Differential organ infection studies, potyvirus elimination, and field performance of virus-free garlic plants produced by tissue culture

Presence of potyvirus in single garlic (Allium sativum L.) cloves from the same bulb, and in five single leaves excised from commercial field-grown individual plants was studied using ELISA. It was found that the viruses were not present in all organs of the same plant, since some cloves of the same bulb were infected with potyvirus but some others were potyvirus-free. Analyzed leaves from a given plant also exhibited irregular distribution of potyvirus. This study also aimed to obtain potyvirus-free plants from two commercial garlic cultivars (Taiwan and Chileno) using cloves subjected to thermotherapy, chemotherapy or meristematic dissection followed by in vitro culture. Thermotherapy (sequential treatment at 32°C for a week, 36°C for 2 weeks, and 38°C for 3 weeks) was found to affect survival of explants and 36.5% cloves from Taiwan and 26.8% from Chileno cultivars were recovered after the treatment. ELISA tests showed that 63% of the cloves of Taiwan that survived the treatment and 70.9% of Chileno explants were potyvirus-negative. Regarding chemotherapy (205 μM Ribavirin solution), the explants (cloves) survived, but only an average of 27.0–34.8% were negative for the presence of potyvirus. When meristematic dissection was applied, an average of 41.7% explants of Taiwan and 34.2% of Chileno survived the treatment, and approximately 64% of these explants from both cultivars were potyvirus-negative. Potyvirus-free garlic plants grown in field conditions showed longer stems with a major fresh and dry weight per bulb, and also exhibited a higher yield than non-treated plants.     

In vitro propagation of three <Emphasis Type="Italic">Agave</Emphasis> species used for liquor distillation and three for landscape

In vitro bud clusters of Calathea orbifolia (Linden) Kennedy were obtained and subcultured in semi-solid (agar) medium and temporary immersion system (TIS) for 12 weeks. Uniform young plants were selected and transferred to soilless mix in a growth chamber for ex vitro acclimatization during 35 days, followed by growing in a shaded greenhouse for 65 days. Comparison of in vitro leaf anatomy, ex vitro photosynthetic behaviors and growth was made between two cultural systems. Plants in TIS produced thicker leaf chlorenchyma and aquiferous parenchyma, lower stomatal frequency and more epicuticular wax than did those in semi-solid medium. Plants from semi-solid medium had consistently lower leaf Fv/Fm values than plants from TIS. Leaf Fv/Fm value in plants from TIS decreased to 0.65 at day 7 after transfer and increased soon up to 0.76 thereafter. In contrast, leaf Fv/Fm value in plants from semi-solid medium reduced to 0.27 at day 7 after transfer and increased slowly up to 0.68 at day 35. During ex vitro acclimatization, plants in TIS had substantial higher photosynthetic rates than plants in semi-solid medium. Plants from TIS had subsequent higher leaf area, fresh and dry weights than plants from semi-solid medium.     

<Emphasis Type="Italic">In vitro</Emphasis> propagation of ten threatened species of <Emphasis Type="Italic">Mammillaria</Emphasis> (Cactaceae)

Mammillaria species are the most numerous within Cactaceae family, and some of them are threatened with extinction as a result of human activities. In this work, results of in vitro propagation are presented for ten Mammillaria species, testing 20 combinations of indole-3-acetic acid (IAA) and kinetin. Best results on shoot formation were obtained using kinetin at two levels: 27.9 and 46.5 μM. All IAA levels tested were able to induce de novo shoot formation in M. bocasana, M. densispina, M. hahniana, M. hutchisoniana, M. orcutii, M. pectinifera, M. perbella, M. picta, M. rhodantha, and M. zephyranthoides. Depending on the IAA level tested, four responding groups were observed concerning their highest shoot-formation number. For all species, the highest average of shoot formation was achieved with 5.7:46.5 or 11.4:46.5 μM IAA/kinetin, yielding 4.8 and 4.7 shoots per explant, respectively, in 60 d. Rooting of regenerated shoots was achieved by leaving the explants in their shoot-induction medium or transferring them to half-strength MS medium. Hardening of regenerated plants was successfully achieved by planting them in peat moss substrate after a desiccation treatment at room temperature for 3 d.     

Micropropagation for fraser photinia (Photinia × fraseri)

Embryo suspensor masses were induced by culture of isolated mature zygotic embryos of Fraser fir (Abies fraseri [Pursh] Poir.). Maximum induction frequencies were observed after 10 weeks culture on one-half strength Murashige and Skoog medium containing 10 μM thidiazuron and on one-half strength Verhagen and Wann medium containing 10 μM cytokinin [6-(dimethylallylamino)purine, 6-benzyladenine, or thidiazuron). Proliferation of embryo suspensor masses occurred on one-half strength Verhagen and Wann medium supplemented with 10 μM cytokinin. When embryo suspensor masses were transferred to media containing 5-80 μM abscisic acid, cotyledonary-stage embryos were formed. Somatic embryos germinated on medium lacking plant growth regulators, but abnormal cotyledonary-stage somatic embryos with stunted cotyledons and reduced embryo axes were also observed. This revised version was published online in June 2006 with corrections to the Cover Date.