Kiran Nawaz

Global invasive Cochliobolus species: cohort of destroyers with implications in food losses and insecurity in the twenty-first century

Matching the global food demand by 2050 and to ensure the stability of food security in over than 99 countries, it is necessary to scale up the production of food such as sorghum, wheat, rice, maize and sugarcane which are however natural hosts of Cochliobolus species. Cochliobolus species major epidemics such as the Great Bengal famine, Southern corn leaf blight, and Northern leaf spot blight were associated with substantial economic losses in the past decades. Thus, there is an urgent need to establish a specific coordinated global surveillance program for the migration of invasive Cochliobolus species, planning contextual control programs engaging all agricultural stakeholders and information sharing in real time for prevention of disastrous Cochliobolus disease outbreak effects. We discuss pertinent outcome of interactions of cash crops with Cochliobolus species having devastating impact on the livelihood of farmers and food security. While post-genomic era elucidated prominent differences among Cochliobolus heterostrophus, C. carbonum, C. victoriae, C. lunatus and C. miyabeanus, their destructive potentials and implications in food losses remained unearthed. Intriguingly, the annual colossal losses caused by Cochliobolus species in the production perspective of sorghum, wheat, rice, maize, cassava and soybean is estimated over 10 billion USD worldwide. This paper provides a comprehensive analysis of the invasive Cochliobolus species distribution and diversity, evolving pathogenicity, persistent diseases, threats and epidemics, consequences on food crops production and increasing global food insecurity issues.

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 ...

First Report of Postharvest Fruit Rot of Tomato (Lycopersicum esculentum Mill.) Caused by Penicillium olsonii in Pakistan

A previously unnoticed fruit rot of tomato was observed during a survey in 2016 in the nursery of the University of Punjab, Lahore, Pakistan. Disease incidence was recorded at 9%. The symptoms were initially characterized as small water-soaked lesions on the epidermis that expanded and developed into watery rot. Isolations from symptomatic skin and tissue of the pericarp yielded species of Penicillium. A representative isolate of Penicillium was identified on the basis of morphological characteristics and by sequencing the internal transcribed spacer region of DNA and partial sequencing of the β-tubulin gene using ITS1 and ITS4 (White et al. 1990) and Bt2a and Bt2b (Glass and Donaldson 1995) primers, respectively. The associated fungus was identified as Penicillium olsonii. The colony of P. olsonii reached a diameter of 80 mm after 7 days of incubation at 25 ± 2°C on potato dextrose agar. The colony appeared white earlier in growth and then became dull green with conidiogenesis. The reverse side of the colony was pale yellow to cream yellow. The colony texture was velvety, occasionally with clear exudates and no pigmentation. The mycelium was white. Conidiophores were unbranched, smooth walled, and measured 650 to 800 × 4.5 to 6.5 µm. The phialides were flask shaped with a short neck and measured 8 to 10 × 2.5 to 3 µm (n = 50). The conidiophores had terminal terverticillate appressed penicillia. The conidia were subglobose to ellipsoidal with granular wall and measured 3.5 to 4 × 2.5 to 3.5 µm. The morphological characteristics were consistent with P. olsonii based on the description by Pitt (1979). The ITS1 region (GenBank accession no. LT900496) of 565 bp showed 100% homology with P. olsonii isolates (KY859385.1, JQ663620.1, DQ117963.1, and AY373925.1) from the NCBI database. The partial β-tubulin gene (accession no. LT900495) of 456 bp showed 100% identity with P. olsonii isolates (KR709179.1, AY674444.1, KU507286.1, and DQ645787.1) from GenBank. Pathogenicity of the fungus was demonstrated on tomato fruit according to Koch’s postulates. Healthy detached fruits of tomato were surface disinfested and stab inoculation was conducted using a needle rubbed over a 5-day-old culture of P. olsonii. A total of 20 control fruits were inoculated with a needle without inoculum and a total of 20 fruits were inoculated with P. olsonii and kept in a plastic bag at 25 ± 2°C for 20 days. Each fruit was inoculated at three points. Black spots appeared on inoculated tomato fruits after 10 days, which expanded to form larger gray-black lesions with evidence of mycelial growth in the center after 10 to 15 days of incubation. On the basis of mycological, molecular, and pathologic characteristics, the fungus reisolated from the fruits was identified as P. olsonii. P. olsonii has been reported previously to cause blue mold on tomato (Chatterton et al. 2012). This study appears to be the first report of postharvest fruit rot on tomato caused by P. olsonii in Pakistan. The occurrence of P. olsonii on other crop plants and its wide host range together suggest potential for this fungus to be a pathogen on a range of plant genera/species.

Invasive Aspergillus terreus morphological transitions and immunoadaptations mediating antifungal resistance

Background and aims Aspergillus terreus Thom is a pathogen of public health and agricultural importance for its seamless abilities to expand its ecological niche. The aim of this study was holistically to investigate A. terreus morphological and immunoadaptations and their implication in antifungal resistance and proliferation during infection. Materials and methods In-depth unstructured mining of relevant peer-reviewed literature was performed for A. terreus morphological, immune, resistance, and genetic diversity based on the sequenced calmodulin-like gene. Results Accessory conidia and phialidic conidia produced by A. terreus confer discrete anti-fungal resistance that ensures survivability during therapies. Interestingly, by producing unique metabolites such as Asp–melanin and terretonin, A. terreus is capable of hijacking macrophages and scavenging iron, respectively. As such, A. terreus has established a rare mechanism to mitigate phagocytosis and swing the interaction dynamics in favor of its proliferation and survival in hosts. Conclusion It is further unraveled that besides A. terreus genetic diversity, morphological, biochemical, and immunologic adaptations associated with conidia germination and discharge of chemical signals during infection enable masking of the host defense as an integral part of its strategy to survive and rapidly colonize hosts.