STOMATAL DENSITY AND CHLOROPHYLL CONCENTRATION AS AN INDICATOR OF POWDERY MILDEW RESISTANCE IN PEA (Pisum sativum L.)

Powdery mildew significantly hampers pea yield and deteriorate its quality as well. The resistance breakdown remained the main reason for failure in each attempt to incorporate powdery mildew resistance in well adapted pea cultivars. A precise selection of powdery mildew resistant source is the key to develop high yielding and stable powdery mildew resistant cultivars. Field screening alone is not an efficient method for making selection for powdery mildew resistance. Different physiological parameters viz., the concentration of total chlorophyll, chlorophyll b, chlorophyll a: chlorophyll b and the number of stomata were found to be in a tight positive correlation with disease severity while, the concentration of chlorophyll a had negative correlation. The differential behaviour of these traits in powdery mildew susceptible and resistant genotypes has suggested their use as reliable criteria for screening against powdery mildew. A 1-5 scale has been devised for screening against powdery mildew in pea; where score 1 is for highly resistant and 5 for highly susceptible genotype. The suggested scale is reliable and reproducible in making selections for powdery mildew resistance.