No abstract

Pathogenesis-related (PR) proteins, induced in plants in response to various biotic and abiotic stresses, have been assumed to play a role in plant defense system. Proteins of the PR5 family, also named thaumatin-like proteins (TLPs), have been detected in numerous plant species. In this research, a novel PR5 gene, designated as TaPR5, was isolated and characterized from wheat leaves (cv. Suwon 11) infected by the stripe rust pathotype CY23 (incompatible interaction) using the rapid amplification of cDNA ends (RACE). TaPR5 was predicted to encode a protein of 173 amino acids with an estimated molecular mass of 17.6 kDa and a theoretical pI of 4.64. The deduced amino acid sequence of TaPR5 showed a significant sequence similarity with PR5 and TLPs from barley and other plants and contained a putative signal peptide at the amino terminus. Southern blot analysis indicated that TaPR5 is coded by a single-copy gene. Quantitative real-time polymerase chain reaction (qRT-PCR) analyses revealed that TaPR5 transcript is significantly induced and upregulated in the incompatible interaction while in the compatible interaction a relative low level of the transcript was detected. TaPR5 was also induced by phytohormones (SA, JA and ABA) and stress stimuli (wounding, cold temperature and high salinity). Using an assay of onion epidermal cells indicated accumulation of TaPR5 protein in the apoplast. The immunocytochemical method showed that the TaPR5 protein was detected on cell walls of wheat leaves in the incompatible interaction at markedly higher labeling density compared with the compatible interaction.

Stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating wheat diseases worldwide. Triticum aestivum-Haynaldia villosa 6VS/6AL translocation lines carrying the Yr26 gene on chromosome 1B, are resistant to most races of Pst used in virulence tests. In order to better utilize Yr26 for wheat improvement, we attempted to screen SSR and EST-based STS markers closely linked with Yr26. A total of 500 F 2 plants and the F 2:3 progenies derived from a cross between 92R137 and susceptible cultivar Yangmai 5 were inoculated with race CYR32. The analysis conWrmed that stripe rust resistance was controlled by a single dominant gene, Yr26. Among 35 pairs of genomic SSR markers and 81 pairs of STS markers derived from EST sequences located on chromosome 1B, Yr26 was Xanked by 5 SSR and 7 STS markers. The markers were mapped in deletion bins using CS aneuploid and deletion lines. The closest Xanking marker loci, Xwe173 and Xbarc181, mapped in 1BL and the genetic distances from Yr26 were 1.4 cM and 6.7 cM, respectively. Some of these markers were previously reported on 1BS. Eight common wheat cultivars and lines developed from the T. aestivum-H. villosa 6VS/6AL translocation lines by diVerent research groups were tested for presence of the markers. Five lines with Yr26 carried the Xanking markers whereas three lines without Yr26 did not. The results indicated that the Xanking markers should be useful in marker-assisted selection for incorporating Yr26 into wheat cultivars.

This manuscript reports a new gene for non-race-specific resistance to stripe rust and molecular markers for incorporating it into wheat cultivars for control of the disease with durable resistance. Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most destructive wheat diseases worldwide. The spring wheat germplasm 'PI 178759' originating from Iraq showed effective resistance to stripe rust in field evaluations over 8 years in Washington state, USA. To map the resistance gene(s), PI 178759 was crossed with 'Avocet Susceptible', and the parents and 176 F2:3 lines were phenotyped in the fields under natural infection and in a greenhouse with selected races of P. striiformis f. sp. tritici. PI 178759 was identified to have high-temperature adult-plant (HTAP) resistance. Resistance gene analog polymorphism and simple sequence repeat techniques were used to identify molecular markers linked to the resistance gene and a chromosome region was mapped using a quantitative trait locus approach. One major gene was mapped to the long arm of chromosome 7B. Flanked by Xwgp5175 and Xbarc32 in a 2.1 cM region, the gene explained 31.8 and 54.7 % of the phenotypic variation in rAUDPC and IT, respectively. Based on genetic distances among markers and allelism tests, the HTAP resistance gene in PI 178759 is different from the previously reported Yr39, Yr52, YrZH84, and YrC591, also located on chromosome 7BL, and is therefore designated as Yr59. The gene and its flanking markers should be useful for developing wheat cultivars with durable resistance.

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