GGE biplot and WAASB assessment of seed-purpose watermelon for fruit yield and 100-seed weight across hot semi-arid environments of India

Watermelon [ Citrullus lanatus (Thunb.) Matsum. & Nakai] belongs to the Cucurbitaceae family and is widely cultivated for both fruit and seed-purpose. In India, indigenous seed-purpose watermelons, locally known as Mateera, Kalingada, or Karingada are predominantly grown in semi-arid regions such as Rajasthan and Gujarat. Unlike sweet dessert types, seed-purpose watermelons are less sweet but are valued for their edible, oil-rich seeds, culinary uses, medicinal properties, and use as animal feed. The present study was conducted using a randomized complete block design with twelve seed-purpose watermelon genotypes across four locations, namely Sardarkrushinagar (Gujarat), Sihori (Gujarat), Mandor (Rajasthan) and Jobner (Rajasthan), over the kharif seasons of 2023 and 2024, to identify stable and high-yielding seed-purpose watermelon genotypes using GGE biplot and WAASB analyses. Fruit yield and 100-seed weight were selected for stability analysis because they represent overall productivity and seed size, respectively. Combined analysis of variance revealed highly significant ( p < 0.001) effects of genotype, environment, and genotype × environment interaction (GEI) for both traits. In the GGE analysis, the first two principal components explained 78.63% (41.46% and 37.17%) of the G + GE variation for fruit yield and 59.69% (36.51% and 23.18%) for 100-seed weight. GGE biplot analysis integrating mean performance and stability identified SKNK-1704 as the most desirable genotype for fruit yield, followed by RMK-2. For 100-seed weight, SKNK-1407 achieved the best combined rank primarily because of its highest mean performance, despite intermediate stability, whereas GK-2 exhibited the greatest stability. The genotype NBPGRK-1 exhibited near-average performance for fruit yield and 100-seed weight, indicating its potential as a consistent performer across diverse environments. Additionally, genotype SKNK-2007 demonstrated broad adaptability for both fruit yield and 100-seed weight. The WAASB (50:50) index further confirmed SKNK-1704 and NBPGRK-1 as the superior genotypes for fruit yield, while NBPGRK-1, SKNK-1407, SKNK-2007, RMK-4, GK-2, and CAZJK-13-2 for 100-seed weight. Collectively, the integrated GGE biplot and WAASB analyses identified SKNK-1704 as a promising genotype for fruit yield, SKNK-1407 showed the highest combined performance for 100-seed weight, whereas NBPGRK-1 emerged as a promising dual-purpose candidate genotype across environments. These findings provide a basis for prioritizing genotypes for further validation and breeding evaluation in seed-purpose watermelon under hot semi-arid environments.