In vitro co-culture system for Prunus spp. and Armillaria mellea in phenolic foam rooting matric

Abstract

AbstractArmillaria and Desarmillaria spp. are causal agents of a devastating root-borne disease of peach. Breeding resistant rootstock requires a reliable screening tool. An in vitro co-culture screen designed for almond was modified by replacing agar-gelled medium with a more aerated phenolic foam and combining resistant and susceptible rootstocks (i.e., common garden experiment) and minimizes variation in inoculum pressure or rooting substrate among replicate vessels. Eight Prunus rootstocks tested (peach, plum, peach × plum, and choke cherry) were rooted and had no decline in health. Susceptible peach rootstock, ‘GF 305’, was cultured for 15 wk in phenolic foam in the same vessel with a resistant peach × plum hybrid, ‘MP-29’, inoculated with Armillaria mellea at week 5, that led to more severe shoot symptoms in the former after an additional 8 wk. This method accommodated peach genotypes that were difficult to root in agar medium. The difference during a uniform challenge with the A. mellea fungus recapitulates resistant/susceptible reactions. The phenolic foam-based co-culture method will work on many Prunus spp. of potential use in rootstock breeding.