Formation of Potential Heterotic Groups of Oat Using Variation at Microsatellite Loci

An evaluation of polymorphism at the microsatellite loci was applied in distinguishing 85 oat (Avena sativa L.) genotypes selected from the collection of genetic resources. The set of genotypes included oats with white, yellow, and brown seeds as well as a subgroup of naked oat (Avena sativa var. nuda Koern). Variation at these loci was used to form potential heterotic groups potentially used in the oat breeding program. Seven from 20 analyzed microsatellite loci revealed polymorphism. Altogether, 35 microsatellite alleles were detected (2–10 per locus). Polymorphic patterns completely differentiated all genotypes within the subgroups of white, brown, and naked oats, respectively. Only within the greatest subgroup of yellow genotypes, four pairs of genotypes remained unseparated. Genetic differentiation between the oat subgroups allowed the formation of seven potential heterotic groups using the STRUCTURE analysis. The overall value of the fixation index (Fst) suggested a high genetic differentiation between the subgroups and validated a heterotic grouping. This approach can be implemented as a simple predictor of heterosis in parental crosses prior to extensive field testing or development and implementation of more accurate genomic selection.

Characterization and Heterotic Grouping of Traditional Assam rice (Oryza sativa L.)

Parents of heterotic hybrids are derived from different heterotic groups with high genetic divergence. Classification of traditional Assam rice germplasm in divergent pools will be advantageous to maximize the heterosis and thereby to ensure food security. In the present investigation, a group of 60 upland rice genotypes were characterized using 53 polymorphic simple sequence repeats (SSR) markers out of 83 molecular markers. The genetic divergence study using unweighted Neighbour-joining (UNJ) method clustered the 60 genotypes into 3 major clusters. The eleven most divergent genotypes identified were crossed in half diallel fashion to determine the mid-parent and better-parent heterosis values for the objective of heterotic grouping. No correlation between heterosis and genetic distance can be attributable to the use of a subset of markers not linked to yield or concerned. In genetic distance based heterotic grouping, the intra-group hybrids were recorded a higher frequency of crosses, grain yield per plant, specific combining ability effect, mid parent heterosis, better parent heterosis and standard parent heterosis value than those of inter-group hybrids. Overall, sn extensive choice of parents with attractive traits constellation leading to increased yield of the hybrids for much better complementation must be stressed along with a substantial hereditary distance for augmentation of yield heterosis.

Efficiencies of Heterotic Grouping Methods for Classifying Early Maturing Maize Inbred Lines

The success of a hybrid breeding program is dependent on available heterotic patterns for exploitation of grain-yield heterosis. The efficiency of the assignment of germplasm lines into heterotic groups is a prerequisite for obtaining useful heterotic patterns among germplasm lines. A total of 256 maize hybrids, comprising 244 top crosses, six diallel cross hybrids, and six checks, were grown under Striga infestation, drought, and optimal conditions, from 2015 to 2017. The study determined the combining abilities of the parental inbreds, classified the inbreds into heterotic groups, and compared the efficiencies of the following four grouping methods for classifying the inbreds: specific combining ability (SCA) effect of grain yield; general combining ability (GCA) effects of multiple traits (HGCAMT); SCA and GCA (HSGCA) for yield; and single nucleotide polymorphism-based genetic distance (SNP-based genetic distance (GD)). Significant GCA and/or SCA mean squares were revealed for most measured traits in all test environments. Sums of squares (SS) due to GCA were higher than SCA SS for measured traits in all test environments. The HSGCA, SCA, and SNP-based GD methods identified four heterotic groups, whereas the HGCAMT identified three groups, in all environments. The additive gene effect was preponderant in the inheritance of most measured traits. The efficiencies of the grouping methods varied with the test environments. The HSGCA and SCA methods were the most efficient for grouping in all test conditions. For practical breeding purposes, the HGCAMT and HSGCA methods were recommended under Striga infestation and drought, respectively. The heterotic patterns, which were revealed in this study, were effective for planning hybridization schemes for developing high-yielding, Striga-tolerant/resistant, and drought-tolerant maize hybrids for stressful environments.

Application of heterotic grouping, standard heterosis and per se performance in breeding high-yielding inbred and hybrid cultivars of pigeonpea

A set of 102 hybrid combinations, developed by crossing three A4 CMS lines and 34 diverse testers, was evaluated to identify potential parental genotypes for breeding new high yielding cultivars. The hybrid combinations were assessed for their per se performance, standard heterosis and combining ability. Significant differences were recorded for parents versus hybrids for yield and its related traits, suggesting the presence of substantial heterotic responses. Highly significant GCA effects for yield were recorded within the female parents and testers. Relatively more number of hybrids involving ICPA 2092, as female parent, exhibited significant positive SCA values for yield, days to flower, plant height, primary branches, pods/plant, seed size and seeds/pod. A total of 45 hybrids recorded significant SCA effects for productivity. The yield superiority of hybrids over the inbred control cultivar ranged from -50.81 to 76.89%. Interestingly, 23 hybrids were also found superior to the first released pigeonpea hybrid ICPH 2671 by a margin of 5.48% to 64.31%. On the basis of their performance in hybrid combinations, the testers were classified into seven heterotic groups. The present study identified two CMS lines (ICPA 2092 and ICP 2043) and 13 testers including ICP 3525, ICPL 20196, BDN 2001-6 and BSMR 198 etc. as potential parental lines for use in breeding medium duration pigeonpea pure line and hybrid cultivars.