RICE RATOONING - IRRI books - International Rice Research Institute

YELLOW DWARF DISEASE IN RATOON RICE 221Table 1. Yellow dwarf disease incidence in main and ratoon rice crops, 1979 (33).Variety/selectionMain crop% incidenceRatoon cropMR363GamasoluHY256MR359IET1785RP 974-5-7-6-2HY258MR161IET3280HY25-10Y4MR343MR292A200IET1444MR367IET2700MR18MR362MA261MR360ADT 32IET4702IET3626IET2295I Sona0.000.000.000.000.000.000.000.000.000.000.000.711.071.072.860.362.141.421.070.7111.508.001.0715.0010.002.500.000.000.000.711.071.071.422.142.873.213.935.716.427.868.5710.3512.5013.2114.2814.6425.0030.0035.0045.0062.0071.50laboratory by leafhopper inoculation. Lines that resisted infection can be used inbreeding for disease resistance.RESISTANCE TO VECTORSOf several varieties tested, MTU 17 was most tolerant of infestation by N. virescensfollowed by IR8 and Pankhari 203; Pikutokumoto showed least tolerance (25).N. cincticeps showed nonpreference for the highly resistant rice varieties Firoz-1,Kalbara, and C4-63A (4).EPIDEMIOLOGYIn India the leafhopper ( N. virescens and N. nigropictus ) population in the field washigh from July to September in Delhi (24), April to September in Bihar (15), andMay to June and October to November in Karnataka (35). Disease incidence waslow in the crops transplanted from January to April. Disease incidence wascorrelated with the vector population. Field collection of leafhoppers in the ratooncrop showed that 4% of them carried the disease. Wherever there is continuouscropping, these active transmitters carry the disease from one season to the other.There was steady increase in the incidence throughout the growth of the first ratoon,peaking in the second ratoon (35). Ninety percent of leafhoppers in epidemic fields inFaizabad (Uttar Pradesh, India) were viruliferous (24).