RICE RATOONING - IRRI books - International Rice Research Institute

106 RICE RATOONINGindependent of the harvest cutting height of the main crop (28). Among the varietiesscreened in Karnataka for ratooning ability and type of tillers, Intan, Mingolo, Intanmutant, Mahsuri, and some experimental hybrids produced more basal tillers thannodal tillers. Although many other genotypes tended to put up ratoon growth, theyhad more nodal tillers than basal tillers. Cutting height and number of nodal tillersproduced are positively correlated ( r = 0.867).At Ponnampet Farm, IET7191 (RPS 32/Pankaj) showed very good ratoongrowth (25). In a preliminary study (1983-85) at the Bangalore Research Station,removing early tillers helped attain uniform flowering and maturity of the ratooncrop of varieties Mangala, CH2, and KMS-1. In fact, cutting back early tillers onKMS-1 plants produced on stubble delayed flowering, so that flowering synchronizedwith flowering of a newly planted Intan mutant-I. Cutting back two timeshelped synchronize flowering with newly planted Intangouri (14). When uncut,single-cut, and twice-cut tillers were allowed on a single plant, the plant could supplypollen for 22 d. This could be of use in hybrid seed production.In 20 crosses of 8 parents in different generations, the recessive and heteroticnature of the genes governing inheritance of ratooning ability was identified (18).Growth durationVarieties with longer growth durations tend to have stronger ratooning ability.Growth of the main crop was 85-175 d and that of the ratoon crop was 40-135 d (9).Growth duration and grain yield correlated strongly. The ratoon crop production oflate-maturing Intan and Mingolo in Karnataka supports this finding. Goodratooning ability of short-duration varieties CH45, PTB-10, N22, CT1351, S705,Mangala, and Intan mutant has also been reported (1-3). This suitability of mediumandearly-maturing varieties for ratoon cropping needs to be investigated. Zandstraand Samson (28) have indicated that high ratoon yields may require selectingvarieties for a ratoon crop with durations longer than 70 d.Plant and grain charactersExcept for seed viability, all other characters (plant height, panicle length, spikeletsize, number of productive tillers, and grain setting) were less pronounced in theratoon crop than in the main crop (16, 17). Grain quality is of great concern. Reddyand Pawar (16) and Saran and Prasad (17) reported ratoon crop seed viability andproductivity as good as that of the main crop. Webb et al (26) reported that theratoon crop of some varieties had relatively fewer uniform kernels. Protein contenttended to be considerably higher in ratoon crop grains than in main crop grains,although it varied greatly. Gelatinization temperature and viscosity values wereconsistently lower in ratoon crop grain samples. Gay (4) reported that the ratooncrop grain of Gulfrose variety graded No. 1. Nadal and Carangal (11) observed thatthe grains produced by the second ratoon were superior to those produced by thefirst ratoon. Nagaraja and Mahadevappa (12) noted that the seed quality of mainand ratoon crops varied with variety and that viability in ratoon crop seedsdeteriorated faster than it did in main crop seeds. However, field performances of avariety raised from the seeds obtained from the main crop and from the ratoon cropdid not differ.