Tree Size, Yield, Fruit Quality, and Leaf Mineral Nutrient Concentration of `Fairchild' Mandarin on Six Rootstock

The influence of six rootstock on growth, yield, fruit quality, and leaf mineral nutrient concentration of 'Fairchild' mandarin ('Clementine' mandarin (Citrus reticulata Blanco) × 'Orlando' tangelo (C. paradisi Macf. × C. reticulata)) is reported for the arid climate of southwestern Arizona. Trees on macrophylla (Alemow) (C. macrophylla Wester) were precocious and produced high yield 4 years after planting. Six-year cumulative yields of trees on Volkamer lemon (C. limon Burro f.), Carrizo citrange (C. sinensis (L.) Osbeck × Poncirus trifoliata (L.) Raf. ), Taiwanica (C. taiwanica Tan. & shin.), and rough lemon (C. jambhiri Lush.) were similar and higher than those of trees on macrophylla and Batangas mandarin (C. reticulata). 'Fairchild' mandarin tree canopies were large with Volkamer lemon and Taiwanica; intermediate with Carrizo citrange, rough lemon, and Batangas mandarin; and small with macrophylla rootstock. Fruit from trees on Carrizo citrange had the highest soluble solids concentration (SSC), while those on Volkamer lemon and rough lemon had the lowest SSC and total acids. 'Fairchild' trees on macrophylla had higher levels of leaf N, Mn, and Fe but lower Ca, while trees on Batangas mandarin and Carrizo citrange had higher leaf K than those on the other rootstock. Trees on Volkamer lemon had higher leaf Zn than those on Carrizo citrange, Taiwanica, rough lemon, and Batangas mandarin rootstock. Considering yield, growth, fruit quality, and/or leaf nutrient concentration, Volkamer lemon, Carrizo citrange, Taiwanica, and rough lemon are suitable for 'Fairchild' mandarin in the arid regions of southwestern Arizona. Trees on macrophylla could be advan- tageous for short-term planting, but would not be satisfactory for long-term planting because of gradual decline in growth and yields. Batangas mandarin is not recommended for 'Fairchild' mandarin due to poor production. Mandarin and mandarin hybrid cultivars are treated as spe- cialty fruit and are only a small part of the citrus acreage in the United States. Nevertheless, the demand for mandarin fruit, particularly 'Fairchild' grown in Arizona, is increasing (Arizona Agricultural Statistics Service, 1988). Mandarin fruit are relatively small with a tender peel and do not store or ship well. Trees tend to over-bear, which contributes to biennial bearing. Rootstock can favorably influence tree yield, bearing habit, fruit quality, and leaf mineral nutrient concentra- tion, and these effects have been reported for commercially important citrus cultivars (Castle, 1980, 1987; Castle and Phil- lips, 1977; Cooper and Lime, 1950; Fallahi et al., 1989; Gard- ner and Horanic, 1966; Hilgeman et al., 1966; Hutchison and Hearn, 1977; Krezdorn and Phillips, 1970; Rouse and Maxwell, 1979; Wutscher, 1977, 1979; Wutscher and Dube, 1977; Wutscher and Shun, 1972, 1973, 1975). The common commercial rootstock for mandarin cultivars are sour orange (Citrus aurantium L.) and Cleopatra mandarin. They have generally been satisfactory and, thus, there are few rootstock studies involving mandarin scions (Castle and Krez- dorn, 1975; Fallahi et al., 1991; Krezdorn, 1977; Iyengar et al., 1982; Sharples and Hilgeman, 1972; Smith, 1975; Wutscher and Shun, 1976); also, there is only limited information con- cerning rootstock effects on 'Fairchild' mandarin performance (Wutscher et al., 1976). The arid climate and high pH of soils of southwestern Arizona limit the selection of rootstock for mandarins. In selecting a rootstock, adaptability to the prevail-