Identification of diverse groundnut germplasm through multienvironment evaluation of a core collection for Asia

In Asia, like elsewhere, the use of genetic resources has been limited in groundnut (Arachis hypogaea L.) breeding programs, resulting in a narrow genetic base of cultivars. Utilization of exotic germplasm in breeding programs is needed to enhance the diversity of cultivars. Core collections, which generally contain 10% of total accessions and represent the diversity of the entire collection, have been suggested as a means to enhance the use of genetic resources. For traits of economic importance, which often display high genotype × environment interactions, multienvironment evaluation is required to choose desirable parents. The groundnut core collection for Asia, consisting of 29 accessions of subsp. fastigiata var. fastigiata, 245 of subsp. fastigiata var. vulgaris, and 230 of subsp. hypogaea var. hypogaea, along with four control cultivars, was evaluated in multienvironments for 22 agronomic traits to select diverse superior germplasm accessions for use as parents in improvement programs. Data were recorded for 12 traits in six environments, eight traits in four environments, and for two traits in two environments. Analysis of data, using the residual maximum likelihood (REML) approach, indicated that variance components due to genotypes were significant for all 22 traits, and genotypes × environment interaction was significant for eight traits. Estimates of broad sense heritability ranged from 35.5% for pod yield per plant to 98.0% for days to cessation of flowering, indicating relative reliability of selection for different traits. On the basis of performance compared to control cultivars in different environments, 15 fastigiata, 20 vulgaris, and 25 hypogaea accessions from 14 countries were selected. The selected accessions and control cultivars were grouped using scores of the first 15 principal components (PCs) in fastigiata, 20 PCs in vulgaris, and 21 PCs in hypogaea. The clustering by Ward's method indicated that the selected accessions were diverse from the control cultivars. These 60 diverse parents will provide the germplasm, which can be used in the improvement programs to broaden the genetic base of groundnut cultivars.