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- Author or Editor: Javier O. Mijangos-Cortés x
To determine the effect of different nitrogen sources and osmotic regulators on minimal growth of Habanero pepper (Capsicum chinense Jacq.) germplasm for in vitro conservation, different concentrations of nitrate, sucrose, mannitol, and sorbitol were evaluated. The micropropagation system based on culture medium was modified in its nitrate concentrations: reduced to 50% and increased to 150%, and osmoregulators were added to the basal culture media: sucrose (6% and 8%), mannitol (2%, 4%, and 8%), or sorbitol (2%, 4%, and 8%). The apical meristems of germinated plants were cultivated in the different treatments for 35 weeks without subculture. Results have demonstrated that mannitol at 2% had the better effect on minimal growth of the plantlets and did not affect the plant physiology and quality. The plantlets remained small in size, turgent, with green leaves and stems and looked like normal plants until to the end of the evaluation period. Changes in nitrogen media concentration did not prove to be adequate for conserving because they affected the plantlet quality (they became chlorotic). The presence of sorbitol and high osmolite concentrations induced minimal growth but reduced the plant quality. Sucrose at mid or low concentrations did not induce minimal growth.
The ontogenesis of direct high-frequency somatic embryogenesis of C. chinense induced from hypocotyl was characterized through a histological analysis of the different phases in the histodifferentiation process during the development of the somatic embryo. The anatomical analysis was carried out since the hypocotyl segments were placed in the culture medium until 45 days of culture. The somatic embryos were induced and maintained in Murashige and Skoog medium supplemented with 2,4-dichlorophenoxyacetic acid (9.5 μm). Samples of tissues and organs were taken every 24 h, fixed in formalin acetic alcohol, and embedded in plastic resin. They were cut into serial sections (5 μm) and stained with toluidine blue. The analysis revealed that the proembryogenic cells originated just from provascular hypocotyl cells. Provascular cells acquired the embryogenic competence 48 h after induction and an intense mitotic division was observed and embryogenic structures were generated first along the vascular strands, which subsequently evolved into somatic embryos. After 2 weeks, there were observed embryos at different stages of development (preglobular, globular, heart-shaped, torpedo-shaped, and cotyledonary). This is the first report dealing with the ontogenesis of the direct somatic embryogenesis of C. chinense, and it is the most complete histological characterization carried out on somatic embryogenesis in the Capsicum genus to date.
A complete and efficient regeneration protocol was developed for Vanilla planifolia ‘Andrews’, an endangered orchid species that represents an important crop in several tropical countries. Axillary buds excised from the first to the eighth node, considering the first to fourth nodes as “young” (zone 1) and the fifth to eighth as “mature” (zone 2), were cultured on Murashige and Skoog (MS) medium supplemented with 5.73, 7.64, 9.55, or 11.46 μm 6-benzylaminopurine (BA) for shoot induction and in combination with 4.45 μm naphthalene acetic acid (NAA) to induce multiple shoot proliferation. Cytokinin concentration and bud position in the stem had a significant effect on the number of shoots regenerated. The greatest shoot formation per explant, for the two tested zones, was obtained with 9.55 μm BA on MS medium supplemented with 100 mg·L−1 myoinositol, 150 mg·L−1 citric acid, 100 mg·L−1 ascorbic acid, and 20 g·L−1 sucrose. Young buds from zone 1 were able to form an average of 18.5 ± 2.4 shoots per explant, whereas buds from zone 2 induced a maximum of 11.0 ± 1.0 shoots per explant. Plants of 2 to 3 cm height developed a root system in half-strength MS medium supplemented with 0.44 μm NAA and, once they reached 5 cm height on average, were transferred to greenhouse conditions for their acclimatization where a 100% rate survival was achieved. The optimal use of both young and mature buds from each mother plant to induce adventitious shoots permitted a marked increase in the number of shoots per explant. By using all buds from the upper stem part (zone 1 + zone 2) and subculturing every 90 d, the multiplication rate was 1.1 to 1.86 × 105 shoots per bud per year.
The variability and genetic parameters of seven agronomic characteristics were estimated for 11 genotypes, and high values of the phenotypic coefficient of variation (PCV) of capsaicin content (CC) were obtained. Heritability (h2) was high for yield per plant (YP; 0.98) and CC (0.93). The principal components analysis (PCA) revealed that the first three components explained 94.02% of the total variation; therefore, genotypes with higher YP values and fruit weight (FW) (AKN-08, ASBC-09) were placed in quadrant I. Those with greater CC and lowest YP and FW (MBI-11, RES-05) were placed in quadrant II. The greatest fruit length (RNJ-04) was placed in quadrant III. Those with the greatest number of fruits per plant (NBA-06, RKI-01, RHC-02, RHN-03, NKA-07, and MSB-12) were placed in quadrant IV. The results showed that the genotypes studied comprise an excellent source of genetic material for Habanero pepper improvement programs.