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Title: First Report of rust caused by Tranzschelia discolor on Peach in Oman

Author
item DEADMAN, M. - OMAN
item AL SADI, A. - OMAN
item AL MAQBALI, Y. - OMAN
item AL SUBHI, A - OMAN
item AL YAHYA, R. - OMAN
item Aime, Mary

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/2007
Publication Date: 5/17/2007
Citation: Deadman, M.L., Al Sadi, A.M., Al Maqbali, Y.M., Al Subhi, A., Al Yahya, R., Aime, M.C. 2007. First Report of Rust Caused by Tranzschelia Discolor on Peach in Oman. Plant Disease. 91:638.

Interpretive Summary: Rust fungi are a very large and diverse group of parasites that attack crop and forest plants. Accurate knowledge of the distribution of rust fungi is important for tracking the movement of these disease-causing fungi. In this research a rust fungus was discovered for the first time in the country of Oman causing disease on peach. Knowledge of the distribution of plant pathogenic fungi is useful to agronomists and plant pathologists as well as plant regulatory and quarantine officials.

Technical Abstract: Peach (Prunus persica L.) is the dominant fruit crop in parts of the northern mountainous regions of Oman. Local cultivars, propagated by seedling, are used to produce fruit for local markets and for shade to fodder crops planted underneath. In February of 2006, leaf samples showing rust symptoms were collected from Balad Seet, 120 km south-west of Muscat. Angular yellow spots were observed on leaf upper surfaces with orange sori below. The disease was observed affecting almost 100% of trees with many leaves having more than 10 sori per leaf. Mostly obovoid, echinulate, orange-brown urediniospores typical of Tranzschelia discolor (Fuckel) Tranzschel & M.A. Litv. were present, measuring on average 13-17 x 26-37 µm, with cell wall 1.3-1.8 µm thick at sides, up to 5.8 µm thick at apex. Lesions were also observed on twigs where spring growth was cracked and yielded urediniospores. Golden capitate paraphyses were present, measuring on average 35-57 µm long, head 13-16 µm diameter, tail 4.9-6.7 µm wide. Teliospores were not observed, due to the time of year of collection. Pathogen identity was confirmed by analysis of a nuclear rDNA sequence spanning from the 5.8S through the ITS-2 into the first 1000bp of the 28S gene (1). The voucher sequence deposited in GenBank (Accession No. DQ995341) shared 100% sequence similarity with T. discolor. A voucher specimen was deposited in the U.S. National Fungus Collections (BPI 875341). Although T. discolor has a world-wide distribution (2) it has not previously been reported from Oman. Peach improvement is a priority to improve local income for growers in the small-scale farms of the mountainous areas and current research is aimed at evaluating introduced cultivars for response to rust disease.