RICE RATOONING - IRRI books - International Rice Research Institute

Yellow dwarf disease in ratoon riceV. Muniyappa, Nagaraju, M. Mahadevappa,and K. T. RangaswamyUniversity of Agricultural SciencesHebbal, Bangalore - 560 024.ABSTRACTYellow dwarf disease was observed in up to 27% of main crop (var. MR249) and in up to82% of ratoon crop (Selection CR-126-6) in Karnataka, India. Plants were infected at allgrowth stages. Yellow dwarf disease was transmitted by leafhoppers Nephotettixvirescens, N. nigropictus, N. cincticeps, N. malayanus, and N. parvus. N. virescenstransmitted the disease to 14 species of plants. Mycoplasma-like organism wasobserved in the phloem sieve tubes of yellow dwarf-infected rice plants. In transplantedcrops, disease incidence was high from September to December, but low fromJanuary to April. The occurrence of disease in the field was decreased to some extentby the application of insecticides against leafhoppers. The varieties or breeding linesMR363, Gamasolu, HY256, CT43, CT57, CT1351-1, CT1351-2, Doddabyra, Gandsali,HR35, lntan Mahsuri, IET5975, and KMP104 showed field tolerance to the disease.Yellow dwarf has been reported in Japan, India, China, Taiwan, Malaysia,Philippines, Bangladesh, and Sri Lanka, and in almost all rice growing areas in India(22, 28, 35, 39, 44).INCIDENCE AND LOSSESThe area severely damaged by yellow dwarf in Japan was about 20,000 ha; the yieldloss amounted to 10,000 t (9). Abeygunawardena (1) recorded 13.8-20.7% infectionin the ratoon crop at Peradeniya, Sri Lanka, and 0.08-2.20% infection atBatalagoda. In Karnataka, India, yellow dwarf incidence was up to 27% on the maincrop (var. 249) and up to 82% in the ratoon crop (Selection CR 126-6).Incidence was lower in the dry-season crop than in the wet-season crop. Highincidence was observed in rabi (35). Rice yellow dwarf was more severe in the ratooncrop than in the main crop (3, 5, 16, 35).SYMPTOMSPlant leaves are pale green at the onset of the disease and become uniformly yellowas the disease progresses. Later-formed leaves become short, narrow, and soft.