UC Riverside

Bread wheat is an allohexaploid crop with a large and complex genome structure. It was one of the first crops domesticated by human beings in the Near East and it had dramatic effects on human history. The amount of energy gained per hour of work from wheat was much higher than hunting and gathering. Ancient farmers continuously selected it to increase seed size, grain yield, and straw yield to feed a growing population; this scenario has not changed for thousands of years. Plant scientists, breeders, and farmers are still working to improve grain yield to support growing demand. Introduction of genetic variation with novel alleles has been a major component of plant breeding, especially after the major genetic bottlenecks of the last century.

I have aimed to retrieve some of the available genetic variation within the Triticeae tribe by screening wild wheat relatives, landraces, modern wheats, and a synthetic wheat population. All of the above materials were evaluated to genetically locate and identify root system traits.

Breeding for drought tolerance requires selection for traits that improve water uptake and use efficiency. Root system traits are a major component to improve water acquisition. Here we report significant genotypic variation for root traits within and between wheat wild relatives, bread wheat landraces, modern wheats, and the Synthetic W7984* Opata M 85 doubled haploid (SynOpDH) mapping population. Up to four-fold difference for root size within wild accessions, eight-fold difference within landraces and modern wheats and fourteen-fold difference within the progeny of the SynOpDH population was observed.

This large range in genotypic variation may provide many useful alleles for breeders, especially those who target rain-fed growth conditions in their breeding programs. Even though studying the root system is technically challenging, and time and labor intensive, an urgent need for drought tolerant crops makes it a necessity. There is a major need for research leading to a complete understanding of the genetic control of the wheat root system. Advances in genotyping technologies, marker assisted selection, and fast / accurate phenotyping may provide useful tools to select root traits such as, deep root biomass, number of seminal and nodal roots, and root angle with less labor and time, to develop drought tolerant wheat cultivated varieties.