Genetics of robustness under nitrogen- and water-deficient conditions in field-grown lettuce

Authors: MACIAS-GONZALEZ, MIGUEL - University Of California; TRUCO, MARIA JOSE - University Of California; SMITH, RICHARD - University Of California - Cooperative Extension Service; CAHN, MICHAEL - University Of California; Simko, Ivan; Hayes, Ryan; MICHELMORE, RICHARD - University Of California

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2020
Publication Date: 6/4/2021
Publication URL: https://handle.nal.usda.gov/10113/7709380
Citation: Macias-Gonzalez, M., Truco, M.J., Smith, R., Cahn, M.D., Simko, I., Hayes, R.J., Michelmore, R.W. 2021. Genetics of robustness under nitrogen- and water-deficient conditions in field-grown lettuce. Crop Science. 61(3):1582-1619. https://doi.org/10.1002/csc2.20380.
DOI: https://doi.org/10.1002/csc2.20380

Interpretive Summary: The demand for high quality lettuce has led to intense farming practices in California where most of the lettuce consumed in the United States is produced. Intensive farming has impacted the availability of clean water and polluted the environment due to past over use of nitrogen fertilizers and water. Robust lettuce cultivars with respect to acceptable yield and quality under lower nitrogen and water conditions may help ameliorate these impacts. We have identified chromosomal regions associated with robustness under limited nitrogen and/or limited water conditions. These regions collocate with those previously related to chlorophyll content, plant vigor, nitrogen uptake, ion accumulation in the leaf, and various other physiological traits. These findings provide the basis for further research to identify the genes responsible for robustness and development of genetic markers that can assist breeders in developing robust lettuce cultivars with respect to nitrogen and waters use.

Technical Abstract: Robustness is the measure of the ability to perform well across multiple environments. The genetics of robustness in lettuce (Lactuca sativa) under limited nitrogen application was studied by two parameters obtained from linear regression analysis. Similarly, robustness under limited water use was assessed by two parameters, relative efficiency component (REC) and susceptibility component (SC). The efficiency, sensitivity, and the effect of reduced irrigation on these parameters was assessed for 50 lines of lettuce in 2011. Efficiency, sensitivity, and plant nitrogen uptake and utilization were important traits in robustness under limited nitrogen application. Eight cultivars were re-evaluated in 2012, 2014, and 2016 under high and low nitrogen treatments in order to estimate the repeatability of efficiency and sensitivity. Repeatability was greater for efficiency than sensitivity. In addition, the genetics of efficiency, sensitivity, REC, SC, nutrient concentration, nutrient content, dry to fresh biomass percentage, bolting, and shoot biomass production were studied by quantitative trait locus analysis (QTL) of a recombinant inbred line population derived from the cultivars Grand Rapids and Iceberg. The population was phenotyped in three experiments and genotyped by sequencing. Major clusters of QTLs for these traits were identified in linkage groups (LGs) 3, 7, and 9. Minor effect QTLs for sensitivity were identified in LGs 3 and 4. Intermediate effect QTLs for SC were identified in LGs 4 and 7. These results provide evidence that the components of robustness under limited nitrogen (efficiency and sensitivity) and water (REC and SC) availability are genetically independent and can be improved through breeding.