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  • Author or Editor: B. Castillo x
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Breeding programs depend upon genetic variation. Visual plant markers traditionally have been used in crop improvement. However, molecular markers provide additional selection criteria. Of the molecular markers available, isozymes are preferred by many researchers because they are expressed in young tissue as codominants and are easily extracted and detected. Mature plants may bias estimation of hybrid purity, whereas estimations of hybrid purity can be obtained at an early stage by enzyme analysis (1, 2, 4).

Open Access

Interactions between irradiance levels (5–40 μmol·m-2·s-1) and iron chelate sources (FeEDTA and FeEDDHA) were observed for Carica papaya shoot tip cultures during both the establishment and proliferation stages of microculture. Reduced levels of irradiance (5 μmol·m-2·s-1) favored shoot tip establishment regardless of the source or level of iron. However, the highest percentage of successful explant establishment (100%), and significantly greater leaf length (1.16 cm; over double the size attained in any other treatment), resulted when a low concentration of FeEDTA alone was used at low irradiance. During the subsequent shoot proliferation stage, however, higher irradiance levels (30 and 40 μmol·m-2·s-1) were required, and FeEDTA failed to support culture growth when used as the sole iron source. The highest multiplication rates (3.6 shoots per explant) and leaf chlorophyll concentrations (0.22 mg/g fresh mass), and significantly improved shoot quality were achieved at 30 μmol·m-2·s-1 irradiance when both iron chelate formulations were combined (each at a 100 μM concentration) in the proliferation medium. Chemical names used: benzylamino purine (BA); ferric disodium ethylenediamine tetraacetate or FeNa2EDTA (FeEDTA); ferric monosodium ethylenediamine di(o-hydroxyphenylacetate), (FeNaEDDHA) or Sequestrene 138Fe (FeEDDHA); indoleacetic acid (IAA); 1-naphthaleneacetic acid (NAA).

Free access

The tropical plant Bixa orellana L. (annatto) is the sole source of bixin, the most frequently employed natural pigment in the food industry. Little is known about the physiology, biochemistry, and molecular genetics of this crop. Our purpose was to establish a set of analytical tools that could be applied in the genetic improvement of B. orellana, particularly for the screening of characteristics such as bixin content and resistance to diseases or pests. Some preliminary results on the study of carotenoid synthesis are presented. In vitro cultures from several B. orellana tissues were established and DNA, RNA, and proteins were extracted from them and analyzed. Similarly, bixin and total carotenoids were quantified.

Free access