Selection against Pratylenchus vulnus populations attacking Prunus rootstocks

Twenty-nine commercial and experimental Prunus rootstocks, most with incorporated root-knot nematode [Meloidogyne javanica (Traub.) Chitwood] resistance, were evaluated against mixtures comprising nine populations of the root-lesion nematode Pratylenchus vulnus Alien and Jensen. Nearly all tested materials were susceptible. Five cultivars with high resistant levels were further challenged with seven P. vulnus populations individually. 'Redglow' (Prunus salicina Lindl. x P. munsoniana Wight and Hedrick) was the only rootstock that showed broad resistance to all populations. The rootstocks 'Torinel' (P. domestica L.), AC-595 (P. domestica x P. insititia L.),'Marianna 4001' (P. cerasifera Ehr. x P. munsoniana), and 'Felinem' [P. dulcis (Mill.) D. A. Webb x P. persica (L.) Batsch] showed resistance to one or a few P. vulnus populations. Several supposedly resistant sources proved to be susceptible. Tests of crosses made between parents of diverse genetic background with partial resistance to P. vulnus indicate that a descendant with potential P. vulnus resistance is difficult to obtain. Pathogenic diversity among P. vulnus populations appears to be high.