Commercial Formulates of Trichoderma Induce Systemic Plant Resistance to Meloidogyne incognita in Tomato and the Effect Is Additive to That of the Mi-1.2 Resistance Gene

Abstract

<i>Meloidogyne</i> is the most damaging plant parasitic nematode genus affecting vegetable crops worldwide. The induction of plant defense mechanisms against <i>Meloidogyne</i> in tomato by some <i>Trichoderma</i> spp. strains has been proven in pot experiments, but there is no information for tomato bearing the <i>Mi-1.2</i> resistance gene or for other important fruiting vegetable crops. Moreover, <i>Trichoderma</i> is mostly applied for managing fungal plant pathogens, but there is little information on its effect on nematode-antagonistic fungi naturally occurring in soils. Thus, several experiments were conducted to determine (i) the ability of two commercial formulates of <i>Trichoderma asperellum</i> (T34) and <i>Trichoderma harzianum</i> (T22) to induce systemic resistance in tomato and cucumber against an avirulent <i>Meloidogyne incognita</i> population in split-root experiments; (ii) the effect of combining T34 with tomato carrying the <i>Mi-1.2</i> resistance gene to an avirulent <i>M. incognita</i> population in sterilized soil; and (iii) the effect of combining T34 with tomato carrying the <i>Mi-1.2</i> resistance gene to a virulent <i>M. incognita</i> population in two suppressive soils in which <i>Pochonia chlamydosporia</i> is naturally present, and the effect of T34 on the level of <i>P. chlamydosporia</i> egg parasitism. Both <i>Trichoderma</i> formulates induced resistance to <i>M. incognita</i> in tomato but not in cucumber. In tomato, the number of egg masses and eggs per plant were reduced by 71 and 54% by T34, respectively. T22 reduced 48% of the number of eggs per plant but not the number of egg masses. T34 reduced the number of eggs per plant of the virulent <i>M. incognita</i> population in both resistant and susceptible tomato cultivars irrespective of the suppressive soil, and its effect was additive with the <i>Mi-1.2</i> resistance gene. The percentage of fungal egg parasitism by <i>P. chlamydosporia</i> was not affected by the isolate T34 of <i>T. asperellum</i>.