Sources of resistance to Plasmodiophora brassicae (clubroot) pathotypes virulent on canola.

Peng, G., Falk, K.C., Gugel, R.K., Franke, C., Yu, F.Q., James, B., Strelkov, S.E., Hwang, S.F., and McGregor, L. (2014). "Sources of resistance to Plasmodiophora brassicae (clubroot) pathotypes virulent on canola.", Canadian Journal of Plant Pathology, 36(1), pp. 89-99. doi : 10.1080/07060661.2013.863805  Access to full text

Abstract

A collection of 955 Brassica accessions including B. rapa (718), B. napus (94), B. juncea (93), B. oleracea (30), B. carinata (12) and B. nigra (8) was screened against Plasmodiophora brassicaepathotype 3 (1 × 106 resting spores cc1 growth medium), the predominant strain of the pathogen on canola in western Canada. A total of 35 accessions (mostly B. rapa) showed at least 50% reduced clubroot severity relative to a susceptible control, with 15 showing complete resistance (clubroot-free). Ten resistant accessions representing Brassica A-, B- and C-genome species were tested further using a 10-fold higher pathogen inoculum dose (1 × 107 resting spores cc1 growth medium) and by testing them against the five pathotypes (2, 3, 5, 6 and 8) of P. brassicae found in Canada. One B. nigra, two B. oleracea and four B. rapa (oriental vegetable) accessions maintained a high level of resistance under the higher pathogen inoculum pressure, while one B. nigra and two B. rapa (turnip) accessions showed moderate resistance. Most of the selected clubroot-resistant accessions showed consistent resistance to each of the five P. brassicae pathotypes found in Canada, except for one B. nigra and two turnip accessions, which varied slightly against different pathotypes. Several promising sources of clubroot resistance were identified in this study that can be used to develop new canola germplasm with a diverse clubroot resistance background for potentially more durable clubroot resistance.

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