Tuesday, 27 August 2013 15:03

LAKE ALFRED, FL—Grapefruit has long been important to Florida's citrus industry, primarily as fresh fruit. However, changing consumer preferences and increased use of grapefruit for processing, researcher continue to look for new rootstocks that will keep the grapefruit industry viable. A team from the University of Florida and U.S. Department of Agriculture–Agricultural Research Services published the results of grapefruit trials in HortScience in which they identified several promising new rootstocks.

According to Bill Castle, (professor emeritus) from the Citrus Research and Education Center at the University of Florida, Institute of Food and Agricultural Sciences, developing new rootstocks for grapefruit varieties is critical to both the fresh fruit and juice industries in Florida. Castle and his colleagues conducted a research study focused on identifying rootstocks that increased juice soluble solids concentration, earliness of maturity, and reduced tree size. The scientists conducted two adjacent trials involving a total of 45 rootstocks; the first consisted largely of 'Marsh' grapefruit trees on citrange and citrumelo rootstocks, and various hybrid rootstocks, while the second trial involved mandarin rootstocks and sour orange and related rootstocks. Trees were grown for 7 years, and yield and juice quality data were collected for the last 4 years of that period.

"We identified two hybrids of Sunki mandarin x Swingle trifoliate orange, a Sunki x Flying Dragon trifoliate orange hybrid, C-35 citrange, and x639, a Cleopatra mandarin x Rubidoux trifoliate orange hybrid as the most promising rootstocks for grapefruit scions," Castle said. The five rootstocks were rated as most promising by comparison with the commercial standard rootstocks, Swingle citrumelo, sour orange, and Cleopatra mandarin and because of their potential for use in modern orchards planted at spacings closer than traditional ones. "That assessment applies to fruit grown for processing, but further trials are needed to determine fruit sizes and peel quality for a more complete assessment of their potential as rootstocks for growing fresh fruit," Castle noted.

"The most successful rootstock in Florida for fresh-market grapefruit has been sour orange for trees grown in the Indian River district. Several rootstocks identified in our trials have considerable promise as replacements for sour orange," Castle said, adding that the research also provided support for his previously reported concept that rootstock performance in field trials can often be sufficiently evaluated within no more than six cropping years.


The complete study and abstract are available on the ASHS HortScience electronic journal web site: http://hortsci.ashspublications.org/cgi/content/abstract/46/6/841

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at ashs.org


Original Article:

Rootstocks Affect Tree Growth, Yield, and Juice Quality of 'Marsh' Grapefruit
William S. Castle, Kim D. Bowman, James C. Baldwin, Jude W. Grosser, and Frederick G. Gmitter, Jr.
HortScience 46:841–848. [Abstract][Full Text][PDF]

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