The use of Beauveria bassiana in biological control of agricultural pests is mainly hampered by environmental factors, such as elevated temperatures and low humidity. These limitations, further amplified in a global warming scenario, could nullify biological control strategies based on this fungus. The identification of thermotolerant B. bassiana isolates represents a possible strategy to overcome this problem. In this study, in order to maximize the probability in the isolation of thermotolerant B. bassiana, soil samples and infected insects were collected in warm areas of Syria. The obtained fungal isolates were tested for different biological parameters (i.e., growth rate, sporulation and spore germination) at growing temperatures ranging from 20°C to 35°C. Among these isolates (eight from insects and 11 from soil samples), the five with the highest growth rate, spore production and germination at 30°C were tested for their entomopathogenicity through in vivo assays on Ephestia kuehniella larvae. Insect mortality induced by the five isolates ranged from 31% to 100%. Two isolates, one from Phyllognathus excavatus and one from soil, caused 50% of the larval mortality in less than four days, reaching values exceeding 92% in ten days. These two isolates were molecularly identified as B. bassiana sensu stricto by using three markers (i.e., ITS, Bloc and EF1-α). Considering these promising results, further studies are ongoing, testing their efficiency in field conditions as control agents for agricultural insect pests in Mediterranean and Subtropical regions.
Th e main aims of this study were to determine the overwintering form and the primary inoculum of Erysiphe necator, the causal agent of grapevine powdery mildew in southern Syria. Eleven vineyards located at fi ve diff erent geographical sites were visited every week from March to November in 2014 and 2015. Th e results of fi eld and histopathological studies showed that E. necator survived as mycelium in dormant grapevine buds during the winter season. Th e fi rst fl ag shoots were observed shortly aft er bud break in spring. Th e number of fl ag shoots varied greatly according to vineyards, cultivars and years, being present on 27.4 to 61.9% of the grapevines in 2014, and on 5.2 to 40% of the grapevines in 2015. Th e percentage of fl ag shoots on the same grapevine also varied according to the year, cultivar and location. It was between 4.3 to 9.4% in 2014, and 2.1 to 3.6% in 2015. Th e disease was observed only on Balady and Black cultivars. Conidia were released from the second week of May to early September. Th e fi rst conidia were trapped around mid-May, and the fi rst secondary symptoms were observed on leaves from mid-May to early June according to the site. Chasmothecia were observed on leaves in 45.5% of the studied vineyards. Th e fi rst observation of chasmothecia on leaves was in July, and their numbers varied greatly between vineyards and years. Chasmothecia were not detected on bark, nor were ascospores trapped at the beginning of the season. Th ese results confi rmed that the ascospores did not have any role in the initiation of spring infection. To the best of our knowledge, this is the fi rst report of the overwintering form of E. necator in Syria.
Powdery mildew caused by Erysiphe necator is the most important fungal disease of grapevine in southern Syria. The purpose of this study was to determine the development of chasmothecia and their role as a primary inoculum in spring. Leaves and/or branches were examined by a stereo binocular from July to December 2014 and 2015. The number of chasmothecia was estimated on both surfaces of the leaves, and their viability was estimated by microscopic examination. During 2 years of survey chasmothecia were detected in 45.5% of vineyards. The initial development of chasmothecia on infected leaves was observed in the second half of July. Their numbers increased from July to October, and the sudden reduction at the beginning of November was noted. Chasmothecia were formed on 38.7% of infected leaves, with 12.5%, 18.4%, and 7.5% on the upper, under and on both surfaces of infected leaves respectively. Chasmothecia were more frequent on the leaf under side (0.6 / leaf) than on the leaf upper side (0.4 / leaf), but their occurrence on both sides together was relatively low (0.2 / leaf), and their numbers were highly variable between vineyards and years. Microscopic examination showed that chasmothecia contained 1-5 (usually three) asci with 1-4 (usually three) ascospores in each asci, and 65.6% of chasmothecia were empty. Their viability decreased between December and February, with an average viability of 1.2% and 0.2% in March and April, respectively. Chasmothecia were not detected on bark and ascospores were not trapped at the beginning of the season. These results indicate that the ascospores have no or little role in the initiation of spring infection. To the best of our knowledge, this is the first report of E. necator chasmothecia development and their role in the initiating infection on grapevine in Syria.
Hamzeh, S., W. Naffaa and M.F. Azmeh. 2022. Occurrence of the Hyperparasite Ampelomyces quisqualis on Golovinomyces neosalviae (Erysiphaceae), Causal Agent of Powdery Mildew on Common Sage (Salvia officinalis). Arab Journal of Plant Protection, 40(2): 158-163. https://doi.org/10.22268/AJPP-040.2.158163 Ampelomyces quisqualis, the oldest mycoparasite of powdery mildew (PM), has been widely studied due to its potential in biocontrol. Many strains of this hyperparasite have been experimented worldwide and some of them were successfully applied for biocontrol, but others have been less efficient. No previous identification of Ampelomyces strains has been done in Syria, but some isolates were morphologically identified in the coastal region. There was no indication of Ampelomyces occurrence in any other location in Syria. During this three years survey (2019–2021), 73 plant samples were collected from five governorates, including coastal and southern regions in Syria. Ampelomyces pycnidia were detected in five samples from the coastal area and a new unpredictable finding of Ampelomyces sp. was found in southern Syria. This new occurrence of Ampelomyces isolate (S.ham82) is documented on a new mycohost; Golovinomyces neosalviae, the causal agent of PM on common sage (Salvia officinalis). Successful isolation of S.ham82 on PDA was conducted and parasitic activity was assessed by artificial inoculation using In vitro detached leaf assay. Morphological characteristics of this isolate were determined and compared with isolate Bah1 from the coastal region. Ampelomyces sp. (S.ham82) pycnidia size were 77.44 (±17.16) x 25.28 (±6.12) µm in natural host, 125.27 (±42.34) x 115.95 (±40.14) µm, 189.51 (±60.06) x 167.64 (±52.41) µm on PDA media pre and post artificial inoculation, respectively, and 88.24 (±20.05) x 27.98 (±5.68) µm on inoculated detached leaves. Conidia were also morphologically characterized and measured 8.11 (±0.87) x 3.88 (±0.51) µm in natural host, 8.86 (±1.65) x 3.18 (±0.80) µm in PDA pre and post artificial inoculation, respectively, and 7.82 (±0.69) x 3.61 (±0.37) µm in inoculated detached leaves. To our knowledge, this is the first report of the natural occurrence of Ampelomyces sp. in G. neosalviae on Saliva officinalis. Keywords: Ampelomyces sp., Common sage, Golovinomyces neosalviae, Syria.
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