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June 24, 2003
Source: Australasian Plant Pathol Journal, New Disease Notes [edited]

First report of stem rot and wilt of chickpea caused by _Sclerotinia minor_in Queensland, Australia
M J Fuhlbohm <michael.fuhlbohm@dpi.qld.gov.au>, JR. Tatnell, MJ Ryley, Queensland Department of Primary Industries. Australasian Plant Pathology Journal, 32 (2), 323-324.

In Australia, 3 closely related _Sclerotinia_ species, _S. sclerotiorum_, _S. trifoliorum_ and _S. minor_, [Sm] infect chickpea [_Cicer arietinum_] (1). Sm isolates have previously been lodged in Victoria and New South Wales. In Western Australia, Sm is suspected to cause significant losses in certain years.

In June 2001, seeds of chickpea cv. Jimbour were sown in 5 rows in a small plot (1 x 2 m) at a Sm-infested site at Kingaroy, Queensland. In September 2001, wilting of stems and leaves, stem necrosis and bleaching near the soil surface were observed on several plants. White mycelium was evident on
diseased tissue and small, black irregularly shaped sclerotia (0.5 - 2 mm) were observed on stems and in pith tissue.

Sections of diseased plant tissue were washed thoroughly and blotted dry on sterile paper. Sections (5 mm) were transferred to PDA amended with 1 percent streptomycin sulphate. Isolation plates were incubated in the dark at 23 C for 5 days. Colonies exhibiting sclerotial morphology of Sm were transferred to fresh PDA plates. Isolate (BRIP 28138) was lodged at BRIP (Queensland Department of Primary Industries herbarium).

Isolate BRIP 28138 was selected for pathogenicity testing. Five 6-week-old chickpea plants of cv. Jimbour were inoculated by placing an infected PDA block adjacent to the stem at soil level. 3 plants inoculated with agar plugs only were used as controls. The pots were incubated in a controlled environment cabinet at 100 percent humidity, 21 ± 1 C and with a 15 h light/9 h dark cycle for 7 days and then moved into a glasshouse for further observation.

Inoculated stems developed symptoms of wilt and necrosis, with white-fluffy mycelium and sclerotial formation on the surface of the stems, whereas control plants remained healthy when examined after 7 days. Sm was re-isolated from the diseased stems of 5 plants.

Stem rot and wilt of chickpea caused by Sm could pose a threat to chickpeas across a significant portion of Australian production areas in certain years, particularly where other host crops such as canola, sunflower and peanut are part of the rotation. The wide host-range coupled with the longevity of its sclerotia may mean that inoculum-reducing strategies are difficult to achieve in rotations incorporating dicotyledonous crops.

Reference:

Bretag TW and Mebalds MI (1987). Pathogenicity of fungi isolated from Cicer arietinum (chickpea) grown in north-western Victoria. Australian Journal of Experimental Agriculture 27:141-148.

[Sm occurs worldwide, primarily in cool, moist regions. In addition to chickpea, its host range includes cabbage, common bean, cucumber, lettuce, peanut, pepper, potato, spinach, sweet potato and tomato. In peanut, crop losses can exceed 80 percent. Other soil-borne pathogens that infect chickpea include Ascochyta blight, Fusarium wilt and Fusarium root rot. Disease management utilizes the use of resistant cultivars. USDA scientists are studying the soil-inhabiting fungus _Sporidesmium sclerotivorum_ which infects and kills the sclerotia of Sm and _S. sclerotiorum_. Spores of _Sporidesmium_ germinate only in the presence of susceptible host plants, and research is being directed at determining the organic compounds that trigger spore germination. -Mod.DH]