Downy mildew disease, caused by Peronosclerospora sorghi, is one of the most serious diseases of maize. The disease is currently managed by seed treatment with metalaxyl fungicides. However, problems regarding environmental pollution resulting from the use of fungicides and development of fungicide resistance within populations of P. sorghi are of increasing concern. Assuming that biological control by means of using antagonistic microorganisms may be an alternative for the management of this disease, the efficacy of biocontrol agents viz., Bacillus subtilis G1, Bacillus amyloliquefaciens B2, Brevibacillus brevis 57 and Pseudomonas fluorescens Pf1 for the management of downy mildew of maize and for promoting plant growth was evaluated. The results indicated that seed treatment with B. subtilis G1 and B. amyloliquefaciens B2 significantly (P = 0.05) increased the germination percentage and seedling vigour of maize as assessed by roll towel method. Among them, B. subtilis G1 was the most effective and recorded 9% and 31% increases in germination percentage and seedling vigour of maize respectively, as compared to the control. A talc- based powder formulation of B. subtilis G1 when applied through seed at the rate of 10 g/kg reduced the downy mildew incidence up to 54% under greenhouse conditions. Results of this study suggest that B. subtilis G1 is a promising bioagent for the management of downy mildew of maize and for promoting plant growth. This antagonist could be further exploited for commercial scale up for ecofriendly management of downy mildew of maize under localized climatic conditions.

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A total of 48 commercial poultry feed samples collected from different poultry feed manufactures in Tamil Nadu, India were examined for the contamination of aflatoxin B1 (AFB1) and Aspergillus flavus. AFB1 in the samples was estimated by sandwich ELISA and the presence of A. flavus was detected by Real-Time PCR assay. Real-Time PCR analysis using A. flavus- specific omt primers confirmed the presence of A. flavus in all the samples tested. ELISA results indicated that the AFB1 contents in the poultry feeds ranged from 1.0 to18.7 ppb, which were below the permissible safe limits for poultry bird consumption and health. The results suggest adoption of good man-ufacturing practices by the commercial poultry feed manufacturers during procurement of feed ingredients, handling, storage and processing which might have suppressed the growth of A. flavus and aflatoxin contamination.

Downy mildew, caused by Peronosclerospora sorghi is one of the important diseases affecting maize (Zea mays L.) production worldwide. Several downy mildew resistant maize lines have been identified. However, variability in the degree of resistance among maize genotypes to P. sorghi has been reported. In the present study the molecular basis of resistance of maize to P. sorghi was studied by using differential-display reverse transcription PCR (DDRT-PCR) technique. Maize seedlings of downy mildew resistant (MAI 756) and susceptible (CM 500) cultivars at two-leaf stage were inoculated with P. sorghi and leaf samples were collected at 0, 3 and 5 days after inoculation and analyzed for differentially expressed cDNAs using cDNA-RAPD approach. A total of 17 cDNA fragments corresponding to transcripts that showed alterations during the defence response of maize to P. sorghi were identified. Genes involved in signal transduction and several genes with unknown functions were found to be upregulated in maize after infection by P. sorghi. Among 35 random primers tested, OPD-05 has identified a differentially expressed cDNA coding for serine/threonine kinase protein in resistant maize genotype. Constitutive and high level expression of serine/threonine kinase gene was observed in the uninoculated plants of resistant genotype, whereas no expression of this gene was observed in uninoculated plants of susceptible genotype. However, the transcript level was induced 3 days after inoculation in the susceptible genotype and slightly reduced 5 days after inoculation. This study represents the first identification of maize serine/threonine kinase gene that is upregulated following infection by P. sorghi.