Abstract
Problem statement: Bacterial Leaf Blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo ) is the most damaging disease in lowland rice grow ing areas in Indonesia. Streptomyces spp. have been known as a producer of antimicrobia l compounds that can be used as biocontrol agents. This study examined the ability of three p romising indigenous Streptomyces isolates which were previously selected from in vitro agar media and greenhouse test to suppress natural infection of Xoo during dry and wet season trials in 2009/2010 a t the Muara Experimental Research Station, Bogor West Java, Indonesia. Approach: Streptomyces isolates (PS4-16, LBR-02 and LSW-05) were applied through seed coating in a peat-based carrie r followed by seedling soaking, spray treatment, or combination of both methods, either singly or in c ombination of two or three isolates. The number of Streptomyces population in the peat carrier at the time of inoc ulation was above 10 7 cell g -1 . The efficacy of Streptomyces was compared to that chemical spray using NORDOX 56 WP (a.i., zinc oxide 56%) and non-treatment. Treated and untreated seeds were grown in plots (5 ×5 m 2 ) and set in a randomized complete block design with four replications. Results: In the dry season experiment, application of Streptomyces spp. reduced BLB severity when compared to that of untreated plots, although did not reduce BLB incidence. PS4-16, applied singly through seed coating followed by seedlin g soaking, reduced the Area Under Disease Progress Curve (AUDPC) at 70 Days After Planting (DAP) to 1458, which was equally effective to the chemical s pray (AUDPC value 1434) and simultaneously promoted plant height and gave the highest rice yie ld. In the wet season trial PS4-16 and LBR-02, appl ied singly or in dual combination through seed coating followed by seedling soaking, suppressed BLB severity, PS4-16 was confirmed as the most effective isolate by reducing the AUDPC to 1923, which was not significantly different to the AUDPC value obtained from chemical spray treatment (1934). Conclusion/Recommendations: All Streptomyces isolates had a tendency to increase plant and yie ld compared to the chemically-sprayed and non-treated plots. For successful biological control of rice BL B, further development of a better formulation for lon g-term storage with an effective population density of Streptomyces and an assessment of its field efficacy in multi-l ocation trials are needed.
Highlights
Xanthomonas oryzae pv. oryzae (Xoo) is the most varieties with race-specific resistance have been the most important disease of lowland rice growing areas in important method to control Bacterial Leaf Blight (BLB) disease
The number on the lines indicated by the same letter in same column indicates no significant difference at the 5% level of Duncan Multiple Range Test (DMRT). *: Method A: seed coating followed by soaking seedlings soaking, Method B: spraying and Method C: combination of method A and B. **: Days After Planting (DAP) = day after planting, averages from 4 replicated plots of 5×5 m2 size.***: Area Under Disease Progress Curve (AUDPC) area under disease progress curve
The number on the lines indicated by the same letter in same column indicates no significant difference at the 5% level of DMRT. * Method A: seed coating followed by seedlings soaking, Method B: spraying and Method C: combination of method A and B. ** Area Under plant Height Progress Curve (AUHPC) area under plant high progress curve
Summary
Sci., 7 (2): 217-223, 2012 preventively and creatively can be an effective method to microorganisms, host, pathogen and a variety of control BLB, but it is toxic to users, consumers and other environmental conditions, which can positively or non-target organism and may persistent in nature negatively affect the biological control activity of accumulate in ecosystems. Actinomycetes are a group of filamentous, Gram positive bacteria with a high G+C
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