Search Results

You are looking at 1 - 10 of 91 items for :

Clear All
Full access

Josue Ortega-Ortega, Francisco Arturo Ramírez-Ortega, Roberto Ruiz-Medrano and Beatriz Xoconostle-Cázares

belong to the genus Coffea (Rubiaceae family), which includes more than 100 mostly diploid species (2 n = 2 x = 22), except for C. arabica (2 n = 4 x = 44), which is autogamous and allotetraploid ( Noirot et al., 2003a ). Most world coffee

Free access

Jane Kahia, Margaret Kirika, Hudson Lubabali and Sinclair Mantell

partially) the action of cytokinin oxidase, which in turn may increase the level of endogenous. Conclusion A relatively simple, straightforward and reproducible method for regeneration of Coffea arabica-robusta × canephora var. Ruiru 11 was developed by

Free access

Gladys M. Nazario and Carol Lovatt

A study was undertaken to identify the pathway(s) leading to the synthesis of caffeine and theobromine in leaves of Coffea arabica. The relative contribution of purine nucleosidcs and bases to the biosynthesis of these alkaloids was assessed by measuring the incorporation of radiolabeled inosine, adenosine, adenine, hypoxanthine, and xanthine into caffeine and theobromine.

The results of this investigation suggest that caffeine and theobromine are end products of two distinctively different pathways. The incorporation of radiolabeled formate, adenosine, and xanthine was significantly greater into caffeine than into theobromine. Furthermore, exogenously supplied theobromine did not dilute the incorporation of [14C]formate, [14C]inosine, or [14C]xanthine into caffeine. In contrast, radiolabeled adenine was incorporated into theobromine but not into caffeine, and exogenously supplied adenine diluted the incorporation of [14 C]adenosine into theobromine, but not into caffeine.

Taken together, these results provide strong evidence that theobromine is not a precursor of caffeine biosynthesis in leaves of C. arabica.

Supported by the Citrus Research Center and Agricultural Experimental Station of the University of California, Riverside,

Free access

Benoît Bertrand, Hervé Etienne and Albertus Eskes

In order to avoid nematode damage to roots of Coffea arabica L. in Latin America, a common practice is interspecific grafting on C. canephora var. Robusta (Pierre) rootstocks. The performance of two C. arabica cultivars, `Caturra' and `Catimor T5175', was evaluated on four rootstocks: C. canephora var. Robusta (`T3561' and `T3757') and C. liberica var. liberica (Hiern) and var. dewevrei (Lebrun), over 5 years in a trial at 1180 m elevation in Costa Rica. Nongrafted plants of the two Arabica cultivars were used as controls. Mortality of plants grafted on the two C. liberica cvs. was >20% vs. 6% to 13% for plants grafted on C. canephora, and 3% to 4% for the two controls. Analysis of accumulated yields over four harvests showed that the rootstocks limited stem girth and reduced yield 10% to 48%. Yield on the C. canephora rootstock was greater than that on the two C. liberica cultivars. However, grafting did not affect female fertility (peaberries, empty berries) or content of several chemicals, such as caffeine, fat, and sucrose. The two C. liberica rootstocks significantly reduced aroma and bean size. Histological studies revealed symptoms of incompatibility, characterized by more dilated and less distinct growth rings and appearance of plugged vascular connections. The poor performance of the rootstocks may therefore be explained by partial incompatibility. However, growth and productivity were also affected by poor adaptations of C. canephora, C. liberica, and C. dewevrei to the lower temperature at high altitudes and by morphological differences in the root systems. These results emphasize the need to develop better adapted rootstock cultivars from C. canephora var. Robusta.

Free access

Mari Tahara, Takeshi Yasuda, Naotsugu Uchida and Tadashi Yamaguchi

Somatic embryos were regenerated from protoplasts isolated from embryogenic callus on young leaf explants from mature coffee trees. Embryos were regenerated on modified Murashige and Skoog medium supplemented with 5 μm BA. Somatic embryos developed into intact plants. Mannitol at 0.5 m was adequate as an osmoticum for isolating protoplasts, but subsequent culture required 0.3 m mannitol. A culture system in which osmolality was decreased gradually accelerated formation of colonies and somatic embryogenesis. Chemical name used: N-(phenylmethyl)-1H-purine-6-amine (BA).

Free access

Domingo R. Loero and Kent D. Kobayashi

Nine years of historical yield, meteorological, and soil data were input into a soil water balance simulation model to generate a daily soil water status value. The values for the number of days and millimeters of deficit (duration and magnitude) were grouped into trimesters and used to estimate yield. The greatest frequency of days with plant moisture stress occurred during the January–March and the October–December periods. The greatest magnitude of stress occurred during the January–March period. Annual coffee yields were best estimated by the model that incorporated variables for the previous year including, April–June deficit magnitude duration, July–September deficit magnitude duration, and the previous year's yield. Model testing with data from nine cultivars over an 8-year period showed that the model estimated yields with a mean error of 17%. The use of this model permitted yield estimation 2 months before anthesis and 8 months before the start of harvest.

Free access

A. Virginia Freire, David A. Lightfoot and John E. Preece

Efficient genetic transformation could enhance coffee breeding, which is limited by its long generation time and narrow genetic base. Three explant types of three coffee cultivars were inoculated with 14 strains of Agrobacterium spp. Callus and hairy roots were produced with 13 of the 14 strains tested. With A. tumefaciens, nopaline strains were more effective than octopine strains. Cucumopine and mannopine strains of A. rhizogenes were both effective in inducing hairy roots and callus. PCR amplification of a 0.72 Kb fragment of T-DNA encoding a portion of the ipt gene was achieved with DNA from A. tumefaciens strain A208 and with putatively transformed tissue inoculated with A208. No amplification was observed with virB in putatively transformed tissue which indicates it was not contaminated with Agrobacterium. We conclude that coffee can be genetically transformed by some Agrobacterium strains.

Free access

Chifumi Nagai, Zhuping Mai and Jerek Jong

Somatic embryogenesis of coffee has been studied for the purpose of obtaining target tissues for stable genetic transformation through use of a particle gun. Eight cultivars of C. arabica were selected for callus induction from leaves. Primary calli were induced within two weeks in over 98% of the leaf disks explanted on MS medium with 2,4-D and kinetin prior to treatment on a secondary culture medium. Somatic embryos were obtained from `Catuai' and `Blue Mountain' after six months from explanting. Somatic embryos were germinated in MS media and developed into plants. Somatic embryos and embryogenic calli are being used for gene transformation experiments with the helium-driven particle gun.

Free access

Ursula K. Schuch, Leslie H. Fuchigami and Mike A. Nagao

Unsynchronized flowering and fruit ripening of coffee prohibits mechanical harvesting and results in high labor costs. Coffee (C.arabica c. Guatemalan) trees were sprayed at the beginning of the 1988 and 1989 flowering season with solutions of benzyladenine (BA), gibberellic acid GA3 (GA), and Promalin (PR) or were pruned in 1988 to determine effects on synchronizing flowering and ripening. Growth regulators affected the time to flowering and harvesting compared to the control, however, treatment effects were dependent on the time of growth regulator application. Application of PR and GA at 100 mg/l in Jan 1988 shortened the average days to flowering by 16 and 13 days, and the average days to harvest by 15 days compared to the control. Pruning of three apical nodes of primary lateral branches in Feb 1988 caused delays in flowering, reduced flower and fruit number per tree, and caused branch dieback.

Open access

Roxana Myers, Andrea Kawabata, Alyssa Cho and Stuart T. Nakamoto

Root-knot nematodes ( Meloidogyne sp.) adversely affect yields of arabica coffee ( Coffea arabica ) in many coffee-growing regions. In Kona, HI, kona coffee root-knot nematodes [ Meloidogyne konaensis ( Eisenback et al., 1994 )] are extremely