RESUMO

Cacti species are plants that are well adapted to growing in arid and semiarid regions where the main problem is water availability. Cacti have developed a series of adaptations to cope with water scarcity, such as reduced leaf surface via morphological modifications including spines, cereous cuticles, extended root systems and stem tissue modifications to increase water storage, and crassulacean acid metabolism to reduce transpiration and water loss. Furthermore, seeds of these plants very often exhibit dormancy, a phenomenon that helps to prevent germination when the availability of water is reduced. In general, cactus species exhibit a low growth rate that makes their rapid propagation difficult. Cacti are much appreciated as ornamental plants due to their great variety and diversity of forms and their beautiful short-life flowers; however, due to difficulties in propagating them rapidly to meet market demand, they are very often over-collected in their natural habitats, which leads to numerous species being threatened, endangered or becoming extinct. Therefore, plant tissue culture techniques may facilitate their propagation over a shorter time period than conventional techniques used for commercial purposes; or may help to recover populations of endangered or threatened species for their re-introduction in the wild; or may also be of value to the preservation and conservation of the genetic resources of this important family. Herein we present the state-of-the-art of tissue culture techniques used for ornamental cacti and selected suggestions for solving a number of the problems faced by members of the Cactaceae family.

Assuntos

RESUMO

Cacti species are plants that are well adapted to growing in arid and semiarid regions where the main problem is water availability. Cacti have developed a series of adaptations to cope with water scarcity, such as reduced leaf surface via morphological modifications including spines, cereous cuticles, extended root systems and stem tissue modifications to increase water storage, and crassulacean acid metabolism to reduce transpiration and water loss. Furthermore, seeds of these plants very often exhibit dormancy, a phenomenon that helps to prevent germination when the availability of water is reduced. In general, cactus species exhibit a low growth rate that makes their rapid propagation difficult. Cacti are much appreciated as ornamental plants due to their great variety and diversity of forms and their beautiful short-life flowers; however, due to difficulties in propagating them rapidly to meet market demand, they are very often over-collected in their natural habitats, which leads to numerous species being threatened, endangered or becoming extinct. Therefore, plant tissue culture techniques may facilitate their propagation over a shorter time period than conventional techniques used for commercial purposes; or may help to recover populations of endangered or threatened species for their re-introduction in the wild; or may also be of value to the preservation and conservation of the genetic resources of this important family. Herein we present the state-of-the-art of tissue culture techniques used for ornamental cacti and selected suggestions for solving a number of the problems faced by members of the Cactaceae family.(AU)

Assuntos

RESUMO

Among the major cucurbit vegetables, melon (Cucumis melo) has one of the greatest polymorphic fruit types and botanical varieties. Some melon fruits have excellent aroma, variety of flesh colors, deeper flavor, and more juice compared to other cucurbits. Despite numerous available melon cultivars, some of them are exceedingly susceptible to several diseases. The genetic background carrying the genes for tolerance and/or resistance for those diseases is found in wild melon landraces. Unfortunately, the commercial melon varieties are not able to produce viable hybrids when crossed with their wild melon counterparts. Plant tissue culture techniques are needed to surpass those genetic barriers. In vitro melon embryo rescue has played a main role to obtain viable hybrids originated from commercial versus wild melon crosses. In this chapter, an efficient and simple embryo rescue melon protocol is thoroughly described.

Assuntos

RESUMO

Garlic (Allium sativum L.) can be affected by a virus complex (1) consisting of two potyviruses, Onion yellow dwarf virus (OYDV) and Leek yellow stripe virus (LYSV), and two carlaviruses, Garlic common latent virus (GCLV) and Shallot latent virus (SLV) (1). To identify the components of the virus complex that could be present in garlic plants in Guanajuato State, which is the second largest garlic producer in the country and where presumptive viral symptoms were initially observed in December 2004, a survey was carried out in six locations: San Miguel de Allende and San Luis de la Paz in northern Guanajuato; Irapuato and Villagrán in the central region; and Salamanca and Valle de Santiago in the southern part of the state. Enzyme-linked immunosorbent assay (ELISA) was carried out to detect LYSV, OYDV, GCLV, and SLV in 195 garlic leaf samples collected during January 2005 from plants with leaf yellow stripe, mosaic, enation, deformation, or dwarfism symptoms. A set of primers, previously reported and specific to the coat protein cistron of LYSV (1), were synthesized and used in a reverse transcriptase-polymerase chain reaction (RT-PCR). The amplified product (1,020 nucleotides) was cloned into plasmid pGEM T-Easy (Promega, Madison, WI) and sequenced (Gen-bank Accession No. DQ841554). Sequence analysis showed that the cloned DNA fragment shared 97% similarity with the coat protein cistron of LYSV isolate no. 3 from Okinawa (GenBank Accession No. AB194632). The fragment was then radioactively labelled and used as a probe in the RNA blot analysis of all samples to confirm the ELISA results of LYSV. Of the 195 samples, 64 tested positive by RNA blot analysis. Forty-one of these were also positive by ELISA for LYSV. Preliminary, positive ELISA results were also obtained for OYDV, GCLV and SLV. To our knowledge, this is the first report of LYSV in the State of Guanajuato and in Mexico. The correct identification of viruses present in garlic will help to use the appropriate strategies to reduce viral incidence in this garlic-producing region. Reference: (1) T. V. M. Fajardo et al. Fitopatol. Bras. 26:619, 2001.