Abstract
Endophytic bacteria could be used as a tool to promote plant growth, enhance abiotic stress tolerance, and inhibit plant pathogen growth. More than 100 bacteria, previously tested to have biocontrol activity against fungal pathogens from our lab, were chosen for pathogen inhibition in vitro with antibiosis assays against strawberry specific pathogens. Three potential endophytic bacteria were tested in the greenhouse for disease reduction and growth performance. Finally, field trials were conducted for fruit yield production. Our results showed that three endophytic bacteria significantly inhibited the growth of the strawberry pathogen Colletotrichum gloeosporioides from antibiosis assays and were identified as Bacillus velezensis strains IALR308, IALR585, and IALR619. Inoculation of these bacteria significantly reduced strawberry disease in greenhouse conditions with pathogen infection. Field trials showed that IALR619 has potential to influence marketable fruit yield when strawberry plants were inoculated twice over the growing season. All three bacteria had the ability to produce auxin and to solubilize phosphate. The antibiotics surfactin and iturin were also detected in IALR585 and IALR619. In conclusion, Bacillus velezensis IALR619 has potential inhibition of strawberry pathogen growth in the greenhouse and possible ability to increase marketable fruit yield in the field.
Highlights
Strawberry (Fragaria × ananassa) is one of the most favorite fruits in the U.S An average American consumes around 3.2 kg of strawberry every year [1]
Research study has shown that loss of methyl bromide for fumigation in the field could result in strawberry yield reduction up to 15% and an increase in pest pressure from early season weed competition and diseases such as anthracnose (Colletotrichum spp.)
The objectives of this study were (i) to screen endophytic bacteria from our endophytic bacteria library against strawberry pathogens in vitro, (ii) to test potential endophytic bacteria for reducing strawberry crown rot caused by Colletotrichum gloeosporioides and for promoting plant growth in the greenhouse, (iii) to conduct endophytic bacterial inoculation in strawberry fields to evaluate strawberry growth and fruit production, as well as note any disease incidence observed in the field, and (iv) to elucidate the mechanisms of fungal pathogen inhibition by these bacteria with genome sequence analysis
Summary
Strawberry (Fragaria × ananassa) is one of the most favorite fruits in the U.S An average American consumes around 3.2 kg of strawberry every year [1]. The long-term sustainability and viability of the strawberry industry depends on overcoming many challenges. A primary challenge in strawberry production is to find alternative solutions to methyl bromide fumigation, which is currently only allowed as a fumigant in strawberry nurseries under critical use exemption. Research study has shown that loss of methyl bromide for fumigation in the field could result in strawberry yield reduction up to 15% and an increase in pest pressure from early season weed competition and diseases such as anthracnose (Colletotrichum spp.). Colletotrichum acutatum and C. gloeosporioides have consistently been identified as the most destructive pathogens in the mid-South region of the U.S [2]. Plant growth-promoting bacteria (including rhizospheric and endophytic) can promote plant growth, enhance abiotic stress tolerance, and inhibit pathogen growth [5,6,7]
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