Changes in Yield Potential of Traditional Rice Cultivars with Variability in Plant Height, Tillers Per Plant, Fertility and Days to Maturity

Aims: To understand the changes in yield potential of traditional rice cultivars with different plant height, tillers per plant, fertility and days to maturity.
Study Design: Completely randomized block design with four replicates. Twenty plants were evaluated in each replicate. Eighty plants were evaluated for each cultivar.
Place and Duration of Study: Faculty of Agriculture, University of Ruhuna, Sri Lanka in 2011-2013.
Methodology: Rice cultivars were grouped (trait groups) according to guidelines of standard evaluation system of the International Rice Research Institute. Rice cultivars were sub-divided as semi-dwarf (<110 cm), intermediate (110 – 130 cm) and tall (>130 cm) according to plant height and very low tillering (<5 tillers/plant), low tillering (5 – 9 tillers/plant), and medium tillering (10 – 19 tillers/plant) according to number of total tillers/plant. All the cultivars were grouped as completely sterile (0%), highly sterile (<50% to trace), partially sterile (50-74%), fertile (75-90%), and highly fertile (>90%) according to filled grain percentage. Two factor ANOVA without replications were performed to see the effect of the 3 each groups of (-plant height, -number of tillers/plant, -fertility percentage, and - days to maturity) rice cultivars on the yield.
Results: Average grain yield of each group was calculated as g/plant basis. Average yield of rice cultivars linearly increased from 7.9 g/plant, 11.13 g/plant to 13.03 g/plant from the group of semi-dwarf, intermediate, to tall. Average yield recorded as 5.39 g/plant, 10.93 g/plant, and 31.28 g/plant in very low tillering, low tillering, and medium tillering groups respectively. In maturity groups, sterile category recorded the least average yield of 4.5 g/plant and partially sterile category recorded 8.0 g/plant, while fertile category recorded the highest yield, 14.9 g/plant. According to ANOVA all these trait-groups significantly (p=0.01) increased the yield of rice cultivars.
Conclusion: Plant height, tillers per plant and days to maturity significantly increase the yield of traditional rice cultivars.