**Association Mapping of Root Traits for Drought Tolerance in Bread Wheat**

Israr Ahmad, Niaz Ali, Habib Ahmad and Inamullah

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/67242

#### **Abstract**

Bread wheat (*Triticum aestivum* L., 2n = 6x = 42, AABBDD) is one of the most important crops, making staple food for more than 40 countries and over 35% of the global population. Drought stress is among the major constraints to wheat production as it affects plant growth, gene expression and yield potential of the crop. Development of elite wheat cultivars with the ability to grow and reproduce in water-limited soils seems to be the most enduring solution of addressing drought stress. A total of 100 lines including well-adapted wheat cultivars were evaluated for important root traits and complemented with 102 PCR-based markers aiming to understand their genetic structure and to identify molecular markers that are closely associated to quantitative trait loci (QTLs) of important root traits. Alleles per locus are counted and polymorphic information content (PIC) values are calculated. Population structure of these lines was analyzed with general linear model (GLM) and mixed linear model (MLM) approaches for identification of QTLs associated with important root traits. The results indicated the presence of two novel QTLs on the homoeologous group 2 and group 5 of wheat that may be related to drought stress resistance. Our results may facilitate the development of agronomically desirable drought stress-resistant wheat germplasm.

**Keywords:** bread wheat, genetic variation, drought tolerance, association mapping, QTL
