Sour orange has been a premier citrus rootstock worldwide due to its ability to perform on challenging soils and to produce and hold high-quality fruit. However, increasingly widespread quick-decline isolates of citrus tristeza virus (CTV) have destroyed entire industries on sour orange in some countries, and are in the process of destroying millions of trees on sour orange in Florida. CTV also threatens other citrus locations planted heavy to sour orange, including Texas and Mexico. An acceptable alternative rootstock to replace sour orange is in high demand but has yet to be developed. Molecular analyses have recently determined that sour orange is probably a hybrid of pummelo and mandarin. We report the production of 12 new mandarin + pummelo somatic hybrids produced by protoplast fusion from selected superior mandarin and pummelo parents, in efforts to develop a suitable replacement sour-orange-like rootstock that is resistant to CTV-induced quick decline. Somatic hybrids from all 12 parental combinations were confirmed by a combination of leaf morphology, flow cytometry, and RAPD analyses (for nuclear hybridity). These new mandarin + pummelo somatic hybrids are being propagated by rooted cuttings as necessary to conduct quick-decline resistance assays and to assess horticultural performance in replicated field trials.
Abstract
Leaves from ‘Washington’ navel and ‘Valencia’ oranges, ‘Dancy’ and ‘Kinnow’ mandarins and ‘Marsh’ grapefruit were analyzed for 5 years. Significant differences between cultivars were found for N, P, K, Ca, Mg and Fe levels but not for Zn, Cu and Mn. Concentrations of the potentially toxic elements, Na, Cl, B, and Li, were significantly different at low non-toxic levels. Lowest values occurred in oranges and highest in ‘Kinnow’ mandarin and ‘Marsh’ grapefruit. Compared with rough lemon, sour orange rootstock decreased N in ‘Valencia’, increased K in ‘Kinnow’ and increased Ca and decreased Mn, Na, B and Li in all cultivars. There were wide annual variations in N, K, P, Ca, Mg, Zn, Mn and Cu levels in all cultivars.
Abstract
Container-grown sour orange seedlings were cleft grafted in 1975, 1976 and 1977 with ‘Redblush’ grapefruit, placed in 2 types of humidity chambers (polyethylene tents and sacks) to increase survival, and evaluated for growth under full sun and 60% shade. Cleft grafting resulted in greater than 90% successful graft unions in all years. The type of humidity chamber used did not influence the percent of successful unions between rootstock and scion. In a 60-day period, grafted plants grown in full sun with a windbreak were 47% larger and produced larger and more luxuriant foliage than similar aged plants grown under 60% shade.
orange rootstock ( Citrus aurantium L.). Fruit grown in this production region is often touted as the ideal because of their oblate shape with a smooth, thin skin, and excellent flavor. The use of sour orange rootstock for grapefruit was reduced for many
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
temperature, soil pH, and host preference for different biological control agents. Use of resistant rootstocks is an ideal and long-term solution to fight Phytophthora diseases. Sour orange is one of the few rootstock that can produce high yields and yet
trees of ‘Sugar Belle/Sour Orange’ and ‘Tango/Kuharske’ were available and all were treated with imidacloprid). This experiment is accurately viewed as comparing specific scion/rootstock combinations rather than scions alone and was essentially two
As a result of its excellent agronomic qualities, sour orange continues to be used for citrus in the regions where citrus tristeza virus (CTV) is rare or absent. In Italy, sour orange was the most widely used rootstock until recently. However, the
Experimental material. Liners were grown from seeds of Carrizo, Cleopatra, Green-7 from the University of Florida (Citrus Research and Education Center, Lake Alfred, FL), UFR-2, UFR-4, rough lemon, sour orange, and US-897. As with most commercial rootstock
important ( Ali et al., 2000 ). A species of multiple use, the sour orange ( Citrus aurantium L.) is also known as bitter or seville orange. It is a universal rootstock for citrus and is used widely in the Mediterranean region ( Navarro et al., 1975 ) It is