From the Citrus Industry
The new Sugar Belle hybrid rootstock LB8-9xS13#16 has quite a history, according to University of Florida Institute of Food and Agricultural Sciences citrus breeder Jude Grosser.
“This is one of several projects I did with Orie Lee toward the end of his Florida Citrus Hall of Fame career/life,” recalls Grosser. “We did a lot of brainstorming together, and he was full of ideas and the energy to make them become a reality!”
Before HLB became the dominant scourge of Florida citrus, Grosser was heavily invested in trying to solve blight. Lee had a great interest in blight, because in several of his most productive blocks the annual tree loss to blight was about 12 percent.
“Evidence was showing that pummelo x mandarin hybrids had superior blight tolerance as compared to other rootstock categories, so I made a lot of pummelo x mandarin hybrids,” says Grosser. “Orie was in a hurry to plant rootstock hybrids to test for blight tolerance, and he had just planted a large block at the Alligator Grove. He suggested we plant trees in between each of the planted trees. We made cuttings from about 125 new rootstock hybrids and we tried to get at least seven liners for each rootstock. We grafted them all with Valencia and planted them one year after the original grove was planted — about 12 years ago.”
According to Grosser, the Alligator Grove has never had psyllid control, and about four years after planting, it was evident that nearly all the trees were infected with HLB. “For the past six years, I have been scoring the individual trees for HLB. There were only two of the trees on the S13 parent (salt tolerant HB pummelo x Cleo). During the 2020 scoring, this hybrid had the highest tree health rating (4.25 out of 5), indicating very good ability to transmit HLB tolerance from the rootstock to the Valencia scion,” he explains.
Grosser says it has become evident from multiple trials that Sugar Belle has exceptional HLB tolerance no matter what rootstock it is grown on. “I thought that maybe we could flip this equation and develop a rootstock that any scion could grow on in the presence of HLB,” he says. “Sugar Belle is not used as a rootstock because it does not come back true-to-type from seed and is purported to be susceptible to phytophthora.”
So, Grosser decided to use Sugar Belle as a rootstock breeding parent to test his hypothesis. He made the first crosses with Sugar Belle in 2015, using a salt-tolerant HB pummelo x Cleo hybrid (S13) and a salt-tolerant HB pummelo x Shekwasha (S10) as the pollen parents.
Since then, Grosser has made other crosses using Sugar Belle. As the rootstocks progressed through the screening process, he says one hybrid jumped ahead of the others. So, he planted two trees at the Citrus Research and Education Center (CREC).
“I planted the hybrid #16 tree on the corner of Block 8, just behind our barn, so I could watch it every time I drove up the road to my greenhouses or field plots. I noticed that psyllids were feeding on the tree during every new flush (despite the CREC spray program), and there was visible psyllid damage on leaves from all flushes,” says Grosser. “Despite starting infected and continuous psyllid re-inoculation, this tree has grown off like a normal pre-HLB tree and looks beautiful today, two years after planting. It has set some fruit, so I will begin to get an idea of fruit quality this coming fall.”
Grosser says the second tree, on a different hybrid, is doing okay, but nothing like #16.
“After what I saw the first year, I grafted an infected Murcott (the most HLB-susceptible variety) onto the rootstock and planted it, and it is also growing incredibly well,” he says. “The Murcott tree is now one year old. We tested the original Valencia tree by PCR in December, and the scion had a ct value of 24, indicating a high titer of CLas (the causal agent of HLB); whereas the roots had a ct value of 32, indicating no active infection. We tested this tree again in April, and the ct value went up to 36, indicating no active infection. So, even starting out infected and under heavy psyllid pressure, the rootstock seems to have suppressed the infection, allowing the tree to thrive.”
Although it has only been two years from planting, Grosser is hopeful that the “HLB tolerance, maybe resistance, holds up over time (like it seems to be doing with its parents). I have pathogen-free material of this rootstock, and we are now making cuttings as needed for large-scale evaluations. We have also started this rootstock in tissue culture for micropropagation.”
A Solution for the devastating bacteria causing citrus huanglongbing?
UC Riverside scientists have found the first substance capable of controlling Citrus Greening Disease, which has devastated citrus farms in Florida and also threatens California.
Oranges afflicted with Citrus Greening Disease. (UCR)
The new treatment effectively kills the bacterium causing the disease with a naturally occurring molecule found in wild citrus relatives. This molecule, an antimicrobial peptide, offers numerous advantages over the antibiotics currently used to treat the disease.
UCR geneticist Hailing Jin, who discovered the cure after a five-year search, explained that unlike antibiotic sprays, the peptide is stable even when used outdoors in high heat, easy to manufacture, and safe for humans.
“This peptide is found in the fruit of greening-tolerant Australian finger limes, which has been consumed for hundreds of years,” Jin said. “It is much safer to use this natural plant product on agricultural crops than other synthetic chemicals.”
Currently, some growers in Florida are spraying antibiotics and pesticides in an attempt to save trees from the CLas bacterium that causes citrus greening, also known as Huanglongbing or HLB.
The Asian citrus psyllid, pictured here, spreads the bacterium that causes Citrus Greening Disease. (Mike Lewis/UCR)
“Most antibiotics are temperature sensitive, so their effects are largely reduced when applied in the hot weather,” Jin said. “By contrast, this peptide is stable even when used in 130-degree heat.”
Jin found the peptide by examining plants such as the Australian finger lime known to possess natural tolerance for the bacteria that causes Citrus Greening Disease, and she isolated the genes that contribute to this innate immunity. One of these genes produces the peptide, which she then tested over the course of two years. Improvement was soon visible.
“You can see the bacteria drastically reduced, and the leaves appear healthy again only a few months after treatment,” Jin said.
Because the peptide only needs to be reapplied a few times per year, it is highly cost effective for growers. This peptide can also be developed into a vaccine-like solution to protect young healthy plants from infection, as it is able to induce the plant's innate immunity to the bacteria.
Jin's peptide can be applied by injection or foliage spray, and it moves systemically through plants and remains stable, which makes the effect of the treatment stronger.
The treatment will be further enhanced with proprietary injection technology made by Invaio Sciences. UC Riverside has entered into an exclusive, worldwide license agreement with Invaio, ensuring this new treatment goes exactly where it's needed in plants.
“Invaio is enthusiastic to partner with UC Riverside and advance this innovative technology for combating the disease known as Citrus Greening or Huanglongbing,” said Invaio Chief Science Officer Gerardo Ramos. “The prospect of addressing this previously incurable and devastating crop disease, helping agricultural communities and improving the environmental impact of production is exciting and rewarding,” he said. “This is crop protection in harmony with nature.”
The need for an HLB cure is a global problem, but hits especially close to home as California produces 80 percent of all the fresh citrus in the United States, said Brian Suh, director of technology commercialization in UCR's Office of Technology Partnerships, which helps bring university technology to market for the benefit of society through licenses, partnerships, and startup companies.
“This license to Invaio opens up the opportunity for a product to get to market faster,” Suh said. “Cutting edge research from UCR, like the peptide identified by Dr. Jin, has a tremendous amount of commercial potential and can transform the trajectory of real-world problems with these innovative solutions.”
UV Riverside news release:
https://news.ucr.edu/articles/2020/07/07/uc-riverside-discovers-first-effective-treatment-citrus-destroying-disease
Nitrogen is the nutrient plants require in the largest quantity for better yield and quality. Nitrogen is also an integral constituent of proteins, nucleic acids, chlorophyll, co-enzymes, phytohormones,and secondary metabolites, and its deficiency can negatively affect yield. Nitrogen-deficient plants are stunted, with narrow, small, pale leaves. Excessive N application increases vegetative growth and susceptibility to diseases that infect fruit, kill spurs, and reduce yields in subsequent years. Managing nitrogen is critical to tree health and productivity, and active understanding of how it plays in the general horticulture of the tree is critical.
In response to evidence of nitrate pollution of groundwater in California, the various Regional Water Quality Control Boards have adopted regulatory programs to protect groundwater resources that requires growers to use best nitrogen (N) management practices to reduce nitrate loading. As a help to growers, this publication has been created to optimize N use efficiency in citrus and avocado crops with the outcome of reducing N leaching.
YES!!!!
USDA Report on Mexican Citrus Industry
This is a recent USDA report on the state of the Mexican citrus industry. It's interesting to hear how this industry is doing faced with HLB. And Drought.
Significant and ongoing drought conditions in many citrus-producing states have resulted in a reduction in all citrus production, compared to the previous report, with orange production forecast to fall forty-five percent. As a result of low orange supplies for processing, fresh concentrated orange juice exports to the United States are expected to fall to nearly half of the MY 2018/19 export level. COVID-19 sanitary measures are affecting domestic consumption of citrus fruit and juice, as many hotels and restaurants have been closed since mid-March. Full consumption effects will depend on the length of ‘stay at home' orders and the long term effect on the hotel and restaurant industries.
Drought and high temperatures
Orange production is estimated at 2,53 million tons for 2019/2020. That is 45% less than previous estimates. It is also the lowest expected harvest since the early 90s. This estimate is based on grower data and discussions with sector representatives.
The persistent drought and high temperatures have had a more drastic effect on orange production that other citrus. That is because many of the orange groves are older and need more energy to produce fruit. Many small farmers also lack irrigation technology. They practice bad pest control too, which compounds cultivation issues. Large-scale growers mostly have several irrigation mechanisms. They use fertilizers and apply other mitigating measures too. These include leaving weeds growing around the tree trunks. This retains moisture.
There have been intense temperatures and lack of rain throughout the growing season. That has resulted in a widespread decline in the orange's quality. Most fruit in the orange-growing region are smaller and of lower quality. In the state of Veracruz, October and November 2019 were the hottest months.
It usually rains throughout the growing season. However, this season, it was concentrated in two months. That resulted in a shorter growing season. The last flowering cycle indicates the harvest's end. This was between December and March. In Veracruz, oranges can usually be harvested until June.
Mexico is typically the world's second-largest producer of limes, and the fruit is the second-largest planted citrus crop in Mexico after oranges. While drought has affected lemon and lime production throughout the country, they have not been as affected as oranges. This can be attributed to newer plants and more widely available irrigation infrastructure. Persian lime trees in Veracruz are newer and more efficient, with 12 blooms, or harvests per year.The Post planted area for all limes and lemons in MY 2019/20 is forecast at 208,000 hectares, similar to previous MY; however, harvested area is expected to decrease eight percent due drought and high temperatures that caused some producers to abandon harvest or replant trees.
Italian lemons (Eureka) are grown in the states of Tamaulipas, Yucatan, San Luis Potosi, Colima, and Nuevo Leon. According to producers, there are currently attempts to grow the Italian lemon in the state of Veracruz with very good results. According to official sources, for MY 2018/19, production of Italian lemons was 131,469 MT on about 9,264 hectares. Sources indicate that lemon supplies for MY 209/20 are tight, and prices are high.
HLB
As with other citrus-producing countries, Mexico is facing issues with citrus greening, or Huanglongbing (HLB). The disease, caused by bacteria introduced by psyllids, makes citrus trees produce misshapen, partially green fruit (taste is typically not affected, but has no marketability for fresh consumption). Mexico's first detection was in 2009, and since then, the National Service of Agricultural Food Safety and Quality (SENASICA) has implemented a monitoring program for the disease. HLB has been detected throughout Mexico in citrus production areas. Producing states, including Veracruz, Tamaulipas, San Luis Potosi, and Nuevo Leon, have had HLB detections. In 2019, Baja California had HLB positive detections along the California/Mexico border region
On the map, dark outlined areas are where citrus is grown and yellow shaded is drought area.
