RESPONSE OF TUNISIAN DURUM AND COMMON WHEAT CULTIVARS TO POWDERY MILDEW UNDER NATURAL INFECTION

Abstract

Cereal production is an important component of agriculture. Powdery mildew (Erysiphe graminis f. sp tritici Em. Marchal), caused by Blumeria graminis (DC.) E.O Speerf. sp. tritici (Bgt), which is one of the most worldwide devastating diseases of durum and common wheat specially in Tunisia. Several works have discussed plant resistance to mildew and its potential risks but, it was neglected or no study was reported for that in Tunisia. There is an increasing need for studies that address the potential side effects of mildew to different wheat cultivars and their outcome and behave via disease criteria. This study focuses to compare the behave of ten Tunisian wheat cultivars to powdery mildew under field conditions during two successive cropping seasons 2011-2013. Using the 5 disease criteria (infected leaf number, pustules per stem and per leaf, number of spores produced per pustule and AUDPC “Area Under the Disease Progress Curve”, based on pustules per leaf) to investigate the plant disease resistance, specially the AUDPC parameter, durum wheat showed susceptibility to natural infection of powdery mildew specially the cultivar Souabaa Eljia with mean AUDPC value of 583.8, while common wheat, the cultivar Hydra, showed resistance with mean AUDPC value of 52.1,while, the improved durum cultivars Nasr and Karim showed an intermediate reaction. Principal Components Analysis (PCA) showed that the variables were grouped in two principal components that explained 76.65% of the total variance. The projection of the point-cloud representing the populations on the plan formed by the principal components «Fact.1» (49.65%), in abscissa, and «Fact.2» (27%) in ordinate, permitted to distribute the accessions in several groups. Two common wheat cultivars (Hydra and Bysra) showed on one hand a high level of resistance to Bgt and on other hand this fungus behaves differently on these cultivars via the conidia production. The cluster analysis suggested that these two cultivars are genetically similar, but the PCA distribute each one in a distinct single group. Hydra affect all the component of resistance tested and seems more efficient than Bysra.