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The scent that could save California’s avocados
Scientists search for pheromone to disrupt insect mating
UC Riverside scientists are on the hunt for a chemical that disrupts “evil” weevils' mating and could prevent them from destroying California's supply of avocados.
Avocado weevils, small beetles with long snouts, drill through fruit to lay eggs. The weevil grubs or larvae bore into avocado seeds to feed, rendering everyone's favorite toast topping inedible.
“They're extremely hard to control because they spend most of their time deep inside the fruit, where they're very well protected from insecticides and natural enemies,” said UCR researcher Mark Hoddle, a UC Cooperative Extension entomology specialist.
Not only are the insects reclusive, they are also understudied, making information about them hard to come by. “All books on avocado pest management will tell you these weevils are bad. They're well recognized, serious pests of avocados, but we know practically nothing about them,” Hoddle said.
One strategy for controlling pests is to introduce other insects that feed on them. However, that is unlikely to work in this case. “Natural enemies of these weevils seem to be extremely rare in areas where this pest is native,” Hoddle said.
To combat avocado weevils in Mexico, an area where they are native, and to prevent them from being accidentally introduced into California, Hoddle is working with Jocelyn Millar, a UCR insect pheromone expert. They are leading an effort to find the weevil's pheromone, with the goal of using it to monitor these pests and prevent them from mating in avocado orchards.
Pheromones are chemicals produced and released into the environment by an insect that can be “smelled” by others of its species, and affect their behavior.
“We could flood avocado orchards with so much pheromone that males and females can't find each other, and therefore can't reproduce,” Hoddle said. “This would reduce damage to fruit and enable growers to use less insecticides.”
Alternative control strategies could include mass trapping, using the pheromone as a lure, or an “attract-and-kill” approach, where the pheromone attracts the weevils to small sources of insecticide.
The work to identify, synthesize and test this pheromone in the field is supported by grants from the California Department of Food and Agriculture, as well as the California Avocado Commission.
An initial phase of the project sent Hoddle to a base of operations three hours south of Mexico City, an area with large weevil populations. Using a special permit issued by the USDA, Hoddle brought weevils back to UCR's Insectary and Quarantine facility.
Hoddle and Sean Halloran, a UCR entomology researcher, captured the chemicals that avocado weevils release into the air. Possible pheromone compound formulas were identified from these crude extracts and are now being synthesized in Millar's laboratory.
“Weevil pheromones have complicated structures. When they're made in a lab, they can have left- or right-handed forms,” said Hoddle. Initially, Millar's group made a mixture of both forms to see if the blend would work as an attractant, as it is far cheaper to make the blend than the individual left- or right-handed forms.
Field work in Mexico with the pheromone cocktail by Hoddle, his wife Christina Hoddle, an associate specialist in entomology, and Mexican collaborators did not get a big response from the weevils, suggesting that one of the forms in the blend could be antagonizing the response to the other.
As the next step, the researchers plan to synthesize the individual forms of the chemicals and test the insects' response to each in Mexican avocado orchards.
Because the levels of avocado imports from Mexico are increasing, the risk of an accidental weevil invasion is rising as well. Hoddle is hopeful that the pheromone will be successfully identified and used to lower the risk this pest presents to California's avocado growers.
“We've been fortunate enough to be awarded these grants, so our work can be implemented in Mexico and benefit California at the same time,” Hoddle said. “The tools we develop now can be used to make sure crops from any exporting country are much safer to import into California.”
You, too, can grow California’s oldest living orange variety
Sweet Mother Orange Tree released from quarantine
The 1000th tree okayed for growing by California's Citrus Clonal Protection Program happens to be the oldest living orange variety in the state.
The program, housed at UC Riverside, is the first of its kind in the world. It began in the 1950s, and its scientists spend up to three years testing and clearing citrus trees of disease so they can be released to commercial and private growers.
By law, every citrus tree newly propagated in California can be traced back to one mother tree created at UCR through the protection program. Program Director Georgios Vidalakis and his group begin their process by testing incoming trees for more than 30 citrus diseases, whether the diseases are known to have emerged in the state or not.
The treatment for any disease identified in that first round of testing is to make a new mini tree from a few cells of the original budwood — short, leafless twigs with buds meant for propagation. “We use special plant cells for this process that diseases cannot penetrate,” Vidalakis said.
After the mini tree grows large enough, program scientists go back and do a second round of testing for disease, making sure they picked the right cells for propagation and eliminating any prior trace of illness.
If it passes the arduous second set of tests, the new tree gets a variety index or VI number that accompanies it for the rest of its life, and it is released to the public.
Dubbed the Mother Orange Tree, Bidwell's Bar is a sweet Mediterranean orange brought to California from Mazatlán, Mexico, and planted in 1856. It was first planted near the Bidwell Bar Bridge near Oroville, then dug up and replanted twice.
Its survival skills are some of the reasons Tom Delfino, former California Citrus Nursery Society director, recommended the old orange tree for the protection program.
“Apparently this variety is very rugged,” Delfino said. “Not only has it survived a lot of cold Northern California winters, but the tree has been dug up and replanted twice — once to protect it from impending flood, and again to make way for the Oroville Dam.”
Much of the state's orange industry is based in areas with warm weather. Delfino, who lives in the San Francisco Bay Area, finds citrus an exciting challenge to grow. By suggesting Bidwell's Bar for approval, he was hoping the protection program would clear it so he could buy its budwood.
On the occasions he has visited the original tree, Delfino said the fruit in reaching distance was always gone. “I think it must be tasty because locals grab it for themselves,” he said. “Makes me even more eager to grow and eat my own. I'm extremely pleased the VI testing is completed so I can acquire it.”
Delfino also hopes that this variety will catch on with commercial growers.
“My thought is our citrus industry is concentrated in the southeastern San Joaquin Valley and is subject to a number of pests that like the warm climate there,” Delfino said. “Though this has seeds, which may be a deterrent, it can be grown in colder areas that discourage some of those insects.”
The tree arrived in California nearly two decades before the better-known Washington Navel orange grown by Eliza Tibbets in Riverside. The navel is named for a structure at the bottom end of the fruit, which resembles a belly button. This structure is actually a separate fruit inside the larger fruit. The Washington Navel is also seedless, contributing to its popularity.
“Bidwell's Bar is an example of what was grown in California before the Washington Navel came to dominate, and now that it has a VI number, others can grow it too,” said Tracy Kahn, curator of the Givaudan Citrus Variety Collection at UCR.
Kahn says it's important to preserve the genetic material from a tree with such significance to California. “Some people were worried it was going to die, but now we have an officially cleared source of this historic tree, and it is protected for future generations,” Kahn said.
New strategies to save the world’s most indispensable grain
Genetic insights help rice survive drought and flood
Plants — they're just like us, with unique techniques for handling stress. To save one of the most important crops on Earth from extreme climate swings, scientists are mapping out plants' own stress-busting strategies.
A UC Riverside-led team has learned what happens to the roots of rice plants when they're confronted with two types of stressful scenarios: too much water, or too little. These observations form the basis of new protective strategies.
“This one crop is the major source of calories for upwards of 45 percent of humanity, but its harvests are in danger,” said Julia Bailey-Serres, UCR geneticist and study lead. “In the U.S., floods rival droughts in terms of damage to farmers' crops each year.”
In particular, the researchers examined the roots' response to both types of conditions, because roots are the unseen first responders to flood and drought-related stress.
Their work is described in a new paper published in the journal Developmental Cell.
One key finding is about a cork-like substance, suberin, that's produced by rice roots in response to stress. It helps protect from floods as well as from drought.
“Suberin is a lipid molecule that helps any water drawn up by the roots make it to the shoots, and helps oxygen from shoots to reach roots,” Bailey-Serres said. “If we reinforce the plant's ability to create suberin, rice has better chances for survival in all kinds of weather.”
The researchers were able to identify a network of genes that control suberin production and can use this information for gene editing or selective breeding.
“Understanding suberin is particularly exciting because it is not susceptible to breakdown by soil microbes, so carbon that the plant puts into suberin molecules in the roots is trapped in the ground,” said Alex Borowsky, UCR computational biologist and study co-author.
The researchers also identified the genes controlling some of rice's other stress behaviors.
“One of our interesting findings is that when rice plants are submerged in water, the root cell growth cycle goes on pause, then switches back on shortly after the shoots have access to air,” Bailey-Serres said.
In the future, the research team plans to test how modifying these stress responses can make the plant more resilient to both wet and dry conditions.
“Now that we understand these responses, we have a roadmap to make targeted changes to the rice genome that will result in a more stress-tolerant plant,” Bailey-Serres said.
Though heavy rains and droughts are both increasing as threats, Bailey-Serres has hope that new genetic technology can increase its resilience before it's too late.
“With genome editing, the fact that we can make a tiny but targeted change and protect a plant from disease is amazing. Though our crops are threatened, new technologies give us reasons to hope,” Bailey-Serres said.
La industria de los cítricos, UC Riverside y UCCE combaten plaga que acaban con los cítricos
El pasado 6 de junio, la industria de los cítricos, la universidad y líderes gubernamentales se reunieron en UC Riverside Citrus Variety Collection para anunciar un esfuerzo conjunto para luchar contra el Huanglongbing (HLB, por sus siglas en inglés), también conocida como la enfermedad del enverdecimiento de los cítricos. El Huanglongbing es una enfermedad bacteriana fatal para los árboles de cítricos.
El esfuerzo dará como resultado la construcción de una planta de bioseguridad nivel 3 en Riverside, cerca de dos millas al norte de la UC Riverside.
La planta de bioseguridad nivel 3 permitirá a los investigadores, incluyendo a muchos de UC Riverside que son expertos en plagas de cítricos, enfermedades y reproducción, conducir trabajo con patógenos de plantas que antes no se podía llevar a cabo en el sur de California. (Solo existe otra instalación similar en California, en UC Davis.)
El nuevo edificio de bioseguridad nivel 3 será construido y pertenecerá a la Fundación para la Investigación de Cítricos de California, la cual es financiada por los productores de cítricos.
Durante la reunión del pasado 6 de junio, Kim Wilcox, rector de UC Riverside, habló sobre la apertura, en 1907, de la Estación de Experimentos sobre Cítricos en Riverside. Esta estación de investigación eventualmente se convirtió en lo que ahora es la UC Riverside. El académico resaltó que esa estación de investigación recibió un impulso después de la helada de 1913 que devastó a la industria de los cítricos.
“Ahora, desafortunadamente, 100 años después, contamos con una amenaza natural diferente, señaló Wilcox. “En este caso no se trata del clima, sino de un insecto. Y de nuevo, la universidad, el gobierno federal y el sector privado se han unido y dicho: ‘Podemos abordar esto'”.
Georgios Vidalakis y Mark Hoddle son dos especialistas de Extensión Cooperativa de la UC con base en UC Riverside, que se beneficiarán de la nueva planta.
Vidalakis es un especialista de la UCCE en patología botánica y director del Programa de Protección Clónica de los Cítricos en UC Riverside. El programa provee de un mecanismo de seguridad para la introducción de variedades de cítricos a California de todo el mundo.
“Tener acceso a plantas vivas que portan la bacteria es muy, muy importante, para nuestro programa, porque nos permite desarrollar y validar técnicas de diagnóstico con mucha más rapidez”, dijo Vidalakis.
Vidalkis cuenta con proyectos en desarrollo en la planta de bioseguridad nivel 3, así como otro en Maryland. Tener su material de experimentación a cientos o miles de millas de él, es una manera difícil, costosa y deficiente de practicar ciencias, manifestó.
“Estas nuevas instalaciones en Riverside ayudarán tremendamente en la lucha contra el HLB”, indicó el experto. “También es una gran inversión para futuras amenazas contra la industria de los cítricos de California”.
Hoddle es especialista en entomología en UCCE y director del Centro para la Investigación de Especies Invasivas en la UC Riverside. En años recientes, Hoddle ha liberado dos especies de avispas nativas de Pakistán, las cuales son enemigos naturales del psílido asiático de los cítricos, portador de la bacteria que causa el HLB.
Hoddle ha llamado a la planta de bioseguridad un recurso crítico en la lucha contra HLB que asistirá enormemente a los investigadores de la UC Riverside.
“Esta inversión permitirá un progreso más rápido y costeable en el desarrollo de estrategias de mitigación y tecnologías innovadoras para el manejo del HLB en las cosechas icónicas delos cítricos de California”, aseguró.
¿Hay papas en mi café?
Tan pernicioso es el PTD que su ocurrencia puede degradar el valor de un cultivo completo en una cuarta o tercera parte. Aún peor, el PTD es solo aparente después de procesar, tostar, moler y preparar el café, y puede ocurrir mucho tiempo después de que ha sido exportado.
Causado, al parecer, por sustancias químicas producidos por microbios que tienen acceso a las cerezas del café a través de una chinche hedionda llamada antestia, el PTD ha atraído la atención de un esfuerzo internacional conocido como 'Potato Taste Project' (proyecto del sabor a papa), que durante dos años ha investigado las causas y buscado la cura para este problema.
Dos estudiantes de la Universidad de California en Riverside (UCR), han jugado papeles importantes en el proyecto del sabor a papa.
“Lauren Wong y Tony Truong hicieron un importante descubrimiento que llevó a solicitar a uno de nuestros fito patólogos de UC Riverside, James Borneman, que hiciera un microbioma de los granos del café de Ruanda”, cuenta Thomas Miller, profesor de entomología en UCR y uno de los miembros del equipo internacional que trabaja en los esfuerzos por mitigar el impacto potencial del defecto en la industria del café especializado de Ruanda.
“Yuxtapusimos granos de café que habían pasado los estrictos criterios contra numerosos lotes de granos que tenían defecto del sabor a papa”, explica Wong, quien se graduó en la primavera del 2013 con licenciatura en ciencias biológicas y trabaja actualmente en el laboratorio de Miller. “Cuando tostamos los granos, descubrimos que todos los microbios del defecto del sabor a papa habían sido aniquilados”.
Truong examinó si los microbios del defecto de sabor a papa se pueden manipular para afectar el sabor del café.
Ni Wong ni Truong han viajado a Ruanda todavía, pero se mantienen en contacto con los investigadores de ese lugar. Con su gran altitud y suelo volcánico, Ruanda es el lugar ideal para cultivar café especializado. Con el fin de atacar el desafío que significa el problema del sabor a papa causado por la antestia, Miller y el resto del equipo internacional viajaron a Ruanda a principios del 2012 para unirse a los investigadores del café de la Universidad Nacional de Ruanda (NUR, por sus siglas en inglés).
En ese entonces, Miller se quedó en Ruanda por dos semanas y participó en reuniones, talleres y numerosas salidas al campo. Desde entonces se ha mantenido en contacto casi diario a través del correo electrónico con Ruanda.
“Esta visita nos ayudó a todos a lograr un mejor entendimiento del defecto del sabor a papa y sus causas”, señala Miller. “Obtuvimos muestras de granos de café para analizarlos en Estados Unidos e iniciamos una colaboración con científicos de Ruanda. También ayudamos a Ruanda en el proceso de buscar y contactar a gente dispuesta a ayudarles a resolver el problema del defecto del sabor a papa”.
La culminación de los primeros dos años del proyecto PTD será una cumbre a realizarse los próximos 1 y 2 de abril del 2014 en NUR. La reunión está siendo organizada por NUR y el Global Knowledge Initiative (Iniciativa Global del Conocimiento) de Washington DC, una organización no lucrativa dedicada a encontrar soluciones a problemas en países en desarrollo.
Usted puede encontrar más información sobre el PTD en www.coffee.ucr.edu.
