Good Breeding Increases Shelf Life

Packaged salad-cut lettuce studied for stability, freshness

Salinas iceberg lettuce. Click here for more information.

SALINAS, CA – The lettuce cut and packaged for food service and salad mixes is an increasingly important component of the produce industry. Lettuce is highly perishable, and the cutting required in processing further shortens its shelf life.

Packaging cut lettuce and other fresh produce in semipermeable plastic films extends shelf life via a technique called “modified-atmosphere packaging”. The success of modified-atmosphere (MA) packaging for lettuce and certain salad greens has led to innovative products, marketing strategies, and enhanced sales to consumers.

Increased demand for the convenient, pre-cut salads and lettuce has led to scientists to search for ways to select lettuce cultivars that stay fresh, colorful, and crisp. Shelf life and visual quality of salad-cut lettuce are affected by many things, including production environment, vegetative maturity, and type of lettuce chosen. Although an increasing variety of lettuce types are being grown, romaine and “crisphead” (such as iceberg) are the most widely produced for salad-cut products

Ryan J. Hayes, a research geneticist, and Yong-Biao Liu, research entomologist at the U.S. Department of Agriculture’s Agricultural Research Service, published the results of a study that should give lettuce breeders and producers enhanced product information and a market edge. During the two-year study, lettuce was processed from field-grown plants of 33 romaine and three “crisphead” cultivars. Shelf life of each cultivar was evaluated after storage in modified-atmosphere bags and in CO₂-free controlled-atmosphere chambers.

Lettuce cultivars ‘Clemente’, ‘Darkland’, and ‘Green Forest’ performed consistently well, ranking in the top 10 in every experiment. ‘Alpi’, ‘Dark Green Romaine’, and ‘Queen of Hearts’ showed clearly unstable shelf life. Hayes noted, “cultivars that performed well in our MA environments will likely be useful as parents in breeding programs to develop new romaine cultivars with an acceptable shelf life. It is also clear that not all crisphead cultivars have good shelf life. Wide variation was observed between the crisphead cultivars Pacific, Salinas 88, and La Brillante.”

In concluding the impact of the study outcomes, Hayes stated; “Breeders can use these methods to characterize or identify breeding lines that are suitable for salad-cut markets before release, and to select for increased shelf life within breeding populations. These practices should facilitate a consistent release of germplasm with high quality in MA environments.”

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The complete study and abstract are available on the ASHS Journal of the American Society for Horticultural Science electronic journal web site: http://journal.ashspublications.org/cgi/content/abstract/133/2/228

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education and application. More information at ashs.org

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Original Article:

Genetic Variation for Shelf-life of Salad-cut Lettuce in Modified-atmosphere Environments
Ryan J. Hayes and Yong-Biao Liu
J. Amer. Soc. Hort. Sci. March 2008 133:228-233. [Abstract] [Full Text] [PDF]

Corresponding author. E-mail rhayes@pw.ars.usda.gov

Digital Cameras, Satellites Measure Crop Water Demand

Crop water demand measured from space

Measurement of canopy cover on 2-year-old almond orchard using the TetraCam camera on a 6.1-m stand. Click here for more information.

FRESNO, CA – Horticultural crops account for almost 50% of crop sales in the United States, and these crops are carefully managed to ensure good quality. But more information is needed about the crops’ growth and response to seasonal and climatic changes so that management practices such as irrigation can be precisely scheduled. Existing research can be difficult to generalize because of variations in crops, planting densities, and cultural practices.

Determining growth stage, size, and water needs are especially important for horticultural crops because most crops are grown in limited water environments and require irrigation. The measurement of “canopy light interception” is a primary means of determining water and irrigation needs. Fractional canopy cover (CC) is a relatively easily measured property that is a good indicator of light interception. Canopy cover, the percent of the soil surface covered by plant foliage, is an important indicator of stage of growth and crop water use in horticultural crops. Methods of using remote sensors to determine canopy cover in major crops have been studied for years, but the studies have not included most horticultural crops.

Thomas J. Trout, Research Leader at the U.S. Department of Agriculture’s Agricultural Research Service, along with colleagues from the NASA Earth Science Division, recently published a study that addresses the relationship of remotely sensed normalized difference vegetation index (NDVI) relative to canopy cover of several major horticultural crops in commercial fields.

The research team measured canopy cover of 11 different annual and perennial horticultural crops in various growth stages on 30 fields in California’s San Joaquin Valley with a handheld multispectral digital camera. Canopy cover was compared with NDVI values calculated from Landsat 5 satellite imagery. According to Trout, “The NDVI was highly correlated and linearly related with measured CC across the wide range of crops, canopy structures, and growth stages, and predicted CC with mean absolute error of 0.047 up to effective full cover. These results indicate that remotely sensed NDVI may be an efficient way to monitor growth stage, and potentially irrigation water demand, of horticultural crops.”

The research indicates that NDVI can potentially provide field-specific and regional estimates of CC for horticultural crops with minimal requirement for supporting information. This new information may also be useful to improve estimates of crop growth stage and water use.

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The complete study is available on the ASHS HortScience electronic journal web site: http://hortsci.ashspublications.org/cgi/content/abstract/43/2/333

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education and application. More information at ashs.org

 

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This press release also available on EurekAlert!

Original Article:

Remote Sensing of Canopy Cover in Horticultural Crops
Thomas J. Trout, Lee F. Johnson, and Jim Gartung
HortScience April 2008: 333–337. [Abstract] [Full Text] [PDF]

Corresponding author. E-mail Thomas.Trout@ars.usda.gov

Saltwater Olives

Saline water irrigation cultivates healthy olives

BEER-SHEVA, ISRAEL – The news that olives are sources of “good fat” has increased worldwide demand for the luscious, versatile fruits. Olives have become extremely popular, enjoyed as condiments, appetizers, spreads, and additions to salads and sauces. Their heart-healthy oil has is also enjoying superstar status in kitchens around the world.

The olive’s reputation as a health food is being borne out by modern science, as studies of olive-consuming Mediterranean peoples have shown. To keep the world’s olive lovers satisfied, an intensive wave of olive planting has occurred in the past decade in many parts of the world. Traditionally, olives have been cultivated in the Mediterranean region. But fresh water is becoming increasingly hard to come by in semiarid areas, and irrigation of most new olive plantations is often accomplished with low-quality sources of water that contain relatively high levels of salt.

The relationship between the use of “saline water” and olive cultivation has been actively studied for many years. According to Professor Zeev Wiesman, Department of Biotechnology Engineering at Ben-Gurion University of the Negev, it is well-known that saline conditions can limit the development of olives, mainly because the salty water interferes with the olives’ root system and causes “toxic accumulation of chloride and sodium ions on the leaves.”

Weisman and other researchers recently published the report of a long-term study in which they established a new saline irrigation controlled experimental olive plot. The plot was planted with 12 local olive cultivars as well as olive varieties from Mediterranean countries, then divided into identical subplots: one irrigated with tap water, the second with moderate saline water. “In the study, we aimed to evaluate and compare the vegetative and reproductive multiannual response of mature yielding trees of the 12 tested olive cultivars drip-irrigated with tap water and moderate saline water in a commercial orchard simulation study in a semiarid area”, stated Weisman.

Olive trees in both subplots were evaluated for trunk growth, olive yield, oil percentage, olive oil yield, and other characteristics. The data clearly showed a significant difference between the tested cultivars in terms of growth, yield, and oil parameters. Researchers concluded that all the tested olive varieties could be cultivated with moderate saline water irrigation. Weisman added: “Although a significant variation in terms of horticultural performance was found between the various tested olive cultivars, the differences may be attributed to the natural characteristics of each cultivar or to their rate of adaptation to the environmental conditions in the tested area, rather than to moderate saline drip irrigation.”

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The complete study and abstract are available on the ASHS HortScience electronic journal web site: http://hortsci.ashspublications.org/cgi/content/abstract/43/2/320

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at ashs.org

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This press release also available on EurekAlert!

Original Article:

Vegetative and Reproductive Response of Olive Cultivars to Moderate Saline Water Irrigation
Sebastian Weissbein, Zeev Wiesman, Yhonathan Ephrath, and Moshe Silberbush
HortScience Apr 1 2008: 320–327. [Abstract] [Full Text] [PDF]

Corresponding author. E-mail wiesman@bgu.ac.il

Reclaimed Wastewater Benefits Florida’s Citrus Orchards

Cities find new uses for treated water in citrus crop irrigation

Navel oranges growing in Florida. Click here for more information.

IMMOKALEE, FL – The Sunshine State has seen rapid growth in population during the last 50 years. The 1997 U.S. Census showed that the population of Florida increased more than five-and-a-half times from 1950 to 2000. Naturally, along with population increases, Florida is experiencing an increase in the amount of municipal waste. Studies confirm that the amount of wastewater generated by cities in Florida has increased more than five-fold since 1950.

Environmental concerns about pollution of surface waters by treated wastewater have caused many communities to consider alternate ways to use secondary-treated, or reclaimed, wastewater. Before 1986, the city of Orlando and Orange County were discharging wastewater into a creek that flows into Lake Tohopekaliga in central Florida. To address concerns that the process would affect the quality water in the lake, city and county officials, along with the U.S. Environmental Protection Agency, devised a plan to use the wastewater for agricultural irrigation.

According to a 2005 report by the Florida Department of Environmental Protection, there are currently 440 “reclaimed water reuse systems” in Florida, irrigating thousands of acres of golf courses, public land, and residential landscapes with 2,385 million liters of reclaimed water per day. Reclaimed wastewater is also being used to irrigate some of Florida’s world-renowned citrus orchards. Because yearly rainfall in Florida is seasonal, with 75% of annual rainfall usually occurring between June and September, citrus growers rely on supplemental irrigation for healthy citrus crops.

In a study supported by the City of Orlando and Orange County (FL), researchers set out to determine whether long-term irrigation with treated municipal wastewater reduced citrus tree health (appearance and leaf nutrient content), decreased fruit loads, impacted fruit quality, or created increases in soil contaminants. Dr. Kelly T. Morgan, a scientist at the University of Florida’s Southwest Florida Research and Education Center, published the study report in the April 2008 issue of HortScience.

Dr. Morgan explained, “Increased water use by the growing population and localized water shortages during low rainfall years have resulted in the development of water use restrictions and decreases in permitted water use for agriculture. Increased use of reclaimed water for agricultural irrigation would not only reduce the wastewater disposal problem for urban areas, but could also reduce the amount of water withdrawn from Florida’s aquifers used for irrigation.”

The yearly monitoring project, which began in the 1990s and ended in 2004, concluded that using reclaimed water for irrigation of citrus orchards showed few detrimental effects on the orchards. Morgan commented, “Appearance of trees irrigated with reclaimed water was usually better, with higher canopy, leaf color, and fruit crop ratings than orchards irrigated with groundwater. Although there was higher weed growth in reclaimed water-irrigated orchards due to higher soil water content, growers apparently have made adequate adjustments to their herbicide practices.”

Researchers concluded that long-term citrus irrigation with high-quality reclaimed water on well-drained sandy soils did not significantly reduce tree viability or yield and required relatively little adjustment in crop production practices: good news for the environment and citrus producers alike.

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The complete study and abstract are available on the ASHS HortScience electronic journal web site: http://hortsci.ashspublications.org/cgi/content/abstract/43/2/459

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at ashs.org.

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This press release also available on EurekAlert!

 

Original Article:

Effects of Reclaimed Municipal Waste Water on Horticultural Characteristics, Fruit Quality, and Soil and Leaf Mineral Concentration of Citrus
Kelly T. Morgan, T. Adair Wheaton, Larry R. Parsons, and William S. Castle
HortScience Apr 1 2008: 459–464. [Abstract] [Full Text] [PDF]

Corresponding author. E-mail ktm@ifas.ufl.edu