Plant & Animal Genomes XV Conference

January 13-17, 2007
Town & Country Convention Center
San Diego, CA

QTL For Shelf Life In Lettuce Co-Locate With Those For Leaf Biophysical Properties But Not For Leaf Developmental Traits.

Fang Z Zhang¹ , Carol Wagstaff¹ , Anne M Rae¹ , Steve D Rothwell² , Graham JJ Clarkson² , Arinda Kaur¹ , William Keevil¹ , Richard W Michelmore³ , Maria J Truco³ , Mark S Dixon¹ , Gail Taylor¹

¹  School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton, S016 7PX, UK.

²  Vitacress Salads Ltd., Lower Link Farm, St Mary Bourne, Andover, SP11 6DB, UK.

³  Genome Center and Plant Sciences Department, University of California, Davis, CA 95616, USA.

We have examined developmental and biophysical leaf characteristics that influence postharvest shelf life in lettuce, an important leafy crop. The traits were studied using 60 informative F9 recombinant inbreed lines (RILs) derived from a cross between cultivated lettuce (Lactuca sativa cv. Salinas) and wild lettuce (L. serriola acc. UC96US23). QTL 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 with leaf size, weight, chlorophyll content, stomatal index and epidermal cell number per leaf, indicating that these pre-harvest leaf development traits confer postharvest properties.
By studying the population in two contrasting environments in northern and southern Europe, the genotype by environment interaction effects of the QTL relevant to leaf development and shelf life were assessed. In total 106 QTL distributed on all nine linkage groups, were detected from the 29 traits. Only five QTL were common in both environments. Several hotspots on the genome were identified, with relatively little overlap between developmental hotspots and those relating to shelf life. However, QTL for leaf biophysical properties (breakstrength, plasticity and elasticity) correlated well with shelf life. The identification of QTL 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.