Root disease caused by Armillaria mexicana and/or A. mellea is associated with tree mortality in peach orchards within their primary production zone of the Mexican sub-tropics.
Scientists of University of Guanajuato have evaluated the resistance and the susceptibility of three Prunus rootstocks to infection by A. mexicana (isolate MEX85) and A. mellea (isolate MEX100) under greenhouse and in field conditions.
As regards greenhouse phase, A. mexicana and A. mellea were independently inoculated on 14 trees (10-month old) of each rootstock in polycarbonate containers: P. persica × P. davidiana Nemaguard, P. persica landrace Criollos of La Goleta genotypes, and P. salicina Japanese plum Mondragon. Four non-inoculated trees of each rootstock were maintained as controls, and variables related to tree growth and disease incidence were monitored for all trees.
At 22 months post-inoculation with A. mexicana in the greenhouse, Mondragon showed the lowest (2.5%) incidence of infected roots (IRI), while Criollos of La Goleta and Nemaguard rootstocks showed the highest (21.6 and 24.6%, respectively) IRI. With greenhouse-grown plants inoculated with A. mexicana, the dry weights and volumes of roots, and dry weights of entire plants were greater (2.2–4.8 times higher) for Criollos of La Goleta; however, abundant mycelia were observed within the root collar and lateral roots of this rootstock. In contrast, A. mellea inoculation resulted in relatively low (17.5%) incidence of root infection. Results show that A. mexicana is more virulent than A. mellea.
As regards field phase, in a commercial orchard with high (35.3% symptomatic and dead trees) incidence of A. mexicana, 21 plants of Mondragon (propagated via stem cuttings), Criollos of La Goleta, and P. mume Japanese apricot were inoculated with the A. mexicana isolate. As in the greenhouse also in the field, Mondragon showed the lowest susceptibility to A. mexicana.
The study shows that Mexican landrace of Prunus persica rootstocks are susceptible to Armillaria mexicana, while Mondragon is identified as a rootstock with resistance to the pathogen, thus the results suggest to use Mondragon rootstock for an efficient management strategy.
Source: Ruben Damian Elias-Roman, Guillermo Calderon-Zavala, Rafael Guzman-Mendoza, Moises Roberto Vallejo-Perez, Ned B. Klopfenstein, Jose Antonio Mora-Aguilera, ‘Mondragon: A clonal plum rootstock to enhance management of Armillaria root disease in peach orchards of Mexico', 2019, Crop Protection, Vol. 121, pag- 89-95.
