2008 Tracy L Kahn (Variety Evaluation for Trueness) - Citrus ...

2008 Annual Report Variety Development Citrus Research BoardCitrus Variety Evaluation for Trueness-to-Type andCommercial PotentialTracy L. KahnBotany and Plant Sciences, UC / RiversideCalifornia leads the nation in the production of fresh citrus for the domesticand export market. The increasing demand for seedless easy-to-peel mandarins andattractive citrus varieties once only available from countries where traditionallyconsumed is fueling changes in the global fresh citrus market. Importation of newcitrus varieties from other parts of the world by the Citrus Clonal Protection Programand the development of new varieties by the UCR Citrus Breeding Program providesCalifornia citrus growers with a diversity of citrus available for production.Our project provides the industry with preliminary data on the characteristics ofnew citrus varieties in California and evaluates trueness-to-type of varieties distributedby the Citrus Clonal Protection Program. Our project also maintains the citrusdemonstration blocks in Lindcove, Thermal and the Citrus Variety Collection (CVC) inRiverisde as resources for the evaluations of new varieties and to allow growers to viewtrees and fruit of existing commercial and new citrus varieties.During the 2007-2008 season our evaluations focused on selected newmandarin, blood orange navel orange, valencia oranges and specialty varietiesincluding ‘Yuzu’, ‘Sudachi’ and a UCR developed pummelo hybrid called ‘Valentine’.Based on availability, fruit for these evaluations was collected from the demonstrationblocks and the CVC to permit us to screen these varieties for adaptability toCalifornia growing conditions and climates. Each of the 48 varieties was sampledfrom two or three trees at each location three to six times during the season.Highlights of our results are described below. Results of this and other groups ofvarieties were discussed at the growers meetings, fruit displays and field days thispast season and will be summarized for future publications and posted on ourwebsite (http://citrusvariety.ucr.edu).

2008 Annual Report Variety Development Citrus Research BoardFigure 2. Photographs of fruit from a 7-year-old tree of‘Miho Wase’ on Carrizo from Riverside California.

2008 Annual Report Variety Development Citrus Research BoardFigure 1. Fruit quality traits for fruit of Satsuma mandarin selections sampled from Lindcove October 10, 2007.Figure 3. Photographs of fruit from a 6-year-old tree of ‘China S-9’ on Carrizo from Riverside California.

2008 Annual Report Variety Development Citrus Research BoarFigure 4. Table of the average percentage acidity and solids-to-acid ratio for fruit of Valenciaselections sampled from three locations during the week of June 16, 2008.Last season we evaluated fruit quality traits of 13 Satsuma mandarinselections three times from Lindcove and Riverside in comparison to ‘FrostOwari’, the mid-season standard and two early season selections, ‘OkitsuWase’ and ‘Kuno Wase’. Fruit quality data for selections sampled fromLindcove at the October sample date are shown in Figure 1. Note thatboth tree samples of fruit of ‘Miyagawa’, ‘Okitsu Wase’, ‘Miho Wase’,‘Frost Owari’, ‘Armstrong’ and ‘China S-9’ had rind at or past color break(5.0) by early October 2007, an indicator of early maturity. In September2008 at the first session of a series of informal Satsuma Tasting eventsat Lindcove Research and Extension Center, ‘Okitsu Wase’, ‘Miho Wase’,‘Miyagawa’, and ‘China S-9’ received the highest ratings for fruitappearance, and ‘Miho Wase’ and ‘China S-9’ had the highest ratings fortaste.

2008 Annual Report Variety Development Citrus Research BoarThis past season, a second year of evaluations were conducted fornew navel orange selections from Lindcove and Riverside four timesduring the season. Fruit of Cogan, Johnson and Parent Washington hadearlier external rind coloration than the other selections in both 2006 and2007 at both locations. All of the selections had solids-to-acid ratiosabove legal maturity (8:1) by middle of November, but only Cogan,Johnson and Parent Washington had ratios at or above 10:1 by thissample date at both locations. Cogan appears to be earlier maturing thanWashington navel and earlier than the others tested. Higher percentageacid levels of Ceridwen and Robyn and Johnson at multiple locations andsample dates indicate they might be later maturing than Ricalate, Coganand Washington.Two seasons ago, we initiated evaluations of ‘Valencia Late’ and‘Harward Late’, two reportedly late Valencia selections in comparisonwith ‘Olinda’ Valencia. Fruit of all varieties sampled at the mid June2008 sample date from Thermal and Riverside had average percentageacidity below 0.7 (Figure 4). Yet when sampled at this same date fromLindcove, ‘Haward Late’ fruit had average percentage acidity below 0.6,but the percentage acidity of fruit of Valencia Late and Olinda was above0.7. At this point, fruit of these new Valencia introductions do not appearto mature later than ‘Olinda’ fruit.NOTICE: The research results included in this publication aresummary reports for the benefit of the Citrus Research Board andthe growers it serves. They are not to be taken asrecommendations from either the individual reporting or theagency doing the research. Some of the materials and methodsmentioned are neither cleared nor registered for commercialuse. The summaries were written by the project leadersidentified. Both technical names and registered trademarks ofmaterials are used at the discretion of the authors and do notconstitute any endorsement or approval of the materialsdiscussed. Questions on possible applications should be directed tothe local University of California Extension Specialist, a licensedPCA, or the appropriate regulatory agency.