Indexing and Recommended Combinations of Rice Varieties for New Breeds with Strong Ratooning Ability

  Objective  To establish an indexing system on rice ratooning ability for studies and breeding of hybrids.

  Methods  Twenty-three varieties including 3 representing different developing ages were cultivated under same conditions in Youxi county, Sanming, Fujian from 2015 to 2017. Correlation, regression and path analyses were conducted on the traits, yield and yield factors on the cultivars.

  Results  The 1^st-season rice yield of the cultivars significantly correlated with the grain number per panicle (r=0.83) with a 54.61% contribution to the yield indicating a critical role of heavy panicles to high yield. In ratooning season, the yield significantly related to the effective panicle number (r=0.70) with a 38.98% contribution rate suggesting a shift of storage capacity in the plants between the two seasons. The effective panicle count and the effective panicle/stem number ratio of the rice plants in the 1^st season significantly correlated with the yield in the following season at r=-0.86 and 0.82, respectively. A prediction model derived from the regression analysis base on the panicle count for the ratooning rice yield was 70.6%-99.6% accurate and, based on the effective panicle/stem number ratio, 76.5%-99.5%.

  Conclusions  As a measure of the ratooning ability of a rice variety, the panicle count and/or the effective panicle/stem number ratio of the plants could be used to appropriately estimate the yield. Accordingly, Nei-6-you 7206, Chuan-you 7185, Chuan-you 7206, and Quan-you 7028 were identified as superior varieties for breeding hybrids with a strong ratooning ability.