QTLs for shelf life in lettuce co-locate with those for leaf biophysical properties but not with those for leaf developmental traits

• Published in: Journal of experimental botany Vol. 58; no. 6; pp. 1433 - 1449
• Main Authors: Zhang, Fang Z, Wagstaff, Carol, Rae, Anne M, Sihota, Arinder K, Keevil, C. William, Rothwell, Steve D, Clarkson, Graham J.J, Michelmore, Richard W, Truco, María José, Dixon, Mark S, Taylor, Gail
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.01.2007; Oxford Publishing Limited (England)
• Subjects: Biological and medical sciences; biomechanical properties; Biophysical; Cell walls; Chlorophyll - metabolism; Chlorophylls; Crosses, Genetic; England; Epidermal cells; Fundamental and applied biological sciences. Psychology; Lactuca - genetics; Lactuca sativa; Leaf area; leaf development; Lettuce; Metabolism; microbiology; Phenotypic traits; Photosynthesis, respiration. Anabolism, catabolism; Plant cells; Plant Leaves - anatomy & histology; Plant Leaves - genetics; Plant Leaves - growth & development; Plant physiology and development; Plants; Portugal; post-harvest; QTLs; Quantitative Trait Loci; Research Papers; Shelf life; England; Portugal; Biophysical; shelf life; microbiology; biomechanical properties; QTLs; lettuce; post-harvest; leaf development; Agronomic character; Development; Plant leaf
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/erm006

Developmental and biophysical leaf characteristics that influence post-harvest shelf life in lettuce, an important leafy crop, have been examined. The traits were studied using 60 informative F9 recombinant inbed lines (RILs) derived from a cross between cultivated lettuce (Lactuca sativa cv. Salinas) and wild lettuce (L. serriola acc. UC96US23). Quantitative trait loci (QTLs) for shelf life co-located most closely with those for leaf biophysical properties such as plasticity, elasticity, and breakstrength, suggesting that these are appropriate targets for molecular breeding for improved shelf life. Significant correlations were found between shelf life and leaf size, leaf weight, leaf chlorophyll content, leaf stomatal index, and epidermal cell number per leaf, indicating that these pre-harvest leaf development traits confer post-harvest properties. By studying the population in two contrasting environments in northern and southern Europe, the genotype by environment interaction effects of the QTLs relevant to leaf development and shelf life were assessed. In total, 107 QTLs, distributed on all nine linkage groups, were detected from the 29 traits. Only five QTLs were common in both environments. Several areas where many QTLs co-located (hotspots) on the genome were identified, with relatively little overlap between developmental hotspots and those relating to shelf life. However, QTLs for leaf biophysical properties (breakstrength, plasticity, and elasticity) and cell area correlated well with shelf life, confirming that the ideal ideotype lettuce should have small cells with strong cell walls. The identification of QTLs for leaf development, strength, and longevity will lead to a better understanding of processability at a genetic and cellular level, and allow the improvement of salad leaf quality through marker-assisted breeding.