RICE RATOONING - IRRI books - International Rice Research Institute

Ratoon rice researchin Karnataka, IndiaM. Mahadevappa, T. Gopala Reddy, and NagarajuDepartment of Seed Science and Technology, UAS, Bangalore-560024, IndiaABSTRACTRice ratoon cropping can increase rice production without increasing land use wheremoisture, inputs, and seasonal conditions are too short to raise a second crop.Published data on ratooning are meager and discontinuous, resulting in slow adoptionof this system. Varieties differ widely in ratooning ability, type of tillers produced,growth duration, grain quality, and yield. Occurrence of yellow dwarf/grassy stuntdiseases on the ratoon crop of several genotypes screened warns breeders of the needto evolve varieties with resistance. Intan, Mingolo, and lntan mutant currently underexperimentation in Karnataka possess resistance to those virus diseases. Work onselecting genotypes with cold tolerance, ratoonability, and desirable growth duration atBangalore helped identify seven genotypes that possess all three characters.On riceland where moisture, soil, and seasonal inadequacies prevent raising anupland crop or a newly planted rice crop, rice ratoon cropping is suggested as a wayto increase rice production without increasing land area. Hill valley bottoms inKarnataka, India, were identified as potential areas for a ratoon cropping systemand research was initiated at the Agricultural University Research Stations atMadikeri and Mandya in the 1970s (9, 10). The excellent ratooning ability of Intanrice encouraged researchers to initiate trials in research stations and in farmers’ fieldssimultaneously. Ratoon crop yields were 2-3 t/ha (19-24). We review here the resultsof that research, including collaboration with IRRI, and suggest future lines ofresearch.VARIETAL DIFFERENCESRice genotypes exhibit considerable variation in such characters as ratooningability, types of ratoon tillers produced, ratoon growth duration, ratoon grainquality, and ratoon crop yield. Wide varietal differences have been reported for oneor more of these characters in studies involving more than 3,000 genotypes (9).Ratooning ability and inheritanceHaque (6) reported zero to 60% ratooning ability in the IRRI lines he studied. Somevarieties produced nodal ratoons, others produced the desirable basal ratoons,