expression.
O uso de fungicidas no controle do oídio do pimentão tem se mostrado ineficaz, sendo a resistência genética a melhor alternativa. As fontes de resistência identificadas em Capsicum annuum L. são raras e não satisfatórias. O objetivo deste trabalho foi estudar a herança da reação de C. annuum ao oídio. Três progenitores resistentes e homozigóticos, HV-12, Chilli e /124 e três suscetíveis, 609, 442 e 428 foram usados na obtenção de sete híbridos e respectivas gerações F2: HV-12 × 609, 442 × HV-12, 428 × HV-12, Chilli × 609, /124 × 609, Chilli × HV-12 e /124 × HV-12. A epidemia de oídio ocorreu de maneira natural a partir de inóculo mantido em plantas de pimentão suscetíveis. As avaliações das reações ao oídio foram feitas na fase de frutificação, através de uma escala de notas de 1 (resistente) a 5 (altamente suscetível). O delineamento experimental utilizado foi inteiramente casualizado. Foram estimados, os números de locos, ação gênica, coeficiente de herdabilidade, ganho de seleção esperado e o progresso observado em F3 e possíveis relações de alelismo entre os genes que governam a resistência. O cruzamento HV-12 × 609 foi o único em que a reação de resistência mostrou ausência de dominância. Nos demais cruzamentos detectaram-se efeitos dominantes e epistáticos. A herança foi caracterizada sendo governada por no mínimo quatro pares de genes. As herdabilidades e ganhos de seleção estimados foram altos. O mecanismo de resistência dos progenitores resistentes /124, Chilli e HV-12 mostraram diferenças de expressão e natureza genética.
RESUMO
The use of fungicides to control powdery mildew in sweet pepper has been ineffective and genetic resistance is the best alternative. Resistance sources identified in Capsicum annuum L. are rare and unsatisfactory. The purpose of this work was to study the inheritance of C. annuum reaction to powdery mildew. Three homozygous powdery mildew resistant parents, HV-12, Chilli and /124 and three susceptible lines, 609, 442 and 428 were used to obtain seven F1's and respectively their generations F2: HV-12 x 609, 442 × HV-12, 428 × HV-12, Chilli × 609, /124 × 609, Chilli × HV-12 and /124 × HV-12. The powdery epidemic was natural using inoculum from highly sporulating susceptible pepper host. Powdery mildew host reaction evaluations were carried out during the fruit production using a rating system based on disease severity scales varying from 1 (resistant) to 5 (highly susceptible). The experimental design was completely randomized. The following genetic parameters were estimated: locus numbers, gene action, heritability coefficient, expected selection gain and observed progress in F3 generation, and possibly allelic relationship among resistance genes of different resistance sources. The HV-12×609 cross was the only one that showed absence of dominance. Other genetically analyzed crossings showed dominant and epistatic effects. Resistance was characterized as being due to at least four pairs of genes. The heritability and selection gains estimates were high. The resistance mechanisms of /124, Chilli and HV-12 showed differences in their expression.
O uso de fungicidas no controle do oídio do pimentão tem se mostrado ineficaz, sendo a resistência genética a melhor alternativa. As fontes de resistência identificadas em Capsicum annuum L. são raras e não satisfatórias. O objetivo deste trabalho foi estudar a herança da reação de C. annuum ao oídio. Três progenitores resistentes e homozigóticos, HV-12, Chilli e /124 e três suscetíveis, 609, 442 e 428 foram usados na obtenção de sete híbridos e respectivas gerações F2: HV-12 × 609, 442 × HV-12, 428 × HV-12, Chilli × 609, /124 × 609, Chilli × HV-12 e /124 × HV-12. A epidemia de oídio ocorreu de maneira natural a partir de inóculo mantido em plantas de pimentão suscetíveis. As avaliações das reações ao oídio foram feitas na fase de frutificação, através de uma escala de notas de 1 (resistente) a 5 (altamente suscetível). O delineamento experimental utilizado foi inteiramente casualizado. Foram estimados, os números de locos, ação gênica, coeficiente de herdabilidade, ganho de seleção esperado e o progresso observado em F3 e possíveis relações de alelismo entre os genes que governam a resistência. O cruzamento HV-12 × 609 foi o único em que a reação de resistência mostrou ausência de dominância. Nos demais cruzamentos detectaram-se efeitos dominantes e epistáticos. A herança foi caracterizada sendo governada por no mínimo quatro pares de genes. As herdabilidades e ganhos de seleção estimados foram altos. O mecanismo de resistência dos progenitores resistentes /124, Chilli e HV-12 mostraram diferenças de expressão e natureza genética.