This study aimed to evaluate hybrids obtained by the cross among temperate × tropical elite maize lines, and to determine the genetic diversity and population differentiation of these inbred lines. ...Forty-nine hybrids were evaluated for seed yield, plant and ear heights, and for severity of Phaeosphaeria maydis and Exserohilum turcicum in four environments in Brazil. Hybrids were obtained from a partial diallel that involved seven tropical and seven temperate lines. Twenty-two SSR primers were used to evaluate the genetic relationship among the lines. Diallel showed the existence of significance for GCA and SCA effects; the genetic control of the traits was associated with additive and nonadditive genetic effect. Results showed that exotic and previously protected temperate maize germplasm may provide novel alleles for resistance to P. maydis and E. turcicum and increase yield in tropical maize. Tropical inbred lines were allocated in different heterotic groups, suggesting an admixture condition among temperate and tropical materials.
Breeding new maize varieties that take up more N from the soil and increase N fixation is a crucial source of combined nitrogen in agricultural systems. Thus, this study aimed to select superior ...maize parental lines efficient in the use of nitrogen and Azospirillum brasilense. Three experiments were conducted in two agricultural seasons aiming to allocate all diallel hybrids in three different nitrogen conditions. The experiments were performed in a RCB design with two replications, and the diallel was analyzed using the mixed model approach. The general combining ability and Azospirillum use efficiency were applied to select the best parental line. The most promising hybrid combinations were “I-08 x II-06”, “I-02 x II-04”, and “I-01 x II-02”. Parents involved were selected for the development of hybrids. Parents I-01, I-02, I-08, II-01, II-02, II-04, II-05, and II-06 were selected to explore the basic population in the A. brasilense-use efficiency breeding program.
The bean fly (
Ophiomyia spp.
) is the most destructive insect pest of common bean (
Phaseolus vulgaris
L
.
) causing significant yield losses. The objectives of this study were to determine the ...combining ability effects and deduce gene action controlling the inheritance of bean fly resistance and agronomic traits among common bean genotypes, and to select superior genotypes for breeding. Eight selected complementary parents were crossed using a half-diallel mating design to derive new families. Parents and 28 F
2
families were evaluated in two locations using were evaluated in two locations using a 6 × 6 lattice square design with two replications. Bean fly resistance parameters such as bean fly damage severity (BDS), pupae count (PC) and plant mortality rate (PMR) and agronomic traits such as days to 50% flowering (DTF), days to maturity (DTM), number of pods per plant (NPP), number of seed per pod and grain yield (GYD) were collected. Results revealed significant genotype × location interaction effects on resistance parameters and agronomic traits allowing selection of unique families adapted to different production environments. There were negative correlations between grain yield (GYD) and bean fly damage severity (
p
< 0.01, r = − 0.60), pupa count (
p
< 0.01, r = − 0.34) and plant mortality rate (
p
< 0.01, r = − 0.53), implying that direct selection for bean fly resistant genotypes would improve GYD. Genotypes A429 and A55 exhibited negative general combining ability (GCA) effects for bean fly damage parameters and positive GCA effects for GYD. Good combiners for number of pods per plant (NPP) and GYD were the genotypes A55, MW365 and Sinoni, while MW466 exhibited desirable GCA effects for days to 50% flowering (DTF) and days to 90% maturity (DTM). These parental lines with desirable GCA effects for bean fly resistance and agronomic traits were selected for future breeding. Families such as Sinoni/A55, Kabanima/A55 and MW365/Kabanima showed desirable BDS, PC and PMR (SCA) effects for bean fly resistance and grain yield. Families such as Kabanima/A55, Sinoni/A55 and NUA45/MW365 exhibited desirable and significant SCA effects for traits such as NPP, number of seeds per pod (NSP) and GYD. Families with desirable SCA effects will be utilised in selecting desirable recombinant inbred lines and breeding populations for improving bean fly resistance and agronomic performance. The Baker’s ratios indicated that additive gene effects were more important for bean fly resistance and GYD. Recurrent selection would be the best strategy for improving bean fly resistance and grain yield using this germplasm.
To evaluate gene effects and heritability of fruit and flower characters in melon, three experiments were performed. In the first experiment, 48 genotypes of different melon groups were planted to ...choose the monoecious melon. To investigate the sex modification regarding fruit traits, seven parents, including a monoecious type and andromonoecious types, crossed in a full diallel scheme to obtain all possible combinations. Evaluation amongst all genotypes revealed one Cantaloupensis and all Flexuosus genotypes with monoecious flowers. Floral and fruit characters of F1 hybrids obtained from the diallel cross, were recorded. All hybrids that have been crossed with the monoecious parent revealed the monosexual progenies. Most of the floral characters with high GCA/SCA values remarked the additive gene effect. There were also cytoplasmic effects on flower and fruit traits. The significant GCA /SCA estimates observed for fruit traits such as yield, fruit length, fruit length to width, flesh thickness referred to the importance of additive gene effects. It could be demonstrated that classic hybridization holds great potential in controlling flowering habit and yield‐related fruit traits.
Identification of testers is crucial for hybrid maize breeding programme. However, limited information is available about ideal testers for characterising the combining ability of Striga resistant ...maize inbreds. This study was conducted to assess the relative value of three inbred testers with varying resistance reactions to Striga for determining the combining ability of Striga resistant inbreds. Ninety testcrosses involving 30 Striga resistant inbreds and three testers were evaluated under artificial and natural Striga infestation and non‐infested conditions at two locations for 2 years. Lines x tester interaction was significant (p ≤ .05) for most traits, indicating differential ranking of lines by the testers. The GCA effects of testers for most traits were high, highlighting the predominance of additive gene action in controlling the overall performance of testcrosses. The resistant and tolerant testers exhibited desirable GCA effects, broader testcross performance, greater genetic variances and consistent ranking of testcrosses under both growing conditions than the susceptible tester. These testers can be successfully used for identifying superior Striga resistant inbreds to develop high yielding and resistant hybrids for commercialization.
Parent selection is the core of hybrid breeding. The breeding strategy involving the parental identification of superior open-pollinated progeny of Populous tomentosa germplasm resources can ...significantly improve the efficiency of parental matching. However, due to some factors such as loose powdering time and pollen competitiveness, the offspring derived from open-pollination families which do not undergo completely random mating. Although hybrid combinations based on the male identification method have a high combining ability, this method cannot easily cover the mating combinations of all male and female specimens in the germplasm bank. In addition, the performance of superior plants in open-pollinated families also affects the selection result. If the trait performance value is higher than the population average, then the special combining ability of the reconstructed hybrid combination may be overestimated. Obtaining a solution to the above problems is of great significance for improving the efficiency and accuracy of selecting hybrid parents of P. tomentosa. In this study, 24 pairs of SSR (Simple Sequence Repeats) molecular markers were used to analyze the genetic differentiation of P. tomentosa germplasm resources. The results showed that the genetic variation of the P. tomentosa population was derived from individuals within the provenance, indicating that high genetic diversity is preserved in provenances. The correlation analysis showed that there was a significant positive correlation between the special combining ability of planting height and diameter at breast height (dbh) of the 34 full-sib progeny population and the genetic distance between the parents. Then, the genetic distance between 18 female plants with high fertility and 68 male plants with large pollen quantity was analyzed using this correlation. Fifteen female parents and 12 male parents were screened out, and 52 hybrid combinations with high specific combining ability for growth traits were predicted. Furthermore, for the male parent identification of superior individual plants, we constructed the breeding parent population including 10 female parents and 5 male parents, generating 14 hybrid combinations with potentially high combining ability. The results of the hybridization test showed that the specific combining ability of plant height and dbh was significantly higher than the controlled pollination. Moreover, genetic distance and paternal identification can be used to rapidly and efficiently construct hybrid parent combinations and breeding parent populations.
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