THE BIOLOGY AND GENETICS OF DENSE PANICLE IN TWO CULTIVARS OF RICE, ORYZA SATIVA LINN

Abstract

A cross was made between two local cultivars of rice: AWGU DWARF-W (a heavy-tillering variety of long maturity) and IJ-86W (a tall, medium maturing variety). A total of 9 panicle parameters were measured on 743 F₂ panicles and the data were subjected to statistical analyses.

Principal Component Analysis showed that one principal component shows positive loading for number of spikelets, number of primary branches, length of primary branches, length and number of secondary branches and panicle length, all of which contribute 52% to the total variability. The second component shows high positive loading for number of secondary branches and mean number of secondary branches while the third component shows high loading for number of primary branches per ciliate ring.

The correlation matrix shows that spikelet number correlates highly positively with length of primary branches, length and number of secondary branches while length of primary branches was highly positively correlated with number and length of secondary branches. Regression analysis with number of spikelets as dependent variable shows that number of secondary branches, length of secondary branches and length of primary branches explain 90%, 78% and 71%, respectively, of the variability. Stepwise regression with spikelet number as dependent variable isolated number of secondary branches, length of primary branches and number of primary branches which resolve into the two number factors considering the high correlation between number and length of primary branches.

Chi-square analysis confirms a 15 normal: 1 dense panicle ratio in the F2 fitting di-hybrid inheritance in which dense panicle is conditioned by homozygous recessive genes at two independent loci. The implication of this result for breeding for yield is discussed.