Relative resistance of newly released apple rootstocks to Phytophthora cactorum

Abstract

Carisse, O. and Khanizadeh, S. 2006. Relative resistance of newly released apple rootstocks to Phytophthora cactorum. . New rootstocks from series SJM (St-Jean-Morden) and SJP84 (ST-Jean-1984) have been evaluated for agronomic qualities since 1970 and 1975, respectively. As a result of the evaluation, seven and nine rootstocks from the SJM and SJP84 series, respectively, were selected. However, these were not evaluated for crown rot resistance. Excised shoot assay was used to evaluate resistance of 22 apple rootstocks to crown rot caused by Phytophthora cactorum (Leb. and Cohn.) Schroet. The pathogenicity of four isolates of P. cactorum to apple rootstocks was confirmed using the same excised twig assay. For both tests, relative lesion length was used as a measure of susceptibility. The analysis of variance showed that there was a significant effect of rootstocks, isolate and the interaction between rootstock and isolate. In general, apple rootstocks were more susceptible to isolate PC04-02 followed by isolates PC04-03 and PC04-01 and less susceptible to isolate PC04-04. The selection SJM189 was the least susceptible to P. cactorum and SJP84-5162 and SJM15 were the most susceptible suggesting that these rootstocks may not be suitable in orchards with favourable conditions to P. cactorum infection. Excised twigs of the SJP84-5180, SJP84-5189, SJP84-5174, O.3, SJP84-5230, O.3A, SJP84-5198, SJM167 and M.44 showed low to moderate susceptibility, whereas, rootstocks SJP84-5231, SJM150 and M.26 showed moderate susceptibility to P. cactorum. Rootstocks SJM188, SJP84-5217, MM.111, SJM127, SJP84-5218 and MM.106 showed high susceptibility to P. cactorum. The present results confirmed that none of the released or commercial rootstocks are completely resistant to P. cactorum and an integrated approach including resistance, chemical control and cultural practices is recommended to manage P. cactorum in apple orchards. De cette évaluation, sept porte-greffes de la série SJM et neuf de la série SJP84 ont été choisis. Toutefois, ces porte-greffes n'ont pas été évalués pour leur résistance à la pourriture du collet. Un test sur pousses excisées a été utilisé pour évaluer la résistance de 22 porte-greffes de pommier à la pourriture du collet causée par Phytophthora cactorum (Leb. and Cohn.) Schroet. Ce test a également été utilisé pour évaluer la pathogénécité de quatre isolats de P. cactorum. Dans les deux cas, la longueur relative des lésions a été utilisée comme mesure de la sensibilité des porte-greffes. Les résultats de l'analyse de variance ont indiqué qu'il y avait un effet significatif du porte-greffe, de l'isolat et de l'interaction porte-greffe-isolat sur la longueur des lésions. En général, les porte-greffes étaient plus sensibles à PC04-02 suivi des isolats PC04-03 et PC04-01 et moins sensibles à l'isolat PC04-04. Le porte-greffe SJM189 était le moins sensible à P. cactorum. Les porte-greffes SJP84-5162 et SJM15 étaient les plus sensibles, indiquant que ces porte-greffes ne sont probablement pas recommandables pour ...

Understanding Root Rot Disease in Agricultural Crops

“…P. cactorum is another pathogen capable of producing high yield losses in fruit trees. In Canada and certain US regions, it has been identified as the most important cause of crown rot of apple [186]. The use of rootstocks resistant to P. cactorum and other Phytophthora spp has been considered a good management practice.…”

‘SJM44’ Apple Rootstock

“…& Cohn) Schroet. than 'M.26' but less resistant than 'M.9' (Carisse and Khanizadeh, 2006) (Table 3) using the procedure used by Norelli et al (2002).…”

“…x LSD = least significant difference at the 0.05 level. Data collected from Carisse and Khanizadeh (2006), and http://www.cyberfruit.info/apple/applerootstocks/pdf/disease-susceptibility.pdf. Fig.…”

‘O3A’ Apple Rootstock

“…& Cohn) Schroet. (Carisse and Khanizadeh, 2006; http://www. cyberfruit.info/apple/apple-rootstocks/pdf/ disease-susceptibility.pdf).…”