Archivio Journal of Plant Pathology

Abstract:

Xanthomonas arboricola pv. juglandis (Pierce) Vauterin et al. (1995) is the causal agent of walnut bacterial blight, the major nut and foliage disease of Persian (English) walnut (Juglans regia). The disease limits walnut production in most regions of the world. All new walnut tissues are susceptible to infection and necrosis can occur in catkins, female flowers, leaves, fruit and green shoots (Miller and Bollen, 1946). Over time, the bacterium has been classified into different genera under different names, i.e. Pseudomonas juglandis Pierce (1901); Bacterium juglandis (Pierce) Smith (1905); Phytomonas juglandis (Pierce) Bergey et al. (1930); Xanthomonas juglandis (Pierce) Dowson (1939) and Xanthomonas campestris pv. juglandis (Pierce) Dye (1978), which is officially accepted in the International standards for naming pathovars of phytopathogenic bacteria (Dye et al., 1980). Recently, however, it was re-classified by Vauterin et al. (1995) as Xanthomonas arboricola pv. juglandis (Xaj). Xaj is the causal agent of two new emerging diseases of Persian (English) walnut (J. regia) known as vertical oozing canker (VOC) (Hajri et al., 2010), and apical necrosis (Moragrega and Ozaktan, 2010; Moragrega et al., 2011). According to molecular studies based on fluorescent amplified fragment length polymorphism (FAFLP), in France VOC is caused by a distinct genetic lineage of the bacterium which is also able to induce blight symptoms on leaves and fruits (Hajri et al., 2010). Bacterial strains isolated from apical necrosis lesions in Spain are also able to infect walnut leaves, causing typical blight lesions (Moragrega et al., 2011).