Changes in tomato plant anti-herbivore defences after soil application of a biofungicide containing Bacillus subtilis (Serenade ASO)

ABSTRACT

Plants have limited resources to allocate to defences against infection and herbivory. While interactions between plant responses to microbial and herbivore attack are complex, it is often the case that the induction of one response will act antagonistically to the other. Recent studies have shown that plant growth promoting rhizobacteria, which improves overall plant health and general stress resistance, can enhance both anti-microbial and anti-herbivore defences. We investigated how soil application of the biofungicide Serenade ASO (Bacillus subtilis strain QST 713), which primes plant defences against fungal and bacterial infection and promotes plant growth, affects anti-herbivore defences by measuring both constitutive and induced defences. We applied Serenade one or two times to the soil of tomato plants and measured the numbers of type IV glandular trichomes on leaves, the weight gain of a generalist caterpillar (beet armyworms; BAW), and the activity of two enzymes associated with defence against insects (polyphenoloxidase and peroxidase). Serenade treated plants grew faster and foliage from treated plants had significantly higher numbers of glandular trichomes and higher polyphenoloxidase and peroxidase activities than untreated plants. However, Serenade treatment did not affect the degree of induction of plant defences when damaged by BAW feeding and did not slow the growth rate of BAW relative to plants not treated with Serenade. Therefore, the biofungicide Serenade increased plant growth and altered the densities of trichomes and the activities of two defensive enzymes in plants, but it did not affect overall susceptibility of the plants to a generalist herbivore.

KEYWORDS:

• Induced systemic resistance
• integrated pest management
• multitrophic
• plant growth promoting rhizobacteria

Acknowledgements

We thank Bayer Crop Science US for providing a sample of Serenade ASO.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Undergraduate Research Opportunities Program (UROP) Faculty Mentoring Grants for Summer Undergraduate Research and Creative Works at the University of Hawaii at Manoa, and USDA National Institute of Food and Agriculture (NIFA) Hatch project (HAW09051-H), managed by the College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the USDA.