- Author: Therese Kapaun
- Contributor: Rachel Rattner
The Lane Late navel block at Lindcove was planted in 1991 and consists of 230 trees on 29 different rootstocks. Rachel Rattner is a PhD student at UC Riverside working with Dr. Mikeal Roose in the Dept. of Botany and Plant Sciences. She is investigating the impact of small RNA molecules on fruit quality. Small RNAs are naturally found in plants, and their role is to regulate the expression of genes during citrus development. Small RNAs are a recent area of study in plants and have been shown to be important in plant development, as well as in vital processes such as nutrient uptake and responses to environmental stresses. There is evidence that some of these molecules may be species-specific and can move from shoots to roots and vice versa. Therefore, small RNAs produced in different varieties of citrus rootstocks may regulate gene expression, and ultimately fruit quality, in the scion. The results from this project will be useful to citrus breeders in the future.
Rachel is sampling Lane Late navels at Lindcove REC for her project. In this photo Rachel is being assisted by Claire Federici (Staff Research Associate at UC Riverside) and is slicing immature fruit and separating juice vesicles from the segment walls. These vesicles are quickly frozen on dry ice in the field to preserve the integrity and current state of the RNA molecules present at the time of slicing.
Rootstock selection is an important component of commercial citrus production worldwide. Soil type, scion compatibility, mineral tolerance, disease tolerance, and growth traits are the primary concerns when choosing a rootstock type.
Hybrid species of trifoliate rootstocks are popular with growers in California's San Joaquin Valley. Carrizo and C-35 are two of the most common varieties for oranges and mandarins. Both share the same scientific name, Citroncirus hybrid sp.
Many of the research plots at Lindcove REC utilize the common commercial varieties of both scion and rootstock, for example Parent navel on C-35, or Nules clementine on Carrizo. This allows the results of experiments to more closely resemble actual fruit production that comprises a hefty share of the domestic and overseas markets.
This month the staff at Lindcove REC are transplanting rootstock seedlings grown in cone flats to larger pots. The seedlings will grow quickly during the fall and will be large and healthy for budding next March.
A new planting of 500 Tango mandarin trees is scheduled for this month and field preparations are well underway. Senior Agricultural Technician Jose Hernandez uses heavy equipment to dig a trench for the irrigation line.
The new orchard will provide trees for insecticide trials for Dr. Beth Grafton-Cardwell's citrus IPM program. She plans to study the uptake and impact of systemic insecticides on various pests and the growth and development of young trees. Beth is an IPM Specialist and Research Entomologist with the University of California, as well as the Director of Lindcove Research and Extension Center. For more than 20 years Beth has been carrying out pesticide trials to determine the efficacy and suitability of selected chemical formulations for use against citrus pests in California. To learn about key pests of citrus and pest management tools and information, log on or subscribe to Beth's Citrus Bug Blog.
The trees were propagated here at Lindcove REC. Center staff grew the Carrizo rootstocks from seed in the greenhouse, and budded the trees with budwood purchased from the Citrus Clonal Protection Program.
The emergence cycle of captured walnut twig beetles (WTB) is being documented at LREC. The tiny beetles, in addition to a suite of other log-dwelling insects (including their parasitoids), emerge nearly year-round from infested walnut logs that are housed in outdoor enclosures. The insects are collected weekly, and then sorted, sexed, and counted. In 2013, WTB emerged from March-September, with peak emergence in mid-late June. In 2014, peak WTB emergence peak occurred in May-June, and emergence counts are falling off rapidly now that it is midsummer. One notable week's collection was May 13-20, with 1940 emerged WTB from one of the six emergence chambers.
Dr. Elizabeth Fichtner (Farm Advisor, Tulare UCCE) has recently acquired Yelena Martinez, a participant in the College of Sequoias SURGE (Student Undergraduate Research Group Experience) program, to assist Katie Wilson (UCCE Tulare) and Therese Kapaun (LREC) with the staggering number of weekly counts during the peak season. This photo shows Yelena viewing insects under a dissecting microscope and separating the different species into containers. Katie and Therese will continue to monitor and count emergences for at least the next twelve months.
WTB has been recently found to be associated with Thousand Cankers Disease, a fungal pathogen of several walnut species in North America. The pathogen was also recently reported on black walnut in Italy. More information on the disease, as well as the beetle can be found at:
UCCE In a Nutshell Newsletter Tulare County (pages 5-7)
Dr. Carol Lovatt (UC Riverside, Dept. of Botany and Plant Science) and Elizabeth Fichtner (UC Cooperative Extension Tulare County) continue olive research at Lindcove REC. A foliar application of plant growth regulator treatments in combination with urea was applied to mature olive trees this week to determine the potential value of these products to reduce or eliminate the alternate bearing cycle in olives.
Toan Khuong is seen here applying the foliar spray. Toan is a Staff Research Associate in Dr. Lovatt's lab at UC Riverside.