Colonization ability as an indicator of enhanced biocontrol capacity—An example using two Bacillus amyloliquefaciens strains and Botrytis cinerea infection of tomatoes

Abstract

An understanding of biocontrol activities is important when developing microorganism‐based alternatives to conventional fungicides. From our bacterial collection, we selected two strains (BBC023 and BBC047) for their outstanding antagonistic capacity against fungal phytopathogens and growth‐promoting abilities towards Arabidopsis thaliana. According to physiological and molecular characterizations, both strains were classified as Bacillus amyloliquefaciens and were tested against Botrytis cinerea in vitro and in a tomato. Both strains secrete lipopeptide‐like compounds that contribute to their in vitro antagonism. SEM‐images showed altered B. cinerea mycelial structures that were consistent with previous reports of the direct action of lipopeptides against fungal hyphae. The strains were applied to the roots (R), leaves (foliar ‐ F) or root/leaves (R/F) on tomato plants. All treatments significantly reduced the severity of B. cinerea infection (measured as a control index). However, only root applications (R and R/F) led to growth promotion in the tomato plants. We detected the production of indole acetic acid (IAA) and 2,3‐butanediol as growth promotion traits in the two strains. For both strains, the R/F treatment showed the highest control index, suggesting a synergic effect of direct antagonism against B. cinerea and resistance induction in the plant. In addition, in vitro antagonism of BBC023 and BBC047 against B. cinerea was similar; whereas in the F application, strain BBC047 significantly improved plant resistance and maintained a higher population density over time on tomato leaves, compared to BBC023. BBC047 was also able to produce a complex and robust biofilm in Msgg medium compared with that of BBC023. We linked the reduced biocontrol of BBC023 on leaves with its limited ability to generate robust biofilms and colonize the phylloplane. At last, we highlight the potential of the native Bacillus strains as promising alternatives for the development of bioproducts for sustainable agriculture.

Crop Protection against Botrytis cinerea by Rhizhosphere Biological Control Agent Bacillus velezensis XT1

“…Growth promotion capacity has, in some cases, been linked to the mode of application used. Salvatierra-Martínez et al (2018) [ 13 ] demonstrated that only radicular applications of B. subtilis strains BBC023 and BBC047 are capable of enhancing biomass production. Similarly, Esitken et al (2010) [ 63 ] found that not all PGPR strains of the genus Bacillus act in a similar fashion in strawberry plants and that crop yields, in some cases, increase following root applications of Bacillus strain M3 and, in other cases, after foliar applications of Bacillus OSU142.…”

“…According to the Spanish Ministry of Agriculture, Fisheries and Food (MAPA), in the 2017/2018 period, Spain was one of the largest producers of strawberries in Europe (26%), with exports of 461.3 million euros, and of tomatoes in the world, with 4.7 million hectares devoted to this crop. In 2016, world tomato production reached 177 million tons according to the Food and Agriculture Organization of the United Nations Statistics Division (FAOAST), with Spain accounting for around 812,571 tons (MAPA) [ 12 , 13 ].…”

Root inoculation of green bell pepper (Capsicum annum) with Bacillus amyloliquefaciens BBC047: effect on biochemical composition and antioxidant capacity

“…Bacillus amyloliquefaciens BBC047 strain was provided by CEAZA (Centro de Estudios Avanzados en Zonas Áridas, La Serena, Chile). Recently, Salvatierra‐Martínez et al characterized its capacity to promote plant growth and to control grey mold disease ( Botrytis cinerea ) in tomato. For inoculation, the strain was cultivated in LB media for 36 h (30 °C, 150 rpm) until the beginning of the stationary phase (10 9 CFU mL −1 ).…”

Modes of Action of Microbial Biocontrol in the Phyllosphere

“…B. amyloliquefaciens strains have been proven to be successful biocontrol agents in the field for a wide range of pathogens, such as Sclerotinia sclerotiorum causing canola stem rot ( Fernando et al, 2007 ), and fusarium head blight on durum wheat ( Schisler et al, 2002 ). Salvatierra-Martinez et al (2018) described biocontrol activity of two B. amyloliquefaciens strains against B. cinerea on tomato plants. These two trains had similar antagonistic effect in vitro , while strain BBC047 showed better results in planta .…”

“…Adaptation factors are often overlooked in biocontrol research. However, low efficacy of biocontrol agents in field studies is often due to a lack of adaptation rather than a lack of biocontrol factors (Zeriouh et al, 2014;Salvatierra-Martinez et al, 2018). Moreover, a successful biocontrol agent needs a variety of adaptation and biocontrol factors to inhibit a pathogen and improve plant health (Köhl et al, 2019).…”