Intraspecific strains of Pythium aphanidermatum induced disease resistance in ginger and response of host proteins.

Intraspecific strains of Pythium aphanidermatum induced resistance in ginger against rhizome rot and activated biosynthesis of selected host proteins. Pre-inoculation of plants with IR strain (avirulent) or co-inoculation with SR2 (virulent) caused significant reduction in disease severity. Analysis of protein profiles of ginger leaves of inoculated and non-inoculated plants by SDS-PAGE and Image Master VDS-ID Gel Analysis version : 3.0 revealed that some specific defence proteins/stress proteins increased in inoculated plants. Five such proteins having molecular weight 56, 32, 27, 18 and 14 kDa were detected in leaves of plant treated with IR + SR2 strains. On the contrary, mycelial protein profiles and submerged growth of strains were studied separately and together. Mycelia of IR, SR2 and IR + SR2 exhibited 26, 23 and 25 protein bands, respectively although, 21 bands were common between IR and SR2. Growth of SR2 in synthetic medium was much higher than that of IR, but the growth of two strains together was lower than SR2 alone. To characterise strains, their differential growth response to DL-beta-aminobutyric acid (BABA), a known defence activator of ginger was also tested. Results suggested that at least 5 specific defence proteins/stress proteins were involved in microbially induced resistance in ginger and inducer strains were distinct in their specific protein profiles and sensitivity to BABA.

Identification and characterization of some PR-proteins induced by kitazin and Rhizoctonia solani causing sheath blight of rice.

Significant reduction (68.38%) in sheath blight disease of rice was noticed when foliar spray of a systemic fungicide, kitazin (480 micrograms mg-1), was applied twice at an interval of 2 days before inoculation. SDS-PAGE analysis of proteins of Rhizoctonia-infected rice leaf sheaths revealed the presence of 16 proteins ranging from 20 to 90 kDa (approx.). Six were identified as constitutive defense proteins (increased after infection), 6 as secondary defense proteins (formed de novo) and the rest 4 appeared non-defense proteins. Non-inoculated kitazin-treated leaf sheaths showed 15 proteins of which 5 were constitutive and 4 secondary defense proteins (both are PR-proteins). Among the PR-proteins, five beta-1,3-glucanases and one chitinase was identified and characterized. One rice chitinase (MW 20 kDa) and 2 glucanases (60 & 69 kDa) showed serological relationships with tobacco chitinase (32 kDa) and tobacco glucanase (33 kDa) respectively. The implications of results have been discussed in relation to biotic and abiotic induction of PR-proteins in rice.

Metal uptake by mycelia during submerged growth and by sporocarps of an edible fungus Volvariella volvacea.

Uptake of a few metals by V. volvacea was determined during submerged growth of the organism in sublethal concentration of each metal salt. The uptake of Pb2+ and Hg2+ was 5 and 5.23 micrograms g-1 respectively while that of Cu2+ was 500 micrograms g-1 under experimental conditions. Treatment of spawned substrate separately with different metal salts showed maximum and minimum uptake of Pb2+ (100 micrograms g-1) and Cd2+ (2.93 micrograms g-1) respectively by sporocarps. All metal salts at test concentrations reduced biological efficiency of sporocarp production but markedly by Co2+. Cd2+ and Co2+ were highly toxic to mycelia and sporocarps respectively. The uptake of Cu2+ by mycelia and Pb2+ by sporocarps were highest among the five metals tested. Metal toxicity, tolerance and uptake capacity of V. volvacea differ considerably with concentration of metal ions.

Isolation, characterization and biological activities of a toxin from Bacillus megaterium (B-23).

Fungitoxic substance was isolated from the culture filtrate of B. megaterium (B-23). Age of culture and pH of medium influence the fungitoxicity of its culture filtrate. Partially purified toxin was thermolabile, non-dialysable, ethyl acetate soluble, vanillin-sulphuric acid positive and effective within a range of pH 5-9. It exhibited maximum UV absorption at 224 nm. Its melting point was 242 degrees C. The efficacy of this compound was tested on 4 jute parasites namely, C. corchori, C. gloeosporioides, M. roridum and A. citri, of which M. roridum and C. corchori were least and most sensitive to the toxin respectively.