Citrus HLB, often referred to as “citrus greening,” is a destructive disease of citrus that is distributed throughout most citrus-producing countries worldwide, where it generates substantial economic losses ( Bové, 2006 ). The suspected causal
Ute Albrecht and Kim D. Bowman
Ockert P.J. Stander, Jade North, Jan M. Van Niekerk, Tertia Van Wyk, Claire Love, and Martin J. Gilbert
netting have been tested to determine their effects on tree physiology and fruit development and quality ( Manja and Aoun, 2019 ; Mupambi et al., 2018 ; Stamps, 2009 ; Wachsmann et al., 2014 ; Zhou et al., 2018 ). In Citrus spp., nonpermanent netting
Jinq-Tian Ling, N. Nito, and M. Iwamasa
Protoplasts were isolated from embryogenic calli of Citrus reticulata cv. Ponkan and Citropsis gabunensis, and fused in electric fields. The maximal fusion efficiency was obtained by application of AC at 75 V/cm (1.0 MHz) and DC square-wave pulse at 1.125 KV/cm for 40 usec. Fusion-treated protoplasts were cultured on MT medium without phytohormone, solidified with 0.6% agar. Colonies from the protoplasts were proliferated on MT medium with zeatin 1 mg/l and 0.9% agar. Selection of somatic hybrid callus was based on chromosome count and isoenzyme analysis. The somatic hybrids were tetraploid (2n=36). C. reticulata and C. gabunensis were both homozygous at Got-1 locus, but distinguishable easily because band of the latter migrated faster than that of the former. In zymogram of somatic hybrid, both parent bands were retained and a new hybrid band was also evident between them. Embryos from somatic-hybrid callus regenerated intact plant. The hybrid plants showed intermediate morphological characteristics of the parents.
S. Singh, B.K. Ray, S. Bhattacharyya, and P.C. Deka
Multiple shoots were obtained from shoot tips (2 to 3 mm) derived from mature plants (5 to 6 years old) of Citrus reticulata Blanco cv. Khasi mandarin and C. limon Burm.f. cv. Assam lemon when cultured on Murashige and Skoog (MS) medium, supplemented with (mg·liter-1) 1.0 BAP, 0.5 kinetin, and 0.5 NAA. Root induction was observed when 7-week-old single shoots (≈ 2 cm long) of both Citrus species were cultured on MS medium supplemented with (mg·liter-1) 0.25 BAP, 0.5 NAA, and 0.5 IBA. These plantlets were successfully established in the soil. Chemical names used: naphthalene acetic acid (NAA), indole 3-butyric acid (IBA), and benzylamino purine (BAP).
Mebelo Mataa and Shigeto Tominaga
The effects of root restriction, induced by root restriction bags, was evaluated on `Yoshida' Ponkan mandarin (Citrus reticulata Blanco). Trees were planted in 0.02-m3 volume root wrap bags (RWBs), which were made from woven polystyrene fiber, or root control bags (RCBs) made from nonwoven UV-stabilized Duon polystyrene fibre with plastic bottoms. A direct soil planted, nonrestricted root treatment (DPC) was included as a control. After 3 years, reductions in height (14% to 29%), canopy volume (66% to 43%), girth (10% to 22%), and leaf area (8% to 12%) were recorded in both of the root restriction treatments. Greater reductions occurred in the RWB treatment. Photosynthesis, transpiration, water potential, and leaf carbohydrate content were not affected by root restriction although soil moisture content was lower in the root restricted treatments. Fruiting efficiency (i.e., number of fruit per unit volume of tree canopy) improved only in the RWB treatment over the control. Total soluble solids and the fruit color index were enhanced by root restriction.
Andrew J. Krajewski and Etienne Rabe
To investigate the effects of bud age on sprouting and flowering, bearing Clementine mandarin trees were hand-pruned at monthly intervals from late spring to fall. This pruning resulted in regrowth bearing axillary buds ranging in age from 9 to 5 months. After winter rest and during the return bloom, sprouting and flowering were assessed on axils on terminally positioned stems of these ages. The proportion of axillary buds sprouting and the number of spring shoots produced by each sprouting axillary site decreased with decreasing bud age. The proportion of axils sprouting one or more inflorescences, and the average number of flowers per stem also decreased with decreasing bud age. The number of axillary sites per stem, also significantly affected sprouting and flowering. Our results demonstrate the potential of hand-pruning to manipulate sprouting and return bloom depending on when in the summer or autumn the trees are pruned.
Yuan Yu, Chunxian Chen, Ming Huang, Qibin Yu, Dongliang Du, Matthew R. Mattia, and Frederick G. Gmitter Jr.
genetic relationships between C. sinensis , C. aurantium , and Citrus clementina with C. maxima and C. reticulata ( Wu et al., 2014 , 2018 ; Xu et al., 2013 ). The phylogenetic origin of some secondary species and important citrus cultivars
Ed Stover, Randall Driggers, Matthew L. Richardson, David G. Hall, Yongping Duan, and Richard F. Lee
had more than mild symptoms ( Table 1 ). Again, this group of resistant progeny had no Citrus species. The kumquat hybrid C. halimii , two accessions of C. reticulata , C. nobilis , and C. sunki were the only Citrus species in the group that
Milica Ćalović, Chunxian Chen, Qibin Yu, Vladimir Orbović, Frederick G. Gmitter Jr, and Jude W. Grosser
[( Citrus clementina × C. reticulata ) × ( C. reticulata × C. sinensis ) ( Aleza et al., 2010 )] and Safor [( C. clementina × C. reticulata ) × ( Citrus unshiu × C. nobilis ) ( Cuenca et al., 2010 )]. As an alternative, the combination of two
Gaetano Distefano, Giuseppina Las Casas, Stefano La Malfa, Alessandra Gentile, Eugenio Tribulato, and Maria Herrero
development of ovules in relation to fruit set in mandarins, cv. ‘Clementine’ ( Citrus reticulata , Blanco) Acta Hort. 321 621 625 Gómez, N.L. García, E.A. Castillo, A.M. Corona, T. Almaguer, G