CLONAL VARIABILITY IN THE RESPONSE OF SITOBION-AVENAE (HOMOPTERA, APHIDIDAE) TO RESISTANT AND SUSCEPTIBLE WHEAT

The development and reproduction of 60 clones of Sitobion avenae (Fabr icius), collected in the Rennes Basin, were compared on a resistant Tr iticum monococcum (Linnaeus) line (Tm44) and a susceptible Triticum ae stivum (Linnaeus) cultivar (Arminda). All clones had lower larval surv ival and mean fecundity when reared on Tm44 in comparison with Arminda . They all performed equally well on Arminda whereas there was a marke d and continuously distributed variation in performance parameters amo ng clones maintained on Tm44. The plant species, from which clones ori ginated, significantly affected aphid performances on resistant Tm44. A more detailed experiment was carried out with four clones, shown to differ in their level of fitness on Tm44. Their performances were comp ared on resistant (Tm44 and Tm46) and susceptible (Tm47 and Arminda) w heat genotypes. On the basis of larval development time and intrinsic rate of natural increase (r(m)), two types of response were distinguis hed among the four clones: clones Sal and Sa39 appeared to be less aff ected by Tm44 and Tm46 resistance than Sar2 and Sa48. Moreover, Tm46 w as much less resistant to clone Sal than was Tm44. These results are d iscussed in relation to the origins of the variation in performance of S. avenae on resistant wheat, and their implications in plant breedin g for resistance to S. avenae.