Effect water activity on in vitro mycelial growth of Neofusicoccum spp. infecting blueberry

Abstract

Stem canker in blueberries (Vaccinium corymbosum L.) is a diseasewhich is widely distributed around the world and of growing importancein Chile, associated with Neofusicoccum species. The purpose of thepresent work was to study the effects of water activity (aw) andtemperature on mycelial growth in vitro of N. arbuti, N. australeand N. parvum, obtained from blueberries with symptoms of stem canker.According to the results obtained, 25 �C was the optimum temperaturefor mycelial growth of N. arbuti, N. australe and N. parvum. Thesespecies presented minimal growth at 35 �C and none at 0 and 5 �C.The effect of aw on mycelial growth was significant (P?0.001) andvaried with the species of Neofusicoccum and the temperature. At25 �C, the optimum temperature, the three species of Neofusicoccumpresented minimum growth with aw of 0.900 and 0.920, while optimummycelial growth was found with aw equal to 0.990. Independent ofthe Neofusicoccum species, the effect of temperature (T) and aw onmycelial growth was best explained by y = -721.62 + 0.24T + 788.92aw.(R2 adj = 0.77, P?0.001), suggesting that T and aw jointly explained77% of the total variation on mycelial growth of Neofusicoccum spp.The results obtained provide important information for a better understandingof the biology of these plant pathogenic fungi, and suggest thattemperature and aw could be important parameters for understandingfactors that affect the inoculum production, colonization and infectionby Neofusicoccum spp. in blueberry plantations.