No abstract

Experiments were conducted to evaluate the effect of some culture media on the vegetative and reproductive growth of Alternaria brassicicola and Bipolaris sorokiniana. Twenty one (21) treatment combinations each with three replications were employed. Potato Dextrose Agar (PDA) was used as the basic growth medium in this study. Supplementation with different plant extracts with this medium produced differential growth and sporulation of the tested fungi. PDA media supplemented with mustard leaf extract showed significantly highest vegetative growth (7.8 cm) and PDA with the combination of mustard leaf, tomato fruit, carrot fruit and cabbage leaf extracts showed the highest sporulation (11×105 spores/ml) of A. brassicicola. In case of B. sorokiniana, the highest vegetative growth (7.4 cm) and highest sporulation (45×104 spores/ml) were obtained by the supplementation of mustard and wheat leaf extracts respectively. Plant extract supplementation proved better than PDA as growth medium of A. brassicicola and B. sorokiniana.

No abstract

Isolation and identification of native fluorescent Pseudomonads from the rice rhizosphere were evaluated for their growth suppressing ability against blast disease of rice causing pathogen (Magnaporthe oryzae). Twenty strains of fluorescent Pseudomonads were isolated and identified initially based on their cultural and in vitro growth suppressing ability against M. oryzae. Among them BdPf-4, BdPf-8, BdPf-9 and BdPf-10 exhibited complete in vitro growth suppression (100%) against M. oryzae following dual culture in growth medium. Molecular identification of the antagonistic Pseudomonas fluorescens was done using 16S rDNA primers. Gel-electrophoresis of PCR products of all the isolates confirmed the fluorescent Pseudomonads showing band at 1500 bp. Phylogenetic analysis of the sequenced data revealed that BdPf-8 (MN256392.1), BdPf-9 (MN256393.1), BdPf-10 (MN256394.1) have 100% homology with Pseudomonas putida (MT184822.1) from India, Bacterium sp. (MK823484.1) from China, Pseudomonas sp. (KY324900.1) from Brazil respectively. Seed priming by different strains of P. fluorescens significantly increased vigor index of rice seedlings. The highest vigor index (2274.8) and (2211.6) which was 184.42% and 176.53% higher over control treatment was found in BdPf-16 (MN256399.1) and BdPf-10 (MN256394.1) respectively. These results revealed the possibility of potential use of some of the strains of native P. fluorescens for management of blast disease of rice.

Experiments were conducted under laboratory condition to examine the efficacy of Chitosan and Yeast Elicitor to suppress the growth of seed-borne fungi of cucurbitaceous vegetables. Seeds of bottle gourd, sweet gourd, snake gourd, wax gourd and cucumber were collected from seed traders of Mymensingh districts and different seed borne fungi were isolated, purified and identified. Fourteen fungal species belonging to twelve genera consisting of Aspergillus flavus, Aspergillus niger, Botrytis cinerea, Fusarium moniliforme, Fusarium oxysporum, Phoma exigua, Rhizopus stolonifer, Macrophomina phaseolina, Penicillium spp., Curvularia lunata, Chaetomium spp., Colletotrichum spp., Cercospora spp. and Alternaria alternata were isolated and identified. Four concentrations of Chitosan and Yeast Elicitors solutions (200, 500, 1000 & 2000 ppm) including one positive control Vitavax-200 WP (0.35%) were evaluated for controlling seed-borne fungi. Among the seed treating agents Chitosan (2000 ppm) and Yeast Elicitor (2000 ppm) showed better performance in suppressing the seed-borne fungi. Chitosan (2000 ppm) showed superior performance than Yeast Elicitor (2000 ppm). Results from the present study revealed that application of elicitors as seed treatment is a potential alternative of chemical fungicide for selective vegetables.J. Bangladesh Agril. Univ. 16(2): 187-192, August 2018

Induced resistance (IR) is a unique physiological state characterized by reduced plant susceptibility to (a)biotic stress. Our previous studies showed that exogenous foliar application of dehydroascorbate (DHA), the oxidized form of ascorbic acid, induces systemic resistance against root-knot nematode Meloidogyne graminicola in rice. In the present study, the potential of DHA in protecting rice plants against M. graminicola was evaluated in lab, pot, and field studies. In an experiment where the interval between foliar treatment and inoculation was varied, 20 mM DHA was found to protect rice plants from M. graminicola for at least 14 days. Pot and field studies confirmed that 10 or 20 mM DHA are highly effective in reducing gall formation and led to a significant increase in rice seed yield. A half dose of DHA (10 mM) combined with another IR-stimulus - piperonylic acid (PA) 300 µM - was at par with DHA 20 mM, leading to reductions in gall formation of more than 80%. In in vitro bioassays, DHA was found to be highly nematicidal to the second-stage juveniles of M. graminicola, with more than 90% mortality within 3 h of exposure to 10 or 20 mM concentrations. While seed treatment had no effect, root drenching or root dipping was also effective in reducing rice susceptibility to M. graminicola, next to foliar treatment. As a dual-action compound with extended protection and ease of application, DHA has great potential for effective nematode management in rice.

No abstract

No abstract