Host range and phytotoxicity of Stemphylium solani, causing leaf blight of garlic (Allium sativum) in China

Abstract

Since 2004, a new leaf blight disease on garlic of high severity has been observed in Dangyang County, Hubei province, China. Initial symptoms consisted of multiple, small, irregular to oval, white leaf spots, which enlarge to produce sunken purple lesions, sometimes surrounded by a bright yellow margin. As the disease progressed, lesions expanded and merged, resulting in withering of leaf tips. After isolation and pathogenicity testing, the causal agent of leaf blight of garlic was identified as Stemphylium solani from cultural and morphological characteristics, and subsequent analysis of the internal transcribed spacer region of ribosomal DNA. When fungal plugs of two S. solani isolates were inoculated onto 11 garlic cultivars and 20 other crop species, leaf spots appeared on all inoculated plants, but two garlic cultivars (Qingganruanye and Ruanruanye) and three crop species (Capsicum annuum, Brassica napus and Amaranthus mangostanus) showed the smallest leaf spots. In cross-inoculation experiments, no indications of host specificity were observed, but S. solani isolated from garlic was generally the most virulent on five plant species, while the isolate from leek (Allium odorum) was generally the least virulent. Toxicity testing of the crude culture filtrates indicated that garlic isolates produced toxin(s) that were not heat-labile and induced different levels of phytotoxicity toward various garlic cultivars and crops.

A Comparative Analysis of Culture Media for Optimizing the Mycelial Growth and Sporulation of Stemphylium vesicarium Cause of White Blotch of Onion

“…Remarkable variations were also observed in conidial color of 24 isolates of S. vesicarium on PDA, where deep brown, brown and light brown color conidia were observed. The current findings were well supported by some reported works [17,19,21], which worked on Stemphylium solani and Stemphylium lycopersici and observed tan to light brown colored conidia. Koike et al [19] and Zheng et al [21] found brown colored conidia of Stemphylium botryosum and Stemphylium solani.…”

Isolation, Purification, and Biological Activity of a Phytotoxin Produced by Stemphylium solani

“…Symptoms of the disease start as small white spots (1 to 3 mm) enlarging to elongated purple necrotic lesions along the vein, followed by blighting of the leaf tips. Similar symptoms were produced by culture filtrates of S. solani, and a strong correlation was also found between garlic cultivar sensitivity to S. solani and sensitivity to S. solani culture filtrates (29), suggesting the possible involvement of phytotoxins in lesion symptom development. We recently found that S. solani isolated from garlic produced toxins that were non-host-specific, and caused symptoms normally associated with leaf blight on a variety of plants (29).…”

“…We used ethyl acetate to extract the SS-toxin from culture filtrate. Variable phytotoxicity of different batches of culture filtrates was observed in this study, and this might be related to the age of cultures, since toxin production of S. solani isolates was reduced after transferring for several generations (29).…”

“…Changbanpo), with some tests on a resistant cultivar, Qingganruanye, which rarely shows disease in the field. The methods follow Zheng et al (29). Briefly, for each treatment, 10 leaves at the three-leaf stage were detached, abaxial surface lightly wounded, and a 30-μl solution applied to the wound site.…”

Effect of SS-toxin, a metabolite of Stemphylium solani, on H+-ATPase activity and standard redox system in plasma membranes from seedlings leaves of garlic (Allium sativum)

“…The symptoms of the disease initially consist of small white spots enlarging to elongated purple necrotic lesions along the vein followed by blighting of the leaf tips. The pathogen produces a non-host-specific toxin, SS-toxin, which is capable of causing symptoms normally associated with leaf blight (Zheng et al 2009). However, the chemical structure and precise mode of action of SS-toxin has not been elucidated.…”