Assessing Early-Season Vigor Variation of 100 Eelite Diverse Rice Panels Using Morpho-Physiological Traits.

Early-season vigor is important for plants to develop canopy development for optimum light interception. Developing screening tools to assess root and shoot system variability will be useful for rice breeder to develop new genotypes with superior performance during the juvenile stage. A 3-year study was conducted under optimum water and nutrient conditions in a sunlit pot-culture. Several shoot, root, and physiological parameters were in all experiments, 25-30 days after seeding. No significant year or experimental time period interaction was recorded for the measured parameters. Therefore, the results were combined to assess genetic variability among the rice lines from all the three studies. Individual responses index, maximum value for each trait divided by all rice lines, was first developed and summed all trait values to derive cumulative vigor response indices (CVRI) for all rice lines. Using means and standard errors, rice lines were classified into different groups. The CVRI values varied from 9.502 (RU1504156) to 16.165 (N-22) among the 100 rice lines. Majority of the rice lines were exhibited low (42) and moderately (42) CVRI and 11 and five were classified as high and very high CVRI values, respectively. The identified rice lines will be valuable resource for breeders to develop new genotypes best suited for early-season vigor. The newly developed rice with improved vigor during early-season will be more productive in developing robust canopy for optimum radiation interception and out compete weeds, and thus yield better in US-Midsouth conditions.