WAASB-based stability analysis and validation of sources resistant to Plasmopara halstedii race-100 from the sunflower working germplasm for the semiarid regions of India

Stable agronomic performance in semiarid regions is a prerequisite for sunflower to obtain high seed and oil yields. Hence, efforts were made to evaluate 28 sunflower genotypes, including those of the USDA (USA) and the INRAE (France) collections and germplasm maintained at ICAR-IIOR, Hyderabad, India, in four semiarid locations in India from 2021 to 2022. The screening of the selected genotypes for sunflower downy mildew (SDM) caused by Plasmopara halstedii race-100 in India was undertaken from 2017 to 2020, and a validation experiment was performed in 2021. Weighted Average of Absolute Scores (WAASB) and Multi-Trait Stability Index (MTSI) were adopted for stability analysis. The Additive Main Effects and Multiplicative Interaction (AMMI) analysis of variance showed highly significant effects of climate, genotype, and the interaction between the two. Only 56.13% of the total genotype-by-environment (GEI) variation was explained by the first two principal components (PCs), thus indicating the complexity of the GEI and suitability of the WAASB statistics. Based on the WAASB study, the most stable genotypes identified for yield were GMU-494, LTRR-341, EC-601901 and, GMU-481 for oil content as well. Based on the WAASBY scores, the most stable genotypes identified for seed yield were GMU-770 (96.76) and EC-178168-2 (96.53), and those for oil content were GMU-481 (93.64) and EC-601901 (91.30). The simultaneous MTSI was employed for selecting high-yielding genotypes with medium to high oil content. The MTSI revealed the ideal genotype EC-198078, which was closer to the hypothetical ideotype with the lowest MTSI coupled with a high WAASBY score and resistant reaction to SDM. The population structure based on 20 simple sequence repeat (SSR) markers depicted the Delta (k) value (k = 4), which indicated four populations within the collection of 28 sunflower germplasm accessions. Based on multi-year screening, 13 sources of resistance to SDM were identified and validated for semiarid regions, with 3 being new sources. The identified stable genotypes coupled with SDM resistance may be useful for the development of inbred cultivars or may be used to develop superior populations in sunflower.