Salinas Valley Agriculture - Agriculture and Natural Resources Blogs

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Highlighting agricultural developments, problems, research, & issues for central coast CA

Developing Baby Leaf Spinach with Reduced Cadmium Accumulation

Author: Rachel F. Greenhut
Author: Juliana Osorio Marin
Author: Richard Smith
Author: Timothy K Hartz
Author: Allen Van Deynze
Author: E. Charles Brummer
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Published on: April 9, 2018

Spinach is an accumulator of cadmium (Cd) and an important crop in the California Salinas Valley, where some agricultural soils have naturally high levels of Cd. Soil Cd content is a major factor determining Cd uptake by crops, and recent studies highlight cases of “worrying Cd concentrations” in some leafy vegetables grown in high Cd soils. Cadmium is a rare but toxic element, and consumption of contaminated foods is a main source of chronic human exposure. The US does not set standards for Cd content in domestic foods; however, international standards limit total Cd content in spinach and other foods for international trade. Accordingly, strategies used by California farmers to reduce the Cd content of spinach are to not grow spinach on high Cd soils, and on soils with moderate levels of Cd, fertilizing with zinc which reduces Cd uptake. Another tool to help growers reduce Cd uptake by spinach is the use of cultivars that take up less Cd.

Breeding for low Cd accumulation is a promising approach since it has been successful in wheat, rice and other species. With support from the California Leafy Greens Research Board, our UC Davis spinach breeding program and collaborators aimed to 1) quantify the genetic variation in Cd accumulation among existing spinach genotypes, and 2) identify candidate genes that regulate Cd accumulation as a first step in the development of molecular markers for low Cd accumulation. Our long-term goal is to develop spinach cultivars with low Cd accumulation when grown in high Cd soils.

We developed an effective method to screen spinach for genetic variation in Cd accumulation in the greenhouse using low seed quantity, which is useful for early breeding cycles in cultivar development. Screenings were conducted using high Cd field soil (2.8 ppm Cd) and Cd content of harvested spinach was determined in the lab by Inductively Coupled Plasma Atomic Emission Spectrometry. Using this method, we screened wild genotypes, landraces, advanced breeding material, and named varieties obtained from international germplasm collections, covering a wide range of genetic diversity including 615 spinach accessions from 42 countries of origin. Observed Cd content varied widely among screened genotypes, ranging seven-fold from 3.4 to 24.2 ppm (on a dry weight basis). Some of the observed variation can be attributed to environmental variation. By adjusting to environmental differences and experimental blocks, the remaining variation in Cd content can be attributed to genetic variation among screened genotypes. Predicted genetic variation in Cd content ranged from 6.9 to 11.3 ppm, showing there is genetic potential to breed for low Cd accumulation in spinach. Low and high Cd accumulating genotypes with consistent performance were identified and will serve as a resource for the UC Davis spinach breeding program. Our next steps include field testing of low Cd accumulating genotypes and crossing into elite breeding lines.

Progress was also made identifying candidate genes in spinach for Cd accumulation and low Cd phenotype. We are developing marker assays for screening germplasm accessions to identify alleles in genes previously targeted for breeding low Cd wheat and rice. Initial testing showed alleles at multiple markers in two candidate genes may have an association with Cd content, suggesting that Cd accumulation may be partially controlled by these genes in spinach. Our study paves the way for introgression of the low Cd trait into elite spinach breeding material and provides candidate genes for further exploration of Cd regulation in spinach.

Comments: 1

CropManage Hands-on Workshop in Salinas on April 24 2018

Author: Michael D Cahn

Published on: April 3, 2018

CropManage Hands-on Workshop:
Bringing Irrigation and Nutrient Management Decision Support to the Field

Date: Tuesday, April 24, 2018
8:00am – 12 pm

Location: Monterey County Agriculture Conference Room

1432 Abbott St. Salinas, CA 93901

Learn how to use CropManage to support irrigation and nutrient management decisions and record-keeping
Learn the new version of CropManage (3.0) – also available in Spanish

CropManage is a free online decision support tool for water and nutrient management of coastal crops. Based on in-depth research and field studies conducted by the University of California, CropManage provides real-time recommendations for efficient irrigation and fertilization applications— while maintaining or improving overall yield.

At this free workshop, we will provide hands-on training so that you can learn to use the newest version of CropManage (3.0) which has been updated to be more compatible for in-field use by farm staff. CropManage is now available in Spanish.

Crops currently supported by CropManage include strawberry, raspberry, head, romaine, and leaf lettuce, broccoli, cauliflower, cabbage, celery, bell peppers, spinach, baby lettuce, cilantro, and mizuna.

Who should participate? Vegetable and berry growers, ranch managers, other farm staff, and technical service providers are welcome. The workshop is for both new and current CropManage users.

What to bring? This is a participatory workshop. Please bring a tablet or laptop computer so that you can follow along and participate in the exercises. Each participant will need a user account for CropManage. Please set up a free user account at v3.cropmanage.ucanr.edu before the workshop.

RSVP by Friday, April 20, 2018 to Lennis Arriaga at larriaga@ucanr.edu or 831 759-7353.

AGENDA
8:00 – 8:30 Registration and computer set-up
8:30 – 10:15 Getting started with CropManage 3.0
10:15 BREAK
10:30 – 11:15 Strategies for using CropManage for decision support and record-keeping
11:15 - 11:45 Advanced features and interfacing sensors with CropManage
11:45 -12:00 Discussion of new features or changes needed

2.5 Continuing Education Units (CEU) available for Certified Crop Advisers (CCA)

Focus Area: Agriculture

Focus Area Tags: Agriculture

Tags: Irrigation (13), nitrogen (7), nutrient management (6)

Comments: 0

Healthy Soils Program grant workshop and technical assistance available

Author: Lennis Arriaga

Published on: March 26, 2018

Comments: 0

Frost Damage on Vegetables

Author: Richard Smith

Published on: March 2, 2018

Frost damage on vegetables can often occur during cold, clear nights in late winter and spring in the Salinas Valley (Photo 1). Early plantings of lettuce, cauliflower, broccoli, spinach and peas can be affected with lettuce and celery being the most frost sensitive. Frost damage is primarily caused by dehydration of the plant cells as water moves out of the cell into the intercellular space and freezes. The dehydration of the cells and may explain why frost damage can look similar to damage from water stress. Cole crops often display dramatic symptoms of frost damage (photos 2 - 4); symptoms can vary from interveinal chlorosis to necrosis which typically occurs on older leaves. Light frosts down to 32° F are mostly tolerated by cool season vegetables, and slow transitions to cold temperatures allow plants to acclimate to colder temperatures. This year however, starting about February 20^th, we made an abrupt change from unseasonably warm temperatures to nighttime temperatures in the high 20's in Salinas (CIMIS South weather station), and lower temperatures in the south end of the valley (CIMIS King City weather station). Samples of frost damage began coming into our office shortly thereafter.

Symptoms of frost damage vary on the crops, but the most common symptoms on lettuce include a lifting of the epidermis from the rest of the leaf (Photo 5). The damage to the epidermis allows the tissue underneath to dry out (Photo 6). However, on lettuce we also see a variety of other symptoms that occur depending on the severity of the frost and the acclimatization of the plant (Photos 7 to 11). This year we also saw frost damage on peas (Photos 12 & 13) which is more frost tolerant than lettuce.

The severity of frost damage can be made worse by dry conditions in the field. Moisture has two effects on the severity of frost: 1) wet soils provide more warmth for crops than dry soil, and 2) greater soil moisture assures that the plants are better hydrated and can, to some degree, withstand the drying effects of frost. Highlighting these concepts, in 2015 we observed a cauliflower field in King City where the frost event occurred as they were in the process of irrigating the field. The areas of the field that had not been watered had more severe frost symptoms than the area of the field that had been watered.

Frost damage can at times be confused with herbicide damage. For instance, if Goal is used as a pre- or post-plant on cole crops it can cause necrotic areas on the leaves (Photo 14). Spotting on lettuce or spinach can be caused by herbicide drift, but the spotting will tend to be more rounded (Photo 15). Frost damage can also be confused with some foliar diseases.

Frost damage is a non-systemic issue that may or may not affect the yield of the crop. The impact on yield will depend on how severely affected or stunted the plants were by the frost event.