Antibiosis and antixenosis of chrysanthemum cultivars to the aphid <i>Aphis gossypii</i>

Abstract

Abstract An assessment was made of the antibiotic and antixenotic resistance of three cultivars of autumn flowering chrysanthemum (derived from Dendranthema morifolium (Ramat) Tzvelev and D. indicum (L.) Desmoulins) to the aphid Aphis gossypii Glover. Antibiosis was also assessed at the top, middle and lower leaves of the plant. The three cultivars showed a range of resistance with Hero being the most susceptible, Surfine the most resistant and Purple Anne intermediate. There was a trend for antibiosis to improve with position down the plant, however there were cultivar by position interactions. Antixenosis was assessed at two levels, the first being under conditions where the aphid had complete access to the plant in caged choice assays and the second being under conditions where the aphid only had host odour to assess under olfactometer choice conditions. Preferences under the caged choice conditions found Hero to be the most preferred cultivar while there was no preference shown between Purple Anne and Surfine. However, olfactometer assessments showed Hero to be the least preferred of the three cultivars and, again, no preferences could be found between Purple Anne and Surfine.