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Abstract
Groundnut (Arachis hypogaea L.) is a multi-purpose legume serving millions of farmers and their value chain actors globally. Use of old poor-performing cultivars contributes to low yields (< 1 t/ha) of groundnut in sub-Saharan Africa including Tanzania. The objectives of this study were to determine the extent of genetic variation among diverse groundnut collections using phenotypic traits and simple sequence repeat (SSR) markers to select distinct and complementary genotypes for breeding. One hundred and nineteen genotypes were evaluated under field conditions for agronomic traits and susceptibility to rust and leaf spot diseases. The study was conducted in two locations across two seasons. In addition, the 119 accessions were profiled with 13 selected SSR markers. Genotype and genotype by environment interaction effects were significant (p < 0.05) for days to flowering (DTF), late leaf spot score at 85 and 100 days after planting, pod yield (PDY), kernel yield (KY), hundred seed weight (HSW) and shelling percentage (SP). Principal components analysis revealed that plant stand, KY, SP, NPP (number of pods per plant), late leaf spot and rust disease scores accounted for the largest proportion of the total variation (71.9%) among the tested genotypes. Genotypes ICGV-SM 08587 and ICGV-SM 16579 had the most stable yields across the test environments. Moderate genetic variation was recorded with mean polymorphic information content of 0.34 and gene diversity of 0.63 using the SSR markers. The majority (74%) of genotypes showed high membership coefficients to their respective sub-populations, while 26% were admixtures after structure analysis. Much of the variation (69%) was found within populations due to genotypic differences. The present study identified genotypes ICGV-SM 06737, ICGV-SM 16575, ICG 12725 and ICGV-SM 16608 to be used for development of mapping population, which will be useful for groundnut improvement. This study provided a baseline information on characterization and selection of a large sample of groundnut genotypes in Tanzania for effective breeding and systematic conservation.
Highlights
Cultivated groundnut (Arachis hypogaea L., AABB, 2n = 4x = 40) is an allotetraploid and a predominantly self-pollinating legume crop cultivated in most parts of the world
The ANOVA revealed that the 3-way interaction involving genotype, location and season had significant (p \ 0.05) impact on initial plant stand (IPS), Final plant stand (FPS), days to flowering (DTF), PH, number of pods per plant (NPP), PYD, kernel yield (KY), hundred seed weight (HSW) and shelling percentage (SP) (Table 3)
The trait associations revealed significant correlation between rust and late leaf spot severity and number of pods per plant providing a means for direct selection to improve yield and disease resistance
Summary
Cultivated groundnut (Arachis hypogaea L., AABB, 2n = 4x = 40) is an allotetraploid and a predominantly self-pollinating legume crop cultivated in most parts of the world. About 26.54 million hectares of groundnut is cultivated globally with an annual production of approximately 43.92 million tons of shelled grain (Upadhyaya et al 2012; FAOSTAT 2014). Africa accounts for about 31.6% of the global production. Most African countries do not meet their domestic demand for groundnuts. The subSaharan Africa (SSA) region has one of the lowest groundnut productivity levels (\ 1 t/ha) in the world. FAOSTAT (2020) estimated monetary value of US$132 for importation of groundnut in Africa by 2020 to cover the shortfall due to low productivity in the region
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