efficacy of native strains of trichoderma harzianum in biocontrol of pistachio gummosis

to identify trichoderma isolates for potential biocontrol of crown and root rot inpistachio, 100 samples of soil taken from rhizosphere, fertilizer channels and from soil surfacewere collected from kerman, yazd, khorasane razavi and semnan provinces during 2009-2011. overall, 32 isolates of trichoderma harzianum were obtained mostly from rhizospheresoil using either general or special environmental surroundings. the antagonistic potential ofthe isolates against p. melonis was screened using the dual culture technique. a total of 11isolates were employed for further assessment of their capability to inhibit p. melonis, invarious assays under in vitro and as well in vivo conditions. overall, the results indicated thatthe incidecne of interactions through different mechanisms reduced mycelialy growth of p.melonis to different degrees, ranging from 38.1 to 63.6%, 25.4 to 58.7%, 50 to 89.6% and 44.7to 71.77% in the simultaneous vs non-simultaneous dual cultures, and volatile vs non-volatilecompounds, respectively. in greenhouse experiments, and in mixed inoculations withtrichoderma harzianum strains and p. melonis it was observed that, root length and plantheight increased respectively from 1.5 to 2.7 and from 1.4 to 2.1 times of inoculation withpathogen alone, as well as 1 to1.9 of root length and 1 to 1.6 times the plant height ascompared with non-inoculated control plants. incidence of t. harzianum isolates before,simultaneous with, and following pathogen inoculations (in pots) significantly influenced themortality of seedlings with the respective ranges of 0 to 31%, 0 to 56%, and 12.5 to 75%. thisis the first report on the introduction of t. harzianum isolates to pistachio orchards, along withtheir interactions with gummosis (crown and root rot) causal agents.