Plant Pathology Science

Walnut is one of the most important fruit trees in Iran, which is always exposed to pathogens, especially bacteria. The three most important bacterial diseases of walnut in Iran are bacterial blight (Xanthomonas arboricola pv. juglandis), skin cankers (Brenneria nigrifluens, Brenneria rubrifacians) and crown gall (Agrobacterium tumefaciens). Bacteriological characteristics and pathogenicity of pathogenic bacteria, methods of managing these diseases, along with suggestions for identifying resistant genotypes of walnut trees by molecular methods are described in this article.

Introduction: Bacterial canker caused by Pseudomonas syringae is one of the most damaging diseases in apricots. This experiment was conducted to evaluate relative resistance to the disease in 22 selected local apricot hybrids including AD507, AD405, and HS731 which were recently released as Jalil, Parsi and Shanli. Material and Methods: Evaluation methods included artificial inoculation of two-year-old seedlings in an orchard and of cut shoots in the laboratory. Initially, the pathovar identity of localP. syringae strains were determined using LOPAT and GATTa tests and three isolates were used as inoculum. The inoculation was done in the seedling stem and after one year and 1.5 years, canker length was recorded. Result: The pathovar of all isolates was identified as P. syringae pv. syringae. The longest and shortest cankers were observed in AD1033 and AC113 with averages of 34.76 mm and 8.35 mm, respectively. The cut shoot bioassay was not practical for apricots. The hybrids were classified into four groups including highly resistant, resistant, moderately resistant, and susceptible. Conclusion: AD1033, AD1042, AD940, AD811, HS210, DM101, HS203 have been classified as susceptible and should not be used in breeding programs and orchard establishment/replacement. Jalil, Parsi, and Shanli were rated as resistant, and moderately resistant, respectively.