Adaptabilidade comparativa de espécies fúngicas causadoras do pé-preto da videira no Nordeste brasileiro e reação de cultivares

Abstract

The Northeast region accounts for 99% of Brazilian exports of fine table grapes (Vitis vinifera L.), mainly produced in the São Francisco Valley. Black foot is a disease present in all grape producing regions worldwide, especially in nurseries and young vineyards. This disease was recently reported in the Brazilian Northeast, caused by Campylocarpon fasciculare, Campylocarpon pseudofasciculare, Campylocarpon semiaridus and Cylindrocladiella pseudohawaiiensis. Despite the importance of black foot disease of grapevines worldwide, the fitness components of fungal species associated with the disease are poorly understood. To investigate the saprophytic and pathogenic fitness of C. fasciculare, C. pseudofasciculare, C. semiaridus and C. pseudohawaiiensis, this study compared the effect of temperature on mycelial growth and sporulation, effect of water potential (s), salinity, pH and fungicides on the mycelial growth of the pathogens, as well as the aggressiveness in detached vine shoots of grapevine. A second objective of this study was to analyze the reactions of the main rootstocks cultivars used in São Francisco Valley to Campylocarpon species and C. pseudohawaiiensis. The higher sporulation capacity demonstrated by C. pseudofasciculare and the lower sporulation capacity of C. semiaridus can justify the higher and lower prevalence in the Brazilian Northeast, respectively. The greater aggressiveness presented by C. semiaridus may indicate that a new etiological agent is adapting to the conditions of cultivation in the Brazilian semiarid, in which several species of Campylocarpon and C. pseudohawaiiensis may be causing black foot disease simultaneously. Therefore, the results of this study suggest that C. semiaridus developed compensation mechanisms to maintain competitiveness in relation to other species, evidenced by the reduced spore production capacity associated with high aggressiveness. The five evaluated grapevine rootstocks were susceptible to the fungal species tested and the smaller lesion lengths were caused in the Freedon rootstock. This genotype may be a potential source of resistance, and its choice at the time of implantation of new vineyards may be an important tool in the management of the black foot disease in the São Francisco Valley.