Characterisation of Aroma and Yield Traits in F2 Rice Populations
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Aromatic rice varieties are regarded as the high-quality types in the market especially the supa local rice grown in Uganda and the basmati rice imported from India. Both rice varieties fetch a higher price in the market compared to other non-aromatic varieties. However, several studies had reported that aromatic types have poor agronomic traits such as low yield, susceptibility to pests and diseases, susceptibility to lodging and strong shattering. The objectives of this study were to; a) To assess the levels of aroma in the F2 populations of rice developed from four rice cross-combinations; b) To assess the yield potential of the F2 segregating populations developed from four rice cross-combinations; c)To assess the relationship between aroma and other agronomic traits. The experimental material consisted of four cross-combinations of rice varieties namely; ARC2 X Met16, ARC4 X Met16, Basmati370 X ARC1 and ARC4 X Komboko and their parents namely; ARC1, ARC2, ARC4, Basmati370, Komboko and Met16. The rice varieties were obtained from the cereals program at NaCRRI. The experiment was set up in an alpha lattice design in two replicates at NaCRRI in season 2019B. At tillering, fifty individual F2 plants of the rice crosses was assessed for aroma using the method of Potassium hydroxide. The evaluation of aroma for each individual plant was conducted by four panelists by smelling each sample. Aroma was assessed using a rating scale of 1-3 adopted from IRRI; with one indicating no aroma, two indicating mild aroma and three indicating high aroma. Several agronomic and yield trait data was also collected on fifty plants from each rice cross namely; Plant height, number of tillers, number of panicles, 100-seed weight and seed yield and Data analysis was done using GenStat statistical package (14th Edition) to generate the analysis of variance (ANOVA) that was used to test for significant differences between the means and a Least Significant Difference (LSD) at P=0.5 was used. The study showed that the aroma of the genotypes (rice parents and crosses) was significantly different and Rice cross ARC4 X Met16 was rated best in its aroma (1.52) by all the four panelists. The study further revealed that plant height of the rice parents and crosses were significantly different and rice cross ARC4 X Met16 had the highest plant height (68.6cm). There was also a significant difference in the number of panicles, number of tillers, 100 seed weight and seed yield of the rice parents and crosses. Rice cross ARC2 X Met16 showed the highest mean number of panicles (4.0), tillers (4.90), 100 seed weight (2.23g) and seed yield (5,956kg/ha).Six strong positive correlations were observed between the following traits; number of panicles/number of tillers (r = 0.8965), 100 seed weight/number of tillers (r = 0.8919), seed yield/number of tillers (r = 0.8919), 100 seed weight/number of panicles (r = 0.8944), seed yield/number of panicles (r = 0.8944), seed yield/100 seed weight (r = 1.0000).A positive correlation was also observed between plant height and rice aroma score (r = 0.5733). From the results, the following crosses; ARC4 X Met16, ARC2 X Met16 were identified because of their positive strong traits (high aroma, height and yield traits) hence a source of valuable germplasm for breeding of high yielding aromatic rice. The two promising hybrids ARC4*Met16 and ARC2*Met16 are recommended for further breeding in other generations to validate whether my findings of (high aroma and high yield respectively) will be the same in other generations. The rice crosses should be further screened under different environments for several seasons to conclusively determine yield and aroma stability.