Almond variety research shared

It takes 4 ½ days for a drop of oil to drip its way through the 800-mile Trans Alaska Pipeline System. Yet it takes 4 ½ years to create an almond cross and see the fruit. Then add another 10-15 years to determine if the almond variety is suitable or not.

Making the oil to almond connection during the 34th Almond Industry Conference in Modesto, Calif., in December was University of California, Davis (UC Davis) Plant Science Professor and Geneticist Tom Gradziel. He shared with growers the latest results of UC Davis-almond variety research partially funded by the Almond Board of California.

UC Davis’ Extension Postharvest Physiologist Carlos Crisosto is also a key part of the research team.

In field trials of the released Winters almond variety, Gradziel reported consistent high yields in several Sacramento Valley evaluation trials. Yields in the Kern County Regional Variety Trails are lower and comparable to the Carmel variety due to the high incidence of alternaria leaf spot disease at the site. Both varieties are similarly susceptible.

When alternaria leaf spot occurs, Gradziel said the result is defoliation and yield reduction for that year. Defoliation causes further tree stress and reduced flower bloom.

“Self-fertility in the Winters variety was found at a low level in 2006 field studies,” the almond breeder said. “While not enough to produce consistent high levels of self-pollenation, the result is good cropping especially in years of poor weather during flowering.” Developed as a pollenizer for the early Nonpareil bloom, the Winters flowering period has consistently shown good bloom overlap with early Nonpareil bloom over the last 10 years of evaluation.

Meanwhile, Gradziel noted the released Carmel source (FPS#1) continues to show low levels of bud failure in the 16-year-old evaluation plot in Kern County. California nurseries have utilized the breeding selection as a principal propagation source when establishing trees to propagate grower stock.

Since the trees are one generation removed from the FPS#1 source, Gradziel said California nurseries are evaluating the individual tree sources using UC Davis-developed procedures to identify individual trees whose vegetative progeny result in the lowest levels of bud failure.

Along with the selection and testing of more traditional advanced lines, the utilization of new germplasm has improved resistance, self-compatibility, and improved the size and quality of kernels.

Positive qualities

“In the UCD 36-52 selection, positive qualities include high kernel quality (high oleic acid which confers good processing quality and phytonutrient value and lower susceptibility to rancidity in storage), good productivity, partial self-fertility, and improved resistance to navel orangeworm and associated aflatoxin contamination,” said Gradziel.

Because of its pluses and the potential as an alternative/replacement variety for the premium quality Spanish variety Marcona, he said the 36-52 would be released in ’07. Several growers in the Central Valley plan to use it.

“The 36-52 is an example of an intermediate breed line that is the size of what we like in a California type but it is almost identical to the Marcona type both in terms of size and characteristics,” he reported. “It has the highest oleic acid content of any almond variety we have measured which is an indication of high roasting quality and good storage durability.”

The 36-52 likely will be released by the name Sweetheart.

As to the UCD 2-19E selection, Gradziel called it very productive but a potential alternate-bearing pollenizer for the Nonpareil late bloom. Recent plantings in the Sacramento Valley and the San Joaquin Valley will test whether consistent high yields are possible with irrigation and fertilizer management.

In 2004, 22 UC Davis experimental selections were planted in medium-scale (10-100 tree) grower test plots in Kern and Colusa County with an eye on self-compatibility, pest and disease resistance, kernel quality, and/or tree productivity. The 2006 harvest showed promise in several selections while some displayed major deficiencies.

In 2006, 20 additional UC Davis selections focusing on improved disease/pest resistance and self-compatibility were propagated for planting in ’07 in the Sacramento and San Joaquin Valley test sites. The selections are having high insect/disease pressures.

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