Variation of Yield and Associated Components in the USDA Rice Mini-Core Collection.

Rice is a staple food crop that feeds over half of the world’s population. Genetic improvement for grain yield is critical for global food security. The USDA rice mini-core collection of 217 entries has proven to well represent the diversity found in the whole NSGC collection of about 20,000 accessions. In 2009, the mini-core was evaluated in a field trial near Stuttgart, Arkansas using a randomized complete block design with three replications. Each plot contained nine plants spaced 0.3 x 0.6 m, and three plants were sampled to determine yield and 13 yield components. Heading, with a wide range of 34-182 days from seedling emergence (17 entries failed to head), had the highest broad-sense heritability (98%), followed by plant height (94%) ranging from 81 to 231 cm, and panicle length (90%). Nine traits had high heritability estimates, including grain yield per plant (GYP) of 84%, grain yield per panicle of 80%, and plant weight of 88%. The heritability was the lowest for 1000 seed weight (50%). Grain yield per plant (GYP) had the highest positive correlation with plant weight (r=0.78), followed by tillers per plant (r=0.74). Correlations of GYP with plant height (r=0.43), kernels/panicle branch (r=0.37) and panicle length (r=0.31) were all significant at 0.001 probability. The wide range in variation for the 14 yield characteristics among the 217 accessions demonstrates the value of the germplasm collection for yield improvement by breeders. Genetic markers linked to these traits will help design breeding strategies for gene transfer.