STUDIES ON ALTERNARIA ROT IN CITRUS FRUITS AND ITS CONTROL

Abstract

Citrus (Citrus sp.) is considered as one of the most important fruit crops. It is cultivated world wide especially in warm regions. Citrus occupies the third stage in the world after grapes and apples. Meanwhile, citrus is considered the first crop in Egypt for fresh use, juice and export. Citrus fruits are attacked by a number of pathogens from flowring to harvesting stages and subsequently by post-harvest pathogens that affect on fruit production at quantative and qualitative standareds. Considerable, fungal diseases, especially Alternaria rot in citrus fruit was the most important diseases wchich affect on production. The major goal of this study is to throw some lights on disease incidence, distribution and survey of Alternaria rot of citrus fruits in different growing regions, isolation and identification of the causal pathogen at microscopic examinitation and molecular level. Moreover pathogenicity tests, also varietal susceptibility. On the other side, the antagonistic action effect of different bio-agents and fungicides against the causal pathogen was studied. The obtained results could be summarized as follows: 1- In this study data indicated that disease survey in the nurseries and orchards of citrus during 2011 till 2012 revealed that, fruit-rot disease was presented in all the observed Governorates i.e. Beheira, Kalyobia, Ismaelia, Beni-Suief, Giza, Menofia, Gharbia and Dakahlia, Governorates. Also, the highest percentage of disease survey was obtained in Beheira being (22.10%) followed by Kalyobia being (21.40%), Ismaelia (15.81%), Beni-Suief (12.70%), Giza (10.97%) and Menofia (9.60%) Governorates, while the lowest percentage of disease survey was noticed in Gharbia and Dakahlia, being (4.30 and 4.03%) respectively. Also, the results showed that, the highest percentage of Alternaria alternata fungal isolates was reached about (42.23%) compared with A. citri the percentage was (41.38 %) meanwhile, the percentage 16.39% was other fungi. The results also, indicated that the A. alternata isolates was the highest frequency isolates which isolated from leaves and the percentage was reached about (12.66%) while, the hi