In the citrus world there is a relative tolerance to the bacteria that causes Huanglongbing, or Citrus Greening. Grapefruit and some orange varieties are very sensitive and some mandarin varieties are much more tolerant, meaning they live longer in the presence of the bacteria. Work is being done to use mandarin juice as a substitute for the traditional glass of orange juice. A recent bulletin out from the University of Florida has this news. This does not mean that Asian Citrus Psyllid and Huanglongbing are any less of a threat to citrus at this point. Just a way of prolonging an industry until true solutions can be found.
GAINESVILLE, Fla. — Some people like to wake up and drink a glass of fresh Florida orange juice. With the greening disease ravaging Florida's citrus industry, University of Florida Institute of Food and Agricultural Sciences researchers want to make orange juice from disease-tolerant fruit.
Huanglongbing (HLB), or citrus greening as it's commonly called, has destroyed 80 percent of citrus in Florida, a state where citrus is an $8.6 billion-a-year industry, according to UF/IFAS research. About 90 percent of the state's oranges are used to make orange juice, UF/IFAS researchers say.
So it's critical that scientists find sources for orange juice upon which consumers can rely. UF/IFAS researchers have found some mandarins that are tolerant to citrus greening.
In a newly published study, UF/IFAS researchers also found that consumers sense little, if any difference in the smell and taste of certain specific mandarins, compared to oranges.
“We found out what makes orange taste like orange and mandarin taste like mandarin, even though they are very close species,” said Yu Wang, a UF/IFAS assistant professor of food science and human nutrition and lead author of the study.
“If we use greening-tolerant mandarin for orange-juice making, the first thing we need to know is the difference between them,” Wang said. “This will provide more possibilities and flexibilities for the citrus industry in particular in the HLB era.”
In the past, researchers used traditional methods such as gas chromatography-mass spectrometry to study the flavor differences in orange and mandarin, Wang said. But people's senses of taste and smell are much more sensitive than analytical equipment, so scientists integrated sniffing into the study, she said.
It's important to remember that oranges are descendants of mandarin and pummelos, said Fred Gmitter, a UF/IFAS horticultural sciences professor and co-author of the study. So there's already a lot of mandarin's genetic makeup in an orange.
The problem is that oranges are very sensitive to citrus greening, Gmitter said.
“While we find other selections in the breeding program, mostly mandarin, hold of up a lot better against greening, we are finding some of these selections produce fruit that more closely resemble orange in appearance,” Gmitter said. “But more importantly, here, that they also very closely resemble orange in flavor.”
The study is published in the Journal of Agricultural and Food Chemistry:
The latest National Agricultural Statistics Service (NASS) results are out for the citrus crop. These are results that are collected by the USDA to gauge production in the different growing areas of the country. From this most recent data, it is clear that citrus production is diminishing with time, most likely the effect of Huanglongbing. This is about a 60% decline from 2015.
The impact of this reduced production has reached out to not just growers, but also the juice industry they support, or are supported by. There's been a decline in the number of juice plants since 2014 which are reliant on volume to stay in business. If plants close, growers have fewer options for their juice citrus. http://www.theledger.com/news/20140705/at-least-one-juice-processor-expected-to-close
Most commercial crop production figures are collected by state and summarized on a state basis with the Agricultural Census every 10 years - https://www.agcensus.usda.gov/. The last was done in 2012.
Daily market prices for these different commodities can be seen on a wholesale basis by city, at USDA's Market News Service - https://www.marketnews.usda.gov/mnp/fv-home . This gives current prices and archived prices for products sold in different markets. It gives a general idea of what the grower will be paid for a given crop.
All of these sources are helpful for deciding where crop prices and markets are going. If you have time check them out.
The International Citrus Conference was just held and about 1,500 people came from all over the world to share their experiences and research in citrus. It included marketers, growers, government officials and researchers who all had citrus as their interest. It was remarkable the volume of information, everything from world production figures and marketing, new varieties, breeding technology, plant diseases and pests, water management and of course HLB and ACP, probably the two most fearsome world-wide problems.
On the whole it was most hopeful to realize how much has been accomplished in the last several years to deal with the threat of HLB. The biology of ACP is better understood in different situations, the disease progression in different citrus species is being recognized as being more or less aggressive, and how to manage the insect and disease are better understood. Unfortunately, new threats (however none as mush as HLB) are being identified, such as citrus longhorn beetle. Oh, my.
Read the Abstracts at:
What this means is that there is different feeding behavior on different scion varieties that is unaffected by the rootstocks used in this study. This does not mean "a" rootstock can not have an effect, just that the ones used in this trial did not.
EFFECT OF DIFFERENT CITRUS SCION AND ROOTSTOCKS
COMBINATION ON FEEDING OF Diaphorina citri
Alves GA1, Beloti VH1, Carvalho SA2 & Yamamoto PT1
1Escola Superior de Agricultura ‘Luiz de Queiroz'/
Universidade de São Paulo, Piracicaba, SP, Brazil; 2Instituto
Agronômico (IAC), Centro de Citricultura, Cordeirópolis, SP,
Brazil; e-mail: firstname.lastname@example.org
The Asian citrus psyllid (ACP) is the vector of bacteria associated to the huanglongbing and has a host range of more than 50 species of the Rutaceae family. The knowledge about the feeding behavior in different hosts can show useful aspects for future studies of plant resistance and ACP management. Therefore, was evaluated the effect of different combinations of scion and rootstock of citrus in the feeding of ACP adults. For this, we tested Valencia, Pera and Hamlin sweet orange, Ponkan mandarin and Sicilian lemon grafted on Rangpur lime and Sunki mandarin rootstocks.
The flushes were individualized with cages made of transparent plastic cup and “voile” tissue. To collect the honeydew, discs of filter paper were placed at the base of each flush. The adults fed for a period of 72 h. After this, the discs were removed and immersed on the ninhydrin solution. After 24 h, the drops area of honeydew was determined using the Quant software. The feeding was more intense on sweet orange varieties, with a highest value observed to Valencia (0.902 cm2) and the smaller area to Ponkan mandarin(0.269 cm2). Unlike observed for scion varieties, when different rootstocks for the same scion variety were tested, no difference was observed in the consumption of ACP.
Rootstocks can have a tremendous effect, but not in this case with the rootstocks used
Beth Grafton-Cardwell our IPM Specialist who is Lindcove Research and Extension Director and a UC Riverside Entomologist recently gave a talk on the different approaches being taken to confront Asian Citrus Psyllid and Huanglongbing. A summary of a lot of her points is available at:
She brought up some points that I think need to be better known. Some early detection techniques are being developed so that infected trees can be quickly identified and removed so that they do serve as a reservoir of inoculum that can increase the spread of the bacterial disease. These techniques are based on measureable levels of different chemicals.
Sick trees produce different volatiles (Volatile Organic Compounds can be “sniffed” by machines or trained dogs)
Sick trees produce proteins that can be measured
Trees produce small RNAs in their defense response that can be measured
The bacteria produce proteins that can be measured
The micro-organisms associated with sick trees are different than those associated with healthy trees and these can be measured.
All of these techniques are being tested out right now and being refined. It will mean faster diseased tree identification and removal. This will still mean chemical control of the psyllid to control disease spread.
Early detection is just one of the techniques being employed to fight this insect/disease complex. Every conceivable possibility is being explored, including:
Psyllid traps – attract and kill
Psyllid deterrents – chemicals that would drive psyllids away from citrus
Antibiotic treatments to control the tree infection
Heat treating trees to destroy the bacteria in the tree
Resistant rootstocks and scions (traditional breeding and genetic engineering)
Utilize an altered citrus tristeza virus to introduce anti-HLB genes into plants (Genetically Engineered)
Altering the psyllid so it can't vector the disease and releasing the ‘nupsyllid' to replace the wild ones (GE)
Treat trees with chemicals (interference RNAs) that prevent the psyllid from picking up the disease
Wow. Many of these are a long way off, but some might be coming out soon. We still need to deal with the psyllid so that when infected insects become more widespread, the disease will not spread as fast as it has in Florida and other citrus growing areas.