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Rootstock Effects on Fruit Quality among ‘Ray Ruby’ Grapefruit Trees Grown in the Indian River District of Florida
| Content Provider | Semantic Scholar |
|---|---|
| Author | McCollum, Greg Bowman, Kim D. |
| Copyright Year | 2017 |
| 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 United States Department of Agriculture (USDA) rootstock breeding program, ‘US-852’, ‘US897’, ‘US-942’, and ‘US-812’ (all Citrus reticulata 3 Poncirus trifoliata hybrids), ‘x639’ (C. reticulata3 P. trifoliata), along with industry-standard ‘Sour Orange’ and ‘Swingle’ citrumelo were evaluated in a commercial orchard trial in Indian River County, FL. Fruit-quality data were collected in 2011–12 (eight harvests), 2012–13 (five harvests), and 2014 (single harvest). In each season, 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 semidwarfing rootstock) produced the smallest fruit. Peel thickness (measured only in the 2011–12 season) was greatest in ‘Sour Orange’ early in the season, but not toward the end of the season. Misshapen (‘‘sheep-nosed’’) fruit occurred more frequently on ‘Sour Orange’ than on other rootstocks, although the incidence of sheepnosing was minor. Analysis of variance (ANOVA) for fruit-quality data collected in January of each of the 3 years confirmed that ‘Sour Orange’ and ‘Swingle’ produced the largest fruit and ‘US-897’ produced the smallest fruit. Total solids were the highest in ‘US-897’ and the lowest in ‘x639’ and ‘US-852’. Taken together, our data indicate that ‘US-942’ and ‘US-897’ rootstocks produced fruit with quality characteristics that equaled or exceeded ‘Sour Orange’ and ‘Swingle’, the two most common rootstocks used in the Indian River district. The Indian River district of Florida is the world’s major production region for grapefruit (Citrus paradisi Macf.), and Indian River grapefruit are valued for their high quality. In contrast to the deep, well-drained sandy soil characteristic of Florida’s ‘‘central ridge,’’ soils in the Indian River district are typically shallow, poorly drained, and referred to as ‘‘flatwoods’’ (Harris et al., 2010). Grapefruit, like all commercial citrus, is produced as a composite tree consisting of a scion grafted onto a rootstock. Historically, ‘Sour orange’ (Citrus aurantium L.), believed to be a hybrid of Citrus maxima · Citrus reticulata Blanco (Grosser et al., 2004), has been a favored rootstock for citrus in the Indian River district. However, with the exception of lemons, citrus scions grown on ‘Sour orange’ are susceptible to Citrus tristeza virus (CTV), and when the brown citrus aphid, vector of CTV, arrived in Florida, ‘Sour orange’ fell out of favor. Subsequently, ‘Swingle’ citrumelo [‘Duncan’ grapefruit (Citrus paradisi) · Poncirus trifoliata (L.) Raf.] replaced ‘Sour orange’ as the most commonly used rootstock for citrus in the Indian River district (Stover and Castle, 2002). Unfortunately, although ‘Swingle’ is well suited as a rootstock in the deep sands of the Florida central ridge, it has proven to be a poor rootstock for the flatwoods soils typical of the Indian River district (Bauer et al., 2005; Castle et al., 2016). Improved citrus rootstocks for grapefruit are essential if sustainable production is to be maintained (Castle et al., 2011). Citrus rootstock breeding has been conducted by the USDA in Florida for more than a century (Soost and Rouse, 1996). The use of hybrids between Citrus spp. and Poncirus trifoliata, a member of the Rutaceae that is sexually compatible with Citrus, has been, by far, the most productive strategy for the development of new citrus rootstocks in the USDA breeding program and in other citrus rootstock breeding programs. Between 1999 and 2010, five new citrus rootstock cultivars were released by the USDA. Four of these new rootstocks (‘US-852’, ‘US-812’, ‘US-897’, and ‘US-942’) are hybrids of Citrus reticulata (mandarin) · Poncirus trifoliata (trifoliate orange). ‘US-852’, released in 1999 (Bowman and Wutscher, 1999), is a hybrid of ‘Changsha’ mandarin · ‘English Large Flowered’ trifoliate orange. ‘US-812’, released in 2001 (Bowman, 2001; Bowman and Rouse, 2006), is a hybrid of ‘Sunki’ mandarin and ‘Benecke’ trifoliate orange. Trees grown on ‘US-812’ rootstock are medium-sized with a wide range of scions and consistently yield large quantities of good-quality fruit. ‘US-812’ also exhibits resistance to citrus blight and has the CTV resistance gene ctvR. ‘US-897’ was released in 2007 (Bowman, 2007) and is a hybrid of ‘Cleopatra’ mandarin · ‘Flying Dragon’ trifoliate orange. This hybrid rootstock has field tolerance to the Phytophthora–Diaprepes disease complex, resistance to CTV, good fruit productivity, and good fruit quality (Bowman et al., 2016a). Trees produced on ‘US-897’ are compact, making this rootstock attractive to growers who want to increase tree density. This is especially important in Florida as tree densities are increasing from a previous average of 140 trees per acre to as many as 300 trees per acre currently. ‘US-942’ citrus rootstock was released in 2010 (Bowman and McCollum, 2010). Trees grown on ‘US-942’ are medium-sized with a wide range of scions and consistently yield large quantities of good-quality fruit (Bowman et al., 2016a). ‘US-942’ also exhibits field tolerance to the Phytophthora–Diaprepes disease complex, resistance to citrus blight, has the CTV resistance gene ctvR, and is a hybrid of ‘Sunki’ mandarin · ‘Flying Dragon’ trifoliate orange. The ‘x639’ rootstock, developed in South Africa in the early 1950s, is a hybrid of ‘Cleopatra’ mandarin (Citrus reticulata) · Table 1. Trial planting details and proportion of trees dead in 2011 (5–6 yr age). Rootstock Planting arrangement Number of trees planted Number of trees died Percent tree death US-897 6 · 112 672 12 1.8 b US-812 6 · 76 456 12 2.6 b US-852 6 · 76 456 14 3.1 b Swingle 6 · 76 456 16 3.5 b US-942 6 · 112 672 24 3.6 b x639 6 · 76 456 23 5.0 b Sour orange 6 · 76 456 48 10.5 a Mean separations for significant analysis of variance within columns, by Duncan’s multiple range test at P < 0.05. Planting arrangement = reps · number of trees per rep. Received for publication 1 Nov. 2016. Accepted for publication 5 Dec. 2016. This research was supported in part by grants from the Florida Citrus Research and Development Foundation. Mention of a trademark, warranty, proprietary product, or vendor does not imply an approval to the exclusion of other products or vendors that may also be suitable. The U.S. Department of Agriculture prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or family status. We acknowledge the technical assistance of Emily Domogtoy, James Salvatore and Wayne Brown. Corresponding author. E-mail: greg.mccollum@ ars.usda.gov. HORTSCIENCE VOL. 52(4) APRIL 2017 541 Poncirus trifoliata. Although previously not commonly used in Florida, currently there is considerable interest in ‘x639’ rootstock. In 2014, ‘x639’ was used for the production of 622,000 nursery trees, accounting for 14% of all nursery propagations and making it the second most widely propagated citrus rootstock in Florida (Kesinger, 2015). ‘Ray Ruby’ fruit are valued for their red flesh, low seed count, and pink blush that develop in the rind. In addition to their deep red color, ‘Ray Ruby’ juice is sweeter than it is for comparable varieties (Saunt, 1990). To be successful, new rootstock hybrids must produce not only good fruit yields but also fruit with acceptable quality. According to Castle (1995) and Castle et al. (2010), yield is the major factor when selecting citrus rootstocks, although rootstock effects on fruit and juice quality can impact financial returns, particularly for fresh fruit production (Castle, 2012; Castle et al., 2010). The objective of the work reported herein was to determine the effects of Table 2. Effects of rootstock on ‘Ray Ruby’ grapefruit quality parameters, 2011–12 harvest season. |
| Starting Page | 541 |
| Ending Page | 546 |
| Page Count | 6 |
| File Format | PDF HTM / HTML |
| DOI | 10.21273/HORTSCI11435-16 |
| Volume Number | 52 |
| Alternate Webpage(s) | https://crec.ifas.ufl.edu/extension/citrus_rootstock/rootstock-literature/2017.%20G.%20McCollum,%20K.%20Bowman,%20Rootstocks%20Effects%20on%20Fruit%20Quality%20Among%20'Ray%20Ruby'%20Grapefruit%20Trees%20Grown%20in%20the%20Indian%20River%20District%20of%20Florida.pdf |
| Alternate Webpage(s) | https://doi.org/10.21273/HORTSCI11435-16 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
