Delwar M. Hossain

Characterization of a novel plasma membrane protein, expressed in the midgut epithelia of Bombyx mori, that binds to Cry1A toxins.

ABSTRACT We describe the properties of a novel 252-kDa protein (P252) isolated from brush border membranes of Bombyx mori. P252 was found in a Triton X-100-soluble brush border membrane vesicle fraction, suggesting that it may be a component of the midgut epithelial cell membrane. P252 was purified to homogeneity, and the amino acid sequence of two internal peptides was determined, but neither of the peptides matched protein sequences in the available databases. The apparent molecular mass of the purified protein was estimated by denaturing gel electrophoresis to be 252 kDa, and it migrated as a single band on native gels. However, gel filtration chromatography indicated an apparent mass of 985 kDa, suggesting that P252 may exist as a homo-oligomer. The associations of P252 with Cry1Aa, Cry1Ab, and Cry1Ac were specific, and Kd constants were determined to be 28.9, 178.5, and 20.0 nM, respectively. A heterologous competition assay was also done. P252 did not exhibit Leu-pNA hydrolysis activity, and binding to the Cry1A toxins was not inhibited by GalNAc. Binding assays of P252 with various lectins indicated the presence of three antennal N-linked high-mannose-type as well as O-linked mucin-type sugar side chains. While the function of P252 is not yet clear, we propose that it may function with Cry1A toxins during the insecticidal response and/or Cry toxin resistance mechanism.

Production of high yield short duration Brassica napus by interspecific hybridization between B. oleracea and B. rapa.

Brassica napus is a leading oilseed crop throughout many parts of the world. It is well adapted to long day photoperiods, however, it does not adapt well to short day subtropical regions. Short duration B. napus plants were resynthesized through ovary culture from interspecific crosses in which B. rapa cultivars were reciprocally crossed with B. oleracea. From five different combinations, 17 hybrid plants were obtained in both directions. By self-pollinating the F1 hybrids or introgressing them with cultivated B. napus, resynthesized (RS) F3 and semi-resynthesized (SRS) F2 generations were produced, respectively. In field trial in Bangladesh, the RS B. napus plants demonstrated variation in days to first flowering ranging from 29 to 73 days; some of which were similar to cultivated short duration B. napus, but not cultivated short duration B. rapa. The RS and SRS B. napus lines produced 2–4.6 and 1.6–3.7 times higher yields, respectively, as compared to cultivated short duration B. napus. Our developed RS lines may be useful for rapeseed breeding not only for subtropical regions, but also for areas such as Canada and Europe where spring rapeseed production can suffer from late spring frosts. Yield and earliness in RS lines are discussed.

First report of white mould caused by Sclerotinia sclerotiorum on jackfruit

Symptoms of white mould were first observed on jackfruit (Artocarpus heterophyllus) in Rangpur, Bangladesh, during February 2012. Fluffy, white mycelia developed on the fruit surface, along with large irregular black sclerotia. Morphological characteristics and the internal transcribed spacer sequences of ribosomal DNA identified the fungus as Sclerotinia sclerotiorum.

Marker-assisted selection of low erucic acid quantity in short duration Brassica rapa

Abstract Low erucic acid (LEA) rapeseed, which has accumulated mutant fatty acid elongase genes at the BnFAE1.1 and BnFAE1.2 loci of the A- and C-genome, respectively, is an important oilseed crop. Short growing turnip rape (B. rapa) is also important as a catch crop in the continuous cropping of rice in Asia but there is no LEA B. rapa cultivar for cultivation in South Asia. In order to develop LEA turnip rape cultivars, high erucic acid turnip rape cultivars were interspecifically crossed as recurrent parents to a canola quality rapeseed. In the meantime, we monitored incorporation of the mutant bnfae1.1 (e1) gene into A-genome of turnip rape, using a dCAPS primer pair, which can amplify PCR fragment only for the mutant e1 gene from A-genome. The early backcross progenies showed poor seed set, but which was improved in advanced progenies. Finally, homozygous e1e1 genotypes were established in the selfed progenies of BC2–BC3, and their LEA content was confirmed by gas-chromatography analysis. Our results and promising lines will contribute to LEA-trait selection in turnip rape and rapeseed breeding.

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.

Biological control of tomato collar rot induced by Sclerotium rolfsii using Trichoderma species isolated in Bangladesh

Abstract This study evaluated three Trichoderma strains (T. harzianum TR05, T. virens TR06 and T. asperellum TR08) originating from Bangladesh as potential biological control agents against collar rot of tomato under greenhouse conditions. After seed treatment with TR05, a disease incidence of collar rot (5.36%) was lower than for TR06 (34.2%) and TR08 (20.8%). Germination percentage of tomato was highest for TR05 (90.3%). In soil treatment, inoculation with TR08 resulted in the lowest disease incidence (9.78%), and the disease incidence was statistically no different from that for TR05 (16.4%). Thus, TR05 and TR08 have potential as biological control agents of collar rot in tomato.

First report of white mould caused by Sclerotinia sclerotiorum on Marigold (Tagetes erecta) in Bangladesh.

Marigold (Tagetes erecta) is one of the commercial ornamental flowers commonly grown in Bangladesh. In January 2011, rotten flowers of marigold covered with fluffy white mycelia were found in Rangpur, Bangladesh. Symptoms began from petals and subsequently expanded to the whole flower and the lower part of the plant. Dark brown lesions with necrotic tissues appeared on the infected leaves and stems. Seriously infected plants showed flower dropping and branch wilting. A fungus showing hyaline and septate mycelia was isolated from the infected tissue using potato dextrose agar. The fungus formed round to irregular-shaped sclerotia. Apothecia development from sclerotia were also observed on moist sand. The partial sequence (531 bp, GenBank accession No. AB937102) of the internal transcribed spacer region of rDNA was determined by the method described in Rahman et al. (2015). The result showed a 100% identity with those of Sclerotinia sclerotiorum, which is known as a pathogen to various plants (Purdy, 1979). Pathogenicity of the isolate to marigold was examined by detached leave and flower assays using the mycelial block. After incubation at 20°C with 90% relative humidity in 12 h light/12 h dark conditions, all inoculated leaves and flowers were rotten, while no symptom developed on the controls. The fungus was re-isolated from the symptomatic tissues and Koch’s postulates were confirmed. In Bangladesh, the fungus is becoming an emerging threat to various hosts (e.g. Rahman et al., 2015). To our best knowledge, this is the first report of S. sclerotiorum infection on marigold in the country.