ROLE OF GUTTATION FLUID IN THE SPREAD OF BACTERIAL BLIGHT OF RICE
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Date
2013
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Punjab Agricultural University, Ludhiana
Abstract
The role of guttation fluid on bacterial blight development and spread was investigated at different crop growth stages and nitrogen doses applied. Maximum amount (4.0ml/plant) of guttation fluid was collected from the plants inoculated at tillering stage. Similarly highest population density of Xanthomonas oryzae pv. oryzae (5.28 log cfu/ml) was also recovered in guttation fluid collected from X. oryzae pv. oryzae inoculated plants at tillering stage as compared to seedling and booting stage of crop. High bacterial load in guttation fluid were also reflected in high bacterial blight severity (12.2 %) and spread (up to 60cm from inoculated plant) at tillering stage. However, the disease failed to develop when the plants were inoculated at booting stage. Morning rain simulation washed off the guttation fluid from the leaf surface which resulted in significantly lesser disease severity and spread on rain simulated plots as compared to non rain simulated plots. When rain was simulated at tillering stage in bacterial blight susceptible cv. Pusa 1121, there was increase in population densities of X. oryzae pv. oryzae in guttation fluid collected from no rain simulated (6.28 log cfu/ml) plants as compared to rain simulated (5.84 log cfu/ml) plants after 7 days of inoculation. Application of high nitrogen doses significantly increased the disease severity and spread. Increased amount of guttation fluid per plant was observed in plots supplied with enhanced nitrogen doses. This also resulted in increase in total bacterial load per plant. Highest mean log cfu of X. oryzae pv. oryzae was obtained from treatment where nitrogen was applied @ 72 kg urea/acre (6.02 log cfu/ml) while minimum (4.72 log cfu/ml) was recorded from the plots when no nitrogen was applied. Electron microscopic studies also revealed intense colonization by X. oryzae pv. oryzae in rice leaves supplied with high nitrogen dose. Disease spread was also observed to maximum in plots supplied with 72 kg urea/acre (up to 80 cm from inoculated plant). A Bio-PCR based laboratory protocol was developed and tested for the detection of latent presence of X. oryzae pv. oryzae in the guttation fluid collected from asymptomatic plants.
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Keywords
sowing, intercropping, wheats, tillage equipment, seed drilling, crops, mustard, fertilizers, land resources, chickpeas