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Fusarium oxysporum f. sp. phaseoli ( Fop) is a soil pathogen that causes wilt in common bean ( Phaseolus vulgaris L.) and is one of the most important diseases of this crop. The use of resistant cultivars is the most effective method of controlling losses from this pathogen, and studying the inheritance of Fop resistance could provide useful insights for developing cultivars with resistance. Thus, the aim of this study was to determine the inheritance of resistance to fusarium wilt in common bean. The parents, F and F plants from seven crosses between resistant and susceptible parents of a partial diallel scheme 3 × 5 were inoculated with the isolate FOP UFV 01. During each generation, the plants were individually evaluated to determine disease severity. Among the eight parents, five were resistant, and three were susceptible to fusarium wilt. Only two phenotypic classes were observed in the parents (resistant and susceptible). Based on the performance of the F generation, all the individuals were resistant, indicating that resistance is dominant over susceptibility. Different results were obtained for the segregation of plants from the F generation based on the methods applied to determine the inheritance of resistance. However, the maximum likelihood estimator method, which was the most suitable methodology, showed that Fop resistance in common bean is a dominant trait governed by few major genes plus polygenes. These findings can support breeding programs in obtaining Fop-resistant cultivars. [ABSTRACT FROM AUTHOR]

For in vivo production of doubled haploid (DH) lines in maize, the rate of haploid induction is of crucial importance. Maternal haploid induction depends primarily on the inducer used as a pollinator. However, the source germplasm used as a maternal parent and the environmental conditions for induction may also influence haploid induction and these aspects have not been examined in tropical maize so far. The objectives of our study were to (i) monitor the variation for haploid induction rate (HIR) among diverse source germplasm in tropical maize, (ii) determine the relative importance of general (GCA) and specific (SCA) combining abilities for HIR, and (iii) investigate the influence of summer and winter seasons and genotype × season interactions on this trait. Ten inbreds were mated in a half diallel design. The resulting 45 F single crosses were pollinated with the haploid inducer hybrid RWS × UH400 during the summer 2008 and winter 2009 seasons in a lowland tropical environment in Mexico. HIR of the single crosses averaged over seasons ranged from 2.90 to 9.66% with an overall mean of 6.74%. Mean HIR was significantly ( P < 0.01) higher during the winter (7.37%) than summer season (6.11%). Significant ( P < 0.01) variation was observed due to GCA effects of parental inbreds of single crosses but not for SCA, GCA × season and SCA × season interactions. Our study underpins that a higher HIR in tropical maize can be obtained by selecting appropriate source germplasm and undertaking pollination under favorable environmental conditions. [ABSTRACT FROM AUTHOR]

Common bean populations from crosses between lines of different races are thought to be more promising for selection of high yield potential than those from intra-racial crosses. Three distinct diallel crosses were made to test this hypothesis and to determine the possibility of substituting diallel crosses for multivariate techniques that estimate genetic divergence. The crosses were between races Mesoamerica × Mesoamerica, Mesoamerica × Durango and Jalisco, and Mesoamerica × Nueva Granada. The parents and the resulting F4 populations were evaluated at Lavras-MG, Lambari-MG and Patos de Minas-MG, Brazil. The diallel analysis of seed yield was done and the genetic divergence estimated by Mahalanobis distance. Estimates of general and specific combining ability indicated that some inter-racial populations were more promising for selection to increase seed yield than intra-racial populations. However, due to their undesirable seed color and size, and growth habit, especially in a short term breeding program, the chances of obtaining high yielding lines with an acceptable bean is reduced. Genetic divergence was not a good measure to choose the parents because usually, the most divergent groups included were not adapted lines. [ABSTRACT FROM AUTHOR]

Compared with annual cultivated rice, perennial rice had great advantages of soil erosion control, labor saving, water and fertilizer management, etc. As the key organ for perenniality, rhizome can help grasses to achieve rapid expansion to occupy more environmental resources, and withstand the harsh environmental conditions. Oryza longistaminata, a perennial wild relative of rice with vigorous rhizomes, is an ideal donor for transferring perenniality to Asian cultivated rice (Oryza sativa). However, some hybrid F1 between O. longistaminata and cultivated rice didn't have rhizomes. Obtaining rhizomatous hybrid progeny becomes a prerequisite for the rhizomes study. In this work, four varieties of O. sativa and three accessions of O. longistaminata were used to carry out an incomplete diallel cross experiment. It was found that most F1 hybrids had rhizomes with varying length and numbers. Data analysis showed that the general combining ability (GCA) of the female parents had significant effect on rhizome-related trait of the F1s. Nevertheless, the GCA of the male parents and special combining ability of the hybrid combination played minor effect. And we speculated that the appropriate choice for female parents is more crucial to obtain rhizomatous hybrid. As the first incomplete diallel cross between O. longistaminata and O. sativa, this work would be benefit to appropriate parent selection for genetic research and breeding of perennial rice. [ABSTRACT FROM AUTHOR]