摘要
Studies on basic aspects of bacterial blight(BB)were conducted for three years from 2014-2018 in the Kuttanad tracts of Kerala state,India.Effects of concentration of pathogen,age of seedlings,position of leaves for artificial inoculation and wounding on disease severity were conducted.Screening trials with varieties released from the Kerala Agricultural University and survival of BB on weeds of rice ecosystem were also tried.Standardization of an inoculation method that required only less labor and time was attempted in comparison with other common methods.Relationship of disease severity with stomatal frequency and phenotypical characters like angle and width of leaf and intermodal length were also tried.Bacterial concentration of 1×10^(8) CFU/mL and method of leaf clipping at 35 days after sowing(DAS)were used for all artificial inoculation experiments.Disease severity was assessed based on International Rice Research Institute(IRRI)score chart.Results of the studies revealed the following facts.Inoculation of the lower most two leaves alone exhibited a disease severity of 48.25 per cent.Highest disease expression was observed with a bacterial concentration of 1×10^(9) CFU/mL.In the newly developed artificial inoculation method of leaf clipping of 35 days old excised leaves gave good result with a disease severity as high as 90 per cent at 8 days after inoculation(DAI).It was observed that the disease severity showed an increasing trend up to 40 min after wounding and then declined afterwards up to 240 min.Kerala Agricultural University varieties Kayamkulam-2 and Pattambi-5 emerged as resistant varieties.Lowest internodal length and mean stomatal frequency were exhibited by the resistant variety Ptb-5.These resistant varieties could be suggested for breeding programs involving bacterial leaf blight(BB)resistance.The first report of new alternate hosts of BB like Isachne miliacea and Eleocharis dulcis will be helpful for the field control of disease.
