RICE RATOONING - IRRI books - International Rice Research Institute

VARIETAL IMPROVEMENT FOR RICE RATOONING 253Table 2. Seed set of plants in F 3 populations and varieties with different resistanceto rice ragged stunt virus (RRSV).PopulationFertility (%)0 0-25 25-50 50-75 75-100Susceptible checkIR20IR8234-0T-9-2Resistant checkSITOPASSegregating populationsIR46630IR20/SlTOPAS//BR118-3B-17lR46641SITOPAS/IR26702-52-3//IR8234-0T-9-296.995.035.685.077.81.20.50.72.41.71.31.72.55.05.20.51.012.04.59.40.11.849.23.15.9Table 3. Outstanding ratooning rices cited in the literature. aBelle Patna (9); Blue Bonnet (9); Century Patna 2 (9);Century Patna 231 (9); CRM10-3628 (9); Gulfrose (9); IET3273 (26);IET3305 (26); IET3629 (26); IET4555 (26); lntan (9, 23, 30);IR5-47-2=IR5 (9); IR8-288-3= IR8 (9); lR1561-228-3 (2);lR1924-30-2-2 (17); lR2058-78-1-3-2-3= 146 (9, 31)IR2061-214-3-8-2=1R48 (2); lR2061-423-1 (17); lR2061-464-2 (2);lR2061-632-3-1 (2, 17); lR2070-747-6-3-2 =IR32 (31);lR2145-13-3 (17); lR2145-20-4 (17); lR2797-105-2-2-3 (31);lR2863-38-1-2 =IR44 (9); lR4722-36-1 (9); lR8608-183-2-3-3 (31);lR978452-2-3-2 (31); lR9802-50-1-2-2 (31); lR9852-19-2 (31);lR13429-109-2-2-1 =IR56 (10); lR13471-57-3 (31); lR15315-26-3-2 (31);lR19657-34-2-2-3-3A (10); Milbuen 5 (9); Swazi 2 (9)a References in parentheses.The resistance donor is the Indonesian variety Sitopas. It is clear that Sitopas has asignificantly higher proportion of normal-yielding but virus-infected plants than thecheck varieties. Among the F 3 progenies from crosses involving Sitopas, asignificant number of plants are similar to Sitopas in resistance.SOURCES OF VARIABILITYHistorically, ratooning is an afterthought. The sources of variability reflect this;breeders have used leading local varieties and introductions for ratooning trials.Table 3 lists varieties and lines reported outstanding in ratooning trials. Fewhave been reported more than once. A common base with rices of superior ratooningability is lacking.BREEDING STRATEGYA realistic breeding objective should be to develop a profitable main crop-ratooncrop combination. But main crop performance should come first.