Evaluation of Seedling Stage Resistance of Commercial Bread Wheat Cultivars to Black Rust Disease using GGE Biplot Method

Wheat is of great importance in the nutrition of human society, especially in third world countries. Stem rust or black rust is the most common, widespread and destructive wheat disease in Iran and around the world. The extent of damage of this disease, depending on its severity, can vary from reduced yields to complete destruction of farms. The development of genotypes with the black rust resistance gene is one of the most important strategies to combat this destructive disease, considering the importance of wheat in the nutrition of human society, especially in third world countries. Identifying sources of resistance to import them in breeding programs leads to the development of resistant genotypes.

89 bread wheat cultivars along with Morocco as susceptible control were studied with the aim of identifying stem rust resistance cultivars in the seedling stage to six races of the disease in randomized complete block design with two replications. All stages of plant assessment were carried out in the Cereal Research Department, Seed and Plant Improvement Institute (SPII), Karaj, Alborz, Iran, in 2019. In the GGE Biplot graphics model, each disease races (PKTTF, PKSTC, PKSTF, PTRTF, TTTTF and PTTTF) were considered as an environment, Therefore, based on the singular value decomposition of cultivars' response to races, graphical analysis was performed.

PKTTF, PKSTC, PKSTF, PTRTF and TTTTF were classified into a group based on the degree of correlation between them and Pishtaz, Sivand, Adl, Pishgam, Niknezhad and Alvand cultivars had resistance to those races. PTTTF race was placed in the second group and Hamoon, Marvdasht, Zarrin, Gohar, Darab 2 and Sabalan cultivars showed resistance against this race. Pishtaz and Adl illustrated stable resistance reaction for all six studied races. The severity of virulence of the studied races confirmed the high pathogenicity of PTTTF on the investigated germplasm. The orders of pathogenicity of other races from highest to lowest were PKTTF, TTTTF, PTRTF, PKSTF and PKSTC.

The multivariate graphical GGE biplot method was effective in investigating the resistance of commercial wheat cultivars and provided valuable information on the identification of cultivars with genes resistant to black rust disease. By introducing these cultivars in breeding programs, an effective step can be taken to develop cultivars resistant to this disease and to deal with it genetically.