Influence of susceptible and resistant potato cultivars on the population of the potato cyst nematode Globodera rostochiensis Ro1 and on potato yields in a highly infested field in Australia

The potato cyst nematode, Globodera rostochiensis, is a quarantine pest in Australia affecting a relatively small number of properties in three different production areas in the State of Victoria. The effects of susceptible (Trent, Sebago and Coliban) and H1-resistant potato cultivars (Atlantic, Crop 13 and Nicola) on nematode populations were compared in two trials in a naturally infested field in the 2008/09 season (Trial 1) and in the 2009/10 season (Trial 2). The latter included a bare fallow treatment. The reproduction factor Pf/Pi (final compared with initial nematode population) was used to determine treatment effects. Initial population density was very high, averaging 111 and 119 eggs g⁻¹ soil in Trial 1 and 2, respectively. The Pf/Pi of population density (eggs g⁻¹ soil) was greater after growing susceptible cultivars (average 1.74 and 2.92 in Trials 1 and 2, respectively) than after growing resistant cultivars (average 0.72 and 0.61 in Trials 1 and 2, respectively), or after a bare fallow (1.09) in Trial 2. This correlated with higher Pf/Pi values of cysts 500 g⁻¹ soil and eggs cyst⁻¹ for susceptible cultivars than for resistant cultivars. Average Pf/Pi values greater than one in both trials are consistent with more cysts and an increased population density after growing susceptible cultivars. There was a trend of population decline, that is, Pf/Pi < 1, after growing resistant cultivars (average Pf/Pi values of eggs cyst⁻¹ of 0.77 and 0.35 and of eggs g⁻¹ soil of 0.72 and 0.61, for Trials 1 and 2, respectively). However, Trial 2 showed that these Pf/Pi values were not significantly less than those for the bare fallow (0.68 eggs cyst⁻¹ and 1.09 eggs g⁻¹ soil). The susceptible cultivars Trent and Sebago produced lower yields than the resistant cultivars in both trials. In contrast, the susceptible Coliban yielded as well as the resistant cultivars, suggesting a high level of tolerance of this cultivar to infestation by the nematode. The resistant cultivar Crop 13 produced 34% and 36% greater total yields in Trials 1 and 2, respectively, than the once popular, but susceptible cultivar Sebago. This is the first report of the effects of potato cultivars on a population of the potato cyst nematode in an Australian field. The use of H1-resistant potato cultivars can feasibly reduce populations of G. rostochiensis Ro1 on infested land and reduce PCN risk on land regulated as “linked” with infested land.