Muhammed Ali Hossain

Genetic diversity of the bacterial wilt pathogen Ralstonia solanacearum using a RAPD marker

Bacterial wilt caused by Ralstonia solanacearum is a destructive disease of many economically important crop species. A significant variation in wilt incidence and severity in eggplant and potato was observed among the growing areas surveyed. R. solanacearum isolates obtained both from eggplant and potato belong to biovar III, while isolates from eggplant belong to race 1 and isolates obtained from potato belong to race 3. Random amplified polymorphic DNA (RAPD) technique was used as a tool for assessing genetic variation and relationship among seven isolate groups of R. solanacearum viz., RsB-1, RsB-2, RsB-3, RsP-1, RsP-2, RsP-3 and RsP-4, consisting in a total of 28 isolates. Out of the RAPD markers used, amplification with four decamer primers produced 70 bands with sizes ranging from 100 to 1400 bp. Out of 70 bands, 68 bands (97.06%) were polymorphic and two bands (2.94%) were monomorphic amongst the seven R. solanacearum isolates group. The Unweighted Pair Group Method of Arithmetic Means (UPGMA) dendrogram constructed from Neis genetic distance produced two main clusters of the seven isolates of R. solanacearum. The isolates RsB-1, RsB-2, RsB-3 and R-4 grouped in cluster І, while RsP-2, RsP-3 and RsP-4 grouped in cluster ІІ. The highest intra-variety similarity index (Si) was found in RsB-1 isolate (86.35%) and the lowest one in RsP-2 (56.59%). The results indicated that relatively higher and lower levels of genetic variation were found in RsP-3 and RsB-3, respectively. The coefficient of gene differentiation (G(st)) was 0.5487, reflecting the existence of a high level of genetic variations among seven isolates of R. solanacearum. Comparatively higher genetic distance (0.4293) and lower genetic identity (0.6510) were observed between RsB-2 and RsP-4 combinations. The lowest genetic distance (0.0357) and highest genetic identity (0.9650) were found in RsB-1 vs. RsB-2 pair. Thus, RAPD offers a potentially simple, rapid and reliable method to evaluate genetic diversity analysis in R. solanacearum.

Effects of plant extracts on controlling wheat blast disease caused by Magnaporthe oryzae Pathotype triticum in Bangladesh

The present research work was conducted to evaluate the efficacy of twelve plant extracts viz. Neem (Azadirachta indica), Bishkatali(Polygonum hydropiper), Nishinda (Vitex negundu), Allamonda (Allamanda cathertica), Acasia (Acacia auriculiformis), Tulsi (Ocientific tenuiflorum), Mehendi (Lmetawsonia alba), Datura (Datura metel), Bishkochu (Alocasia fornicate), Black cumin (Nigella sativa), Garlic (Allium sativum), Mehogoni (Swietenia macrophylla) @ 1:10 along with two fungicides Provax and Nativo @ 0.2% as check against Magnaporthe oryzae Pathotype triticum which is responsible for wheat blast disease at Department of Plant Pathology, Bangladesh Agricultural University and Plant Pathology Division, Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh-2202. This experiment was conducted in two phases viz. laboratory and pot experiment. In the laboratory experiment, the efficacies of plant extracts were evaluated by the measurement of percent inhibition of radial mycelial growth of M. oryzae Pathptype triticum. The highest percentage of mycelial inhibition (93.75%) was recorded in case of four plant extracts namely Tulsi, Mehendi, Datura and Garlic followed by Black cumin seed extracts (90%) at 10 days after inoculation, where as Allamonda leaf extract showed lowest percentage of mycelial growth inhibition (7.5%). On the basis of in vitro test five plant extracts were selected to conduct pot experiment to evaluate the disease incidence and severity, and some yield contributing parameters in treated and control plants. Minimum percentage of disease incidence and severity were recorded in case of Garlic clove extract ( 16.28 and 3.5) treated plants and the Mehendi leaf extract treated plants showed highest % of disease incidence and severity (66.0% and 68.0%). Garlic clove extracts also showed best performance for yield contributing parameters namely ear length (9.20 cm), number of ear/pot (13.25), number of healthy ear/pot (13.0), number of total and healthy spikelets/ear (34.20 and 33.40),number of total and healthy grains/ear (23.00 and 21.80) and weight of 1000 total and healthy grains/pot (56 and 52 gm) followed by Black cumin, whereas Mehendi leaf extract treated plants showed lowest value for all the yield contributing parameters among the plant extracts used in this experiment. Both in in vito and pot experiment Garlic extract showed best performance and it might be used for the eco-friendly management of blast disease and increase the yield of wheat.

Responses of rice (Oryza sativa L.) genotypes to different levels of submergence

The study aims at identifying some submergence-tolerant rice genotypes through morphological and molecular characterization and their genetic variability analysis. Ten rice genotypes including two submergence-tolerant checks, two susceptible varieties and six advanced lines were evaluated for submergence tolerance in the laboratory and in the field during January-December 2015. The experiment was conducted in the field following randomized complete block design in a two-factor arrangement using five replications. Ten characters, viz. days to flowering, plant height, tiller number plant-1, effective tiller plant-1, and yield plant-1 etc. were studied for four treatments. A significant genotype×environment interaction was observed for all traits studied in this experiment. The yield was reduced for all genotypes at a different level of submergence stress compared to control. Binadhan-11, Binadhan-12, RC 249 and RC 251 showed tolerance, whereas RC 192, RC 193 and RC 225 showed moderate tolerance in submerged condition. The phenotypic coefficient of variance (PCV) was higher than the genotypic coefficient of variance (GCV) in all the studies traits. High heritability (75-97%) was found for all traits. High heritability along with high genetic advance was found for days to flowering (45.55) and plant height (40.05). Molecular characterization of the used genotypes was done with three SSR markers viz. RM 24, and submergence specific SC3 and SUB1. SC3 was found reliable for detection of submergence tolerant genotypes due to the highest gene diversity (0.840) compared to others. The banding pattern of the submergence specific markers SC3 and SUB1 identified in Binadhan-11, Binadhan-12, RC 192, RC 193, RC 225, RC 227, RC 249, and RC 251, which possess the SUB1 gene. Finally, clustering also separates the tolerant genotypes from the susceptible by dividing them into different clusters. The identified genotypes might be useful for the breeding programme for the development of submergence tolerant as well as resistant rice variety in Bangladesh.

Effect of Media Composition on Vegetative and Reproductive Growth of Alternaria Brassicicola and Bipolaris Sorokiniana

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. article history Received: 5 October 2017 Accepted: 28 November 2017