Boosting potato defence against late blight : a study from field to molecule

Sammanfattning: For more than one century efforts has been made to obtain potato (Solanum tuberosum) cultivars resistant to late blight. However, introduced resistance has repeatedly been overcome by Phytophthora infestans (Mont) de Bary. Today late blight control is dependent on the frequent use of fungicides, but development of fungicide resistance and increasing fungicide restrictions by EU are of major concern. Methods with less fungicide requirement is therefore of crucial importance for a more environmentally sound and sustainable late blight control in the future. In this study the potential of integrating BABA-induced resistance in existing late blight management with fungicides was investigated in field. The fungicide dose could be lowered with up to 25% when combined with BABA, without any decrease in late blight control or metabolic cost in terms of tuber yield. BABA was shown to directly activate basal defence responses and hormone signaling in potato. The BABA-induced hypersensitive-like lesions and major changes in the amino acid balance indicate that BABA induces resistance by stress imprinting. Furthermore the potential of using a biosurfactant, produced by Psuedomonas koreensis strain 2.74, to control late blight in greenhouse was demonstrated. The biosurfactant was shown to have a direct effect on zoospores and also to induce PR-1 accumulation in the apoplast of potato leaves. Future experiments will reveal if the biosurfactant induces other defence mechanisms in potato. This study demonstrated how integration of different control methods could lead to unchanged or even improved late blight control despite the decrease in fungicide dose.

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