- Author: Ben Faber
From Peru This Week, Hillary Ojeda:
Unfavorable climate conditions around the world have increased demand from Peru.
In February, the Ministry of Irrigation and Agriculture confirmed that Peru is the second largest exporter of avocados. This will prove crucial in the coming months, as production around the world is at a shortage.
“Prior to the season a higher production was expected in Peru for 2015 compared to 2014, but now it turns out that the total Peruvian harvest is a bit lower,” Ine Potting (Mission Produce) told Fresh Plaza.
The produce news portal reports that the avocado market is currently experiencing a shortage due to primary exporters struggling to produce up to expectations.
“Due to hail in Mexico, which affected a lot of the Flor Loca harvest blossom, and the drought in California, the harvests there will also be less than satisfactory. This means that there will be more demand from the United States for avocados from Peru,” says Ine.
Considering these circumstances, the price is increasing (of green varieties as well in addition to Hass avocados) and less shipments will make it Europe this season.
Peru's avocado industry made US$ 308 million in 2014 and exported a record amount of 177,800 tons of the and creamy Hass avocado variety. These results secured its place as second largest exporter of the large berry, after Mexico.
- Author: Ben Faber
From The Packer:
South Florida university researchers are using dogs and drones to sniff out a disease that's killing the region's avocado trees.
The Florida International University researchers are sending dutch sheppards and belgian malinois into avocado groves to locate trees infected by the lethal laurel wilt disease, which is spread by the redbay ambrosia beetle.
Detection is a major problem and trees can start to wilt within two weeks.
By the time infected trees are detected, the fungus has likely spread to nearby trees via root grafting, said DeEtta Mills, a biological sciences professor.
She and Kenneth Furton, a university provost and forensic chemist, are leading research that trains and deploys five dogs into Miami-area groves.
Drones flying above the groves can detect symptomatic trees, which signal researchers to direct the dogs to infected areas.
The dogs run through the groves and with their powerful noses, have been 90% accurate in locating infected trees, Mills said.
Because of permitting paperwork delays by the Federal Aviation Administration, the researchers haven't been able to use the drones.
The researchers hope to receive approval for drones by August and are relying on growers to point them to infected trees.
The drones provide higher accuracy and can better cover larger areas because running the dogs too long can overheat them and wear them out, Mills said.
Their heavy panting can dull their sniffing senses so after about 20 minutes, the researchers return them to kennels in air conditioned vans, Mills said.
The dogs are trained with diseased wood and infected tree samples detected by the dogs are sent to researchers who examine DNA to verify contamination, she said.
“These dogs, they love to do this and it's amazing to watch them,” Mills said. “These ‘girls' come out of the kennels of the van and ask us where we would like to send them and what we would like them to do. They're extremely highly-driven dogs. If we can get permission to use the drones, it will help us identify areas we need to go in with the dogs and help us verify infection much faster so the dogs won't have to cover as much ground.”
Canine detection is another way of helping save the state's multi-million dollar avocado industry and ultimately, the North American industry.
Florida growers have lost about 4,000 of nearly 800,000 trees and the disease has spread throughout the Mid-Atlantic and into Mississippi.
If it travels farther west, the dogs and drones detection system could also help growers in California and Mexico protect their much larger production, she said.
The Miami university is also working with University of Florida researchers and growers.
N.B. These techniques could also be used to trace Polyphagous Shot Hole Borer infested trees, as well.
- Author: Ben Faber
Polyphagous Shothole Borer which is an ambrosia beetle that normally feeds on dead trees is going after live trees - over 100 species including sycamore, alder and coast live oak. It also goes after avocado. The California Avocado Commission has sponsored the placement of traps that have lures for PSHB. The traps are near avocado orchards but also likely spots where they might show up, such as campsite where people would bring firewood that might be infested with the beetle. The map here shows where the traps are located and where PSHB have been trapped. There are also traps in Santa Barbara County which are not yet shown on this map.
- Author: Ben Faber
Some call it tip burn which is often what you see on an avocado as it goes into flowering. The areas where avocado are grown typically have a lot of salts in the water, but also specific salts like sodium and chloride. Over the irrigation season (which is all year long there is little or no rain), the salts in the water/soil are taken up by the tree. In adequate rainfall years, there is enough water to leach those accumulated salts from the root system. When we go for several years with low rainfall and we keep irrigating with the poor quality irrigation water, the trees develop die back at the tips and is conditions worsen more and more of the leaf is called. This can get to the point where you can not call it die back any longer. It's called leaf drop. I've recently seen a number of orchards that are completely defoliated. No leaves. We have had a number of homeowner calls asking what the problem is and what they can do about it. The damage is done and those leaves are not coming back. It's possible to reduce the damage if one acts early on by applying more water than is usually applied to aid the leaching process, but if it is poor quality water, there will still be damage, but possibly not defoliation. With high priced water or where water is being rationed, many growers and homeowners do not have themake the option of putting on the excess water. There is no chemical or equipment that is going to make the situation better. When you trees defoliating, you want to cut out those that are diseased or you know have been poor producers and put what water you have on the remaining trees in better condition.
This advice is good for other evergreen tree crops like citrus, although they are not as sensitive as avocado. Avocado is an indication of how bad it really is.
- Author: Vanessa Ashworth
- Author: Mary Lu Arpaia
- Author: Philippe Rolshausen
Department of Botany and Plant Sciences, University of California, Riverside
An unusual population of avocado trees may soon suffer the same fate as many commercial orchards elsewhere in California: its water supply will be cut off and the trees fed to a wood chipper. And yet these trees (Fig. 1) potentially hold a key to the avocado's future: they are the cornerstone of scientific research at the University of California, Riverside, aimed at unravelling the genetic underpinnings of agricultural traits and at placing avocado breeding on a molecular footing.
It is well known to plant breeders that the traits observed in a promising selection are rarely transmitted to its offspring. This is because the so called phenotype (what you see or measure) is a poor predictor of the genotype (the underlying genetic machinery). Unfortunately, for breeding to make any progress, phenotypic traits need to have a genetic basis. Traditional breeding, which cannot distinguish between phenotype and genotype—only works because it starts our with a large pool of trees and, by chance, ends up with a few selections that show promise as future cultivars. In avocado, the selection efficiency of traditional breeding is in the order of 0.1-0.2%; in other words, only 1–2 promising selections are recovered for every 1000 trees that have been laboriously (and expensively) screened over the course of a minimum of 5–10 years. Clearly, a better understanding of the relationship between phenotype and genotype would make the breeding process more efficient.
Recognizing this need, Professor Michael Clegg of (then) UC Riverside established a carefully designed experimental population of avocado trees, later known as the Clegg Collection. It consisted of over 200 progeny from a single cultivar Gwen mother tree, and each progeny tree was clonally propagated four-fold, taking the total number of trees to ca. 800. The seedlings were grafted to a uniform Duke 7 rootstock to further reduce the impact of non-genetic variability. Between the fall of 2001 and spring of 2003 half of the trees (two clonal replicates of each unique genotype) were planted out at UC Riverside and the other half at South Coast Research and Extension Center, Irvine.
In this experimental design, every tree genotype is represented twice at each of two locations. Any variation between the clonal replicates at the same location sheds light on how much of a trait is environmental and how much of it is genetic. Only the genetic component is useful for breeding purposes. The environmental component is the “noise” that misleads breeders and, regrettably, often has a large influence on agriculturally relevant traits.
Since 2003 the Clegg trees have been put to good use. First, a quantitative genetic study was initiated to address the mismatch between genotype and phenotype and, specifically, to determine whether certain vegetative growth characteristics are amenable to breeding. This work (Chen et al. 2007) revealed that about 30% of the total phenotypic variation in growth rate and flowering was genetic in origin and thus amenable to breeding.
While the initial value of the Clegg experimental population arose from its utility in teasing apart genetic and environmental effects on a phenotype, the trees soon acquired additional roles. Genetic markers offer the opportunity of placing phenotypic measurements in a molecular framework. Microsatellite markers were used to determine the pollen parent of each ‘Gwen' progeny tree, revealing that approximately three quarters of the genotypes had been pollinated in roughly equal proportions by ‘Bacon', ‘Fuerte', and ‘Zutano', with the remaining quarter sired by miscellaneous cultivars or rogue pollen sources. What better opportunity than to examine genetic variation of traits in the context of the pollen parent. An interesting finding from this line of study was that ‘Gwen' ´ ‘Fuerte' progeny had significantly wider canopies and shorter stature than their half-sibs sired by ‘Bacon' or ‘Zutano' (Fig. 2). The fact that tree width and height is amenable to breeding is an encouraging result in the context of high-density planting such as that commonly practiced in apple.
At a time when avocado was gaining cudos as a healthy fruit with excellent nutritional qualities and beneficial effects in the treatment of high cholesterol and cancer, the Clegg Collection was next harnessed in a study on fruit nutritional composition. Data was gathered on fruit nutrient content in each genotype. Again, taking advantage of the experimental setup, the environmental “noise” associated with each measurement was stripped away to extract the
genetic portion that proved to be appreciable (Calderón-Vázquez et al. 2013).
The next step was to connect this data with a new type of molecular marker. These markers—so called SNP markers (Single Nucleotide Polymorphisms)—were developed using gene sequences from a subset of the Clegg trees. They were designed to reside in genes known to control the accumulation of particular fruit nutrients. Statistical analyses revealed that beta-sitosterol contents were being tracked by one of the SNP markers: in other words, the presence of this marker in an individual was indicative of high beta-sitosterol levels in its fruit.
Markers that are highly predictive of desirable traits and are relatively easy to measure in young seedlings are the nuts-and-bolts of marker-assisted selection, a breeding method that draws on molecular tools. Consequently, a third project was initiated that harnessed the SNP marker that predicted high fruit beta-sitosterol contents. Progeny from trees of the Clegg population were screened using the marker. Out of an initial pool of over 600 seedlings 73 seedlings (12%) were identified that had the desirable form (allele) of the marker, and 12 seedlings (2%) were eventually planted out. The selection intensity of marker-assisted selection therefore is at least 10-fold higher than under traditional breeding.
A loss of the Clegg Collection would surely represent an opportunity lost. Many more projects could be envisaged that address the genetic determination of a trait, its association with SNP markers, the influence of the pollen donor, or the utility of a marker for marker-assisted selection. The Collection has also been the nucleus of a genetic mapping project. Significantly, the SNP markers developed for these trees are also relevant for studies beyond fruit nutrient content because their biosynthetic pathways intersect with those underlying plant stress and disease responses. This property makes the candidate genes equally relevant for studies on pathogen or salinity tolerance and a key resource that could help secure the future of avocado production in California during turbulent times.
Literature Cited
Chen, H., V. E. T. M. Ashworth, S. Xu, and M. T. Clegg. 2007. Quantitative genetic analysis of growth rate in avocado. J. Amer. Soc. Hort. Sci. 132 (5): 691–696.
Calderón-Vázquez, C., M. L. Durbin, V. E. T. M. Ashworth, L. Tommasini, K. K. T. Meyer, M. T. Clegg. 2013. Quantitative genetic analysis of three important nutritive traits in the fruit of avocado. J. Amer. Soc. Hort. Sci. 138 (4): 283–289
The Clegg Collection: the trees shown here are growing at UC Riverside