بررسي مقاومت نسبي ده رقم كلزا به بيماري سياه با عامل Phoma lingam

EVALUATION OF RELATIVE RESISTANCE OF TEN CANOLA CULTIVARS TO PHOMA UNGAM

Canola stem canker or blackleg, caused by Phoma lingam is a disease of world-wide importance on oilseed rape. Pathogenicity of ten isolates on Hayola 401 cultivar of canola under greenhouse conditions was studied and the most virulent isolate with 17% disease severity was selected for cultivars resistance studies. The relative resistance of ten cultivars namely Hayola 401, Hayola 308, Talaye, Zarfam. Sarigol. Fornax, Modena, Okapi, Option 500 and RGS 003 to P. lingam was studied in greenhouse conditions, using randomized complete block design with three replications. Disease severity was assessed ten days after inoculation with pathogen, by measuring the chlorotic and necrotic area in leaves by means of leaf area meter apparatus. Analysis of variance indicated significant differences among the cultivars in resistance to this fungus (P<0.01). According to mean disease severity in inoculation experiments the cultivars were placed into four groups. Sarigol and Hayola 401 with disease severity of 19.35 and 17.5 percent were the most susceptible cultivars. In contrast, Fornax and Talaye with disease severity of 5.86 and 5.82 percent were the least susceptible cultivars. Other cultivars were of intermediate susceptibility. This is the first study on evaluation of relative resistance of some commonly grown canola cultivars in Iran to a virulent Iranian isolate of P. lingam.