A Novel Phenotyping Platform Allows Selection for Cereal Root Traits

Crop root architecture is important for acquisition of resources such as phosphorus, nitrogen and water. However, selection for specific root architecture remains challenging due to limited ability to phenotype and select for root traits.

When moisture remains deep in the soil during periods of terminal drought stress, access to this deep soil water is important for productivity of cereal crops. In cereals, vertical angle of seedling roots has been associated with narrower lateral root architecture and greater root length density at depth in mature plants, leading to improved access to deep soil moisture.

But, how can we select for such root architecture?

A high-throughput root trait screening technique was developed for seedlings (Richard et al, 2015, Plant Method). The potential for phenotypic selection for seedling root angle using this method was investigated. A panel of 22 wheat (Triticum aestivum L.) lines, adapted to Australian environments subject to terminal drought stress, revealed genetic diversity in seedling root angle with a range of 72 to 106°. After phenotypic selection was applied to early generation lines from bi-parental populations, a shift was observed in mean seminal root angle in populations selected for ‘narrow’ or ‘wide’ root angle, respectively. Only two rounds of selection significantly shifted the mean root angle as much as 10° in some populations. By combining this efficient, high-throughput phenotyping method with rapid generation advance using the speed breeding technique, lines expressing either narrower or wider seedling root angles were developed within only 18 months.

Genomic regions under selection were revealed by comparing allele frequencies in the ‘narrow’ versus ‘wide’ populations, indicating that marker-assisted selection may be possible.

Our results indicate that valuable variation for root traits can potentially be selected phenotypically or using markers in cereal crops to enrich breeding populations for lines with adaptive root architecture.