The Practical Role of Induced Resistance for Crop Protection.

Plants have evolved a highly sophisticated immune system to resist pathogen attack comprising both preformed and inducible mechanisms. Over the last 50 years, various biological and chemical inducers have been used to artificially trigger the defense response in plants, thereby promoting an induced resistance (IR) to subsequent pathogen attack. IR has proven effective for disease control in laboratory and glasshouse conditions but has seldom equalled the level of protection offered by synthetic pesticides in the field. However, renewed interest in IR for crop protection is being driven by legislation to reduce the use of synthetic chemicals in agriculture. Inducers can contribute to integrated crop management strategies when used in combination with fungicides, bactericides, and with other biological control options. Integrating inducers in this way can reduce chemical inputs without loss of efficacy. Moreover, advances in our understanding of plant defense are informing the development of new inducers and guiding new strategies for their implementation in sustainable crop protection. This review will discuss the use of IR in selected cropping systems and describe opportunities for optimizing its potential, including the development of more effective inducers and their integration with conventional and cultural control options.

Integrated Use of Aureobasidium pullulans Strain CG163 and Acibenzolar-S-Methyl for Management of Bacterial Canker in Kiwifruit.

An isolate of Aureobasidium pullulans (strain = CG163) and the plant defence elicitor acibenzolar-S-methyl (ASM) were investigated for their ability to control leaf spot in kiwifruit caused by Pseudomonas syringae pv. actinidiae biovar 3 (Psa). Clonal Actinidia chinensis var. deliciosa plantlets ('Hayward') were treated with ASM, CG163 or ASM + CG163 at seven and one day before inoculation with Psa. ASM (0.2 g/L) was applied either as a root or foliar treatments and CG163 was applied as a foliar spray containing 2 × 107 CFU/mL. Leaf spot incidence was significantly reduced by all treatments compared with the control. The combination of ASM + CG163 had greater efficacy (75%) than either ASM (55%) or CG163 (40%) alone. Moreover, treatment efficacy correlated positively with the expression of defence-related genes: pathogenesis-related protein 1 (PR1), ß-1,3-glucosidase, Glucan endo 1,3-ß-glucosidase (Gluc_PrimerH) and Class IV chitinase (ClassIV_Chit), with greater gene upregulation in plants treated with ASM + CG163 than by the individual treatments. Pathogen population studies indicated that CG163 had significant suppressive activity against epiphytic populations of Psa. Endophytic populations were reduced by ASM + CG163 but not by the individual treatments, and by 96-144 h after inoculation were significantly lower than the control. Together these data suggest that ASM + CG163 have complementary modes of action that contribute to greater control of leaf spotting than either treatment alone.