Situation of apricot chlorotic leafroll MLO in Roussillon (France)
Observations made during the last twenty years have shown that 80 % of decline of apricot trees (Prunus armeniaca) in Roussillon (eastern Pyr‚n‚es) were due to apricot chlorotic leafroll MLO. Surveys have been carried in young apricot orchards since their plantation in 1981 or 1982, on 48 different plots (7244 trees, 28 ha) in this region. The aim was to study the behaviour towards this disease of three apricot cultivars (Rouge du Roussillon, Screara and B‚liana) grafted on five different rootstocks (Prunus domestica Brompton and Reine Claude, myrobalan GF 31, Mariana GF 8-1 and Manicot seedling). Selected trees have been visually inspected twice a year, in winter and in summer, until they reach the growth stage of eight leaves. In doubtful cases, the presence of the pathogen was confirmed by indexing on susceptible apricot cultivars Luizet or Priana, grafted on Prunus persica GF 305. The results showed that in plots of susceptible trees (like cv. B‚liana grafted on Mariana, or cv. Screara on Mariana), the disease spread rapidly and more than 35 % mortality was reached at growth stage 8 leaves. The most tolerant association was cv. Rouge du Roussillon grafted on Brompton. On these tolerant trees, multiplication rate of the disease and symptoms are reduced, and mortality remains under 5 %. The authors concluded that in regions where the disease is endemic, the choice of tolerant cultivars is essential to maintain a satisfactory production of apricots.
Sources
Cornaggia, D.; Audubert, A.; Desvignes, J.C. (1994) Enroulement chlorotique de l'abricotier en Roussillon - Influence du matériel végétal.
Phytoma - La Défense des végétaux, no. 460, 20-23.