Reaction of the south warm agro-climate zone elite wheat lines of Iran to stem rust at seedling and adult-plant stages

Wheat stem rust, caused by Puccinia graminis f.sp. tritici, which has caused heavy damage to wheat in the past, is a potential threat to the production of this crop. Considering the history of this disease in the south warm agro-climate zone of Iran and the possibility of the disease epidemics if the environmental conditions are provided, the examination of wheat cultivars and breeding lines to stem rust is a part of the south warm wheat breeding program at Cereal Research Department, Seed and Plant Improvement Institute (SPII). In this way, it is tried to increase the resistance of wheat cultivars that are going to be introduced in this zone.

The present study was carried out to determine the reaction of 56 elite wheat lines of the south warm breeding program including 28 lines obtained from the program in 2015 (named ERWYT-S-94) and 28 other lines from 2016 (named ERWYT-S-95) to stem rust at seedling and adult-plant stages. Investigating the seedling stage resistance was carried out by determining the reaction of experimental lines to three common races of Kelardasht, Mazandaran, and one Ug99 race collected from Shavour, Khouzestan in the greenhouse in Karaj. Investigating the adult-plant resistance was carried out under artificial inoculations in the field in Kelardasht during two cropping years of 2015-16 and 2016-2017 for the ERWYT-S-94 materials and two cropping years of 2016-2017 and 2017-2018 for the ERWYT-S-95 materials.

Based on the results of the present study, the line S-94-25, being resistant to four races of P. graminis f.sp. tritici at seedling stage, showed high resistance to stem rust at adult-plant stage so that the maximum disease rate of 20MR was observed for this line during the two years of experiment. The line S-94-16 also showed high resistance against two races of Kelardasht at seedling stage, and the disease rate at adult-plant stage was a maximum of 20MR. In addition, the line S-94-22 having resistance to three races from Kelardasht and the line S-94-27 with resistance against two races from Kelardasht and the race collected from Shavour at seedling stage, were less susceptible to the disease at adult-plant stage with a maximum disease rate of 30MS. Furthermore, the line S-95-22 with resistance to two races of Kelardasht and the Shavor race and the line S-95-12 with resistance to one race of Kelardasht and the Shavour race at seedling stage, showed less susceptibility to the disease at adult-plant stage with the maximum disease of 40MRMS. Due to importance of wheat stem rust in the south warm agro-climate zone, it is necessary to transfer disease resistance genes to new wheat lines and introduce disease resistant cultivars in this climate.