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June 4, 2003
Source: Amer Phytopathol Soc, DISEASE NOTES [edited]


First Report of Ascochyta Blight of Chickpea Caused by _Ascochyta rabiei_ in Chile

R. Galdames and M. Mera, INIA-Carillanca, Temuco, Chile. Plant Dis. 87:603, 2003; published on-line as D-2003-0324-01N, 2003. Accepted for publication 6 Mar 2003.

Chickpea (_Cicer arietinum_ L.) plants with foliar and stem lesions fitting the description of Ascochyta blight [Ab] were observed in October 2002 in 4 chickpea crops located in the La Araucania Region
(38 deg S, 72 deg 24 min W) of southern Chile. Large, circular foliar and stem lesions containing pycnidia arranged in concentric circles were observed (1). Stem breakage also was observed.

Isolates were obtained from mature pycnidia developed on stems by culturing a spore suspension on PDA and chickpea seed meal agar. A pathogenicity test was performed by inoculating 25 plants with a
suspension of 1.2 million conidia/ml and incubating at 22 deg C and 75 percent relative humidity. Foliar and stem lesions were observed 5 and 7 days after inoculation, respectively. 4 check plants sprayed with sterile distilled water showed no symptoms.

Fungal colonies obtained from inoculated plants showed the same cultural characteristics as the original isolates. Cultural morphology was consistent with the description of _Ascochyta rabiei_ (Pass.) Labrousse (teleomorph _Didymella rabiei_ (Kovacheski) v. Arx (= _Mycosphaerella rabiei_ Kovacheski)) (3). Conidia produced on PDA were predominantly aseptate, 3.90 to 5.85 micrometers wide, and 9.75 to 11.7 micrometers long.

Affected plants (cv. Kaniva) originated from seed introduced at commercial volumes (69 tons) from Victoria, Australia in August 2002. _A. rabiei_ can be disseminated via infected seed (1). Ab symptoms have been observed in small patches in several crops near Temuco, the capital of La Araucania Region.

Chickpea production is currently relatively small in southern Chile, but plans to promote its cultivation may be hindered by this outbreak. The only other country to report Ab of chickpea in South America was Bolivia (2).

References:
(1) W. J. Kaiser. Epidemiology of Ascochyta rabiei. Pages 117-134 in: Disease-resistance Breeding in Chickpea. K. B. Singh and M. C. Saxena, eds. ICARDA, Aleppo, Syria, 1992.
(2) W. J. Kaiser et al. Plant Dis. 84:102, 2000.
(3) E. Punithalingam and P. Holliday. No. 337 in: CMI Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1972.

[Of the diseases affecting chickpea, Ab is regarded as the most damaging worldwide. Only chickpea is susceptible to Ab, and all parts of the plant can be infected. Yield reductions of up to 50 percent are not unusual. Management of Ab includes crop rotation using non-host crops, not planting chickpea for at least 3 years on the same site, and avoiding cropping close to previously blighted fields.

Information obtained from Fred Muehlbauer and Walter Kaiser of USDA at Pullman, WA, indicated that cv. Sierra was tested in Bolivia and demonstrated some resistance to Ab. Unfortunately, resistance to Ab
is short-term, and does not cover the entire crop season. Application of chemical fungicides can be beneficial.

A relevant URL: <www.nps.ars.usda.gov/menu.htm?newsid=2151> - Mod.DH]