Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2016
Publication Date: 4/1/2017
Citation: McCollum, T.G., Bowman, K.D. 2017. Rootstock effects on fruit quality among 'Ray Ruby' grapefruit trees grown in the Indian River district of Florida. HortScience. 52(4):541-546. https://doi:10.21273/HortSci.11435-16. Interpretive Summary: Citrus is produced by scions grafted onto rootstocks. Rootstocks can have significant impact on citrus productivity, fruit and juice quality and eventually profitability. Grapefruit produced in the Indian River district of Florida are valued for their high quality, that has typically been seen with fruit produced on sour orange rootstock. However, a replacement for sour orange is needed to maintain sustainable grapefruit production. Our objective in this experiment was to determine the effects of rootstock on quality of Ray Ruby grapefruit. Four recently released USDA hybrid citrus rootstocks were compared with industry standards sour orange and Swingle. Results indicate that two USDA rootstocks, US-897 and US-942 produced fruit with equal of superior quality to the industry standards and it is suggested that they are good candidates for the production of grapefruit in the Indian River district of Florida.
Technical Abstract: The objective of this experiment was to compare fruit quality parameters of ‘Ray Ruby’ grapefruit grown on seven rootstocks. Four recent releases from the USDA rootstock breeding program, US-852, US-897, US-942 and US-812 (all Citrus reticulata x P. trifoliata hybrids), X639 (C. reticulata x P. trifoliata), along with industry standards Sour Orange (C. aurantium) and ‘Swingle’ citrumelo were evaluated in an orchard trial in Indian River Co., FL. Fruit quality data were collected in 2012 (eight harvests), 2013 (six harvests) and 2014 (single harvest). In each year, rootstock effects on fruit size, total solids, and solids acid ratio were significant. Sour Orange and ‘Swingle’ produced the largest fruit, whereas US-897 (a semi-dwarfing rootstock) produced the smallest fruit. Peel thickness (measured only in the 2011-2012 season) was greatest in Sour Orange early in the season, but not towards the end of the season. Misshapen (“sheep nosed”) fruit occurred more frequently on Sour Orange than on other rootstocks, although the incidence of sheep-nosing was minor. Analysis of variance for fruit quality data collected in January of each of the three years confirmed that Sour Orange and Swingle produced the largest fruit and US-897 the smallest fruit. Total solids were highest in US-897 and lowest in X639 and US-852. Taken together, our data indicate that US-942 and US-897 rootstocks produced fruit with quality characters that equaled or exceeded Sour Orange and Swingle, the two most common rootstocks used in the Indian River district.