Resistance and tolerance of ten carrot cultivars to the hawthorn-carrot aphid, Dysaphis crataegi Kalt., in Poland

Damage caused to cultivated carrots by the hawthorn-carrot aphid, Dysaphis crataegi Kalt. (Hemiptera: Aphididae) is one of the factors limiting carrot production in Poland. Planting resistant and tolerant cultivars could reduce yield losses due to the damage caused by this pest. This study was conducted to evaluate the resistance and/or tolerance of 10 carrot genotypes to hawthorn-carrot aphid. Their field resistance was determined under field conditions based on five indicators, namely, mean number of alates (migrants) per plant and mean percentage of plants colonized by them, mean seasonal number of aphids per plant, mean number of aphids per plant and mean percentage of infested plants at peak abundance. Antibiosis experiments were conducted under laboratory conditions and pre-reproductive, reproductive time, fertility, and demographic parameters, represented by the net reproduction rate (R(o)), intrinsic rate of increase (r(m)) and mean generation time (T), were calculated. Five cultivars, Afro F(1), Nipomo F(1), Samba F(1), White Satin F(1), and Yellowstone showed field resistance. Antibiosis experiments revealed significant differences among the carrot cultivars in the length of the reproductive period, female fecundity in the time equal to the pre-reproduction time, and total progeny of hawthorn-carrot aphid. The intrinsic rate of natural increase (r(m)) for apterous aphids varied significantly, ranging between 0.181 (Nipomo F(1)) and 0.343 females/female/day (White Satin F(1)). Additionally, the estimated net reproductive rate (R(0)) was the lowest on Nipomo F(1), and this genotype was determined to be resistant. Our results suggest that a very high density of trichomes on the leaf petioles (71.94 trichomes/cm(2)) could adversely affect the feeding, bionomy, and demographic parameters of hawthorn-carrot aphid on the cultivar Nipomo F(1). In addition, Napa F(1) and Kongo F(1) demonstrated high tolerance. Considering all the results collectively, four genotypes, Afro F(1), Kongo F(1), Napa F(1) and Nipomo F(1), were relatively resistant/tolerant to the hawthorn-carrot aphid.