RICE RATOONING - IRRI books - International Rice Research Institute

INHERITANCE OF RATOONING ABILITY IN CHINESE VARIETIES 241Ratooning ability was defined as the number of ratoon tillers derived from thestubble at 10 d (or maximum ratooning) after the main crop harvest.The bud of the third node from the top was kept and most of the buds of thesecond nodes were kept by leaving the stubble of the main crop up to 16.5 cm abovethe ground.RESULTS AND ANALYSISHybrid vigor for ratooning abilityThe hybrid vigor of the F 1 varied from -72.29% to 233.62% among the differentparent combinations (Table 2). The ratooning ability of F 1 in crosses with Ai-Nan-Zao is generally lower than that of crosses with Shu-Fong No. 1 (11), the former evenhad crosses with negative hybrid vigor. The hybrid vigor differed distinctly amongthe F 1 s from crosses with Tai-Guao-Dao-Xuan, Shong-Zao-Xian No. 26, andHon-Mei-Zao, respectively. For example, the heterosis of (Ai-Nan-Zao/Tai-Guao-Dao-Xuan) F 1 is strongly negative, -72.29% or -66.8%, whereas that of its reciprocalF 1 is positive, 56.68%; that of Shu-Fong No. 1 (11)/Tai-Guao-Dao-Xuan) F 1 ispositive, 93.38% (or 71.57%), and its reversal F 1 is up to 233.62%.There is a significant difference between the normal and reciprocal crosses,which suggests the existence of significant cytoplasmic effects. The heterosis of thecrosses with Shong-Zao-Xian No. 26 did not differ significantly between thereciprocal crosses. The heterosis of the crosses with Hon-Mei-Zao (Ai-Nan-Zao/Hon-Mei-Zao) F is 16.74%, and that of its reciprocal F 1 is 49.12%. There is ahighly significant difference between the reciprocals, and this shows significantcytoplasmic effect. But the cytoplasm of Hon-Mei-Zao, when incorporated with thenucleus of the pollen cell of Ai-Nan-Zao, shows a weakly minus value for itsheterosis. However, it shows a highly positive value when incorporated with thenuclear of the pollen cell of Shu-Fong No. 1 (11). This indicates that the differencebetween reciprocals results from the incorporation of different nucleus genes, ratherthan from the cytoplasm.Narrow-sense heritability of ratooning abilityThe narrow-sense heritability (h 2N ) in the tiller regeneration ability of the reciprocalsand its significant F value were estimated (Table 3). 1) The h 2N of the reciprocalcrosses with Tai-Guao-Dao-Xuan in ratooning ability is not significant by the F test,except for Ai-Nan-Zao/Tai-Guao-Dao-Xuan; 2) the h N 2 among the reciprocalcrosses with Shong-Zao-Xian is distinctly different. In a normal cross, e.g., Shu-Fong No. 1 (11)/Shong-Zao-Xian No. 26, h N 2 = 65.56% + 14.70%, with highlysignificant F value, but in its reciprocal, h N 2 = 23.01% + 19.01%, with nonsignificantF value; 3) in Shu-Fong No. 1 (11)/Hon-Mei-Zao, h N 2 = 70.15% + 14.07%, largerthan its reciprocal h 2N = 41.82% + 17.00%, and they are all highly significant.In Ai-Nan-Zaol Hon-Mei-Zao, h N 2 = 38.52% + 20.69% which is significantonly at the 10% level. But the h N 2 of its reciprocal cross = 57.03% + 16.49%, which ishighly significant.