Resistance to aphid, Therioaphis Maculata (Buckton) in lucerne

A field experiment was carried out at Main Forage Research Station, Anand Agricultural University Anand, during rabi, 2009–10 to screen 27 varieties/genotypes of lucerne for resistance against aphid, Therioaphis maculata (Buckton). Each variety/genotype was sown in Randomized Block Design with three replications in plot size of 4×3m. Ten tillers were selected randomly from each and observations were recorded early in the morning at weekly intervals. ARP-3-1, ARP-2-1 and ALP-3-4 were found moderately resistant. Studies to find out the degree of association between the aphid population with morphological and biochemical characters revealed that these were not significant except for plant height, number of tillers per meter row length and number of leaves per tiller in the first cut. Fifteen days after second cut, it was not significant except for plant height and number of leaves per tiller. Among biochemical constituents amount of chlorophyll ‘a’, crude fiber and calcium showed highly significant negative correlation; chlorophyll ‘b’, total chlorophyll, nitrogen and sugar content were highly significantly positively correlated with incidence of aphid population; phosphorus, crude protein and magnesium were significantly positively correlated; and potassium, dry matter and ash content were significantly negatively correlated with incidence of T. maculata.