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Sheath rot disease of rice caused by Sarocladium oryzae (Sawada) (=Acrocylindrium oryzae, Sawada) has become an important production constraint in all rice-growing countries. Pathogenicity, phytotoxic metabolites, and random amplified polymorphic DNA (RAPD) markers were used to assess the level of genetic variability of S. oryzae derived from rice cultivars, CR1018, IR36, and IR50, of different locations in North East and South India. Variability in pathogenicity, phytotoxic metabolite production, and DNA polymorphisms was detected among S. oryzae isolates. Results indicated that S. oryzae isolates produced both cerulenin and helvolic acid at concentrations 0.3-0.62 and 0.9-4.8 microg mL(-1) of culture filtrate, respectively. Isolates that produce higher concentration of helvolic acid induced a high percent incidence of sheath rot disease. Oligonucleotide primers, GF and MR, generated either a simple (up to 2 bands) or complex (up to 6 bands) RAPD pattern. According to their level of similarity, S. oryzae isolates from North East and South India were grouped separately into two major clusters and 13 genotypes. Molecular- and pathogenicity-based classifications were not correlated, but a high level of genetic variability within S. oryzae isolates was identified. The molecular variability of S. oryzae isolates will be an important consideration in breeding programs to develop durable resistance for sheath rot disease.

The effects of carbon sources (sucrose, glucose, fructose and mannitol) and auxins [indolebutyric acid (IBA) and α-naphthaleneacetic acid (NAA)] on in vitro propagation of banana (Musa spp. AAA) were studied. Over all carbon sources tested, sucrose induced highest frequency of shoot proliferation. Optimal shoot proliferation rates were achieved on the Murashige and Skoog (MS) medium supplemented with sucrose and glucose combination (1:1) at the concentration of 30 g dm -3 . Similarly, higher frequency of root induction was obtained at IBA and NAA combination (1:1; concentration of 2 mg dm -3 ) than at other concentrations of IBA or NAA alone or their combinations.