Re­searcher dis­cov­er­ing ways to con­trol rot in stored ap­ples

The Daily Courier - - LIFE & ARTS -

An ap­ple a day may keep the doc­tor away, but the mould on it could make you sick.

Rhi­an­non Wal­lace, a PhD can­di­date at UBC Okana­gan’s cam­pus, has de­vel­oped a way to stop, or at least con­trol, blue mould — a pathogen that can rot an ap­ple to its core.

Wal­lace’s re­search has de­ter­mined that bac­te­ria, orig­i­nally iso­lated from cold Saskatchewan soils, may be the an­swer to pre­vent­ing mould growth and ap­ple rot while the fruit is in stor­age or trans­port.

“The ma­jor­ity of post-har­vest fun­gal pathogens are op­por­tunis­tic,” ex­plains Wal­lace, who is work­ing with UBC bi­ol­ogy pro­fes­sor Louise Nel­son. “If a fruit is phys­i­cally dam­aged, it is at an in­creased risk of rot­ting dur­ing stor­age. So a tiny blem­ish on the fruit from har­vest or han­dling can turn into a con­duit for at­tack by fun­gal pathogens and sub­se­quently re­sult in the de­vel­op­ment of mould.”

The fun­gal pathogen Peni­cil­lium ex­pan­sum, also known as blue mould, de­stroys mil­lions of stored ap­ples each year.

Post-har­vest rot can re­sult in yield losses of up to 20 per cent in de­vel­oped coun­tries such as Canada, while de­vel­op­ing coun­tries can lose up to 50 per cent of the crop, Wal­lace says.

The goal of her re­search is to re­duce the amount of pro­duce lost due to post-har­vest blue mould. Tra­di­tion­ally, post-har­vest rot has been con­trolled with chem­i­cal fungi­cides, but Wal­lace says these treat­ments have be­come less ef­fec­tive as the pathogen has de­vel­oped re­sis­tance and there is con­sumer push­back to the chem­i­cals. The re­search by Wal­lace and Nel­son aims to pro­vide a safer and more sus­tain­able al­ter­na­tive to fungi­cides.

Wal­lace sug­gests the so­lu­tion may lie in a par­tic­u­lar bac­terium spe­cific to Saskatchewan soil. Pseu­domonas flu­o­rescens, due to its prairie roots, can sur­vive in cold stor­age — a char­ac­ter­is­tic that is key to deal­ing with cold-stored pro­duce like ap­ples.

Dur­ing tests con­ducted at a B.C. Tree Fruits Co­op­er­a­tive stor­age fa­cil­ity, Wal­lace de­ter­mined these bac­te­ria can pre­vent blue mould from grow­ing on McIn­tosh and Spar­tan ap­ples while in stor­age. In ad­di­tion, dur­ing these ex­per­i­ments, the bac­te­ria pro­vided con­trol of blue mould on ap­ples that was com­pa­ra­ble to a com­mer­cially avail­able bi­o­log­i­cal con­trol agent and a chem­i­cal fungi­cide.

“What is novel about our re­search is that we show the bac­te­rial iso­lates we tested have an ar­ray of mech­a­nisms to in­hibit or kill Peni­cil­lium ex­pan­sum (blue mould) on ap­ples while fungi­cides gen­er­ally act only by a sin­gle mode,” Wal­lace said. “These find­ings sug­gest that the de­vel­op­ment of re­sis­tance by blue mould against our soil bac­te­ria is un­likely.”

She notes that while all three iso­lates of P. flu­o­rescens tested pro­vided con­trol of blue mould, the level of con­trol pro­vided by each isolate var­ied with ap­ple va­ri­ety.

Wal­lace’s re­search, sup­ported by the Cana­dian Hor­ti­cul­ture Coun­cil and Agri­cul­ture and Agri-Food Canada, was re­cently pub­lished in the jour­nal Posthar­vest Bi­ol­ogy and Tech­nol­ogy. Fur­ther sup­port came from the BC Tree Fruits Co-op­er­a­tive and Agri­cul­ture Canada’s Sum­mer­land Re­search and De­vel­op­ment Cen­tre.

Photo con­trib­uted

Rhi­an­non Wal­lace, a PhD can­di­date at UBC Okana­gan’s cam­pus, has de­vel­oped a way to pro­tect ap­ples from rot­ting.

Photo con­trib­uted

Blue mould growth on a Spar­tan ap­ple.

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