Effects of Six Pratylenchus vulnus Isolates on the Growth of Peach-Almond Hybrid and Apple Rootstocks

Abstract

The effects of six geographic isolates of Pratylenchus vulnus on the growth of GF-677 peach-almond hybrid and M-26 apple rootstocks were determined under greenhouse conditions. Plantlets were obtained from micropropagated plant material, and nematode isolates were reared in monoxenic cultures. All isolates suppressed growth on GF-677 compared with the uninfected controls. Isolate PvRO-S from Spain affected top weight of GF-677 more adversely than PvAT-F from France. Final population densities (Pf) of all P. vulnus on GF-677 were greater than 14.7 times the initial densities (Pi). They increased 61.5-fold on plants infected by PvWA-U from the United States. PvWA-U-, PvAT-F, and geographic undetermined PvU-UK isolates did not affect the growth of M-26 apple rootstock compared with PvAP-S, PvRO-S (both from Spain), and PvWA-A from Argentina isolates, which severely suppressed shoot growth of this rootstock. On M-26, Pf of the more parasitically fit isolates PvWA-A, PvAP-S, and PvRO-S were greater than those of nondamaging PvWA-U, PvAT-F, and PvU-UK isolates (>41.4 vs. <14.7 times the Pi). PvWA-U and PvAT-F reproduced more on GF-677 than on M-26 (>28.6 vs. <6.5 times the Pi). Isolate PvRO-S reproduced well and was quite destructive on both rootstocks. Results confirm the existence of strains with different damage potentials among geographically separated populations of P. vulnus