Lentil root system architecture characterization and the indirect selection of smaller root systems through breeding

Context: Future productivity increases of lentil in the face of changing climates and their expansion into areas traditionally considered marginal for commercial production will require greater tolerance to a range of abiotic constraints, particularly in relation to edaphic conditions. Variation in root system architecture presents a possible means of addressing these constraints. Whilst considerable attention has been paid in the past to aboveground traits; little attention has been given to how root traits can improve adaptation to new environments and productivity. Objective: This study aimed to characterise the diversity in root traits present in the Australian lentil germplasm and how breeding may have impacted these traits. Method: The study examined 36 genotypes of lentil registered over the past 27 years in Australia. The experiments were carried out under glasshouse conditions in 2021 and in the field in 2020 and 2021. Results: Results showed a significant variation in both shoot and root traits. Late maturing genotypes accumulated more root biomass, which was associated with a negative impact on yield, harvest index and 100 grain weight. Root traits that varied substantially among genotypes included root biomass, length, depth, surface area, root: shoot ratio and diameter below 60 cm. Geneotypes were catergoised into two major root forms based on root length distribution, 'Shallow' and 'Deep'. Assessment of genotypes registered since the inception of the breeding program showed an indirect selection for smaller roots with early maturity and increasing yield. Conclusion: Lentil varieties released for broadacre cropping in Australia have been selected for shoot architecture and yield, which has inadvertently resulted in variation in root architecture. Thus, these variations and plasticity in root architectural responses can be directly targeted for the future development of climate-ready crops.