|Galeano, Carlos - University Of California|
|Luo, Yaguang - Sunny|
|Antonise, Rudie - Keygene Nv|
Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2014
Publication Date: 7/1/2014
Citation: Hayes, R.J., Galeano, C.H., Luo, Y., Antonise, R., Simko, I. 2014. Inheritance of decay of salad-cut lettuce in a recombinant inbred line population from ‘Salinas 88’ x ‘La Brillante’. Journal of the American Society for Horticultural Science. 139:388-398.
Interpretive Summary: Fresh-cut lettuce packaged as salad-mixes are increasing popular to consumers. The cutting involved in processing these products can shorten its shelf-life, and production, processing and shipping environments are tightly controlled in order to promote long shelf-life. Lettuce cultivars can also differ in shelf-life. New lettuce cultivars bred with resistance to pests and environmental stresses must possess shelf-life at least as good as currently used cultivars in order to be used by growers, packers, processors, and consumers. New cultivars bred with extended shelf-life that reduce post-harvest spoilage increase overall production efficiency by reducing the frequency that lettuce must be replaced in the market place. The objective of this research was to determine the inheritance of shelf-life in a lettuce population derived from a cross between the slow decaying cultivar Salinas 88 and the rapid decaying cultivar La Brillante. The variation in shelf-life among the progeny from this cross can be used to determine the number and strength of shelf-life quantitative trait loci (QTL), which are regions on lettuce chromosomes harboring genes for shelf-life. Knowing the inheritance of shelf-life gives lettuce breeders an opportunity to construct the most efficient breeding strategies that increase the likelihood of developing improved cultivars. In this research, three QTL controlling the rate of decay of fresh-cut lettuce were detected on chromosomes (ch) 1, 4, and 9. For all QTL, slow decay was conferred by the ‘Salinas 88’ version, or allele, of the QTLs. The QTL on ch 4, sl-4.1, was the most important determinant of decay and was a significant factor in determining shelf-life regardless of lettuce production environment and packaging condition. Lettuce with the La Brillante allele of sl-4.1 resulted in rapid decay, becoming unusable in one to two weeks after harvest. In contrast, lettuce with the Salinas 88 allele of sl-4.1 lasted one month or more. In additional research, the effect of sl-4.1was found to be specific to fresh-cut lettuce and had no effect on the decay of whole heads. Selection for slow decay of fresh-cut lettuce will likely be effective at developing cultivars with suitably long shelf-life. However, shelf-life evaluations are time consuming and require large amounts of field grown lettuce. sl-4.1 is a good QTL to develop molecular markers for marker assisted selection, a breeding method were laboratory analysis of DNA based molecular markers can be used to select for the Salinas 88 allele of sl-4.1 without the need to evaluate fresh-cut lettuce for shelf-life.
Technical Abstract: Fresh-cut lettuce packaged as salad-mixes are increasing popular to consumers. New cultivars must possess shelf-life at least equivalent to currently used cultivars in order to be adopted, while those bred with extended shelf-life that reduce post-harvest loss could increase overall production efficiency. Understanding the inheritance of shelf-life is needed to develop efficient breeding strategies for this trait. In five California and Arizona field experiments, a population of 95 recombinant inbred lines (RILs) from Salinas 88 x La Brillante was grown and evaluated for decay of cut lettuce in modified atmosphere packages flushed with N2 or air. A subset of RILs was evaluated for decay of whole heads. The greatest range of RIL means for decay of cut lettuce was observed between 29 and 50 days after harvest (DAH). During this time period heritability of RIL means ranged from 0.51 to 0.87 and correlations between field experiments ranged from 0.47 to 0.84 (P < 0.01). A linkage map with 14 linkage groups (LG) of 106 SNP and 214 AFLP® markers was used in multiple interval mapping and mixed model composite interval mapping. Three quantitative trait loci (QTL) for decay of cut lettuce were detected on LGs 1, 4, and 9. The QTL on LG 4 (sl-4.1) was a major determinant of decay, with R2 ranging from 0.57 to 0.86 between 29 and 43 DAH. QTL x environment and QTL x QTL interactions contributed less than 13% to the total variation. RILs with the ‘Salinas 88’ allele of sl-4.1 had slower decay when packaged in air compared to N2, while no difference between air and N2 was detected with the ‘La Brillante’ allele. Genetic variation among RILs for whole head decay was found, but could not be attributed to sl-4.1. Decay of cut lettuce in Salinas 88 x La Brillante is a highly heritable trait conditioned by few QTL and phenotypic selection is likely to be effective. However, shelf-life evaluations are time consuming and require large amounts of field grown lettuce. Therefore, sl-4.1 is a good QTL to develop molecular markers for marker assisted selection.