Tuber and root resistance of potato genotypes against Meloidogyne chitwoodi in the presence of Avena strigosa, related to tuber quality

Relative tuber infestation and quality of two Meloidogyne chitwoodi resistant potato genotypes, AR04-4096 and 2011M1, were compared in glasshouse experiments at initial population density (P-i) = 16 second-stage juveniles (g dry soil)-1 in the presence and absence of the bristle oat, Avena strigosa. When A. strigosa was added, Pfroot+soil (P-f = final population) on both AR04-4096 and 2011M1 increased 130x, P-ftuber increased 1.9 and 3.7x, respectively, while P-ftuber x fresh root weight (FRW)(-1) was the same. Nematode hatch from peel of AR04-4096, without A. strigosa, was delayed by 3 weeks but relative hatching rate was increased. Although the RStuber (RS = Relative Susceptibility) of both AR04-4096 and 2011M1 were lower than 1%, in the presence of A. strigosa tuber quality of 2011M1 dropped below the marketable level, while that of AR04-4096 was hardly affected. We conclude that: i) P-ftuber is influenced by root mass; ii) root quality influences nematode hatch; iii) tuber quality is not an estimator for tuber resistance, and the reverse; iv) root resistance is equal to tuber resistance.