JXB Advance Access originally published online on March 7, 2007
Journal of Experimental Botany 2007 58(6):1433-1449; doi:10.1093/jxb/erm006
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© 2007 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)
RESEARCH PAPER |
QTLs for shelf life in lettuce co-locate with those for leaf biophysical properties but not with those for leaf developmental traits
1School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton S016 7PX, UK
2Vitacress Salads Ltd, Lower Link Farm, St Mary Bourne, Andover SP11 6DB, UK
3Genome Center and Plant Sciences Department, University of California, Davis, CA 95616, USA
To whom correspondence should be addressed. E-mail: g.taylor{at}soton.ac.uk
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.
Key words: Biophysical, biomechanical properties, leaf development, lettuce, microbiology, post-harvest, QTLs, shelf life
* Present address: Centre for Advanced Studies, Cardiff University, 43–45 Park Place, Cardiff CF10 3BB, UK.
Present address: School of Food Biosciences, University of Reading, Whiteknights, PO Box 226, Reading RG6 6AP, UK.
Present address: School of Biosciences, University of Nottingham, Sutton Bonnington Campus, Loughborough LE12 5RD, UK.
Received 12 October 2006; Revised 13 December 2006 Accepted 22 December 2006