November 19, 2003
From: American Phytopathological Society, Plant Disease Notes [edited]

First report of pink seed of lentil and chickpea caused by Erwinia rhapontici in Canada
H. C. Huang, R. S. Erickson, and L. J. Yanke, Agriculture and Agri-Food Canada Research Centre, P.O. Box 3000, Lethbridge, AB, T1J 4B1, Canada; T. F. Hsieh, Department of Plant Pathology, Taiwan Agricultural Research Institute, Wufeng 413, Taichung, Taiwan; and R. A. A. Morrall, Department of Biology, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada. LRC Contribution No. 38703047. Plant Dis. 87:1398, 2003; published on-line as D-2003-0911-01N, 2003. Accepted for publication 15 Aug 2003.

A new disease of lentil (_Lens culinaris_ Medik.) and chickpea (_Cicer arietinum_ L.) caused by _Erwinia rhapontici_ (Millard) Burkh. was found in seed samples from commercial fields in Saskatchewan, Canada in 2002. Infected seeds had a pink or pinkish-brown discoloration of the seed coat. Isolation from surface-sterilized pink seeds resulted in bacterial cultures that produced a water-soluble pink pigment on potato dextrose agar (PDA).

Four isolates from different lentil crops, LRC 8265, LRC 8310, LRC 8309, and LRC 8313 and one isolate from a chickpea crop, LRC 8266, were tested as previously described (2). Results of the tests were identical to those for pink bean isolates of _E. rhapontici_ (2) with the following minor exceptions: all were negative for Voges-Proskauer; LRC 8266 was positive for tagatose; LRC 8266, LRC 8309, and LRC 8313 were negative for lactose; and LRC 8266 and LRC 8309 were positive for 5-keto gluconate.

For pathogenicity tests, each isolate was inoculated into 30 pods from 6 lentil plants (cv. Laird), 30 pods from 6 desi chickpea plants (cv. Myles), and 30 pods from 6 kabuli chickpea plants (cv. Sanford) by the method described for pink seed of pea (1) and bean (2). Each pod was inoculated with 0.1 ml (0.2 ml for kabuli chickpeas) of bacterial suspension, approximately 100 million CFU/ml, by injection through the mid-rib at the basal end. The same number of uninoculated and water-inoculated pods served as controls. Plants were kept in the greenhouse (20 +/- 5 deg C) for 4 weeks, after which isolations of the pathogen were performed as described above.

In duplicate experiments, all the isolates caused pink lesions on pods and seeds of lentil, desi chickpea, and kabuli chickpea. The frequency of infected seeds among the 5 isolates (4 lentil and one chickpea) ranged from 50 to 100 percent on lentil, 73 to 100 percent on desi chickpea, and 43 to 100 percent on kabuli chickpea. _E. rhapontici_ was reisolated from seeds with lesions but not from asymptomatic seeds.

The study demonstrates that in addition to pea (1) and common bean (2), _E. rhapontici_ is also the causal agent of pink seed of lentil and chickpea. The observation that lentil isolates can infect chickpea and vice versa suggests that host specificity may be lacking in _E. rhapontici_.

To our knowledge, this is the first record of _E. rhapontici_ on lentil and chickpea.

References:
(1) H. C. Huang et al. Can. J. Plant Pathol. 12:445, 1990.
(2) H. C. Huang et al. Plant Dis. 86:921, 2002.