A routine test for the relative susceptibility of potato genotypes with resistance to Meloidogyne chitwoodi

The population dynamics of Meloidogyne chitwoodi on eight potato genotypes was compared to the susceptible cv. Desiree in four glasshouse experiments. The initial nematode densities consisted of log series 2x , with −4 < x < 8. Seinhorst’s logistic model was fitted to the final population densities to estimate the parameters maximum multiplication rate (a), maximum population density (M) and the ratios RSa, RSM and M/a. Average RSa and RSM of the seven resistant genotypes were smaller than 0.29%. The M/a ratios on six resistant genotypes and cv. Desiree were the same, 1.3, indicating Pi independence of RS. One genotype stood out with M/a = 8.6, whereby RSa < RSM. Both RS and M/a were unaffected by pot size or experimental conditions. Screening protocols at Pi = 24 second-stage juveniles (g dry soil)−1 in 2 or 3 kg pots were evaluated for distinctiveness between the two genotype groups. Based on the results, an optimal protocol for a routine resistance test is proposed