Falling leaves in Autumn: How will warmer autumns impact inter-species interactions?

Phoma stem canker is a major disease of oilseed rape caused by Leptosphaeria maculans and L. biglobosa. It is responsible for causing annual yield losses worth £80-100M in the UK, despite the use of resistant cultivars and fungicides. L. maculans has often been associated with causing the more damaging stem basal cankers, and the less damaging upper stem lesions to be caused by L. biglobosa.

This difference in lesion location on the plant has been attributed to differences in the timing of the ascospore release in Autumn. James said, “Previous studies have shown that L. biglobosa ascospores are released later in the season than L. maculans, but more recent investigations, including mine, have reported that ascospores of both species are frequently being released at similar times and we are finding both pathogens at the stem basal cankers”.  The release of these ascospores is known to be affected by temperature so this change in the patten of spore release could be a result of a warmer Autumns.

My work has also demonstrated that there are changes in phytotoxin production and disease development because of increased inter-species interactions and competition. Therefore, when L. maculans and L. biglobosa ascospores are released at similar times, phoma leaf spot lesions may appear later or be smaller, resulting in a later application of fungicide creating a new challenge for timely plant protection.

“With warmer Autumns, the internal clocks of the fungi are shifting, showing how climate change can impact pathogen interactions and may cause unforeseen challenges in the future.”