hossein mohammadi dehbalaei

It is essential to identify the sources of seedling and adult plant resistance genes for gene pyramiding, genetic arrangement and creation of wheat cultivars with non-specific resistance or durable resistance. The complete homology of the D genome of Aegilops tauschii with the D genome of wheat, the clear botanical state, wide ecological compatibility, the presence of very high diversity in these traits and the ease of crossing with wheat have made Aegilops tauschii a very important source for gene transfer and wheat breeding. Until now, several genes of resistance to brown rust (leaf rust) were transferred from different species of Aegilops to high-yielding bread wheat cultivars whose resistance to brown rust was broken.

In this research, 25 genotypes of Aegilops tauschii collected from its natural habitats from the Middle East, Central Asia (obtained from the Grain and Legume Seeds Collection of Ilam University) were used. This research was carried out in the Iraqi Agricultural Research Station in Gorgan, Iran in the cropping season of 2019-2019 in the form of a complete block design in three replications and under two disease stress and control conditions. In order to development and appearance of brown rust disease, the sensitive Bolani variety was cultivated around and between the crop rows. In addition, spore of the native races from Gorgan was sprayed over the studied genotypes under the stress condition. Inoculation with a ratio of one to five spores and Talc powder was applied at the two stages at sunset by dusting device.

The results showed that there was a significant difference among different genotypes of Aegilops tauschii in terms of susceptibility and resistance to brown rust disease and the measured resistance components. Statistical analyzes showed a significant correlation between the characteristics of infection intensity, infection type, the area under the curve of disease progression, and various characteristics of performance components. The results of cluster analysis by Ward's method based on Euclidean distance and average algorithm for the resistance traits and the performance component traits were placed the genotypes into four different groups including resistant, semi-resistant, semi-sensitive, and sensitive. Also, based on the results of combined analysis, a significant difference was observed for the yield components including kernel weight, number of kernel per plant, length of spike, number of kernel per spike and number of tillers under two conditions.General

Aegilops tauschii, having different genes for resistance to various diseases, is considered as a valuable parent and a rich gene source for transferring resistant genes to high-yielding cultivars. The results of this research showed that from the resistant and semi-resistant groups, suitable parents can be selected for crossbreeding with bread wheat in order to transfer the resistance gene to leaf rust.

Identification of resistance gene sources in seedling and adult plant stages is important to developing durable wheat cultivars. In this study, 100 genotypes of Aegilops tauschii, collected from natural habitats were evaluated in the experimental field of the Iraqi-mahaleh, Gorgan. Seeds were planted on one meter length lines and inoculated with Golestan leaf rust pathotypes in a randomized complete block design with three replications. The reaction of genotypes was also evaluated in greenhouse, by six Iranian pathotypes based on a completely randomized design with two replications in seed and plant improvement institute (SPII). To evaluate resistance in filed, we used infection type, AUDPC, final disease severity and coefficient of infection indices. The results showed that in greenhouse, the frequency of resistant, moderately resistant, moderately susceptible and susceptible genotypes were 7, 13, 13 and 67 percent, respectively. In field, the regarding frequencies were 14, 49, 7 and 30 percent. The correlation coefficient between final severity of infection, with the values of coefficient of infection and area under the disease progress curve, were 0.97 and 0.95, respectively. Accordingly, 57 genotypes with the desired characteristics, namely final infection intensity of 3.5-40, infection coefficient of 1.4-30 and rAUDPC, 1-32% were identified with MS and MR responses for resistance. Forty-six genotypes were susceptible in seedling stage and resistant in adult plant stage. Some genotypes originated from Afghanistan, Azerbaijan, China and Uzbekistan were resistant to all isolates which could be considered as appropriate sources of resistance to leaf rust disease for breeding of cultivated wheat species.