Avaliação de variação somaclonal em plantas derivadas de Arracacia xanthorrhiza por morfogênese indireta

The objective of this work was to induce and detect somaclonal variation in arracacha (Arracacia xanthorrhiza) plants regenerated via indirect morphogenesis, in order to evaluate the potential of this technique to produce new genotypes for breeding purposes of this crop. Calli were induced from petiole segments on Murashige & Skoog (MS) medium supplied with 0.1 mg L-1 2,4-dichlorophenoxyacetic acid. The regeneration of plants via indirect morphogenesis was carried out on half-strength MS medium without plant growth regulators. Fifteen randomly chosen plants were subjected to flow cytometry and “inter-simple sequence repeat” (ISSR) analysis. Ploidy level remained stable in all tested regenerants (2n=4x=44), with no changes in the genome. Eighteen ISSR primers produced a total of 1,584 fragments in all samples. Two ISSR primers produced four polymorphic fragments in 26.7% of the tested samples. Somaclonal variation in arracacha is a result of plant regeneration via indirect morphogenesis and can be detected by ISSR markers.O objetivo deste trabalho foi induzir e detectar a variação somaclonal em plantas de batata-baroa (Arracacia xanthorrhiza) regeneradas por morfogênese indireta, para avaliar o potencial dessa técnica em produzir novos genótipos para o melhoramento dessa cultura. Calos foram induzidos em segmentos de pecíolos no meio de Murashige & Skoog (MS) suplementado com 0,1 mg L-1 de ácido 2,4-diclorofenoxiacético. A regeneração de plantas pela morfogênese indireta foi realizada em meio de cultura MS meia-força, sem reguladores de crescimento de plantas. Quinze plantas escolhidas aleatoriamente foram submetidas à citometria de fluxo e à análise entre sequências simples repetidas (ISSR). O nível de ploidia manteve-se estável em todas as plantas regeneradas (2n=4x=44), sem mudanças no genoma. Dezoito iniciadores ISSR produziram um total de 1.584 fragmentos em todas as amostras. Dois iniciadores ISSR produziram quatro fragmentos polimórficos em 26,7% das amostras testadas. A variação somaclonal entre plantas de batata-baroa é resultante da regeneração de plantas pela morfogênese indireta e pode ser detectada por meio de marcadores ISSR

Assessment of somaclonal variation in somatic embryo-derived plants of yacon [ Smallanthus sonchifolius (Poepp. and Endl.) H. Robinson] using inter simple sequence repeat analysis and flow cytometry

Background: Yacon ( Smallanthus sonchifolius ) is a root crop native to the Andean region. Low sexual reproductive capacity is amajor constraint facing the genetic breeding of this crop. Biotechnological techniques offer alternative ways to widen genetic variability. We investigated somaclonal variation in regenerants of yacon derived from in vitro somatic embryogenesis using simple sequence repeat (ISSR) analysis and flow cytometry. Results: Twenty tested ISSR primers provided a total of 7848 bands in 60 in vitro regenerants and control plant. The number of bands for each primer varied from3 to 10, and an average of 6.95 bands was obtained per ISSR primer. Eight primers were polymorphic and generated 10 polymorphic bands with 7.19% mean polymorphism. ISSR analysis revealed genetic variability in 6 plants under study. These regenerants had Jaccard's distances 0.104, 0.020, 0.040, 0.106, 0.163 and 0.040. Flow cytometric analysis did not reveal changes of relative nuclear DNA content in regenerants suggesting that the plants obtained via somatic embryogenesis had maintained stable octoploid levels. Conclusions: Our findings show that indirect somatic embryogenesis could be used in yacon improvement to widen genetic variability, especially when low sexual reproductive capacity hinders classical ways of breedin

Simplified in vitro propagation protocol for Tacca leontopetaloides (L.) Kuntze and assessment of genetic uniformity of regenerated plantlets

Tacca leontopetaloides is a tuberous species with nutritional, medicinal, and industrial potential. The aim of the present study was to develop a simplified micropropagation protocol for this species, combining phases of in vitro propagation and rooting, and to assess the genetic stability of in vitro regenerants using ISSR and flow cytometric analysis. In the first step, the effect of four cytokinins (BA, zeatin, kinetin, thidiazuron) at concentrations of 0.1-0.7 mg l-1 on shoot organogenesis was tested. The highest number of shoots was achieved on MS medium supplemented with 0.1 mg l-1 zeatin (4.11 ± 0.35 shoots/explant). Thereafter, this treatment was combined with auxins (NAA, IAA) at concentrations of 0.01-0.07 mg l-1 to study shoot organogenesis and in vitro rooting. A combination of plant growth regulators provided unchanged (high) shoot organogenesis, while the root number per explant increased. The highest number of roots of all tested treatments was produced on MS medium supplemented with zeatin (0.1 mg l-1) in combination with NAA (0.05 mg l-1) (5.00 ± 0.38 roots/explant), suggesting that this medium may be used for both propagation and rooting. Well-rooted plants were transferred ex vitro, with a 97.78% survival rate. Ten randomly chosen in vitro regenerants were subjected to ISSR and flow cytometric analysis. Eleven ISSR primers produced 40 clear and reproducible bands per sample. All amplified products were monomorphic; no polymorphism was detected. Similarly, the results of flow cytometric analysis showed no variation in ploidy level. Thus, the micropropagation method optimized here can be used for highly effective production of true-to-type plants of T. leontopetaloides

Birds girdling activity on exotic tree species as a form of adaptive behavior?

Four tree species in the Kostelec n. . l. arboretum (Czech Republic) have been repeatedly damaged by Dendrocopos medius. The unique aspect of this otherwise common behavior called girdling consists in regularly visiting the same trees every spring, although there are more than 1.200 tree species within the arboretum. We monitored transpiration, leaf phenology and the chemical composition of the xylem sap of girdled and nongirdled trees. Spectral analysis revealed slightly higher amounts of sugars, especially saccharose, in Cladrastis Raf. as the most regularly girdled tree among other conditions, comparing girdled to non-girdled trees. Higher transpiration rates were not confirmed in connection with girdling-quite the opposite-Cladrastis Raf. as the most highly favored tree for girdling showed the lowest transpiration rates (in average 6 kg water per day within spring months) compared to other non-girdled trees. We presume that the birds do not choose a particular tree on the basis of any visible or chemical traits but they examine many trees within their territory. Afterwards they probably remember the position of trees whose xylem sap starts to flow early in the spring compared to other trees, as their transpiration stream is enriched with sweet organic substances that represent an advantage for the forthcoming nesting period

Assessment of somaclonal variation in somatic embryo-derived plants of yacon [Smallanthus sonchifolius (Poepp. and Endl.) H. Robinson] using inter simple sequence repeat analysis and flow cytometry

Background: Yacon (Smallanthus sonchifolius) is a root crop native to the Andean region. Low sexual reproductive capacity is a major constraint facing the genetic breeding of this crop. Biotechnological techniques offer alternative ways to widen genetic variability. We investigated somaclonal variation in regenerants of yacon derived from in vitro somatic embryogenesis using simple sequence repeat (ISSR) analysis and flow cytometry. Results: Twenty tested ISSR primers provided a total of 7848 bands in 60 in vitro regenerants and control plant. The number of bands for each primer varied from 3 to 10, and an average of 6.95 bands was obtained per ISSR primer. Eight primers were polymorphic and generated 10 polymorphic bands with 7.19% mean polymorphism. ISSR analysis revealed genetic variability in 6 plants under study. These regenerants had Jaccard's distances 0.104, 0.020, 0.040, 0.106, 0.163 and 0.040. Flow cytometric analysis did not reveal changes of relative nuclear DNA content in regenerants suggesting that the plants obtained via somatic embryogenesis had maintained stable octoploid levels. Conclusions: Our findings show that indirect somatic embryogenesis could be used in yacon improvement to widen genetic variability, especially when low sexual reproductive capacity hinders classical ways of breeding

Plant responses to cold: transcriptome analysis of wheat

Temperature and light are important environmental stimuli that have a profound influence on the growth and development of plants. Wheat varieties can be divided on the basis of whether they require an extended period of cold to flower (vernalization). Varieties that have a requirement for vernalization also tend to be winter hardy and are able to withstand quite extreme subzero temperatures. This capacity, however, is not constitutive and plants require a period of exposure to low, non-freezing temperatures to acquire freezing tolerance: this process is referred to as cold acclimation. Cold acclimation and the acquisition of freezing tolerance require the orchestration of many different, seemingly disparate physiological and biochemical changes. These changes are, at least in part, mediated through the differential expression of many genes. Some of these genes code for effector molecules that participate directly to alleviate stress. Others code for proteins involved in signal transduction or transcription factors that control the expression of further banks of genes. In this review, we provide an overview of some of the main features of cold acclimation with particular focus on transcriptome reprogramming. In doing so, we highlight some of the important differences between cold-hardy and cold-sensitive varieties. An understanding of these processes is of great potential importance because cold and freezing stress are major limiting factors for growing crop plants and periodically account for significant losses in plant productivity. © 2010 The Authors. Journal compilation © 2010 Blackwell Publishing Ltd