In vitro and in vivo toxicity of nano chitosan against Curvularia lunata, the causal microorganism of fruit rot and blight, a new disease of olive (O. europaea L.)

المجلة: European Journal of Plant Pathology

سنة النشر: 2021

تاريخ النشر: 2021-12-21

During 2019, fruit blight and rot symptoms were observed on olive (O. europaea L.) fruits on trees grown in the Experimental Farm, Faculty of Agriculture, Sohag University, Egypt. Fungal isolates recovered from symptomatic fruits were identified as Curvularia lunata (Walker) Boedijn (two isolates) and A. alternata (Fr.) Keissl. (one isolate). Koch’s postulates were fulfilled by a pathogenicity test conducted in vitro on olive fruits wounded before inoculation with fungal isolates and incubation at 25 ± 0.2 °C in a moist chamber for a week. During incubation, we observed the development of blight and rot symptoms on fruits inoculated with both isolates of C. lunata, similar to the natural symptoms described. Conversely, A. alternata was nonpathogenic to olive fruits. PCR amplification using the specific P1 and P2 primers to C. lunata based on the Clg2p Ras protein gene sequences resulted in approx. 870 base pairs for all DNA of C. lunata analyzed, confirming the identification of C. lunata. In vitro, both chitosan nano and non-nano scale effectively inhibited mycelial growth by reducing linear mycelium and biomass and sporulation of C. lunata. In vivo, chitosan nanoscale at 2.0 mg mL−1 greatly reduced the infection and the lesion diameter of C. lunata inoculated fruits after a week and effectively induced defense-related enzyme activity of PO, PPO, and PAL. This report is the first recording of fruit blight and rots on olive caused by C. lunata, as a new disease. Also, we report the in vitro and vivo toxicity of nanoparticles of chitosan as a natural elicitor, effectively inducing defense-related enzymes against C. lunata.

Defense response of seedling plumule and mesocotyl of sorghum to infection by Sporisorium sorghi, causing covered kernel smut in relation to disease resistance classes

المجلة: Australasian Plant Pathology

سنة النشر: 2019

تاريخ النشر: 2019-11-14

Susceptibility of sorghum seedlings to infection by Sporisorium sorghi, the fungus causing covered kernel smut (CKS) disease, is limited to the period between the sowing of the seed and emergence of the seedling. Microscopy and PCR diagnosis of 7-day-old infected seedlings detected hyphae of S. sorghi in plumule and mesocotyl tissue but not in coleoptile and radicle tissue. Percent infected seedling plumule and mesocotyl tissue detected by microscopy and PCR corresponded well to field resistance classes for CKS in mature panicles of both sorghums tested with Giza-15 being highly susceptible and hybrid Shandweel-305 being resistant. Bulk extracts of phenolics and antioxidants from seedling plumule and mesocotyl tissues of hybrid Shandweel-305 cv significantly inhibited the in vitro mycelial growth of S. sorghi more than those from Giza-15 cv. Moreover, bulk extracts of plumule and mesocotyl tissue of seedlings grown from seed inoculated with S. sorghi teliospores contained higher phenolic and antioxidant content in the resistant hybrid (Shandweel-305) than the highly susceptible cultivar (Giza-15). Similarly, bulk extracts of plumule and mesocotyl tissue of 7-day-old seedlings grown from seed inoculated with S. sorghi teliospores contained higher phenolic and antioxidant content in the resistant hybrid (Shandweel-305) than the highly susceptible cultivar (Giza-15). Ferulic, isorhamnetin and kaempferol acids were detected only in plumule and mesocotyl tissue of resistant hybrid Shandweel-305, whereas ellagic, fumaric and vanillic acids were detected only in highly susceptible Giza-15 cv. Ferulic acid added to malt dextrose broth medium significantly inhibited in vitro teliospore germination and mycelial growth of S. sorghi, especially when added at the highest concentrations. This research established that the mode of seedling infection of sorghum by S. sorghi is almost exclusively through the plumule and mesocotyl tissue. Within these tissues, the presence of the pathogen can induce host production of phenolics, including the fungitoxic ferulic acid and antioxidants at higher concentrations within the resistant sorghum than in the highly susceptible cultivar.

Antifungal activity of Thuja orientalis against transmittedseed-borne Alternaria zinniae, causing leaf spot disease in zinnia (Zinnia elegans L.)

المجلة: Australasian Plant Pathology

سنة النشر: 2019

تاريخ النشر: 2019-11-14

In this study, four species of Alternaria as A. alternata (Fr.) Keissler, A. solani (Sorauer), A. tenuissima (Kunze) Wiltshire and A. zinniae M.B. Ellis were detected in seed samples of zinnia collected from the commercial lots in Egypt. Koch’s postulates performed in pots under greenhouse conditions proved that only A. zinniae was the main causal pathogen of leaf spot. Moreover, it was frequently detected in all seed components of coat, cotyledon, and embryo. Disease severity induced by all isolates of A. zinniae was highly related to growth stages of zinnia, where it increased with the development of plant age from 1 to 8 weeks old. Transmission of A. zinniae infected seed to seedling was at 51.3% (blotter method), whereas using seedling symptom test and test tube agar method exhibited infected seedling of 58.5 and 55.8%, respectively. In the efficacy test of extracts from different materials of thuja against A. zinniae performed in vitro, leaf methanol and water extracts were the most effective treatments, where they completely inhibited spore germination at a concentration of (5 and 3%, respectively) and mycelial growth at (7 and 7%, respectively) followed by seed methanol and water extracts. In the field experiments conducted during 2016 and 2017, a highly significant reduction in the percent of leaf area infected with A. zinniae of zinnia occurred after seeds were treated by soaking in methanol extracts of 3% leaf and 7% seed for 15 min before sowing. Hence, there is a scope to integrate thuja leaf and seed extracts as plant-derived agents for eco-friendly management of A. zinniae on zinnia.