First Report of <i>Stemphylium vesicarium</i> Causing Onion Stemphylium Leaf Blight in Ethiopia

Abstract

A suspected fungal disease was observed on onion leaves during survey in onion fields of the central rift valley of Ethiopia in the offseason in 2019. The disease symptoms were round to oval small spots on onion leaves which coalesce to form blighted leaves that change to brown lesion and black sporulation with time. The disease was of high incidence (up to 95.2%) and severity (up to 4.67) where in some fields it has been causing early plant senescence and reduced bulb size during harvest with massive yield loss, named to be "Yeshinkurt Ebola" to mean "Ebola of onion" by farmers. Dirty white to light grey front colony color and light brown to deep brown reverse colony color with alternative white and brown band fungal growth were isolated from infected onion leaf samples. The conidia were olive brown, oval to ovoid, oblong and ovoid to oblong are born on conidiophores. Pathogenicity of the pathogen was confirmed on 45-days-old onion (cv. Nafis) plant, and it was identified as Stemphylium vesicarium based on cultural, morphological and pathogenic results. This is the first report of S. vesicarium, the causative agent of onion stemphylium leaf blight.

Screening of short-day onions for resistance to Stemphylium leaf blight in the seed-to-bulb stage (stage I) and bulb-to-seed stage (stage II)

“…Small tan to brown water-soaked, oval lesions were observed, and leaf samples were collected for microscopic and molecular identification. The microscopic observation revealed the presence of ovoid to oblong, brown color conidia, and these morphological observations coincided with the previous reports ( Dangi et al., 2019 ; Gedefaw et al., 2019 ; Hassan et al., 2020 ). Also, the amplified product of the internal transcribed spacer (ITS) sequence, identified using NCBI BLAST, had 100% similarity with previously submitted sequences.…”

First report of stemphyllium leaf blight diseases on shallots in West Sumatra, Indonesia

“…The blight becomes necrotic, followed by brown leaf tips, and finally, leaf collapse (Fig 1). Symptoms of disease found in the field were the same as those reported by [1] in the form of small to advanced brown lesions, wet lesions on the leaves, and dark brown to black due to sporulation. These symptoms are common in older plants; furthermore, SLB can cause premature senescence of leave and decrease the quality of the bulb.…”

“…and De Not) which is an important disease in Allium species. It has a wide host range, including garlic [2], chili, leek, asparagus, and onion [1].…”

“…Purple blotch attack the leaves and bulbs and further reduce yield and quality. The symptoms of SLB are similar to purple blotch, so they are often confused, and the disease may be misdiagnosed as purple blotch disease [1].…”

The use of biological agents in controlling diseases of shallots for tss production

“…In planta testing was carried out on attack symptoms that appeared on leaves and flower stalks. Observation of symptoms was carried out using the following scoring system: 0 = no attack, 1 = 10% of affected leaves, 2 = 20-30% of affected leaves, 3 = 40-50% of affected leaves, 4 = 60-70% of affected leaves, 5 = >70% [18]. The degree of damage to leaves is determined by the formula: Observations were made from two weeks after planting, with an interval of one week.…”