Phenotypic recurrent selection in the common bean (Phaseolus vulgaris L) with carioca-type grains for resistance to the fungi Phaeoisariopsis griseola

The efficiency of recurrent selection was assessed in obtaining common bean (Phaseolus vulgaris L) plant lines resistant to the phytopathogenic fungi Phaeoisariopsis griseola. The base bean population was obtained from the partial diallel between seven lines with carioca-type grains and 10 sources of resistance to P. griseola. The plants most resistant to the pathogen were selected in the F2 (S0) generation of the populations (C-0). The best S0:1 plants that presented carioca-type grains were intercrossed to obtain cycle I (C-I). The same procedure was adopted to obtain cycles C-II to C-V. In each recurrent selection cycle, S0:1 progenies selected were also assessed in experiments carried out in Lavras, Brazil, always using as check the Carioca MG (susceptible to P. griseola) and Pérola (tolerant) cultivars. The response to selection for resistance to the pathogen was estimated from the general mean of the S0:1 progenies from each selective cycle compared to the susceptible check Carioca MG. The estimated gain was 6.4% per cycle and the indirect response in grain yield by selection for resistance to the pathogen was 8.9% per cycle. The variability detected among the progenies in the last selective cycles enabled the prediction of additional responses to recurrent selection

Effect of environments on the estimated genetic potential of segregating common bean populations

The objective of this study was to investigate the effect of environments on the estimated genetic potential of common bean populations for the traits hypocotyl diameter and grain yield. We evaluated 48 segregating bean populations in the growing seasons winter 2009 (F2 and F3 simultaneously) and drought 2010 (F3 and F4 generations simultaneously), and 16 controls. The genetic potential of the population was estimated using the methodology of Jinks and Pooni. The coincidence between the best and worst populations in the two growing seasons and different generations for the two characters was low, indicating that the environmental effect interferes with the selection of common bean populations when using the method of Jinks and Pooni. Thus, it is recommended that the genetic potential should be estimated based on the evaluation of a larger number of environments.O objetivo deste trabalho foi verificar o efeito de ambientes na predição do potencial genético de populações de feijoeiro quanto ao diâmetro do hipocótilo e produtividade de grãos. Foram avaliadas 48 populações segregantes de feijão nas safras de inverno de 2009 (gerações F2 e F3 simultaneamente) e seca de 2010 (gerações F3 e F4 simultaneamente), além de 16 testemunhas. A predição do potencial genético das populações foi feita utilizando a metodologia de Jinks e Pooni. Verificou-se baixa coincidência entre as melhores e entre as piores populações nas duas safras e nas diferentes gerações para os dois caracteres, evidenciando que o efeito de ambientes interfere na escolha das populações de feijoeiro, quando se utiliza o método de Jinks e Pooni. Assim, é recomendável que a predição do potencial seja realizada com base nas informações de um maior número de ambientes

Estimate of genetic parameters in Brachiaria decumbens hybrids

The objective of this study was to estimate genetic parameters for agronomic traits and nutritional value in intraspecific hybrids of B. decumbens. For this, a population of 1,415 hybrids was evaluated in field plots at Embrapa Beef Cattle in Campo Grande/MS/Brazil, with seven clippings in order to estimate field green weight (FGW); total dry matter (TDM); speed of regrowth (SR); tiller regrowth density (TRD); regrowth ability (REG); crude protein (CP); in vitro organic matter digestibility (IVD); neutral detergent fiber (NDF) and lignin (LIG). The statistical analyses were carried out using the mixed models methods. Genetic variability for all traits assessed was detected, and estimates of individual heritability were of medium to high magnitude, indicating the possibility of gains with selection. Significant genetic correlations were observed between FGW and TDM (0.99), TDM and SR (0.81), TDM and IVD (-0.71), TDM and LIG (0.71), and CP and IVD (0.70)