Waheed Anwar

First report of Cochliobolus australiensis causing leaf spot of bermudagrass in Pakistan.

Bermuda grass (Cynodon dactylon) plants showing symptoms of light brown to blackish leaf spots were observed during spring 2012 in the parks and grassy lawns of Lahore (Pakistan). Samples from infected plants were collected and a fungus consistently isolated on potato dextrose agar (PDA) at 28±1°C. The fungus was identified as Bipolaris dactylon (telomorph Cochliobolus australiensis) based on its morphological and molecular features. The pathogen identity was verified by the First Fungal Culture Bank of Pakistan (FCBP) and a culture deposited (accession No. FCBP-1288). In addition, the fungal DNA was isolated and the internally transcribed spacer (ITS) region amplified (White et al., 1990), cloned, sequenced and deposited in GenBank (accession No. HE962033). Sequencing of the ITS region of ribosomal DNA showed a 99.8% nucleotide sequence identity with C. australiensis isolates from Texas (HQ608034) and India (AY923860), respectively. Reproduction of symptoms in inoculated healthy plants fulfilled Koch’s postulates and confirmed pathogenicity. B. australiensis had previously been isolated from infected roots of C. dactylon during a survey in Pakistan (Shahzad and Ghaffar, 1995). However, no details were given of foliar symptoms, nor any pathogenicity test was conducted. Therefore, to the best or our knowledge, this is the first confirmed report of B. dactylon causing a leaf spot on Bermudagrass in Pakistan.

Evidence of genetically diverse virulent mating types of Phytophthora capsici from Capsicum annum L.

Chili pepper (Capsicum annum L.) is an important economic crop that is severely destroyed by the filamentous oomycete Phytophthora capsici. Little is known about this pathogen in key chili pepper farms in Punjab province, Pakistan. We investigated the genetic diversity of P. capsici strains using standard taxonomic and molecular tools, and characterized their colony growth patterns as well as their disease severity on chili pepper plants under the greenhouse conditions. Phylogenetic analysis based on ribosomal DNA (rDNA), β-tubulin and translation elongation factor 1α loci revealed divergent evolution in the population structure of P. capsici isolates. The mean oospore diameter of mating type A1 isolates was greater than that of mating type A2 isolates. We provide first evidence of an uneven distribution of highly virulent mating type A1 and A2 of P. capsici that are insensitive to mefenoxam, pyrimorph, dimethomorph, and azoxystrobin fungicides, and represent a risk factor that could ease outpacing the current P. capsici management strategies.

Entomopathogenic fungus Clonostachys rosea as a biocontrol agent against whitefly (Bemisia tabaci)

ABSTRACT Whitefly (Bemisia tabaci) is a notorious insect pest of many economic important crop plants including cotton, tomato, etc. The main objective of the study was to evaluate the efficacy of new biological control agent to replace toxic chemical pesticides from agro-ecosystem. Clonostachys rosea associated with whitefly and aphid (Aphis gossypii) on cotton plants was isolated and characterised on a morphological and molecular basis. Phylogenetic analysis was also performed based on the internal transcribed spacer (ITS) region. Pathogenicity of C. rosea was evaluated in two concentrations against fourth instar nymphal and adult stages of B. tabaci. The study revealed that C. rosea was highly parasitic against fourth instar nymphs than adults at different spore concentrations. Two isolates of C. rosea were identified in this study, and both were morphologically similar. However, differences were observed in the ITS region of the C. rosea isolates. Our results showed that C. rosea has the prospects to serve as a potential biocontrol agent against economically important insect pests.

First report of black pit of potato caused by Alternaria alternata in Pakistan

During April 2015, brown to black colored pits, typical of the disease known as black pit, were observed on 10% of potato tubers (Solanum tuberosum L.) during a survey of fields near Wagha border (31.6047° N, 74.5731° E), Lahore, Pakistan. Symptoms appeared as sunken dark lesions with distinct borders and a corky to leathery texture of underlying tissue. When potato tubers were washed, black patches on potato skin were visible. The tubers were collected for pathogen isolation and surface sterilized with 2% NaOCl solution for one minute and rinsed twice in sterile distilled water. The lesions were excised from the tubers and directly placed on PDA media plates and incubated at 25°C. A fungus with typical Alternaria morphology, which grew out of the tissue, was isolated using hyphal tip method and further purified and identified based on the taxonomic key by Simmons (2007). Colony growth was circular with alternating dark and light concentric sporulation. The mycelia were dark brown and septate. The chains ...