Effect of 2-bromo-2-nitro propaine-1, 3-diol and cowdung extract on growth and virulence of Xanthomonas campestris pv. oryzae

Abstract

The present investigation was taken up to assess the efficacy of two alternative control methods, spraying with bactrinol-100 and cowdung extract in controlling bacterial blight of rice. An attempt was also made to elucidate the factor present in cowdung extract responsible for the control of bacterial blight pathogen. The pathogen was isolated from an infected rice field in kuttanad and tested for sensitivity to antibiotics, bactrinol-100 and cowdung extract under vitro conditions. Under in vitro conditions, terramycin 500 ppm was found to be most efficient in checking the growth and virulence of the pathogen followed by 250 ppm terramycin and 500ppm bactrinol-100. Cowdung extract failed to produce a typical growth inhibition zone. Subsequently the pathogen was inoculated in T(N)1- rice plants raised in pots, the disease was induced and the plants were sprayed with antibiotics, bactrinol-100 and cowdung extract. Under pot culture conditions terramycin 500 ppm reduced the disease intensity to the maximum followed by 500 ppm bactrinol-100. Cowdung extract was found to be better than some of the chemical treatments like terramycin 100 ppm, streptocycline 100, 250 and 500 ppm and bactrinol-100 at 100 and 250 ppm. Under field conditions 500 ppm terramycin gave maximum disease control at both the locations after the first and second spray. The grain yield was found to be maximum after spraying with 500 ppm terramycin at both the locations. The increase in thousand grain weight was found to be maximum in plants sprayed with cowdung extract in jyothi variety and in plants sprayed with 500 ppm bactrinol-100 in C-153 rice variety. Maximum reduction in chaffy grains was achieved after spraying with 500 ppm terramycin at both the locations. Straw yield was maximum in plants sprayed with 100 g/1 of cowdung extract in jyothi variety and in plants sprayed with 500 ppm terramycin in c-153 variety. So it is evident that unless appropriate control measures for bacterial blight are taken in time, significant yield losses can occur in rice varieties like jyothi and c-153. Spraying cowdu ng extract may be very useful to control bacterial blight especially when the disease incidence is mild. It can also be given as a prophylactic spray which may reduce the severity of the disease. These hypotheses have to be proved conclusively by further filed trails. The mode of inhibition of x. campestris pv.oryzae appeared to be due to an overgrowth of the pathogen mainly by bacteria and probably by some fungi present in cowdung extract. On working out the economic aspects of controlling bacterial blight it was observed that economic return was maximum after spraying infected plants with 100 g/1 cowdung extract followed by 500 ppm bactrinol-100. So economically it appears, that the use of cowdung extract or bactrinol-100 would be ideal to control bacterial blight of rice.