Reaction of potato genotypes to the root-knot nematode Meloidogyne spp. in naturally infested fields

The research studied potato genotypes for the reaction to Meloidogyne spp. Two experiments were carried out in the field, the first with 12 potato clones and one cultivar in a field naturally infested with Meloidogyne incognita race 1 and the second with 12 clones and two potato cultivars in a field infested with Meloidogyne javanica. Randomized complete block was the experimental design with 4 and 6 replications, respectively. At 111 days after planting, soil was collected, plants were harvested and evaluations were carried out for estimating final population of nematodes in the soil, total number of juveniles extracted from external tuber surface (tuber skin), Reproduction Factor (RF), tuber mass, number of tubers per plant and tuber average mass. Data were submitted to analysis of variance and grouping of means by Scott-Knott. It was verified a predominance of variation of environmental order in relation to the genetics for the characters that measure the resistance to the species of nematodes, and lower experimental precision for yield characters in the first experiment and greater for the second one. For the first experiment, clones F161-02-07, F131-26-08 and F76-01-07 were classified as resistant. Clones F102-22-07, F131-06-08, F156-19-06, F161-02-07, F183-08-01, F50-01-08 and F76-01-07 showed RF higher than 1. Nevertheless, they were included in the same group as F161-02-07, F131-26-08 and F76-01-07 by the grouping analysis. Clones F22-01-08, F102-22-07, F131-06-08, F131-26-08, F161-02-07, F183-01-08 and F97-07-08 presented the best results for traits related to tuber yield. In the second experiment, all clones and all cultivars were susceptible, with an increase in nematode populations, and although it was not possible to differentiate the genotypes evaluated for RF, there was a great variation in the response of the genotypes. Clones C2519-1206, F102-22-07, F37-01-08, F208-01-06, F31-05-08 and F32-02-06 presented the best results for traits related to tuber yield.