The International Consortium on Agricultural Biotechnology Research (ICABR)


Factors influencing the use transgenic cotton in the
San Joaquin Valley

Brian H. Marsh
University of California,

The southern San Joaquin Valley (SJV) of California has climatic and soil conditions that are conducive to upland (Gossypium hirsutum) and pima (G. barbadense) cotton production. Irrigated land with the long, warm growing season combines to produce exceptional yields of high quality lint. During the early 1920’s, University of California and USDA officials along with growers proposed that if everyone in the SJV grew the same high quality cotton variety they could effectively market California cotton to mills in the eastern United States. A USDA breeding program had identified the variety Acala 8 as a high quality cotton variety adaptable to California. In 1925, the California State Legislature enacted the "one-variety" law. Only the one Acala variety selected as the standard could be grown in the SJV. California cotton growers have been successful in marketing their "one-variety" cotton over the years and have commanded a premium price for it. The standard variety has been improved over the years and at times changed to one of very different parentage. The standard variety was scrutinized in a three-year field and laboratory evaluation for yield, lint quality and other agronomic qualities before potential approval. The "one-variety" law was modified in 1978 to allow any of the approved varieties to be grown. The first Pima cotton varieties were approved for planting in 1991. In 1998, in response to grower concerns about delayed planting from a wet spring, a one-year exemption to the law was passed. Growers wanted short-season cotton varieties. The "one-variety" law was repealed in 1999 opening the SJV to any variety.

Pink bollworm (Pectinophora gossypiella) has been a major pest in Arizona and southern California since the mid-1960s. It has been controlled for the last 33 years in the SJV through a combination of host-free period and the release of sterile adult moths. Other Lepidopterian pests are usually localized problems. The use of transgenic insect resistant varieties have accounted for only 2.1, 4.6 and 3.5 percent of the SJV acreage in 1998, 1999 and 2000, respectively. This includes experimental acreage and seed production for sale elsewhere in the U.S. In contrast, in the Imperial Valley of California, where Pink bollworm is a tremendous problem, more than 90% of the cotton acreage is planted to transgenic insect resistant varieties.

Herbicide resistant cotton has received more interest with SJV growers. Glyphosate and bromoxynil resistant varieties increased from less than 1% in 1998 to 2.4% in 1999. Sixty-one percent of that acreage was in the testing program for approval. Herbicide resistant varieties increased in acreage to 24 percent in 2000. Eight percent was unapproved varieties, predominantly a bromoxynil-resistant variety, 12 percent was an approved glyphosate-resistant Acala variety and four percent of the acreage was in the testing program or for seed increase. Approval is expected for a bromoxynil resistant variety in 2001.

While transgenic traits are important to SJV cotton growers, they are secondary characteristics in varietal selection. Lint quality and yield are still the most important factors.

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