Early Valencias

Varieties: Replacing Hamlins with Early Valencias

early valencias

University of Florida/Institute of Food and Agricultural Sciences plant breeder Jude Grosser makes a case for Florida’s citrus industry replacing Hamlin oranges with early-maturing Valencia oranges that he and others are developing.

“I think that’s a no-brainer because Hamlins are having a really bad time with greening, and orange juice sales are declining,” Grosser says. “Hamlin is half our juice. It’s half of the NFC (not-from-concentrate) product and yet it has inadequate color and flavor to make a Grade A product on its own. It has to be blended with Valencia. So you can imagine what a boost to the quality of our product it would be if you replaced all the Hamlins with Valencias. You’re going to have better color in the bottle; it’s going to be more attractive. And when somebody buys it, takes it home and drinks it, the flavor’s better and so they’re going to want to come back and buy more of it.”

Grosser mentions some existing early Valencias that have had a higher ratio than Hamlins at Christmastime and even at Thanksgiving. Traditional Valencias aren’t harvested until late winter or early spring. “They’re (the early Valencias) not home runs against HLB, but again with the right rootstock and nutrition program, they should be able to work,” he says.

Grosser’s comments address some of the biggest issues facing the Florida citrus industry. Approximately 95 percent of Florida’s oranges go into orange juice, and HLB, also known as citrus greening, has greatly reduced the state’s citrus acreage and production. HLB was discovered in Florida in 2005. There is no known cure, and most growers have struggled to find production programs that let them remain profitable in the face of the disease.


Citrus Leprosis

Citrus Leprosis Rears Its Ugly Head: Know the Details

With citrus leprosis a re-emerging threat to citrus, know the details of the disease.

Citrus Leprosis Details

  • Appearance: “On symptomatic fruit, the spots are usually brown, reddish-brown or tan-colored. The lesions on fruit are limited to the fruit rind only and do not extend into the fruit sections.” And “The symptoms of leprosis are distinctive; however, they could be confused with citrus canker lesions on leaves, fruit and twigs.” Testing confirms the disease.
  • Impact: “Left untreated, leprosis disease will kill a mature citrus tree in about four years. Leprosis affects all citrus types (sweet orange, mandarin, lemon, grapefruit and citranges) as well as Swinglea glutinosa, a citrus relative.”
  • Transmission: “The disease is spread by Brevipalpus mites, commonly called broad mites. The Brevipalpus mites have a broad host range with over 900 plant hosts reported from 513 genera.”
  • Treatment: “Mite control is essential for the control of leprosis. In Brazil, where leprosis has been endemic for many years, 12 or more miticide applications are made yearly. Leprosis-infected trees can be recovered with the pruning of the symptomatic branches, followed by good mite control, but the pruning of individual trees is expensive.”

HLB management

By Jaci Schrekengost

As huanglongbing (HLB) continues to decimate citrus crops, researchers continue to search for new, efficient ways growers can manage the disease.

HLB, also known as citrus greening disease, is vectored by the Asian citrus psyllid. The disease affects the entire tree, including the roots and fruit.

Tripti Vashisth, assistant professor and citrus Extension specialist at the University of Florida (UF), says one main concern with HLB is nutrition based on the size of the roots in HLB-infected trees. She says another researcher found HLB-infected trees have smaller root mass compared to trees that are not infected.

The concern with smaller root mass in these trees is whether they are moving the same amount of nutrients as the trees that do not have HLB.

According to the UF Institute of Food and Agricultural Sciences Citrus Extension website (http://www.crec.ifas.ufl.edu/extension/greening/index.shtml), “Root systems of infected trees are often poorly developed, and new root growth may be suppressed.”

Vashisth says in a new greenhouse study that she and other researchers conducted, it was actually concluded that the roots in HLB-infected trees move nutrients more efficiently than trees that do not have HLB. The issue with nutrients not reaching the top of the tree is due to the smaller mass of the roots.

The way to solve this concern is to allow a constant supply of nutrients to the HLB-infected trees, Vashisth says. “Continuous supply of fertilizer in any form is working best,” she says.

Dual Treatment Tested for HLB Trees

Dual Treatment Tested for HLB Trees

Severe pruning combined with enhanced foliar nutrition did not prove cost-effective.

By Monica Ozores-Hampton, Fritz Roka, Robert Rouse and Pamela Roberts

HLB Trees

Citrus trees affected by huanglongbing (HLB) become diminished, weak and develop dieback resulting in reduced production. Decline in fruit yield ultimately prevents economically acceptable commercial citrus production. Pruning and spraying foliar nutritionals are two practices being considered to restore some level of productivity to HLB-infected trees.

Pruning, also known as buckhorning (Figure 1), is a cultural practice that stimulates strong tree regrowth. While shown to be effective to regrow freeze-damaged trees, buckhorning has never been tested in HLB trees. Citrus growers, however, have implemented foliar treatments of micronutrients and macronutrients as a method to satisfy a tree’s nutrient requirements after HLB has blocked nutrient flow via the phloem, reduced root systems or limited uptake capacity.

The enhanced foliar nutritional treatments do not have bactericidal effects on the bacterial pathogen Candidatus Liberibacter asiaticus (CLas). They may be employed, however, to maintain the nutritional health and productivity of HLB-affected trees.

A study was conducted between 2010 and 2015 to evaluate the horticultural impact, juice quality and economic returns from pruning in combination with an enhanced foliar nutritional treatment on HLB-affected orange trees. The study was located at the University of Florida/Institute of Food and Agricultural Sciences Southwest Florida Research and Education Center in Immokalee within a 5-acre block of 16-year-old Valencia orange trees on Swingle citrumelo rootstock. Trees were planted 15 feet in-row by 22 feet between rows (132 trees/acre) on two-row raised beds with micro-sprinkler irrigation and soil classified as Immokalee fine sand.

HLB Trees

A total of 14 rows on the east side of each bed were buckhorned (Figure 2). The rows on the west side of each bed were not pruned. Each row was split in half, and four foliar nutritional treatments were applied as Boyd, Fortress with KNO3 or urea (four times per year), and a control [(commercial standard), Table 1]. Each nutritional treatment was replicated seven times across the area.
Pruning was done in February 2010 using a commercial hedger and topping machine. Pruned trees were cut back to their scaffold branches, leaving only 10 to 15 percent of the original canopy (Figure 1). The products and amounts of the foliar-applied nutrient treatments are shown in Table 1. In accordance with the UF/IFAS recommendations for citrus, all treatment plots received ground-applied fertilizer twice per year using a slow-release 14-0-18 + magnesium, sulfur and boron, and calcium nitrate 9-1-14 + magnesium, manganese, zinc, iron, copper and boron. The annual total amount of nitrogen was 160 pounds per acre and 205 pounds per acre of potassium oxide.

Data collection consisted of real-time polymerase chain reaction (PCR) for detection of CLas, tree growth (shoot length, tree volume and total shoot leaf area), leaf chlorophyll concentration, fruit yield and juice quality [percent juice, titratable acid (TA), total soluble solids (TSS) as Brix and TSS/TA ratio]. Prices of materials were collected from fertilizer and chemical product vendors to estimate the costs of each foliar treatment.

PCR testing confirmed that all trees were infected with CLas at the beginning of the study. Canopy volume of pruned trees increased throughout the trial, but never grew to equal the canopy volume of non-pruned trees. However, leaf area of pruned trees was consistently greater than the leaf area of non-pruned trees, beginning with the second year of the trial.

 As expected, fruit yields from pruned trees were significantly lower than yields from non-pruned trees in the year after buckhorning. While the pruned trees recovered and set a fruit crop close to the non-pruned trees, the 5-year cumulative yield from the pruned trees remained significantly less than the cumulative yield from the non-pruned trees (Table 2). Pruned trees did not produce a higher yield than non-pruned trees in any year. There were no statistically significant differences among juice-quality parameters between pruned and non-pruned trees or nutritional treatments.

The total cost of pruning was estimated to be $160/acre. When the estimated value of first-year fruit loss was considered, the total cost of buckhorning rose to $560/acre. Since the yields from pruned trees never surpassed the fruit yields from unpruned trees, there were no offsetting gains.

The annual cost of the control foliar nutritional treatments was $40/acre. Fortress treatments were between $295 and $305/acre, depending on whether KNO3 or urea was applied. The Boyd foliar nutritional treatment was $550/acre (Table 1). All treatment costs included materials and application.

HLB TreesEnhanced foliar nutrition treatments provided slight yield benefits, especially in the early years of the trial (Table 2), but the yield differences were not statistically significant. Even if a value were to be put to the numerical yield differences, the added value of the higher yields did not offset the cost of any foliar nutritional treatment beyond the control (Table 3). It should be noted, however, that the control foliar nutritional treatment did contain some micronutrients (Table 1). Given the lack of statistical differences among the nutritional treatments, the amount of micronutrients in the control treatment may have more than satisfied the trees’ requirements.

The results from this trial confirmed that HLB-infected trees can regrow after pruning and produce fruit. The pruning, as used in this trial, was not cost-effective through the first five years after buckhorning. However, the rapid regrowth of pruned trees suggests that a more moderate pruning approach may be more cost-effective at rejuvenating HLB-affected trees and may be an alternative to tree removal and replanting.

Monica Ozores-Hampton and Fritz Roka are associate professors, Robert Rouse is a retired associate professor, and Pamela Roberts is a professor — all with the University of Florida/Institute of Food and Agricultural Sciences Southwest Florida Research and Education Center in Immokalee.

Gene Editing vs. GMO?

Move Over GMOs? Monsanto Experimenting With Gene Editing

Dr. Robert Fraley, Monsanto’s Chief Scientific Officer says gene editing is a new innovation that could reshape how we eat. Monsanto (MON), the world’s largest producer of GMO seeds, is betting that a new technology called gene editing may calm consumers unease about eating modified foods.

Monsanto announced earlier this month that they are investing heavily in gene editing or CRISPR/Cas9—a genome editing technology developed by Broad institute—that will allow scientists to make changes to a plant’s already-existing DNA without adding any foreign DNA (like GMOs allow).

“In the crop world we use [GMOs] to introduce a new gene into a crop, a gene that may confer tolerance to drought, or a protection against insects. With gene editing, we don’t have to put a new gene into the plant. What we are able to do is precisely modify a gene that is already existing in the plant, in the animal, or even in human healthcare applications,” Fraley adds, who says consumers can expect these new products to hit the market in the next 5 years.

http://video.foxbusiness.com/v/video-embed.html?video_id=5436512625001&loc=foxbusiness.com&ref=http%3A%2F%2Fwww.foxbusiness.com%2Ffeatures%2F2017%2F05%2F17%2Fmove-over-gmos-monsanto-experimenting-with-gene-editing.html&_xcf=Watch the latest video at <a href=”//video.foxbusiness.com”>video.foxbusiness.com</a>“Some of the first products are already going through regulatory approval. Just last year, scientists developed a mushroom where they knocked out the gene that causes the mushroom to turn brown, so that will be able to reduce food waste and improve flavor,” Fraley adds.

However, some food experts and scientists are skeptical. “While these new technologies are touted to be more precise than older genetic engineering technologies, it is widely accepted in the scientific community that there can be ‘off target’ effects to the genome when the technologies are utilized. GMOs, including the products of these new technologies, have not been adequately tested—no long-term feeding studies have been conducted—and people are starting to connect these experimental technologies to health concerns,” Megan Westgate, executive director of Non-GMO Project, tells FOX Business.

Dr. V.A. Shiva Ayyadurai, a scientist and CEO of CytoSolve, Inc., says gene editing sounds much simpler than it is – and for him, that is the problem.

“The human body and the human cell are an interconnected complex system of systems. Editing a single gene, has systemic effects, which cannot be done ad hoc. Changing one itsy weeny teeny weeny gene isn’t so simple. One needs to understand how that change affects the concentrations of other chemicals in the plant,” Ayyadurai tells FOX Business.

Jon Entine, executive director of the Genetic Literacy Project and founder of Genetic Experts News Service, says that while gene editing may be an easier sell to consumers than GMOs, it also stands to boost Monsanto’s bottom line.

“CRISPR and other gene editing techniques are scientifically easier than conventional breeding. And, genetic engineering saves time and money—as much as $130 million in 10 years or more, which is the cost and time of getting a GMO approved and commercialized,” Entine tells FOX Business.

Last year, PEW Research Center found that 39% of Americans consider genetically modified foods worse for a person’s health than other foods, compared to 48% of adults who say GM foods are no different than non-GM foods.

Fraley says part of the reason that some Americans have a negative perception of GMOs is because the company didn’t educate people about the science early on said Monsanto’s chief scientific officer Dr. Robert Fraley. “That was a big mistake, and in our [absence] of communicating that other folks were able to position the technology in a negative sense, and it’s taken a long time to build back up the understanding and benefit of these tools,” Fraley says.

More on this…

Engineered Virus to Battle HLB?

Geneticists Enlist Engineered Virus and CRISPR to Battle Citrus Disease

Desperate farmers hope scientists can beat pathogen that is wrecking the US orange harvest

The required public comment period on the application ended last week, and the USDA will now assess the possible environmental effects of the engineered virus.

Field trials of engineered CTV are already under way. If the request is approved, it would be the first time this approach has been used commercially. It could also provide an opportunity to sidestep the regulations and public stigma attached to genetically engineered crops. “There’s a real race on right now to try to save the citrus,” says Carolyn Slupsky, a food scientist at the University of California, Davis. “This disease is everywhere, and it’s horrible.”

The engineered virus is just one option being explored to tackle citrus greening. Other projects aim to edit the genome of citrus trees using CRISPR–Cas9 to make them more resistant to the pest, or engineer trees to express defence genes or short RNA molecules that prevent disease transmission. Local growers have also helped to fund an international project that has sequenced citrus trees to hunt for more weapons against citrus greening.

“There are great scientific opportunities here,” says Bryce Falk, a plant pathologist at the University of California, Davis. “We need to take advantage of new technologies.”

Citrus greening is caused by species from the candidate bacterial genus Candidatus Liberibacter. Spread by sap-sucking, flying insects called Asian citrus psyllids (Diaphorina citri), the bacteria cause citrus trees to make bitter, misshapen fruits that have green lower halves. The disease is also widely known by its Chinese name, huanglongbing.

The first tree in the United States with symptoms was reported in Miami in 2005. “We had the ‘uh-oh’ moment,” says Fred Gmitter, who breeds new citrus varieties at the University of Florida in Lake Alfred.

Some researchers have had accidental success against the disease. Gmitter’s team released a mandarin variety called Sugarbell just as the outbreak was getting under way. Although those trees have since become infected with C. Liberibacter, farmers are able to reap a reasonable crop of sweet oranges if the plants receive proper pruning and nutrition. But it is difficult to build on that success: why the trees are relatively tolerant of the disease remains a mystery.

For years, Southern Gardens Citrus has been genetically engineering plants to express genes taken from spinach that defend against the disease. The company says that the results of field trials suggest some degree of protection. But this approach will take many years to meet regulatory requirements for marketing a genetically modified crop. And consumers may not take kindly to a fruit or juice that comes from a genetically modified tree.

So Southern Gardens Citrus added a different approach, and began the USDA approval process for engineered CTV in February. Instead of modifying the trees, the company wants to alter the genome of a harmless strain of CTV so that it produces the spinach defence gene. The company intends to graft tree limbs infected with the virus onto trees. In April, the USDA announced it would start work on an environmental impact statement, a process that typically takes about two years and will be needed before the department allows the modified virus to be used commercially.

Because the virus does not alter the fruit, this approach may allow farmers to argue that the oranges are not genetically modified, and so avoid regulation and reduce public doubt.

That is also the goal of separate projects looking for genes that confer disease resistance when switched off. If researchers can find such genes, they could use CRISPR to inactivate them. Nian Wang, a plant pathologist also at the University of Florida, is using this approach to edit orange trees, and hopes to know by 2019 whether they are disease-resistant. Others are using RNA interference in psyllids to switch off genes that allow the insects to transmit the bacteria.

For now, one question dominates: whether the citrus industry will still be alive by the time these solutions make it to the groves. “It’s an incredibly devastating disease,” says Gmitter. “Growers needed answers ten years ago.”