has been Flying Dragon trifoliate orange ( Bitters et al., 1979 ) in association with good yield and fruit quality ( Roose, 1986 ). The term “dwarfing” can only be applied to rootstocks that reduce tree volume by at least 75%, thus limiting tree height
François Mademba-Sy, Zacharie Lemerre-Desprez, and Stéphane Lebegin
In vitro propagation of trifoliate orange rootstock (Poncirus trifoliate Raf.) was achieved using axillary buds taken from new flushes of mature trees and then cultured on Murashige and Skoog medium (MS). The addition of growth regulators [0.5 mg·L-1 gibberellic acid (GA3) or 0.1 mg·L-1 6-benzyladenine (BA) and 0.1 mg·L-1 indol-3-butyric acid (IBA)] were necessary to promote bud breakage and shoot elongation. Shoot proliferation was induced on MS medium supplemented with various levels of BA (0.0, 0.5, 1.0, 1.5, and 2.0 mg·L-1) and α-naphthalene acetic acid (NAA) (0.0, 0.1, and 0.5 mg·L-1). Maximal shoot multiplication (9.3 shoots/explant) and elongation (2.3 cm) occurred on media containing either 1.0 mg·L-1 BA alone or with 0.1 mg·L-1 NAA. Shoots rooted better and gave high root number (7.6 roots/shoot) and long roots (5.4 cm) when cultured on a liquid MS medium provided by 0.1 mg·L-1 NAA. Rooted shoots were successfully established in soil (≥90%).
G. Yelenosky, D. Hutchison, and H. Barrett
Ten-month-old seedlings, grown from seed extracted from 22 individual pummelo [Citrus grandis (L.) Osbeck] × trifoliate orange [Poncirus trifoliata (L.) Raf.] citrus hybrid trees that survived -15C freezes near Monticello, Fla., were cold-acclimated in controlled-environment rooms and freeze-tested at -6.7C for 4 h. Freeze damage to open-pollinated progeny was ranked by the number of uninjured seedlings and percentage of leaves killed and wood dieback. Morphological segregation was not associated with differences in freeze survival, and the dominant trifoliate gene was readily evident. Progeny from one tree, identified as 98-71, are considered the most likely candidates for further study in developing cold-hardy citrus trees.
Mikeal L. Roose, Claire T. Federici, and Gregory P. Copenhaver
To assess genetic diversity in the UC Riverside Citrus Variety Collection, all accessions of pummelo (59), citron (24), and trifoliate orange (48) were studied for RFLP variation using 11-18 cDNA probes that had previously been shown to reveal polymorphism in a broad range of citrus germplasm. Inheritance studies have shown that these probes hybridize to at least 20 loci. The taxa studied are believed to represent biological species rather than hybrids. Citrons were nearly monomorphic and most appeared homozygous at all of the loci studied. Pummelos were very polymorphic and highly heterozygous. Trifoliate orange, an important source of disease resistance in rootstock breeding, was nearly monomorphic but moderately heterozygous (17% of loci). Most accessions of trifoliate orange have evidently differentiated only by mutation. One multilocus probe separated trifoliate orange accessions into 3 groups. Two new trifoliate orange accessions had novel alleles at some loci. The use of genetic markers to recognize hybrid accessions classified as members of species will be discussed.
Lina Fu, Lijun Chai, Dekuan Ding, Zhiyong Pan, and Shu’ang Peng
growth, but those grafted on the most commonly used rootstock, trifoliate orange, showed typical chlorosis. To understand possible mechanisms of ‘Zhique’ rootstock tolerant of Fe deficiency, Fe-deficiency chlorosis symptoms of the same ‘Miyagawa Wase
William S. Castle, James C. Baldwin, and Ronald P. Muraro
differ significantly from those on most rootstocks. The smallest trees, 1.6 m, were those on Flying Dragon trifoliate orange. Mean height increased to 3.8 m when the trees were 7 years old with the tallest trees being 4.4 m. Those on Volkamer lemon had
Peter C. Andersen and Brent V. Brodbeck
). Satsuma mandarins, when grafted on trifoliate orange [ P. trifoliata (L.) Raf.] rootstocks, are the most cold-hardy commercial citrus ( Andersen et al., 2012 ; McClendon, 2004 ; Yelenosky, 1985 ). In laboratory studies, satsuma trees have survived
M.L. Marin and N. Duran-Vila
A study was conducted to evaluate the potential of in vitro techniques for genetic conservation of citrus. A tissue culture system was developed using explants of juvenile `Pineapple' sweet orange. It consisted of: a) establishment of primary cultures from nodal stem segments followed by the recovery of plants in vitro; and b) successive cycles of secondary cultures consisting of the culture of nodal stem segments from in vitro-grown plants, rooting of shoots obtained from nodal stem segments, and recovery of whole plantlets. Two parameters, K and K', based on the multiplication factors of the different stages of primary and secondary cultures are proposed to monitor the system as a potential tool for genetic conservation of citrus. The system also can be successfully used for the conservation of juvenile tissues of two sweet orange varieties [Citrus sinensis (L.) Osb.], trifoliate orange [Poncirus trifoliata (L.) Raf.], Mexican lime [C. aurantifolia (Christm.) Swing.], and `Eureka' lemon [C. limon (L.) Burro. f.]. Chemical names used: 6-benzylaminopurine (BA); α- naphtbaleneacetic acid (NAA).
William S. Castle
trifoliate orange somatic hybrid (2.2 m). Tree survival after 10 years was 90% to 100% among the trees on most rootstocks except for the 1578-173, 1573-26, 1575-21, and 1572 hybrids in which many trees succumbed to Phytophthora foot rot. Those hybrids were
Ute Albrecht and Kim D. Bowman
were also identified as highly tolerant to HLB by Folimonova et al. (2009) after controlled inoculations with Ca . L. asiaticus. No well-defined disease symptoms have been observed in trifoliate orange ( Poncirus trifoliata ) trees and seedlings