Special symposium: In vitro plant recalcitrance recalcitrance of woody and herbaceous perennial plants: Dealing with genetic predeterminism

Abstract

As a general group, long-lived perennial plants probably present the most challenging obstacles to the researcher, breeder or propagator utilizing microculture as a tool. These challenges appear during all stages of the microculture process, but are probably most resplendent during the stabilization phase. What may be particularly frustrating is that much of this 'recalcitrance' is genetically driven and is thus difficult to control by environmental and nutritional manipulations in microculture. Perennials have complex seasonal cycles and life cycles, which complicate control of their growth in microculture. As shoot cultures have provided useful tools for overcoming these limitations, the inability to establish stabilized shoot cultures is a major form of recalcitrance. Plants having seasonal growth dynamics dominated by strong episodic or determinant shoot growth are some of the most recalcitrant species because stabilized shoot cultures cannot be readily generated. In some cases, episodic growth may be tied closely to phase state and can thus be controlled by manipulating phase; nevertheless, adequate controls have not been identified for many problematic plants. Another trait contributing to recalcitrance of perennials is the relatively slow growth rate in microculture. Slow growth complicates such procedures as selection of transformed tissues. The high phenolic content of many perennial tissues can interfere with the efficacy of transgenic traits such as b-glucuronidase. Developmentally determined growth characteristics such as plagiotropism may persist through all stages of microculture and complicate the recovery of commercially useful micropropagules. Although some technical approaches can occasionally circumvent immediate microculture limitations, general solutions await the development of a deeper understanding of physiological bases of such genetically predetermined phenomena.

Conservation of holm oak (Quercus ilex) by in vitro culture

“…The achievement of uniform and continuous in vitro shoot growth is highly problematical for woody species with a strongly episodic growth habit (McCown, 2000). In this respect, Quercus species are typical of woody perennials characterized by strong episodic flushes during the growing season (Vieitez & al., 2012).…”

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“…Dubova (1994) obtained 3.0 to 8.6 birch plants per explant on the medium containing 0.5 mg L −1 BAP and 0.05 mg L −1 IBA, which is a significantly larger number than that obtained in the present study, but only juvenile shoots were used in the former research. It is well known that age of the mother plant affects the rate of shoot proliferation in culture (McCown 2000). Shoot proliferation rate usually increases with the increase in concentration of cytokinins until a certain threshold is reached (Jokinen et al 1991).…”

Development of Sanitation Protocol for Leaf Explants of <i>B. huillensis</i> for <i>in Vitro</i> Culture

“…Another feasible reason may be due slow growth in woody plants, the longer life span of trees may add to the problem of contamination in vitro by the symbiotic association of microorganisms. [15] found that the growth rates of shoots and other tissues such as callus of woody plants in microculture are usually slower than observed with herbaceous plant. In a study by [28] it was observed that phase change or maturation in woody plants not only results in changes in growth behavior, but results in increased difficulty in vegetative propagating selected individuals.…”

“…The media was composed of basal woody plant medium (WPM) [15] with full strength supplemented with antifungal namely cefotaxime 0.03 mg/liter in the medium after cooling to body temperature. The pH of the medium was adjusted to 5.6 before autoclaving at 121 degrees centigrade.…”