Seed coat fragments entangled in lint have once again become a contaminant issue with San Joaquin Valley cotton, and once again the controversy swirled around new varieties.

This time it is the new Riata RR and Maxxa GTO from California Planting Cotton Seed Distributors. In the past Maxxa in the early 1990s and earlier Germain's 510 were implicated as varieties prone to seed coat fragments, a problems that can result in lint discounts of two to 10 cents per pound, according to Calcot's vice president of sales Bruce Groefsema.

It was not a major issue and represented less than 1 percent of the cotton ginned last season.

“More than 97 percent of Riata RR and almost 99 percent of Maxxa GTO had no seed coat fragments,” said Lowell Zelinski, CPCSD's vice president, production and operations.

“Seed coat fragments were found in seven-tenths of 1 percent of SJV bales last season. It was not a serious problem, except for those growers who were discounted for seed coat fragments,” he said.

Zelinski, a former private consultant and before that a University of California Cooperative Extension farm advisor in Fresno County, said seed coat fragments is a “complex” issue. He addressed it at CPCSD's grower meetings this spring.

Too dry harvest

Last season, the factor most associated with the contamination was harvesting cotton too dry. Some growers experienced SCF with low moisture in pickers. “It seemed to be associated with cotton picked too dry early last season,” he said. “After it rained in October, the problem disappeared.”

It was also associated with certain gins, he added. “There was one gin with 6 to 7 percent of the bales with seed coat fragments,” he said. “This was based on information from the classing office. We don't know which gin it was. A few other gins recorded 2 to 4 percent. However, the majority of the gins recorded well below those numbers.”

Thirty percent of the valley's acreage last season was planted to Riata RR or Maxxa GTO, yet less than 1 percent of the valley's cotton bales had seed coat fragment problems. He said that was proof implicating a variety as prone to SCF was not valid.

CPCSD is obviously on the defensive since its two most popular varieties have been associated with the problem, and Zelinski was the point man in defending the two varieties.

Fragment factors

He said there have been several factors implicated in higher seed coat fragments, and they are:

  • Small seeded varieties.
  • High lint turnout varieties
  • Varieties with high linters.
  • High fiber strength varieties.
  • Immature seed.
  • Very low or very high moisture content in modules.
  • Excessive field growth.
  • Seed coats can become brittle when cotton is desiccated.
  • High nitrogen or late water.
  • Water stress during bloom.
  • Poor defoliation.
  • Mechanical damage form picking or ginning.

Several of these are what cotton breeders are striving to bring to market in new varieties — high turnout and strong fiber. It will be interesting to watch if the newer varieties also are implicated in high seed coat fragments because of this push to improve lint quality.

Don Van Schuyver, gin manager at Semi Tropic Cooperative West of Wasco, Calif., recalled when 510 was introduced, it gained a reputation for seed coat fragments. However, that went away as ginners learned how to properly process the new variety. He predicted the same would happen with today's newer, more popular varieties.

Despite its early bad reputation, GC-510 went on to become one of the more popular Acala varieties ever introduced into the San Joaquin Valley.

While Riata RR's reputation has been sullied, one of CPCSD's chief competitors does not believe it will hurt the variety in the long run since it has proven to be one of the highest yielding Acalas ever.

E-mail: harry_cline@intertec.com