Colletotrichum acutatum: Causal Agent of Olive Anthracnose Isolation, Characterization, and Fungicide Susceptibility Screening in Punjab, Pakistan.

Anthracnose of olive fruit caused by Colletotrichum acutatum was a severe epidemic disease in Pakistan that occurred in September 2020. The estimated disease incident was recorded as 59%. Anthracnose causes a significant reduction in yield and quality traits. Anthracnose has been found in several orchards. Agricultural practices, environmental factors, and disease aggressiveness vary between orchards. Therefore, we looked at spore size, cultural traits, morphological variation, growth pattern, and pathogenicity of different strains of C. acutatum from various orchards. Molecular and phylogenetic analysis confirmed the isolated strains as C. acutatum. In all, 15 C. acutatum isolates from olive orchards were tested for susceptibility to four commercial fungicides (P < 0.001). The examined isolates' in vitro fungicide sensitivity varied with fungicide concentration. The concentration at which conidial germination was hindered by 50% compared with the control values was observed for difenoconazole, tebuconazole, carbendazim, and cyprodinil, ranging from 0.12 to 2.69 g ml-1. Based on the findings of the fungal growth inhibition studies, carbendazim has been found to be the only fungicide that effectively reduces (P < 0.001) anthracnose caused by C. acutatum strains. Additionally, results revealed that preharvest site treatments of different fungicides greatly decreased anthracnose infections on olive fruit (70 to 90%), and postharvest site applications significantly reduced disease prevalence and severity (75 to 95%). The fungicide carbendazim significantly decreased pre- and postharvest anthracnose infection on olive cultivars. This study suggests that the latter compound might be used to control olive anthracnose in Pakistan while lowering environmental impact and fungicide resistance.

First report of crown gall disease caused by Agrobacterium radiobacter on olive plants in Layyah, Punjab, Pakistan.

Crown galls were observed on one-year-old olive plants (Olea europaea cv. Manzanilla) in the District Layyah (30.9693° N, 70.9428° E) of Punjab, Pakistan. Large tumors were evident on collars region, causing growth stunting, leaf yellowing, and overall plant dieback (Supplementary fig. 1). Total 900 of olive plant were grown including 300 young plants in five hectare orchards, around 25% of the young plants in orchard had gall formation with varying in size (2-15cm), majority of the infected plants were grown near the water channel, where soil moisture level were high (90-100%). Other olive orchards in the same area have not crown gall problem and the tumorigenic strains of bacteria can cause crown gall on plants (Nemanja Kuzmanovic et al. 2015). This study was aimed to determine the pathogen of disease. The randomized collected samples were rinsed with tap water and galls were sterilized with 10% sodium hypochlorite solution for 1.5-3.0 min, washed with sterilized Distilled Water (SDW) then chopped and immersed overnight in SDW at room temperature. Isolations were carried out by plating the internal gall tissues on fresh Luria Bertani agar (LB agar) supplemented with natamycin. After incubating at 28°C for 5 days, 10 single colonies were transferred on new LBA plates for further cultivation at 28°C. After 48 to 72 h, three strains showed white to cream-colored, smooth, convex, glistening, circular with entire edges, and mucoid bacterial colonies resembling Agrobacterium spp. These three strains (BAT01, BAT02, BAT03) also showed biochemical and physiological characteristics similar to A. tumefaciens, including oxidase positive, growth at 35°C and in 2% NaCl, and alkalinity from litmus milk. They were tested negative for utilization of citrate and acid production on potato dextrose agar (PDA) supplemented with CaCO3 (Young et al. 2015). Amplification and sequencing of these three strain's 16S rRNA region and chromosomal recA gene with the universal primers fD1/rP2 and F2898/F2899 verified the identification at species level (Weisburg et al. 1991) . BLAST analysis revealed 100% identity for 16S rRNA and recA gene between the olive crown gall strains. Accession No. of deposited sequences were given in table 1 and the reference sequences GenBank Accessions No. of A. tumefaciens is FM209485.1 and KY913787 respectively. Phylogenetic analysis based on 16S rRNA of the strains from the crown gall and reference strains of various species of Agrobacterium by Maximum-likelihood method with Tamura's three-parameter model using the MEGA X software program confirmed the strain from olive was A. tumefaciens (Supplementary fig. 2). Inoculating the crown part of the plant through wounds of sterile needles plunged into young (2 to 3 day) bacterial culture (107 CFU/ml) and sterile distilled water (SDW) was screened for pathogens on 10 one-year-old olive plants cv. Manzanilla. Plants were grown at 23 ± 3°C, and tumor formation was observed 4 weeks after inoculation. Typical tumours formed and no symptoms found in control plants at inoculation sites and Koch's postulates were fulfilled with re-isolation and amplification of bacteria with recA gene region. This data shows that A. tumefaciens causes crown gall in olive plants. though it is reported before in different olive growing region in the world but This is first time reported in Layyah, Punjab, Pakistan.

Evaluation of antifungal metabolites activity from bacillus licheniformis OE-04 against Colletotrichum gossypii.

Anthracnose disease in the cotton plant caused by fungal pathogen Colletotrichum gossypii. It is supposed to be most critical diseases in the cotton crop as it causes infection and leads to complete damaging of the cotton crop by infecting the leaves, stems, and bolls in the field. The disease control is challenging due to the absence of an effective fungicide without damaging the farmer health and environment. So the series of experiments were designed to assess the antagonistic activity of biosurfactant released by strain Bacillus licheniformis OE-04 against the anthracnose causing agent in cotton and this strain was screened out from forty eight strain of rhizobacteria. We also estimated the heat stability and pH range and toxicity of biosurfactant produced by strain 0E-04. The results showed that biosurfactant has maximum antifungal activity against C. gossypii. In vitro study concluded that the biosurfactant can reduce fungal activity by inhibiting the spore germination of C. gossypii. Moreover, the biosurfactant also has wide pH and temperature range. We observed Antifungal activity of biosurfactant at 5 to 10 pH range and temperature range was also wide from room temperature to 100 °C. We also observed the toxicity of biosurfactant produced by Bacillus licheniformis against zebra fish (Danio rerio). We were noticed that biosurfactant have least harmful effect with maximum concentration. The study confirmed that biosurfactant of Bacillus licheniformis have high pH and heat stability range with least harmful effects so it can be a good replacement of chemical pesticides for cotton anthracnose control.

Development of SNP-Based Markers to Identify Colletotrichum gossypii in Upland Cotton.

Colletotrichum gossypii is a causal agent of anthracnose in upland cotton (Gossypii hirsutum). C. gossypii belongs to the C. gloeosporioides species complex. However, the high level of genetic similarity among the species within the C. gloeosporioides species complex makes the development of a diagnostic assay for C. gossypii challenging. Furthermore, the spore size and cultural characteristics of C. gossypii from different geographical areas can vary. In this study, we examined the morphological variance, growth pattern, and pathogenicity of C. gossypii and developed a molecular diagnostic assay to detect C. gossypii in cotton plants from different regions of China. To overcome any ambiguity in morphological and pathogenic characteristics, a set of primers targeting the ß-tubulin (TUB) gene of C. gossypii was designed. Single-nucleotide polymorphisms (SNP) were used to identify C. gossypii at the species level using DNA sequence alignments of the TUB gene. The SPSCG/F and SPSCG/R primer pair only amplified C. gossypii, and was able to amplify C. gossypii in mixtures of other Colletotrichum spp., even when DNA concentrations were up to 10 times lower than that of the other species. This is the first report of the development of SNP-based markers for the specific identification of C. gossypii.