The feeding nonpreference of adults of Diabrotica speciosa (Germar) for the Achat, Baronesa, Monalisa, N 140-201 and NYL 235-4 potato genotypes was evaluated. Free choice and no choice tests were accomplished, in laboratories and greenhouse conditions, in Jaboticabal, SP, Brazil. In two tests, leaflets disks of plants 40 days-old (sowed in pots) were used. In another six tests, with the same genotypes (except N 140-201), the disks were collected from field grown plants with 30, 50 and 70 d.a.p. In the Petri dishes (replications or blocks), adults of D. speciosa were released in the rate of two/disk; the consumption was evaluated after 24 hours. Two other no choice tests were run in cages, on plants with 15 and 45 d.a.p., where three and 10 adults/plant were released respectively; the leaf area consumption was evaluated four and five days later. The NYL 235-4 genotype was the least consumed (1.08 to 1.12 mg dry weight) in free choice and no choice laboratory tests (plants sowed in pots). With field material (free choice and no choice tests), NYL 235-4 (26.2 and 66.1 mg of fresh weight) and Baronesa (30.2 and 57.9 mg of fresh weight) were the least consumed. In the cage tests (no choice) the lowest consumption was also verified in NYL 235-4 (3.35 cm² and 16.70 cm²/plant). Those results show that feeding nonpreference is the resistance mechanism of the NYL 235-4 potato genotype to the adults of D. speciosa.
Insecta; host plant resistance; antixenosis
