Morphology and Molecular Characterization of Alternaria argyranthemi on Chrysanthemum coronarium in China

Chrysanthemum coronarium is an economically important plant in Asia, and used medicinally, ornamentally and as a vegetable. In April 2017, leaf spot disease on C. coronarium was observed in Shiyan, Hubei, China. A single-spore isolate was obtained and identified based on morphology and sequence analysis using four regions (rDNA ITS, GAPDH, EF-1α, and RPB2). The results indicated that the fungus is Alternaria argyranthemi. The pathogenicity tests revealed that the species could cause severe leaf spot and blight disease on the host. This is the first report of leaf spot disease on C. coronarium caused by A. argyranthemi in the world, which is also a new record of Alternaria species in China.

Evaluation of Biological Efficacy of Trichoderma Species Isolates Against Alternaria Leaf Spot Disease of Sesame.

Alternaria leaf spot disease is a major threat to sesame (Sesamum orientale L.) caused by Alternari asesami. Induced resistance is an alternative to systemic disease resistance response of plants. The present study aims to evaluate Trichoderma species efficacy as biocontrol via induction of resistance against A. sesami in sesame species. During in vitro bio control test, T. harzianum colonize and parallely inhibit the growth of the fungal pathogen. Expression of various defence related enzymes observed in sesame induce resistance against the pathogen infection in the host. T. harzianum coupled with inoculation of A. sesami enhance the remarkable induction of defence enzyme such as peroxidase (POX), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) and also the phenolic content compared with the control. The enzyme activity increased from 48 h of sampling and peaked at 72 h and then decreased after 72 h. In greenhouse and field experiments, soil treatment with a powder formulation of T. harzianum two weeks before planting or at the time of planting reduced significantly the incidence of diseases on both the wild and cultivar Thilarani.The results demonstrate that T. harzianumcan be successfully applied as a biological control against Alternaria leaf spot disease in sesame.