S. Aslam

First Report of Alternaria alternata Causing Postharvest Fruit Rot of Jujube in Pakistan

Jujube (Ziziphus mauritiana Lamk), commonly known as “ber,” is a minor fruit in Pakistan that is cultivated on an area of 5.129 ha. In January 2017, severe fruit rot disease was observed in several markets located in the Faisalabad (31°25′15.7620″N, 73°5′21.4584″E) district of Punjab-Pakistan, with disease incidence ranging from 15 to 26%. Initially, small, oval, light to dark brown lesions (1 to 3 mm) were observed on the fruit surface, which gradually enlarged in size and led to total fruit rot. To isolate the pathogen, small tissue segments were cut from rotted fruit, surface disinfected with 1% NaClO for 2 min, rinsed three times in sterilized distilled water, air dried, and then placed aseptically onto potato dextrose agar (PDA) medium. Tissue samples were cultured at 25°C under a 12-h light/dark photoperiod for 3 days. Isolates were transferred to fresh PDA medium and cultured for 7 days. The cultured isolates consistently yielded dark brown to black colonies (85% isolation rate from 40 fruit tissues). Conidiophores were short, septate, 20 to 52 μm long, and 1 to 3 μm wide. Conidia were in chains (average conidial dimension 20 to 28 × 8 to 10 μm), brown and ovoid, with a short conical beak with both transversal (two to five) and longitudinal (one to three) septa. Based on morphology, the pathogen was identified as Alternaria alternata (Simmons 2007). To confirm the identification, genomic DNA was extracted and amplified using ITS1/ITS4 primers (White et al. 1990) and endopolygalacturonase gene using primers PG3/PG2b (Andrew et al. 2009). The resulting sequences were deposited in GenBank (accession nos. KY859867 and MF371420). BLAST analysis showed 99 to 100% homology to A. alternata sequences KJ957793 and AY295025 isolated from Korea and the United States, respectively. Pathogenicity tests were conducted on 20 surface-sterilized jujube fruit (cultivar Dilbhar) by spraying them with a conidial suspension (10⁶ conidia/ml) using a handheld sprayer. Ten fruit inoculated with sterile water served as a non-treated control. Fruit samples were kept in a moist chamber at 25°C and 70 to 80% relative humidity with a 12-h photoperiod. After 2 to 3 days of inoculation, all fruit displayed small, light to dark brown lesions followed by rotting. Reisolations from symptomatic fruit consistently yielded a fungus identical to A. alternata. Control fruit remained disease-free. Fruit rot of jujube caused by A. alternata has been reported in India and China (Wadia and Manoharachary 1980; Wang et al. 2009). To our knowledge, this is the first report of A. alternata causing postharvest fruit rot of jujube in Pakistan. The disease could represent a threat to jujube cultivation.

Aerobiosis Decreases the Genomic GC content in Prokaryotes by Guanine Oxidation

Oxidative stress is unavoidably faced by oxygen-consuming organisms. Under this stress, guanine is the most fragile base and so most frequently damaged among the four bases. Replication of DNA containing damaged guanines or incorporation of the damaged guanines into DNA strands would cause G to T mutations at a frequency depending on the efficiency of DNA repairing enzymes and the accuracy of replication enzymes. For this reason, aerobiosis is expected to decrease GC content. However, an opposite pattern of base composition in prokaryotes was reported 15 years ago. Although it has been widely cited, its overlook of the effect of shared ancestry determines the necessity to re-examine the reliability of its results. In the present study, by phylogenetically independent comparisons, we found that aerobic prokaryotes have significantly lower whole-genome GC contents than anaerobic ones. When the GC content is measured only at the 4-fold degenerate sites, the difference between aerobic prokaryotes and anaerobic prokaryotes became larger, being consistent with a mutational force imposed by oxidative stress on the evolution of nucleotide composition.Background: Among the four bases, guanine is the most susceptible to damage from oxidative stress. Replication of DNA containing damaged guanines result in G to T mutations. Therefore, the mutations resulting from oxidative DNA damage are generally expected to predominantly consist of G to T (and C to A when the damaged guanine is not in the reference strand) and result in decreased GC content. However, the opposite pattern was reported 16 years ago in a study of prokaryotic genomes. Although that result has been widely cited and confirmed by nine later studies with similar methods, the omission of the effect of shared ancestry requires a re-examination of the reliability of the results. Results: We retrieved 70 aerobe-anaerobe pairs of prokaryotes, and members of each pair were adjacent on the phylogenetic tree. Pairwise comparisons of either whole-genome GC content or the GC content at 4-fold degenerate sites of orthologous genes among these 70 pairs did not show significant differences between aerobes and anaerobes. The signature of guanine oxidation on GC content evolution has not been detected even after extensive controlling of other influencing factors. Furthermore, the anaerobes were not different from the aerobes in the rate of either G to T, C to A, or other directions of substitutions. The presence of the enzymes responsible for guanine oxidation in anaerobic prokaryotes provided additional evidence that guanine oxidation might be prevalent in anaerobic prokaryotes. In either aerobes or anaerobes, the rates of G:C to T:A mutations were not significantly higher than the reverse mutations. Conclusions: The previous counterintuitive results on the relationship between oxygen requirement and GC content should be attributed to the methodological artefact resulting from phylogenetically non-independence among the analysed samples. Our results showed that aerobiosis does not increase or decrease GC content in evolution. Furthermore, our study challenged the widespread belief that abundant G:C to T:A transversions are the signature of oxidative stress in prokaryotic evolution.

Vitamins: Key Role Players in Boosting Up Immune Response-A Mini Review

Vitamins perform different functions in our body and to boost up immune response towards pathogens is one of them. Immunity provides protection to life by its three main such as skin, cellular response, and humoral immune response. Both vitamins quality and quantity within the body promote systematic immune processes by regulating Tlymphocytes, antibodies, and cytokines formation. In this review, we will summarize the role of water soluble and fat soluble vitamins to boost up immunity functions. Vitamins A, C, and E mainly aid in enhancing the skin epithelium barrier function. With the exception of vitamin C, all the vitamins are claimed to be essential for antibody production. Most of the vitamins are applied in our body to produce a cell-mediated response with the production of cytokines and T-lymphocytes. Supplementation of the diet with vitamins in specifically selected appropriate quantities routinely can support body’s natural defence mechanism by enhancing the immune response.

Recent advances in molecular techniques for the identification of phytopathogenic fungi – a mini review

ABSTRACT At present, 1.5 million species of fungi are estimated. Among these less than 5% have been described. Many fungal species cause disease in plants. These diseases cause major economic and production losses in the agricultural industry worldwide. Monitoring plant health and detecting the pathogen early are essential to reduce the disease spread, and facilitate effective management practices. DNA-based methods now provide essential tools for accurate plant disease diagnosis. Recently, effective amplification platforms, probe development, various quantitative PCR, DNA barcoding and RNA-Seq-based next-generation sequencing have revolutionized the research in fungal detection field, and differentiation area. Although the molecular diagnostics techniques have grown extensively over the last couple of decades but still there is a long way to go in the development and application of molecular diagnostics to assist the plant disease diagnosticians. Finally, molecular diagnostic techniques used in plant disease diagnostic clinics need to be robust, reliable, inexpensive and easy to be used that they can compete with, and complement traditional techniques. Challenge now remains residue with the researchers to develop the practical techniques used for diagnostic setting. Examples of the recent advancement in the molecular techniques for diagnosing the fungi causing plant disease are discussed in the review. Abbreviations: PCR: polymerase chain reaction; LAMP: loop-mediated isothermal amplification; RCA: rolling circle amplification; NASBA: nucleic acid sequence-based amplification; ITS: internal transcribed spacer; RT: reverse transcriptase; FEB: Fusarium ear blight; qPCR: real-time PCR; SNPs: single nucleotide polymorphism; HRCA: hyper-branched RCA; FIP: forward inner primer; BIP: backward inner primer; COX I: cytochrome c oxidase I; MBs: molecular beacons.