Growth Spurts

A new early summertime peach variety, called Gulfcrimson, has been released to nurseries by the Agricultural Research Service (ARS).

Gulfcrimson requires just 400 hours of chilling to flower and set fruit. By comparison, a commonly grown variety called June Gold requires 650 hours of chilling.  As wintertime temperatures are trending warmer, with fewer chilling hours, growers in the southeastern U.S. have been suffering reduced crops.

However, in years of insufficient winter chilling, June Gold can’t reliably set fruit, resulting in reduced crops for growers. Gulfcrimson was developed to overcome this problem.

This peach will probably be used as a fresh market fruit, with substantial red skin blush over a deep yellow-to-orange ground color.  The round-shaped peach has flesh that is firm and does not brown when bruised or cut.  Gulfcrimson ripens from mid to late May, the same market period that June Gold typically filled.

Gulfcrimson was released in 2007 for grower trials, and budwood is being made available to nurseries for the production of trees this year. The first light crops of peaches should be available to consumers in 2011, with full crops by 2012.

Although lettuce is highly perishable and cutting shortens its shelf life, cutting and packaging the greens for food service and salad mixes is an increasingly important component of the produce industry.

The growing demand for convenient, pre-cut salads and lettuce has led to scientists to search for ways to select lettuce cultivars that stay fresh, colorful, and crisp.

USDA Agricultural Research Service scientists Ryan J. Hayes and Yong-Biao Liu have published the results of their two-year study that evaluates the shelf life of 33 romaine and three “crisphead” cultivars after storage in modified-atmosphere bags and in CO2-free controlled-atmosphere chambers.

Lettuce cultivars ‘Clemente’, ‘Darkland’, and ‘Green Forest’ performed consistently well, ranking in the top 10 in every experiment. ‘Alpi’, ‘Dark Green Romaine’, and ‘Queen of Hearts’ showed clearly unstable shelf life. Hayes noted, “cultivars that performed well in our MA environments will likely be useful as parents in breeding programs to develop new romaine cultivars with an acceptable shelf life. It is also clear that not all crisphead cultivars have good shelf life. Wide variation was observed between the crisphead cultivars Pacific, Salinas 88, and La Brillante.”

Source: ASHS Journal of the American Society for Horticultural Science

A devastating tropical and subtropical pest, the silverleaf whitefly (Bemisia tabaci), threatens a wide range of crops and is becoming more troublesome.

Of the more than 20 known whitefly biotypes, the most devastating are labeled type B and and type Q. While the B type has been in the U.S. since its discovery in 1985, now type Q has been identified in 25 states. Both types of whiteflies can reduce yield in a broad range of agricultural, fiber, vegetable and ornamental crops.

The aggressive B biotype migrated to the U.S. from its native Middle East and Asia Minor range, threatening agricultural production throughout the southern states until new integrated pest management strategies brought it into check.  Now, the Q type brings new challenges. It was first detected in December, 2004, on poinsettias at an Arizona retailer.

Compared to the B biotype, Q is less susceptible to many pesticide types, which means there are fewer chemical options for its control.  There is also concern that resistance to insecticidal controls may occur more rapidly in the Q biotype.

A Q biotype task force has been set up to develop new control recommendations.

Agricultural Research Service (ARS) entomologist David A. Jenkins has found a low-tech solution for reducing fruit fly infestations in mangoes.

Removing the fruit from the shade of trees appears to reduce fruit fly breeding opportunities.

In a recent study conducted at the ARS Tropical Agricultural Research Station in Mayaguez, Puerto Rico, Jenkins and colleagues collected ripe mangoes that had fallen to the ground beneath the naturalized and ornamental mango trees are widespread in Puerto Rico.

• One group of the collected mangoes was placed in a shady location — either beneath a tree or a cloth — and left outside.
• A second group of mangoes was stored indoors.
• A third group was left exposed to full sunlight.
• A fourth group was covered with a black plastic garbage bag and then left in full sunlight.

The researchers recorded ambient temperatures and the internal fruit temperatures of all the mangoes several times daily.  On clear days, the two sun-kissed groups of mangoes had internal temperatures peaks ranging from 126 degrees F to 138 degrees F.  Even on cloudy days, their core temperatures peaked at 122 degrees F.  These were well above the 77 degrees F peaks in the indoor mangoes and the 99 degrees F peaks in the shaded mangoes.

After three days, the outdoor mango groups were moved inside and monitored for the emergence of larvae and pupae.  Jenkins observed that mangoes stored indoors almost always produced many more larvae than the groups of mangoes that had been basking in the sun.

In areas where mango is not being grown commercially, ripe mangoes that have fallen from the tree remain shaded on the ground until they are gathered up and removed.  When fruit flies use these mangos for breeding, the shade keeps the fruit’s core temperatures from reaching peaks lethal to the pests.

Natural bacterial extracts — X. bovienii and P. luminescens (VS) bacterial compounds — offer peach and pecan growers a safe and effective alternative to chemical fungicides in treating diseases such as brown rot in peaches and pecan scab. Agricultural Research Service (ARS) scientists in Byron, Georgia, developed these natural pesticides to control pecan and peach diseases. Although bacterial methods for controlling fungi are not new, the ARS bacterial compounds have never been used to control disease in these two commodities.

The ARS study results indicated that X. bovienii and P. luminescens (VS) bacterial compounds generally exhibited the greatest suppression of plant pathogens. Applying 6- to 12- percent dilutions of the bacterial compounds achieved 90 to 100 percent suppression of Phytophthora cactorum lesions on pecan leaves. P. cactorum can cause root, collar and crown rots, as well as foliar and fruit infections.

The researchers also used bacterial compound treatments on pecan shoots to control pecan scab disease caused by Fusicladosporium effusum. The treatments reduced spore formation of F. effusum to levels similar to those by chemical fungicides.

Applications for patents on these treatments have been submitted, and partners are being sought to develop the bacterial metabolites for commercial use.

Source: Agricultural Research Service

Projected crop budgets show a potential for increased profit using fall-seeded peas and lentils for spring grazing and as a nitrogen source for a subsequent wheat crop, according to researchers with the Montana Agricultural Experiment Station and Montana State University Extension Service.

Legumes, like peas and lentils, take nitrogen from the air and accumulate it in both the above-ground plant and underground nodules on roots. In the ongoing experiment station study, the legumes also are being used as livestock forage before being plowed into the ground to increase organic matter and nitrogen in the soil.

Using estimates of low and high forage yields, the nitrogen benefit to the following spring wheat crop and the hay benefit of the pea crop will be more than $30 in net per acre from haying for forage and about a $10 per acre net benefit return from grazing. The large returns from haying reflect the currently strong market for hay.

“The estimates of nitrogen and haying or grazing benefits of the pea crop appear to offset the seed and machinery operating costs for peas,” said Dave Buschena, an MSU economist working on the project. These returns should be compared to the cost of chemical or tillage fallow, currently estimated to be almost $25 per acre.

Buschena said the budgets used were for the pea crop to add 50 pounds of nitrogen to the soil under grazing and 40 pounds under haying. These levels are estimates based on previous work. Actual nitrogen benefits
will be less in drier zones and drier years, and greater in wetter conditions.

Source: MSU News Service

A new peanut variety (dubbed Tifguard) developed by Agricultural Research Service (ARS) scientists may help farmers in their battle against two key peanut problems — the peanut root-knot nematode and the tomato spotted wilt virus (TSWV).

While certain peanut varieties exhibit resistance to either the peanut root-knot nematode or the TSWV pathogen, Tifguard is the first variety that has resistance to both. It was developed by hybridizing a TSWV-resistant cultivar with a nematode-resistant cultivar.

Field tests for resistance to peanut root-knot nematode were conducted at two Georgia farms in Tift County that were heavily infested. In testing for TSWV-resistance, Tifguard plants were grown in plots at one of the Tift County farms that also displayed severe TSWV problems. Not only did Tifguard exhibit higher resistance to TSWV, it also produced higher yields than standard check cultivars when grown in fields with little or no nematode pressure. And because of its high level of resistance to both TSWV and root knot nematode, Tifguard had significantly higher yields than all other varieties when grown in two locations with high pressure from both pathogens.

For these reasons, Tifguard should be particularly valuable to peanut growers who have to deal with both root-knot nematodes and TSWV. It was released in 2007 and is currently in seed production. Seed for farmers should be available by the 2009 planting season.

Source: Agricultural Research Service

Nitric oxide, sometimes a toxic byproduct of nitrogen oxidation in soil, may have broader implications in plant processes than previously realized. Recent research has identified its modification of proteins — a process called S-nitrosylation — as an important signaling molecule in plants, as it is in mammals.

In studies using the tropical medicinal herb Kalanchoe pinnata (aka “miracle leaf”) as a model plant, researchers have found that nitric oxide targets a number of proteins and enzymes in plants that regulate photosynthesis, sugar metabolism, disease tolerance, stress tolerance and other important processes.

In collaborative work, researchers with the University of Delhi and the USDA Agricultural Research Service have shown for the first time that nitric oxide inactivates Rubisco, a major enzyme involved in carbon dioxide fixation and photosynthesis in plants.

Kalanchoe represents plants that have a unique method of carbon dioxide fixation that is shared by succulent plants. Kalanchoe has diverse possible medicinal benefits, suggesting the presence of interesting processes at work.

Other scientists have studied nitric oxide targets in the most common model plant, Arabidopsis. Mattoo and collaborators found that Kalanchoe had some nitric oxide targets in common with Arabidopsis, such as Rubisco and drought-protective proteins. They also found new protein targets in Kalanchoe that have not been reported previously.

A paper discussing these results has been published in the FEBS Journal.

Extracts from tree heartwood limit the growth of Phytophthora ramorum, the microbial agent that causes sudden oak death (SOD) in more than 100 plant species.

Since it surfaced on the West Coast in the mid-1990s, SOD has killed an estimated 1 million oaks and tanoaks. For years, scientists have known that tree heartwood contains protective antimicrobial compounds, but it wasn’t known whether these compounds could offer protection against P. ramorum.

In recent studies by Agricultural Research Service scientists extracts from incense cedar, western redcedar, Alaskan yellow cedar, western juniper and Port Orford cedar destroyed P. ramorum spores and inhibited fungal cell growth.

Tree heartwood extracts could provide easy-to-use, environmentally friendly, effective tools for SOD control. Heartwood could be processed into shavings, sawdust, wood chips or liquid extracts. These materials could then be distributed in areas with high human activities — such as park trails, walkways, and bike paths — to reduce spore movement and prevent the spread of the disease.

Source: Agricultural Research

Three new hardy safflower germplasm lines developed by Agricultural Research Service (ARS) scientists are now available.

The germplasm lines — dubbed WSRC01, WSRC02 and WSRC03 — owe their superior winter hardiness to three Chinese safflower accessions maintained at the ARS Plant Germplasm Introduction and Testing Research Unit in Pullman, Washington. They are the first U.S. safflower releases specifically developed for winter hardiness.

Winter-hardy safflower varieties derived from the three new germplasm lines should offer farmers the option of fall plantings, winter ground cover, rotation with other crops like wheat, better weed control, improved water-use efficiency, and higher seed yields than spring-planted safflower crops.

Safflower is primarily grown for three products: oil, meal and birdseed. The oil is mainly used for cooking and in salad dressings and margarine. Safflower oil also is used in paint bases and can be converted into biodiesel. High-fiber, high-protein meal from crushed seeds is fed to livestock, while intact safflower seeds are marketed as birdseed. Dyes are made from the crop’s flowers.

Winter hardiness, which has been lacking in existing varieties, could expand safflower use in the West and the Southern Great Plains. WSRC01, 02 and 03 are adapted to many sites in these regions.

During field trials in eastern Washington State, the three lines showed winter hardiness superior to cold-tolerant safflowers that were used as experimental controls for comparison. The new safflower lines grew to a height of nearly 3 feet, stood upright and produced red flowers. On average, the lines’ seed contained 80 percent linoleic acid and 14 percent oleic fatty acid.

Source: ARS News Service. Agricultural Research Service