Correlation between Fire Blight Resistance and Morphological Characteristics of Pear (Pyrus communis L.)

Fire blight is an important disease of pome fruits, especially pears and quinces. Substitution of susceptible with tolerant cultivars is an economically and technically effective control method. Identifying tree traits associated with disease tolerance, may be helpful to screening and breeding programs, as well as genetic studies of resistance. Disease tolerance was evaluated in the national pear collection of SPII in two main categories of 8 and 20 indigenous commercial cultivars. The disease severity was evaluated using the USDA index in two successive epidemic years. 83 vegetative and reproductive traits were considered based on International Union for the Protection of New Varieties of Plants (UPOV) descriptor in all pears. Cultivars 'Dar Gazi' and 'Tashkandi' demonstrated the highest resistance level among tested cultivars. Among evaluated traits, 15 out of 83 were correlated with disease resistance. Among tree traits that were correlated to the disease resistance, 7 traits were from flowers, the main entrance of pathogen into the host. Low branching, fruit ripening variation, shape of leaf apex and number of buds in the clusters demonstrated the strongest correlation with disease tolerance; followed by other traits such as sepal color of immature fruits, fruit juiciness, size of flower and leaf, and pedicle length. The significant correlated traits could be useful as morphological or physiological markers in breeding programs.