Study on Grapevine Die-Back in Basrah Southern Iraq : Grapevine dieback in Iraq: pathogens,classification,genitic,and histopathology

In Basrah,grapevines suffer from dieback.Lasiodiplodia theobromae and Neoscytalidium dimidiatum were isolated from diseased grapevinesVitis vinifera L.and identified based on morphological characteristics and DNA sequence data of the rDNA internal transcribed spacer (ITS)region . The results of the pathogenicity test conducted under greenhouse conditions for L.theobromae and N.dimidiatum revealed that both species were the causal agents of grapevines diebacks in Basrah, Southern Iraq.A brief description is provided for the isolated species.Histopathological changes of 2-years old grapevine cv.Abbassi inoculated with Lasiodiplodia theobromae(syn.Botryodiplodia theobromae)were studied. Samples were taken at 7 and 25 days after artificial inoculation.At 7 days,cross and longitudinal sections revealed the presence of disorganized cells,degenerated areas and vascular bundles.The intra-and intercellular invasion of the inoculated tissues by the fungus were evident with dark brown color.At 25days,the fungus caused necrosis in xylem parenchyma and xylem vessels,the hyphae colonized the tissues.Dark deposits appeared in vessels and other tissues as well as abundant production of ty.