Key terpene in apple may be involved in susceptibility to infection

Terpenes are important compounds involved in floral fragrance, fruit flavour and interactions between plants and insects (beneficial and pest) and between plants and pathogens. 

Scientists at Plant & Food Research have been studying a key terpene in apple called α-farnesene. This is the only terpene found in ripe, modern dessert apples and may contribute grassy attributes to the aroma of ripe apples. It may also play a role in the development of superficial scald (a postharvest problem) and it acts as a short-range attractant to adult and larval codling moth in apple flowers and young fruit. It’s also likely to be important in herbivory (eating plants), since concentrations increase after leaf wounding by herbivores.

In this study, scientists looked at over 850 different apples and found α-farnesene in every variety, which suggests it must play an important function that has been conserved through evolution. The scientists identified four genes controlling the production of α-farnesene in a cross between ‘Royal Gala’ and ‘Granny Smith’. One of the genes was α-farnesene synthase – the final enzyme in the pathway to making α-farnesene.

When scientists down-regulated α-farnesene synthase in ‘Royal Gala’, the fruit made less α-farnesene and, surprisingly, this made the fruit less susceptible to three important postharvest plant pathogens (Colletotrichum acutatum, Penicillium expansum and Neofabraea alba).

Along with colleagues from China and France, Plant & Food Research scientists are now exploring the mechanism by which the fruit become less susceptible to infection.

Journal Reference:

Souleyre, E, Bowen, J, Matich, A, Tomes, S, Chen, X, Hunt, M, Wang, M, Ileperuma, N, Richards, K, Rowan, D, Chagne, D, Atkinson, R  2019. Genetic control of α-farnesene production in apple and its role in fungal pathogenesis. The Plant Journal. https://doi.org/10.1111/tpj.14504