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Leaf rust caused by Puccinia triticina Erikss. (Pt) is the most widely distributed and important wheat disease worldwide. The objective of the present study was to determine the frequency of Iranian Pt races, their virulence to key resistance genes and map quantitative trait loci (QTL) for resistance to different Pt races from 185 globally diverse wheat genotypes using a genome-wide association study (GWAS) approach. The virulence pattern of the 33 Pt isolates from various wheat-growing areas of Iran on 55 wheat differentials showed that the FKTPS and FKTTS were relatively frequent pathotypes among the 18 identified races. The weighted average frequency of virulence on the resistance genes Lrb, Lr3bg, Lr14b, Lr16, Lr24, Lr3ka, Lr11 and Lr20 were high (> 90%). However, low virulence on the resistant genes Lr2a, Lr9, Lr19, Lr25, Lr28 and Lr29 indicates that these genes are still effective against the pathogen population in Iran at present. GWAS on a panel of 185 wheat genotypes against 10 Pt races resulted into 62 significant marker-trait associations (MTAs) belonged to 34 quantitative trait loci (QTL) across 16 chromosomes. Among them, 10 QTLs on chromosomes 1A, 1B, 3B, 3D, 4A, 6D, 7A and 7D were identified as potential novel QTLs, of which four QTLs (QLr.iau-3B-2, QLr.iau-7A-2, QLr.iau-7A-3 and QLr.iau-7D-2) are more interesting, as they are associated with resistance to two or more Pt races. The known and novel QTLs associated with different Pt races found here, can be used in future wheat breeding programs to recombine different loci for durable resistance against leaf rust races.

Fire blight caused by the gram-negative bacterium Erwinia amylovora is the most destructive disease of pome fruit trees. The pathogen induces the disease by secreting HrpN, HrpW, and DspA/E effector proteins into host tissues triggering oxidative burst. To study the role of these effectors in the course of interaction with host plants, hrpN−, hrpW− and dspA/E− mutants were inoculated on two pear cultivars under in situ (greenhouse and immature fruit) and in vitro systems. In addition, the determinantal role of these effectors on host chloroplasts was studied under activated and inactivated electron cascade of chloroplasts. Results showed that the lack of HrpN and DspA/E effectors postponed the initiation of necrosis and also decreased necrosis progress rate in comparison with the wild type strain. In contrast, hrpW− had the least decline in the pathogenicity of fire blight. The comparison of chloroplast activity confirmed the role of effectors in in situ experiments and also revealed that HrpN could be the main factor for the interaction of the pathogen with host cell chloroplasts.

Septoria tritici blotch (STB), caused by Zymoseptoria tritici has been considered one of the important diseases of wheat in Europe and elsewhere including Iran. The most economical strategy to control the disease is the use of genetic resistance. To this aim, this study was conducted to identify new sources of resistance to STB and to investigate the effectiveness of known Stb genes against six Iranian isolates of Z. tritici. Genetic variability analysis using random amplified polymorphic DNA (RAPD) markers revealed high polymorphic banding patterns indicating that a high genetic variability existed among the isolates. Inoculation assays identified 116 isolate-specific resistances among all interactions (n = 420). Of 52 genotypes, 26 wheat genotypes showed no isolate-specific responses and were susceptible to all isolates, which may explain increasing epidemics of Z. tritici occurring in major wheat-growing regions in Iran. Five genotypes were highly resistant to all isolates. Effectiveness determination of Stb genes revealed that Iranian isolates have a broad virulence spectrum against most of the known Stb genes. Among all Stb genes, Stb15 and Stb16/Stb17 in cultivars Arina, Riband and M3 were the most effective resistance genes and conferred resistance to all isolates tested. Hence, these genes should be effective in breeding programs in Iran to control the disease.

Septoria tritici blotch (STB), caused by Mycosphaerella graminicola has recently become one of the devastating diseases in Iran causing significant yield losses on most commercial bread and durum wheat cultivars. Iran is located in the Fertile Crescent, a region where wheat was historically domesticated; and, thus, landraces derived from this region are of considerable global interest for identification of new sources of resistance to various stresses. Here, we report on the resistance responses of 45 tetraploid wheat landraces collected from different provinces of Iran to eight M. graminicola isolates. In total 138 isolate-specific resistances were found among all interactions (n = 360). The highest number of specific resistances (30 out of 32 interactions) was found in wheat landraces collected from West Azarbaijan. In contrast, all landraces from Kordestan were highly susceptible to M. graminicola isolates and only one isolate-specific resistance was identified among 106 isolate-wheat interactions. Kermanshah landraces showed the highest resistance variation against different isolates. About 57 isolate-specific resistances were identified among 104 interactions. Ilam landraces were highly resistant to STB as 28 specific resistances were observed among 32 interactions. Markazi (n = 2) and Sistan-Baluchestan (n = 1) were susceptible to all isolates tested. Landraces from Lorestan were generally susceptible to isolates tested as 26 susceptible responses were observed out of 32 interactions. Our results indicate that landraces collected from the Fertile Crescent region may possess diverse effective resistance genes or valuable broad spectrum resistance genes, and that their identification is of interest and can be exploited in breeding programs.

Co-evolution of wheat and its devastating pathogen Mycosphaerella graminicola (anamorph Septoria tritici), the causal agent of septoria tritici blotch, a foliar disease of wheat, is suggested to occur in Fertile Crescent as their center of origin and, thus, interaction between pathogen virulence and host resistance is important subject to be addressed. We have investigated resistance spectra of 54 wheat genotypes including a set of differentials carrying known resistance genes and virulence patterns of 14 M. graminicola isolates at seedling stage under controlled environmental conditions. The isolates were collected in Iran from five provinces. Diversity in virulence and aggressiveness was observed among the isolates from four provinces. Isolates collected from Golestan province were virulent to all wheat genotypes from germplasm of Iran, while specific resistances were identified to the isolates from other provinces. Among wheat genotypes, cvs. Chamran, Morvarid and Hirmand had the greatest number of specific resistances as well as partial resistance. Wheat genotypes of the differential set also differed in their reactions to the isolates. Arina, Flame and TE 9111 were specifically resistant to the greatest number of isolates from different provinces. Most isolates were virulent to the other differentials such as cvs. Shafir, Estanzuela federal and Courtot indicating that extensive adaption of virulence to most of the known resistance genes (Stb) has occurred in these regions. The new sources of resistance to highly virulent isolates from Iran may also be utilized in wheat breeding programs to develop resistant cultivars against pathogen populations in other countries.