Diallel crosses for resistance to Macrophomina phaseolina and Thanatephorus cucumeris on cowpea.

This study aimed at identifying and selecting through partial diallel analysis, segregating populations of cowpea resistant to Macrophomina phaseolina and Thanatephorus cucumeris, based on the evaluation of general (GCA) and specific combining ability (SCA), involved in the genetic control of resistance. For this reason, 19 grouped cowpea genotypes, considering the resistance to these pathogens, were crossed in partial diallel scheme 14 x 5, during 2013 and 2014. The 70 F2 populations and the 19 parents were evaluated in a greenhouse as the reaction to pathogens, separately. The diallel analysis was performed according to the model of partial diallel proposed by Geraldi and Miranda Filho (1988). The additive effects predominated in the genetic control of the traits severity of charcoal rot (SEV) and area under the disease progress curve (AUDPC) to web blight, enabling the achievement of genetic gain with selection of resistant strains. Analyzing the effects of GCA, the parents BR 14-Mulato, BRS Tumucumaque and BRS Guariba, have a higher concentration of favorable alleles, highlighting, according to the values of SCA, the combinations BR 14-Mulato x MNC02-675F-4-10, BRS Tumucumaque x IT98K-1092-1, BRS Tumucumaque x MNC02-675F-4-10, BRS Tumucumaque x MNC02-675F-9-2, BRS Guariba x IT98K-1092-1, BRS Guariba x MNC02-675F-4-9, and BRS Guariba x MNC02-675F-4-10, as the most promising and indicated to obtain lines resistant to M. phaseolina and T. cucumeris in cowpea, simultaneously.

Genotypic gain with simultaneous selection of production, nutrition, and culinary traits in cowpea crosses and backcrosses using mixed models.

The aim of this study was to estimate the genotypic gain with simultaneous selection of production, nutrition, and culinary traits in cowpea crosses and backcrosses and to compare different selection indexes. Eleven cowpea populations were evaluated in a randomized complete block design with four replications. Fourteen traits were evaluated, and the following parameters were estimated: genotypic variation coefficient, genotypic determination coefficient, experimental quality indicator and selection reliability, estimated genotypic values ​​- BLUE, genotypic correlation coefficient among traits, and genotypic gain with simultaneous selection of all traits. The genotypic gain was estimated based on tree selection indexes: classical, multiplicative, and the sum of ranks. The genotypic variation coefficient was higher than the environmental variation coefficient for the number of days to start flowering, plant type, the weight of one hundred grains, grain index, and protein concentration. The majority of the traits presented genotypic determination coefficient from medium to high magnitude. The identification of increases in the production components is associated with decreases in protein concentration, and the increase in precocity leads to decreases in protein concentration and cooking time. The index based on the sum of ranks was the best alternative for simultaneous selection of traits in the cowpea segregating populations resulting from the crosses and backcrosses evaluated, with emphasis on the F4BC12, F4C21, and F4C12 populations, which had the highest genotypic gains.