Vegetable Production and Marketing News
JUNE 2000 - VOLUME 10, NUMBER 6

Edited by
Frank J. Dainello, Ph.D.
Extension Horticulturist - Commercial Vegetable Crops
The Texas A&M University System
College Station, Texas 77843-2134

Appearing Within . . .
You may click on an article below or scroll down.

• Dr. Dan Lineberger Elected President of the ASHS
• Comanche County Watermelon Tour
  
• 1999 Yellow-Flesh Potato Trial Results, Dalhart, Texas
• Disease Identification: Onion Slippery Skin
• What is Being Done to Regulate GMOs?

Dr. Dan Lineberger Elected President of the American Society for Horticultural Science

Dan is a pioneer in the development of web-based information-transfer technology. As a result of his efforts in this area, he is one of the most respected horticulturists in the United States. Election to the office of President of ASHS is the highest compliment one can be paid by his peers in the field of horticulture.

For a sample of Dan's work with web-based technology, check out the Aggie horticulture web site at: http://aggie-horticulture.tamu.edu

Congratulations Dan !

Coming Event

Comanche County Watermelon Tour
Comanche, Texas
June 15, 2000
8:00 a.m. - Noon
For specific information, contact Bob Whitney, CEA-Ag
Comanche County, at (915) 356-2539.

1999 Yellow-Flesh Potato Trials Results
Dalhart, Texas

By Frank J. Dainello, Creighton Miller,
Doug Scheuring, and Jeff Koyn

Specialty potatoes are also following this trend. In recent years, the yellow-flesh potato has perked the interest of potato connoisseurs. In order to assist Texas potato growers to obtain a significant share of this emerging market, Dr. Creighton Miller, potato breeder at Texas A&M University, has included the development of yellow-flesh potatoes in his program.

During the 1999 growing season, advanced selections from this effort were tested in trials conducted at three locations across the state: Dalhart, Dilley, and Spring Lake. The results of the Dalhart trial are reported herein.

Ten yellow-flesh entries were evaluated in a randomized block design with four replicates. Each entry plot consisted of a single 36-inch-wide raised bed 18 feet 9 inches in length. Plants were spaced 9 inches apart within the bed. The test site was a Dallam loamy sand located in a grower's field near Dalhart. The plots were fertilized with 300 lbs/A N plus 40 lbs/A P2O5 plus 100 lbs/a K20. Supplemental water was applied as needed, using a center-pivot irrigation system. All other cultural practices were as normally applied by the grower. The test was planted on May 18, vine-killed on October 4, and hand-harvested on October 11. Results obtained from this trial are presented in Table 1.

Yukon Gold-CS (Colorado seed source) was found to be the highest-yielding entry in the trials, producing 457.1 cwt/A. Molli was a close second, producing 454.2 cwt/A. However, no statistically significant differences were found -- under the conditions of this study -- between these two varieties and Delikat, FL 1944, Yukon Gold-TX (Texas seed source), and TX1674-/WY.

Although the variety Molli was the next-to-highest-yielding variety, average tuber size (3.1 oz) was less than desirable. A similar situation was evident with tubers of the variety Delikat. FL1994 was also found to be one of the higher-yielding lines in the trial. Unfortunately, this line also produced the highest percentage of culls and No. 2-size tubers (38.4 percent). The lowest percentage of culls and No. 2-size tubers was produced by two of the three TAMU lines: TX1674-W/Y and the yellow-flesh russet selection TX 1523-1 Ru/y.

The variety Valisa produced tubers having a very attractive internal yellow flesh color, but possessed a very unattractive external appearance.

Based on the results of this evaluation, the TAMU breeding line TX 1674-W/Y compared very favorably with both Yukon Gold entries. Although the yield from the Yukon entries exceeded the yield from TX 1674-W/Y, it should be noted that plant-stand in the Yukon varieties was 90 percent or better. For some unexplained reason, stand in the TX 1674-W/Y was only 75 percent. In addition, the overall variety-rating data indicated that TX 1674-W/Y and Yukon Gold-TX were superior to the other entries.

For specific information on this or other yellow-flesh trials in Texas, contact Dr. Creighton Miller, (979) 845-3828, jcmillerjr@tamu.edu or Dr. Frank J. Dainello, (979) 845-8567, f-dainello@tamu.edu

Disease Identification:
Onion Slippery Skin

Causal Agent: Burkholderia gladioli pv. allicola (Sny. Pseudomonas gladioli pv. allicola)

Distribution: Worldwide

Symptoms: Field symptoms often appear as one or two wilted leaves in the center of the leaf cluster. These leaves eventually turn pale-yellow, and die back from the tip, while older and younger leaves maintain a healthy green appearance.

During the early stages of this disease, the bulbs may appear healthy except for a softening of the neck tissue. In longitudinal sections, one or more inner scales will look watery or cooked. The disease progresses from the top of the infected scale to the base, where it can then spread to other scales, rather than spreading crosswise from scale to scale. Eventually, all the internal tissue will rot.

Finally, the internal scales dry out, and the bulb shrivels. Squeezing the base of an infected plant causes the rotten inner portion of the bulb to slide out through the neck, hence the name 'slippery skin'.

Conditions for Disease Development: The bacterium requires moisture for infection, and grows in the temperature range of 5 to 41 degrees C (41 to 105 degrees F). Severe disease can occur during periods of high rainfall combined with strong winds or hail. Heavy irrigation and persistent dews are also conducive to this disease.

This bacterium is soilborne, and can be readily water-splashed to the foliage and necks, where it can enter through wounds. As the plant matures, it increases in susceptibility, with the mature plant being highly susceptible. In warm weather (30 degrees C / 86 degrees F), infected bulbs can decay within 10 days. However, in storage, the decay moves slowly, often requiring 1 to 3 months for total decay.

Control: Onions should be harvested when the bulbs have reached full maturity, and should not be stored until they have been properly dried. Minimizing stem and bulb injury and avoiding overhead irrigation when the crop is approaching maturity can reduce losses from this disease.

What is Being Done to Regulate GMOs?

The use of existing authorities has enabled federal oversight of environmental and food risks from molecularly-modified crops, and avoided the difficulty of implementing new regulatory policies and agencies. In the 1980s, the NRC, various professional scientific groups, and congressional hearings provided science-based guidance for the oversight of molecularly-modified organisms. For example, the NRC published in 1989 "Framework for Field Testing of Genetically Modified Organisms." The NABC held an open forum on "Food Safety and Nutritional Quality" in 1990, and broadly distributed the report of that meeting.

Almost a decade of favorable food experience has accrued with fermentatively-produced chymosin (FPC), a product of molecular biotechnology used for cheese-making. In 1990, it became the first food product approved by the FDA. Today, FPC has an 80 to 90 percent market share in cheese-making in the U. S. and Canada. It is approved as 'vegetarian', 'kosher', and 'halal', and is fifty-fold more pure than the traditional product -- rennet, from the stomachs of slaughtered calves.

In 1992, the FDA published its policy document "Statement of Policy: Foods Derived from New Plant Varieties." Its regulatory policy is based on substantial similarity between the molecularly-modified product and its unmodified parent. The NABC has criticized the implementation process (but not the policy) in letters to the Vice-President, FDA Commissioner, Secretary of Agriculture. EPA Administrator, and Secretary of Health and Human Services. The NABC, an organization committed to open dialogue, was concerned about the absence of opportunity for public discussion of the policy prior to its publication. The FDA is holding three sessions across the country to clarify its regulatory process and experience and to listen to the public, to determine if there are significant risks that are not being assessed.

The FDA should make its voluntary consultation mandatory and be as forthcoming as possible, providing information on pre-market approvals, including key safety data, so as to build trust. Its July 1999 "Foods Derived from New Plant Varieties Derived Through Recombinant DNA Technology" is such an example.

An organization seeking to market a new product (usually a company) has the responsibility to obtain, and show to the regulatory agency, data on safety or favorable benefit-to-risk statistics. This process, well established for agrochemicals and pharmaceuticals, is used for molecularly-modified organisms.

Some have suggested the need for more public-sector involvement in food-safety research, to assure further the safety of foods from both traditional and molecular-biotechnology sources. The public would need to fund such research.

One or more of the agencies mentioned previously regulates all products of molecular biotechnology. At an October 6-7, 1999 hearing on agricultural biotechnology by the Senate Agriculture, Forestry and Nutrition Committee, representatives of the regulatory agencies stated that there was no evidence that any genetically-engineered crop is unsafe as a food source. A representative of the Consumer's Union agreed, but stated also that the absence of evidence of danger is not assurance of safety.

The workshops at the 1999 NABC Annual Meeting in Lincoln, Nebraska did not identify concern over food safety as an issue.

At the Senate hearing, the EPA representative stated that the agency had considered the effects of the Bt crops on nontarget organisms at the time of approval, and concluded that risk to insects, such as the monarch butterfly, was not significant in comparison to risks from other pest-control methods. They are reassessing the issue, and a preliminary discussion of the 1999 data tends to confirm their earlier conclusions.

The network of regulatory agencies has several years of successful experience with genetically-engineered crops. There is no evidence of need for significant changes in the regulatory system for food sources modified by molecular processes -- other than mandatory, not voluntary, consultation and improvements in communication, with a more transparent output.

In the view of many academic scientists, the system is being overworked for biobased pesticides.

Labeling is a contentious issue. The right to know is important. FDA policy will require labeling of food products entailing substantial changes. For example, products made from rice which has had major increases in beta-carotene or iron presumably would be labeled because of the substantial change in nutrient composition. Similarly, foods from plants with an added protein that is a recognized allergen would be labeled, if they were even approved.

Should foods from plants with no substantive compositional changes and no demonstrated beneficial or negative health effects, such as those from genetically-engineered plants to-date, be labeled? Does such labeling help the consumer select more healthful foods? If a large number of consumers demand labeling of food from sources modified by molecular processes, then a maximum content of that source in the food product would need to be established; for example, a maximum of 5 percent of non-organic content allowed in organic foods may be appropriate. Without labeling, organic foods (which at this time exclude genetically-engineered sources) may be an option for consumers who do not wish to consume foods from molecularly-modified sources, albeit at a generally increased cost.

- From The National Agricultural Biotechnology Council Report, No. 11, "World Food Security and Sustainability: The Impacts of Biotechnology and Industrial Consolidation," 1999.