Virulence of Lasiodiplodia theobromae the causal of grapevine die-back disease in Egypt

El-Shaery, S.A.*; G.M. El-Habbaa**; Abdou, M.M Mahdy**; F. G. Mohamed** and Mourad, M*.

Abstract

Isolation trails from die-backed grapevine shoots during season 2011 confirmed that Lasiodiplodia theobromae was more frequently isolated fungus than others from symptomatic shoots collected from the five different vineyards in the surveyed governorates. Lasiodiplodia theobromae-B (Beheira isolate) recorded the highest frequent one while the lowest one was in Sharkia. Testing the five isolates of L. theobromae (B, G, M, D, and S) on wounded shoots (5 mm long, 2mm deep at distance 30 cm down the terminal bud) using disk technique induced grapevine die-back symptoms while, the other isolated fungi i.e., Alternaria alternata, Aspergillus niger and Fusarium solani, were not able to induce die-back symptoms onto artificially inoculated grapevine shoots. Increasing the incubation period of inoculated grapevine shoots from 7-30 days increased gradually the averages of die-backed areas for all tested L. theobromae isolates with significant differences among them at all incubation periods. Also, all five isolates of L. theobromae (B, G, M, D, and S) were able to cause die-back symptoms onto grapevine shoots at all incubation periods using spore suspension technique. Also, L. theobromae-B isolate (Beheira isolate) was highest infective one causing die-back symptoms at 30 days post inoculation followed by L. theobromae-G and M isolates respectively. All tested cultivars i.e., Thompson seedless, Flame seedless, Crimson and Romi Ahmer were susceptible to infection with L. theobromae isolate-B, however, Thompson seedless cv. was the highly susceptible one to infection with dieback disease.

Key words

Lasiodiplodiatheobromae, isolation, pathogenicity, grapevine,