Sources of Resistance to Spotted Alfalfa Aphid (Therioaphis Maculata. Buckton) in Medics

Screening of fifty-five lines representing ten annual species of genus Medicago alongwith five entries of common perennial lucerne (M. sativa) for resistance to spotted alfalfa aphid under field and laboratory conditions revealed significant differences amongst the entries, in respect of leaf damage score, aphid population per unit stem, survival and reproductive behaviour of parent aphids and the off springs produced over a period of five days. M. rugosa and M. scutellata exhibited maximum antibiosis followed by M. littoralis and others. Interspecific hybrids showing good fertility and seed set have been obtained involving species, M. truncatula xM. littoralis, M. intertexta x M. ciliaris at diploid level while crosses at tetraploid and octoploid level amongst the species, M. rugosa, M. scutellata and M. sativa were not successful indicating a remote possibility of resistance gene transfer from the former species.