Evaluation and Association Mapping of Bread Wheat (Triticum aestivum) pre-breeding Lines for Reaction to Leaf Rust (Puccinia triticina)

Abstract

Bread wheat was domesticated 8,000 years ago and spread over the world and became the staple food of major civilizations in Europe, Western Asia, and North Africa. Today, around 95% of the wheat grown in the world is hexaploid wheat, Triticum aestivum (2n= 42 chromosomes). In order to meet the food demand of a growing human population and address food security challenges, it is essential to enhance economically important traits of bread wheat. Genetic resources conserved in gene banks are often considered to be important gene pools for breeding programmes. However, they require additional work, such as thorough evaluation and preselection efforts, to discover their crucial value and meet breeders' objectives. Within this context, the objectives of our study were to 1) carry out an evaluation of 480 bread wheat prebreeding lines derived from interspecific crosses with different crop wild relative species for resistance to leaf rust and 2) identify associated markers using the GWAS approach. The 480 lines were evaluated for resistance to leaf rust at the seedling stage under controlled conditions using a mixture of three isolates in an augmented experimental design. The study revealed a high genetic component of leaf rust with a heritability of 0.8. Approximately 34% of the lines showed resistance or immunity to leaf rust, 22% exhibited moderate resistance, and 43.54% displayed moderate susceptibility to high susceptibility. The highest number of lines expressing an Immune and resistant type of disease reaction was recorded in lines crossed with Aegilops bicornis var. bicornis (62%) followed those issued from crosses with Aegilops ovata IGAECO96-21(14%). The GWAS analysis performed using 3897 DarTag markers, revealed four DarTag markers on 1D, 3A , 5A and 6D to be in significant linkage with the disease resistance. In conclusion, this study highlights the importance of crop wild relatives as a source of valuable genetic diversity resistance to leaf rust. The associated markers presented here can improve the efficiency of breeding new resistant bread wheat varieties.