Pathotypes and heterogeneity of Italian populations of Globodera rostochiensis and G. pallida

Abstract

Investigations were undertaken on the pathotypes and heterogeneity of Italian populations of the potato cyst nematodes, Globodera rostochiensis and G. pallida. All nematode populations were collected from the field and reproduced on a susceptible potato cultivar. To identify pathotypes, the differential Solanum spp. clones were grown in pots containing 1000 cm3 of soil infested with 5 eggs/cm3 of either nematode species, in a glasshouse at 20 ± 2 °C. Seventy days after potato emergence, the nematode population density in each pot was determined and the pathotype identified according to nematode reproduction rate. There were sixteen populations of G. rostochiensis and ten of G. pallida. All populations of G. rostochiensis reproduced more or less exclusively on both Solanum tuberosum cv. Spunta (susceptible) and cv. Saturna (possessing the H1resistant gene), so were considered pathotype Ro2. Of the populations of G. pallida, six were pathotype Pa3 as they reproduced on all of the differential clones, three did not reproduce on the clone (Vtn)262.33.3 of S. vernei and were classified as Pa2, and one population could not be clearly classified. The heterogeneity of seven populations of G. rostochiensis was investigated by examining the reproduction of ten single cyst derived populations for each of the original populations on potato cvs Spunta and Saturna, and on clone KTT/60.21.19 of S. kurtzianum. All of the single cyst populations derived from five of the parent populations were identical to their parent populations as they reproduced only on the first two cultivars, while one from a population from Puglia and five from a population from Calabria also reproduced on clone KTT/60.21.19.