Cultivar Contributes to the Beneficial Effects of Bacillus subtilis PTA-271 and Trichoderma atroviride SC1 to Protect Grapevine Against Neofusicoccum parvum

Abstract

Grapevine trunk diseases (GTDs) are a big threat for global viticulture. Without effective chemicals, biocontrol strategies are developed as alternatives to better cope with environmental concerns. A combination of biological control agents (BCAs) could even improve sustainable disease management through complementary ways of protection. In this study, we evaluated the combination of Bacillus subtilis (Bs) PTA-271 and Trichoderma atroviride (Ta) SC1 for the protection of Chardonnay and Tempranillo rootlings against Neofusicoccum parvum Bt67, an aggressive pathogen associated to Botryosphaeria dieback (BD). Indirect benefits offered by each BCA and their combination were then characterized in planta, as well as their direct benefits in vitro. Results provide evidence that (1) the cultivar contributes to the beneficial effects of Bs PTA-271 and Ta SC1 against N. parvum, and that (2) the in vitro BCA mutual antagonism switches to the strongest fungistatic effect toward Np-Bt67 in a three-way confrontation test. We also report for the first time the beneficial potential of a combination of BCA against Np-Bt67 especially in Tempranillo. Our findings highlight a common feature for both cultivars: salicylic acid (SA)-dependent defenses were strongly decreased in plants protected by the BCA, in contrast with symptomatic ones. We thus suggest that (1) the high basal expression of SA-dependent defenses in Tempranillo explains its highest susceptibility to N. parvum, and that (2) the cultivar-specific responses to the beneficial Bs PTA-271 and Ta SC1 remain to be further investigated.

Combining an HA + Cu (II) Site-Targeted Copper-Based Product with a Pruning Wound Protection Program to Prevent Infection with Lasiodiplodia spp. in Grapevine

“…has also been highlighted by Mutawila et al [52], probably related to the plant defense responses that differ between cultivars. These different defense responses to T. atroviride have been recently reported by Leal et al [62], where the authors observed that T. atroviride may act as a priming stimulus for Tempranillo plantlets, while no stimulus could be verified for Chardonnay. This is in agreement with our PCA analysis which showed a negative correlation among treatments with T. atroviride (Esquive), likely due to a difference of efficacy amongst cultivars, which reinforces the importance of the cultivar in wound colonization by Trichoderma spp.…”

Diversity of Neofusicoccum parvum for the Production of the Phytotoxic Metabolites (-)-Terremutin and (R)-Mellein

“…Np-Bt67 induced severe apoplectic form of Botryosphaeria dieback and strong disease symptoms characterized by (i) large cankers, (ii) dead branches, and (iii) stem necrosis as already reported for this particular N. parvum isolate [ 15 , 18 ]. Np-B and its mutant NpB-UV9 were equally pathogenic, but less pathogenic to grapevine than Np-Bt67 (no dead branches, no apoplectic foliar symptoms, reduced stem necrosis, reduced cankers).…”

“…This up-regulation could contribute to (-)-terremutin detoxification. Now considering the phenylpropanoid pathway and derivatives, the fact that Botryosphaeriaceae are known to metabolize grapevine phytoalexins [ 19 ] suggests that the weak up-regulation of PAL and STS could only slightly benefit to the pathogen metabolism [ 15 ]. Phytoalexin production could also increase consecutively to a CHI downregulation, as observed in plantlets treated with (-)-terremutin and in infected cuttings.…”

“…Controls were inoculated with PDA plugs without mycelium, and then, cuttings were maintained in the same culture chamber conditions. Symptoms of Botryosphaeria dieback were evaluated 4 months post-inoculation by measuring the canker area, the length of necrosis on green shoots, and the percentage of dead branches per treatment as described by Laveau et al [ 50 ], Espinosa et al [ 51 ], Trotel-Aziz et al [ 18 ] and Leal et al [ 15 ].…”

“…Severe infection, namely apoplexy, is due to increased internal longitudinal necrotic lesions leading to the occurrence of typical foliar symptoms with discolorations and finally to a full dead branch [ 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. The severity of disease symptoms varied with grapevine cultivars, inoculated tissues, and abiotic conditions [ 9 , 12 , 13 , 14 , 15 , 16 ]. These symptoms are thought to result from the synergistic actions of the plant cell wall-degrading enzymes and phytotoxic metabolites produced by these fungi [ 17 , 18 , 19 , 20 ].…”