RICE RATOONING - IRRI books - International Rice Research Institute

SCREENING FOR RATOONING ABILITY IN KARNATAKA 267Table 2. Correlation coefficients among main crop characteristics with ratoonyield.Days to Main crop Ratoon cropTillers/plant 50% yieldyieldflowering (ha)(ha)Tillers/plantDays to 50% floweringMain crop yieldRatoon crop yield1.00 0.111.000.350.341.000.300.46*0.58**1.00r = main crop flowering duration/ratoon flowering duration = 0.14.Table 3. Correlation coefficients among ratoon characters with ratoon yield.Days to50%floweringRegenerated Ratoon Panicles/ 1000- Ratoontillers ht Plant grain yieldwtDays to 50% floweringRegenerated tillersRatoon heightPanicles/plant1000-grain weight0.46* 0.330.230.050.340.060.310.010.24-0.55**0.38*0.88**0.38*0.290.35*The ratoon crop stand was impressive in cultivar BPT-2685, which had darkgreen leaves, probably due to high N content. We did not observe any significantassociation between days to flowering in the main crop and in the ratoon crop. Mostdry matter in the ratoon crop accumulated in shoots, but ratooning ability wasdependent upon higher root weight and volume. This supports the conclusion ofChauhan et al (1) that IR44 ratoon tillers are dependent on the main crop rootsystem until at least 21 d after harvest.Grain filling was excellent in many cultivars and ratoon stands of manygenotypes were as good as the main crop stand. Genotypes such as BPT-2226,BPT-2685, IET-7431, and KMS-5914 had superior ratoon crop stands. Many ofthem are late maturing and can be exploited for ratooning.In the main crop, a large variability was observed in tillers/plant, days toflowering, and yield. In the ratoon crop, variability was observed in number ofregenerated tillers, root and shoot weights, days to flowering, yield, 1000-grainweight, and germination percentage,There was 40-50% reduction in days to 50% flowering of the ratoon cropcompared to the main crop. Similarly, ratoon crop yields ranged from 3.17 to71.24% of the main crop yields. The harvest index ranged from 0.16 to 0.49 in theratoon crop, which is indicative of biomass production along with its compartmentalizationbetween grain and straw (Table 1).Correlation coefficients between grain yields of main and ratoon crops werehighly significant (Table 2) ( r =0.58). However, the main crop flowering duration didnot affect ratoon flowering duration. Among the ratoon characters, number ofregenerated tillers had the highest association with ratoon yield ( r =0.88) (Table 3).The path analyses revealed that main crop yield and number of regeneratedtillers had higher direct effect on ratoon crop yields (Fig. 1, 2).