Comparison of the Efficacy of Trichoderma and Bacillus Strains and Commercial Biocontrol Products against Grapevine Botryosphaeria Dieback Pathogens

Abstract

Grapevine trunk diseases (GTDs) cause significant yield losses worldwide and limit the lifespan of vineyards. In the last few years, using biological control agents (BCAs) for pruning wound protection has become a promising management strategy for the control of these pathologies. This study aimed to compare the antifungal activities of a grapevine-native Trichoderma harzianum isolate and a high-potential Bacillus velezensis strain against two pathogenic Botryosphaeriaceae species in artificially inoculated, potted, grafted plants under controlled greenhouse conditions, taking three commercial biocontrol products (based on T. atroviride I-1237, T. harzianum T-22, and Bacillus subtilis BS03 strains) as a reference. To reproduce certain field conditions more realistically, inoculation of the protective agents and the pathogens was conducted simultaneously immediately after pruning instead of allowing the BCAs to colonize the wounds before pathogen inoculation. Significant differences in necrosis lengths were detected for both Neofusicoccum parvum- and Diplodia seriata-infected plants, and a remarkable protective effect of Bacillus velezensis BUZ-14 was observed in all cases. Trichoderma-based treatments showed different efficacies against the two pathogenic fungi. While the three tested BCAs resulted in significant reductions in vascular necrosis caused by N. parvum, they did not significantly reduce D. seriata infection compared to the untreated inoculated control. The B. subtilis strain was not effective. The reported results provide support for the potential Bacillus velezensis may have for pruning wound protection against Botryosphaeriaceae fungi, encouraging its evaluation under natural field conditions.

Evaluating treatments for the protection of grapevine pruning wounds from natural infection by trunk disease fungi

“…A notable exception was observed with the biocontrol agent T. atroviride I-1237, which consistently demonstrated effectiveness against Botryosphaeria dieback infections throughout each growing season, irrespective of the location. These outcomes align with prior research highlighting T. atroviride I-1237 as a protective agent against Botryosphaeria pathogens (Langa-Lomba et al 2023; Reis et al 2017, 2022). It is worth noting, however, that these previous studies primarily employed artificial infections, neglecting the presence of multiple pathogens and variations in concentrations.…”

Biocontrol of almond canker diseases caused by Botryosphaeriaceae fungi

“…53 Other strains of Pseudomonas spp. and B. velezensis have also demonstrated their efficacy against fungal trunk diseases in other crops, such as grapevine, 37,39,55 as well as in the control of apple and pear ring rot disease caused by B. dothidea. 48,[74][75][76] Isolation of endophytic bacteria from healthy, asymptomatic trees, growing in an infested orchard has been described as a powerful technic to obtain bacterial species to be used as (A) (B) Figure 3.…”

“…and B . velezensis have also demonstrated their efficacy against fungal trunk diseases in other crops, such as grapevine, 37,39,55 as well as in the control of apple and pear ring rot disease caused by B . dothidea 48,74–76 …”

“…BCAs based on Trichoderma species have been successfully assayed for the control of Botryosphaeriaceae pathogens in woody crops, most of them in grapevine and Prunus spp. [36][37][38][39][40][41][42][43][44] Specifically, T. atroviride SC1 has been registered in California as a biological control agent against almond canker pathogens. 15 In addition, several bacterial strains from the genus Bacillus, Streptomyces, Pseudomonas and Xenorhabdus have demonstrated, alone or in combination with other BCAs, their antagonism against Botryosphaeriaceae species in several crops.…”

“…In this sense, putative biological control agents (BCAs) have been described which reduce the damage caused by Botryosphaeriaceae species in different crops. BCAs based on Trichoderma species have been successfully assayed for the control of Botryosphaeriaceae pathogens in woody crops, most of them in grapevine and Prunus spp 36–44 . Specifically, T .…”