Red rot disease of sugarcane caused by Colletotrichum falcatum is one of the most destructive diseases of sugarcane (Saccharum officinarum) worldwide. The pathogen spreads primarily through infected sugarcane setts and hence the use of disease-free planting materials is essential for preventing disease development in the field. In the present study a polymerase chain reaction (PCR) assay was developed for accurate and sensitive detection of C. falcatum in planting materials. Randomly amplified polymorphic DNA (RAPD) analysis identified a 566 bp PCR fragment that was specific to C. falcatum. The DNA sequence of this fragment was determined and used to design oligonucleotides amplifying a 442 bp sequence characterised amplified region (SCAR). The specificity of the SCAR primers was evaluated using purified DNA from C. falcatum and other Colletotrichum spp. as templates in PCR. The results indicated that the SCAR primers were highly specific to C. falcatum since the 442 bp fragment was amplified only from DNA of isolates and races of C. falcatum but not from any other Colletotrichum spp. tested. The detection sensitivity of C. falcatum was 0.1 ng for genomic DNA of C. falcatum and 5 ng for DNA extracted from infected sugarcane tissue. This new PCR-based assay is a convenient tool for detection of this important pathogen in seed canes to ensure production of sugarcane.

The potential of antagonistic rhizobacteria in the management of bacterial blight of cotton caused by Xanthomonas axonopodis pv. malvacearum (Xam) was evaluated under greenhouse and field conditions. In this study, 93 bacterial isolates from the rhizosphere of cotton were screened for their efficacy in inhibiting the growth of Xam in vitro. Among them, 21 isolates were found to inhibit the in vitro growth of Xam. These isolates were identified as Pseudomonas fluorescens and Bacillus subtilis based on phenotypic characteristics, biochemical properties and using 16S-23S intergenic transcribed spacer-Polymerase Chain Reaction (PCR). Among the 21 isolates, the isolates P. fluorescens Pf32 and P. fluorescens Pf93 and B. subtilis B49 exhibited the maximum inhibitory activity against Xam. Talc-based powder formulations of the effective antagonistic isolates of P. fluorescens (Pf32, Pf93) and B. subtilis (B49) were developed and evaluated individually and in combination for their efficacy in the management of bacterial blight of cotton under greenhouse and field conditions. The P. fluorescens isolates Pf32 and Pf93 and Bacillus subtilis isolate B49 survived well in the talc-based formulation for more than 90 days. The application of a mixture of Pf32, Pf93 and B49 to seed, soil and foliage significantly reduced the bacterial blight incidence and increased the plant height, number of branches and number of bolls under field conditions. The plots treated with a mixture of Pf32, Pf93 and B49 recorded the maximum yield of 1915 kg/ha and 1512 kg/ha in trial I and trial II compared to 1210 kg/ha and 987 kg/ha in the untreated control, respectively.

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Effect of Seed-BorneSarocladium Oryzae, the Incitant of Rice Sheath Rot on Rice Seed QualityRice seeds collected fromSarocladium oryzaeinoculated plants produced more discoloured grain, chaffiness and recorded much lower seed germination than seeds collected from healthy plants in all the three cultivars tested. The germination, chaffiness and discolouration in healthy plants were found to be in the range of 70.50 to 93.50 per cent, 5.5 to 17.75 per cent and 4 to 18 per cent respectively. There was a progressive and significant reduction in total sugar, reducing sugar and non reducing sugar content of rice seeds with varying degree of seed infection caused byS. oryzaeThe increase in phenol content due toS. oryzaeinfection ranged from 15.74 to 70.78 per cent and increase being proportional to the per centS. oryzaeseed infection.

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