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Disease Detection and Losses

Incidence of Seedborne Ascochyta lentis in Lentil Germ Plasm. Walter J. Kaiser, Research plant pathologist, Western Regional Plant Introduction Station, U.S. Department of Agriculture, Agricultural Research Service, Washington State University, Pullman 99164; Richard M. Hannan, biological technician, Western Regional Plant Introduction Station, U.S. Department of Agriculture, Agricultural Research Service, Washington State University, Pullman 99164. Phytopathology 76:355-360. Accepted for publication 14 October 1985. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1986. DOI: 10.1094/Phyto-76-355.

A foliar blight of lentil (Lens culinaris) was observed in June 1981 in several plant introductions in cold-tolerance trials planted in the fall of 1980 at Pullman and Central Ferry, WA. Ascochyta lentis was the predominant fungus isolated from discolored, necrotic lesions on the foliage and seeds of diseased lentil. Isolates of A. lentis were pathogenic to the foliage of lentil, but not to the foliage of chickpea (Cicer arietinum) or pea (Pisum sativum). The fungus was isolated from 1.5-3.5% of the original introduced seed from three of five lentil PI accessions included in the 1980-1981 cold-tolerance trials. Infection by A. lentis of seeds harvested from these trials (increase seeds) ranged from 0.5 to 68.5% and from 10 to 42.5% at Pullman and Central Ferry, respectively. Many seeds from heavily infected accessions were shriveled and discolored, and seed quality was adversely affected. Also, seed size was significantly correlated to the level of seedborne infection. A total of 17,060 original seeds from 284 accessions from 30 countries were screened for seedborne A. lentis. The fungus was isolated from 2.0% of the seeds which represented 16% of the accessions and 16 countries. Most severe infections were found on original seeds from Australia, India, Italy, Spain, and Turkey. Other fungi pathogenic to lentil that were also isolated, but less frequently than A. lentis, included: Botrytis cinerea, Fusarium avenaceum, Macrophomina phaseolina, Phoma medicaginis var. pinodella, and Rhizoctonia solani. Incidence of seedborne A. lentis from original infected seeds (5.0-61.7%) in 20 exotic PI accessions to increase seeds grown in typical spring plantings at Pullman was 0-2.5%. Ascochyta lentis remained viable in original seeds of several accessions stored for more than 30 yr. The fungus survived over 3 yr in naturally infected lentil pods and seeds at 4-6 C or in a shelter outdoors, and for 1.5 yr on the soil surface, but it lost viability within 29 wk at a soil depth of 16 cm.