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First Report of Rust Caused by Tranzschelia discolor on Peach in Oman

Peach (Prunus persica L.) is the primary 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 shade fodder crops planted underneath the peach canopy. In February of 2006, leaf samples showing rust signs and symptoms were collected from Balad Seet, 120 km southwest of Muscat. Angular, yellow spots were observed on leaf upper surfaces with orange sori on the undersides. The disease was observed to be affecting almost 100% of trees, with many leaves having more than 10 sori per leaf. Lesions producing urediniospores were also observed on twigs where spring growth had cracked. Urediniospores typical of Tranzschelia discolor (Fuckel) Tranzschel & M.A. Litv. were obovoid, echinulate, orange-brown, and measured on average 13 to 17 × 26 to 37 μm, with the cell wall 1.3 to 1.8 μm thick at the sides and as much as 5.8 μm thick at the apex. Golden capitate paraphyses were also present, measuring on average 35 to 57 μm long, head 13 to 16 μm in diameter, and tail 4.9 to 6.7 μm wide. Teliospores were not observed because of 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 1,000 bp of the 28S gene (1). A voucher specimen was deposited in the U.S. National Fungus Collection (BPI 875341). The voucher's rDNA sequence deposited in GenBank (Accession No. DQ995341) shared 100% sequence similarity with T. discolor (Accession No. DQ354542). Although T. discolor has a worldwide distribution (2), it has not previously been reported from Oman. Improving the quality of peach production in Oman is an agricultural priority because it boosts the economy of smallscale farms in the mountainous regions. This work will facilitate the current research aimed at evaluating cultivar response to rust disease.

References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) P. F. Bertrand. Rust. Page 23 in: Compendium of Stone Fruit Diseases. J. M. Ogawa et al., eds. The American Phytopathological Society, St Paul, MN, 1995.