I. Hossain

Compost tea as soil drench: an alternative approach to control bacterial wilt in brinjal

An experiment was conducted in the field laboratory, Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh, to evaluate the efficacy of compost tea and poultry litter extract along with their economic feasibility of their usage in controlling bacterial wilt of brinjal under natural incidence condition. A significant variation was observed among the treatments on the incidence and severity of bacterial wilt in brinjal. The results showed that the lowest wilt incidence was recorded in T2 (Compost tea as soil drenching), T5 (Poultry litter as soil application) and T6 (IPM Lab Biopesticide as soil application) while the highest wilt incidence was recorded in control treatment in both counting periods. Similar trend regarding the performance of these treatments was observed on the bacterial wilt severity of brinjal. The effects of compost tea and poultry litter extract on the growth and yield parameters of eggplant were observed to be significant. The results revealed that plant height, number of branches per plant, number of fruits per plant and fruit yield per ha were recorded as maximum in T2 (Compost tea as soil drenching), followed by T5 (Poultry litter as soil application) and T6 (IPM Lab Biopesticide as soil application), while the minimum plant height, number of branches per plant, number of fruits per plant and fruit yield were recorded in control treatment (T1). The other treatments showed significant effect in increasing all the growth and yield parameters of brinjal as compared to control. Benefit cost analyses (BCR) showed that T6 (IPM Lab Biopesticide as soil application) resulted in the highest BCR (99.21) as compared to control, followed by T7 (BAU-Biofungicide as foliar spray) and T2 (Compost tea as soil drenching) with BCR 35.7 and 19.5, respectively. The results indicated that an investment of Tk. 1.00 may lead to a profit up to Tk. 99.21 by soil application of IPM Lab Biopesticide which gave the maximum profit in the present study. T7 (BAU-Biofungicide as foliar spray) followed T2 (Compost tea as soil drenching) where the investment Tk. 1.00 returned a profit of Tk. 35.70 and Tk. 19.5, respectively. Soil drenching of compost tea showed comparatively lower BCR but the highest percent increase of gross margin was obtained when compost tea was applied as soil drench (T2). Therefore, it may be concluded that soil drenching of compost tea may be an alternative approach to control bacterial wilt of brinjal along with other possible organic amendments.

Native Trichoderma strains isolated from Bangladesh with broad spectrum antifungal action against fungal phytopathogens

Nineteen Trichoderma isolates, collected from different locations in Bangladesh, were characterised through phenotypic, biochemical and molecular means. Besides, they were assessed for their antifungal action in vitro. The isolates were divided into three groups: T. asperellum, T. virens and T. harzianum. A dual culture assay and a culture filtrate assay against 6 phytopathogens revealed that 9 of the 19 isolates showed significant antifungal activities. The isolate T. harzianum TR05 showed the highest inhibition against Fusarium oxysporum, Rhizoctonia solani, Fusarium circinatum and Phomopsis vexans, followed by T. asperellum TR08 and T. virens TR06. TR08 had the highest inhibition against Sclerotium rolfsii and Pythium aphanidermatum, followed by TR05 and TR06. These findings were in agreement with their activities of extracellular hydrolytic enzymes, including chitinase, β-1,3-glucanase, and proteinase. Our results suggest that isolates TR05, TR06 and TR08 have the potential to be effective biocontrol agents against the phytopathogenic fungi.

Analyses of genetic diversity of bacterial blight pathogen, Xanthomonas oryzae pv. oryzae using IS1112 in Bangladesh

Bacterial blight (BB) is caused by Xanthomonas oryzae pv. oryzae (Xoo), a most destructive disease of rice, mostly in Asia, including Bangladesh. Altogether 96 isolates of Xoo were collected from 19 rice-growing districts of Bangladesh in both the rain-fed and irrigated seasons of 2014 to assess their pathotypic and genetic variation. Pathotypic analyses were carried out on a set of 12 Near Isogenic Lines (NILs) of rice containing a single resistance gene and two check varieties IR24 and TN1 by the leaf clipping inoculation method. A total of 24 pathotypes were identified based on their virulence patterns on the NILs tested. Among these, pathotypes VII, XII and XIV, considered as major, containing a maximum number of isolates (9.38% each), are frequently distributed in seven northern to mid-eastern districts of Bangladesh. The most virulent pathotype I was recorded in the Habiganj and Brahmanbaria districts. The molecular analysis of variability among the isolates was carried out through PCR analysis using multi-locus primers Jel1 and Jel2 (based on the repetitive element IS1112 in the Xoo genome). Using the genotypic data, a dendrogram was constructed with 17 clusters along with 17 molecular haplotypes at the 65% similarity index. Cluster I was composed of 46 isolates considered as major, whereas clusters X, XI, XII and XVII were represented by a single isolate. A phenogram was constructed based on virulence to interpret the relationship between the pathotypes and the molecular haplotypes. At the 50% similarity level, among 10 clusters, cluster I, considered as major, consisted of a maximum of 10 pathotypes out of 24. In case of haplotypes, a maximum of 7 haplotypes were obtained from pathotype XII, whereas pathotypes IX, X, XV, XXII and XXIV were represented by a single haplotype. However, the present study revealed that different isolates belonging to the same pathotypes belonged to different haplotypes. Conversely, genetically similar haplotypes were also detected from different pathotypes collected from separate districts. This relationship appeared due to a high degree of DNA polymorphism among strains within many pathotypes existing in Bangladesh.

Pathotypic variation of Xanthomonas oryzae pv. oryzae in Bangladesh

Bacterial Blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo), a destructive disease of rice. Altogether, 96 isolates of Xoo were collected from 19 rice growing districts of Bangladesh in irrigated and rainfed seasons during 2014 to assess pathotypic variation. Pathotypic analyses on a set of 12 Near Isogenic Lines (NILs) of rice containing resistance genes viz. Xa1, Xa2, Xa3, Xa4, Xa5, Xa7, Xa8, Xa10, Xa11, Xa13, Xa14 and Xa21 and two check varieties IR24 and TN1 by leaf clip-inoculation technique. A total of 24 pathotypes were identified based on their virulence patterns on NILs tested. Among these, pathotypes VII, XII, and XIV considered as major, containing maximum number of isolates, (9.38% each) frequently distributed in North to Mid-Eastern districts of Bangladesh. Most virulent pathotype I recorded from Habiganj and Brahmanbaria. This pathotypic variation explained the pathogenic relatedness of X. oryzae pv. oryzae populations from diverse geographic areas in Bangladesh.

Effect of antibiotics and BAU-biofungicide in controlling bacterial leaf blight of litchi

The experiment was carried out in the net house, Department of Plant Pathology, Bangladesh Agricultural University (BAU), Mymensingh, Bangladesh during 16 July 2012 to June 2013 to find out the suitable management practices for controlling bacterial leaf blight of litchi by applying six treatments viz., (i) T1–Gentamycin @ 0.05%, (ii) T2– Erithromycin @ 0.05%, (iii) T3–Doxycycline @ 0.05%, (iv) T4–Copper sulphate @ 0.05%, (v) T5–BAU-biofungicide @ 2% and (vi) T6–Control. Per cent incidence and per cent severity have been found to decrease by applying BAU-biofungicide, copper sulphate and gentamycin, although other treatments showed good result in decreasing severity of bacterial leaf blight. BAU-biofungicide was found superior among the treatments as it increased 18.83% plant height, 43.50% branch over control and reduced 17.16% disease incidence and 63.03% disease severity over control when applied as foliar spray @ 2%. Copper sulphate reduced 13.85% disease incidence and 50.21% disease severity over control and graded second best control measure for bacterial leaf blight of litchi when applied as foliar spray @ 0.05%.

Management of bacterial leaf blight of mango through antibiotics and bio-fungicide

An experiment was conducted in the net house, Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh, Bangladesh during 15 July 2012 to June 2013 to find out the efficacy of antibiotics and biofungicide for controlling bacterial leaf blight of mango. Six treatments were applied viz., (i) T1–Gentamycin @ 0.05%, (ii) T2– Erithromycin @ 0.05%, (iii) T3–Doxycycline @ 0.05%, (iv) T4–Copper sulphate @ 0.05%, (v) T5–BAU-biofungicide @ 2% and (vi) T6–Control. The treatment BAU-biofungicide was found good in controlling bacterial leaf blight of mango. This treatment increased 23.71% plant height, 53.33% branch over control and reduced 39.31% disease incidence and 48.50% disease severity when applied as foliar spray @ 2%. The second best control measure was found by gentamycin as it reduced 28.46% disease incidence and 46.43% disease severity when applied as foliar spray @ 0.05%, although other treatments reduced incidence and severity of bacterial leaf blight which were applied as foliar spray @ 0.05%.