Heterosis studies for yield and agronomic traits in Thai upland rice

The exploitation of heterosis and heterobeltiosis are the promising way for raising yield potential in crops. Twenty-eight F₁ hybrids and their eight parents were evaluated to estimate the heterosis and heterobeltiosis of yield and other agronomic traits in Thai upland rice. Significant differences of analysis of variance were observed for all studied traits, indicating the existence of worth genetic variability among the hybrids and their parents. The highest significant positive heterosis and heterobeltiosis was attained by Dawk Pa-yawm × Hawm Mali Doi for number of tillers (90.59%; 58.82%) and number of panicles plant⁻¹ (60.35%; 46.14%) and panicle length (heterobeltiosis: 20.05%), but highest significant negative heterosis for plant height (−8.90%). Likewise, Nual Hawm × Khun Nan showed the highest significant positive heterosis and heterobeltiosis for yield components, viz., number of filled grains panicle⁻¹ (57.39%; 52.25%), spikelet fertility (25.01%; 21.16%), 1000 grain weight (heterosis: 12.85%) and grain yield plant⁻¹ (heterosis: 19.86%), but highest significant negative for days to flowering (−17.52%;-6.03%) and days to maturity (−12.00%;-4.91%). These crosses were recommended as the most promising combinations to gain early favorable segregants and developing high yielding upland rice hybrid varieties by heterosis breeding.