Variability for high density grain index and hull weight ratio and their interrelationships with other grain traits in rice (Oryza sativa L.)

Pattern of variability and correlations was analysed for high-density grain index, hull-weight ratio, grain weight, size, shape and volume in 143 rice germplasm accessions of diverse agroecologies and origin. The maximum variability was observed for high-density grain index in the exotic upland collection (CV. 344.5%), followed by indigenous collection from mid-land/low land agroecologies (CV. 120.9%). Indigenous collections in general, had higher variability for all the traits except for hull-weight ratio (CV. 11.5%). The exotic uplands had low mean hull-weight ratio (0.177±0.004). The mean high density grain index was positively associated with grain weight (r=0.408**), grain volume (r=0.400**), kernel weight (r=0.411**), kernel volume (r=0.395**) and kernel breadth (r=0.302**) only in the indigenous collection. The hull weight ratio showed negative and significant relationships with grain weight and volume, kernel weight and volume and kernel length.