Evaluation of components of resistance to powdery mildew in field pea

Field trials were conducted to evaluate 12 field pea (Pisum sativum L.) cultivars and lines (AC Melfort, AC Tamor, Highlight, Tara, 267-PS210713, 89-2910, JI100, JI1543, JI95, JI96, PI273605, PI311112) for resistance to disease progression and components of resistance to powdery mildew (Erysiphe pisi DC.), in comparison to the susceptible check cultivar Radley in 1998 and 1999. The disease progression was measured as area under the disease progress curve (AUDPC) and the components of resistance were leaf area with symptoms (LAS), lesion diameter (LD), lesion numbers (LN), and sporulation (SP). All 12 lines had significantly lower AUDPC, LAS, LN, and SP than the susceptible check, but only five (AC Tamor, Tara, 267-PS210713, 89-2910, JI1543) showed a smaller LD. A greater range of variability was observed for AUDPC, LAS, and LN than for SP among the 12 lines, suggesting that AUDPC, LAS, and LN are more useful for measuring varietal resistance. Since AUDPC, LAS, and LN were highly correlated (P < 0.01), only one component would be required in screening pea lines for powdery mildew resistance. Key words: Powdery mildew, Erysiphe pisi, field pea, Pisum sativum, resistance