Field resistance in three bread wheat lines to the Russian wheat aphid, Diuraphis noxia (Hemiptera: Aphididae)

Abstract

The levels of resistance in three bread wheat lines, SA 2199, SA 1684 and SA 463, to field infestations of Diuraphis noxia were studied in 1986 and 1988 in comparison with susceptible lines. Counts were made of the number of infested plants, number of infested shoots and number of aphids per infested shoot. In 1988, nymphal production of individual aphids in clip cages was also determined. Lower infestation levels were measured on the resistant lines, with the greatest difference found in the number of aphids per infested shoot, which varied from 2.8 on a resistant line to 141.8 on a susceptible cultivar in 1986. In 1988, numbers varied from as low as 0.9 on a resistant line to as high as 79.1 on a susceptible cultivar. Significantly fewer nymphs per adult per day were produced in clip cages on the resistant lines than on the susceptible cultivars. Feeding symptoms on the leaves of resistant plants were restricted to chlorotic spots and no leaf rolling occurred, as in the case of susceptible plants.