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XVII Botrytis Symposium, Santa Cruz, Chile 23rd – 28th October 2016
The XVII Botrytis Symposium held in Santa Cruz, Chile in the Colchagua Valley wine region was a gathering of research scientists working on aspects of Botrytis, a major fungal pathogen of a range of horticultural crops. Given the worldwide importance of B. cinerea most presentations concentrated on this species. The Symposium was divided into several themes covering fundamental science and in-field management of Botrytis. There were many interesting presentations; I enjoyed the opening addresses which reviewed the impact Botrytis has on table grapes grown in Chile and floriculture in Columbia. We learnt of the importance of these two industries to South America and the problems that Botrytis causes. It was particularly interesting to hear how the table grape industry has evolved in Chile since the 1980s. Switching to the cut-flower industry we heard the importance of this industry to the economy of Columbia and losses due to Botrytis blight. Condensation which collects during post-harvest storage leads to Botrytis infection and dipping in a fungicide solution is no longer a practice that is acceptable because of health concerns.
Other presentations that were particularly relevant to my interests on Botrytis management included a joint presentation from Odile Carisse from Agriculture and Agri-Food Canada and Marc Fermaud from INRA, Bordeaux on the aerobiology of Botrytis and conidia production and dispersal in grape and raspberry crops. Using spore traps the authors demonstrated that preflowering Botrytis spores don’t move more than 4 meters in the vineyard or orchard, while at harvest spores spread up to 8 meters. It was hypothesised that this was due to a greater amount of inoculum around harvest. Following the management theme Phil Elmer from the New Zealand Institute of Plant and Food Research presented work on some of the management practices for Botrytis control in wine grapes and highlighted the importance of getting growers to adopt and successfully implement IPDM.
Leaf plucking and removal of canopy trash reduced Botrytis grey mould in wine grapes from 19% to 1. 7% in some New Zealand vineyards once grape growers adopted this practice. The use of sheep for leaf removal was also discussed, and that grape growers needed to re-evaluate pesticide spray programs to ensure that there were no pesticide residues in the meat if the animals were eventually used for human consumption.
There were a number of presentations on host-pathogen interactions. Barbara Blanco-Ulate from UC Davis compared grey mould and noble rot infections in grapes, which was particularly relevant to my personal research interests in viticulture. Grey mould and noble rot are both caused by B. cinerea but involve different host and fungal biochemistries.
Noble rot of grapes is the desirable form of Botrytis, occurring late in the season when berries start to shrivel and sugar concentrates. Wine made from white skinned grapes affected with noble rot is used to make sweet dessert wines. The presentation looked at the difference between noble rot and grey mould of grapes. During noble rot the phenylpropanoid pathway is upregulated and biosynthesis of flavanoids and terpenes are greater. Conversely during grey mould infections, when B. cinerea forms a destructive unwanted rot, flavanoid and terpene biosynthesis are down regulated in grapes.
Another presentation that stimulated further thought was one delivered by Jan Van Kan from Wagenigen University (co-authored with Michael Shaw from the University of Reading). B. cinerea and B. pseudocinerea can be isolated from symptomless plants, such as dandelions, lettuce, primula and cyclamen.
These endophytic isolates were pathogenic when tested on tobacco and tomato, and also the plant species from which they were originally isolated from. A low inoculum density led to an endophytic state, consequently endophytic infections could switch to necrosis overnight.
The conference excursion involved a visit to a vineyard and winery, Via los Vascos, 28 km north-west of Santa Cruz. It was wonderful to stand in the vineyard and see the Andes in the distance.
During this visit I noticed an abundance of dandelions growing in the mid-row area of the vineyard. I thought again about Jan Van Kan’s presentation and cryptic Botrytis infections in companion plants. Could these dandelions and other plant species be a source of inoculum for grape berry infections close to harvest? If so, what might the consequences be for Botrytis management? Aside from speculating about Botrytis movement in vineyards, participants had the opportunity to taste some Carmenere wine, a red grape variety that originated in Bordeaux but is now grown more widely in Chile. The excursion concluded with a reception at a beach resort in the town of Pichilemu.
After a quick paddle in the South Pacific Sea it was time for some Pisco Sour pre -dinner drinks!
The last key note presentation of the Symposium was delivered by Themis Michailides from the University of California who looked at simple techniques to help manage Botrytis infections in kiwi fruit, pomegranates and pistachio.
Grey mould in kiwi fruit generally starts at the stem end of the fruit. Platting out the sepals and stem scar revealed that isolation of Botrytis from these tissues increases as the season progresses.
Kiwi fruit growers now use this technique to monitor Botrytis infections and to decide if the fruit should go to market or be put in cold storage. The technique was also used for Botrytis shoot blight in pistachio, but the amount of Botrytis found indicated that the technique for this industry wasn’t commercially viable.
The Botrytis Symposium contained a good blend of pure science and applied disease management and allowed networking to take place between researchers working on different aspects of this important plant pathogen. Attendance at this conference allowed me to present some of my research on the impact Botrytis has on wine quality when grapes are made from infected grapes and to network with other Botrytis scientists. I am very grateful for the support received from the BSPP through a travel bursary. I am looking forward to the next Symposium to be held in Avignon, France in about three years time.
Christopher Steel National Wine and Grape Industry Centre
