Author
|
Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/9/2008 Publication Date: 3/20/2008 Citation: Hayes, R.J., Liu, Y. 2008. Genetic Variation for Shelf-life of Salad-cut Lettuce in Modified-atmosphere Environments. Journal American Society Horticultural Science. 133(2):228-233. Interpretive Summary: Minimally processed lettuce (Lactuca sativa L.) is an important component of the lettuce industry. The product is highly perishable, and cold storage in conjunction with modified atmosphere (MA) packages that are low in O2 and high in CO2 are used to extend its shelf-life. Given the importance of this market, lettuce cultivars, breeding lines, and populations should be selected that process into salad with stable shelf-life in MA environments. The objectives of this research were to 1) determine if cultivars of lettuce differ for shelf-life in low O2 modified atmosphere environments and 2) develop high throughput method to evaluate potential cultivars for shelf-life. Salad was prepared from field grown lettuce of 33 romaine and 3 crisphead cultivars over two field seasons. Shelf-life of salad was evaluated after storage in MA bags and in CO2-free controlled atmosphere chambers with gas ratios of 0.2% O2 : 99.8% N2, 1.0% O2 : 99.0% N2, or 5.0% O2 : 95.0% N2. Symptoms on leaf blade tissue was water soaked, limp, and dull to dark or black in color, while mid-rib tissue and heart leaves were water soaked and translucent to dark brown in color. The shelf life of these cultivars was different. Oxygen concentration did not affect shelf-life in the controlled atmosphere chamber experiment, and indicates that the observed symptoms in the majority of cultivars were probably not from low O2 damage or CO2 injury, although multiple mechanism of deterioration may be involved. Selection for lettuce cultivars, breeding lines, and populations with extended shelf-life is possible using either MA bags or controlled atmosphere chamber testing methods, and could insure a consistent release of germplasm with stable shelf-life in modified atmosphere environments. Technical Abstract: Minimally processed lettuce (Lactuca sativa L.) is an important component of the lettuce industry. The product is highly perishable; cold storage and modified atmosphere (MA) packaging are used to extend its shelf-life. Given the importance of this market, lettuce cultivars, breeding lines, and populations should be selected that process into salad with stable shelf-life in MA environments. The objectives of this research were to 1) determine the genetic variation in lettuce for shelf-life in low O2 modified atmosphere environments and 2) develop high throughput evaluation methods suitable for a large scale breeding program. Salad was prepared from field grown lettuce of 33 romaine and 3 crisphead cultivars over two field seasons. Shelf-life of salad was evaluated after storage in MA bags and in CO2-free controlled atmosphere chambers with gas ratios of 0.2% O2 : 99.8% N2, 1.0% O2 : 99.0% N2, or 5.0% O2 : 95.0% N2. Symptoms on leaf blade tissue was water soaked, limp, and dull to dark or black in color, while mid-rib tissue and heart leaves were water soaked and translucent to dark brown in color. Genetic variation for shelf-life was detected using either MA bags or controlled atmosphere chambers, and the results from both years and testing methods were significantly correlated. Oxygen concentration did not affect shelf-life in the controlled atmosphere chamber experiment, and indicates that the observed symptoms in the majority of cultivars were probably not from low O2 damage or CO2 injury, although heterogeneous mechanism of deterioration may be involved. Selection for lettuce cultivars, breeding lines, and populations with extended shelf-life is possible using either MA bags or controlled atmosphere chamber testing methods, and could insure a consistent release of germplasm with stable shelf-life in modified atmosphere environments. |
