An Appraisal of The Use of Axillary Buds of Grasses as Clonal Material for Inoculation with Neotyphodium Endophytes

Abstract

When assessing the interactions between Neotyphodium endophytes and their grass hosts it is useful to have access to clonal plant material. A range of endophyte isolates can be used to inoculate clonal material, this allows comparisons to be made between the endophytes without the complication of host plant genotype effects. The inoculation of intact tillers has been achieved (Ravel et al. 1994) but presents difficulties due to infection by saprophytic fungi and bacteria. Attempts have been made to infect plant tissue from within tillers where the tissue is cleaner; callus culture (Johnson et al. 1986) and somatic embryos (Kearney et al. 1991). These two methods are time consuming, the infection success is not high and in addition there is a possibility of somaclonal variation. A method that has been successfully used to access clean plant tissue for inoculation is that of O'Sullivan and Latch (1993). This method involves the excision of tiller meristems, culturing them anexically to produce plantlets and subsequently inoculating them with endophyte. Although this method has proven to be successful it is time consuming and technically difficult. This paper reports on a potentially more simple and rapid method for obtaining endophyte infected clonal material. Within each tiller there is only one apical meristem, however there are several axillary buds which are comprised of meristematic tissue. These buds can be quickly excised and are easily manipulated as discrete units. An examination was made of the possibility of surface sterilising excised axillary buds and infecting them with Neotyphodium endophytes. This appraisal was undertaken using a range of tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne) cultivars and a selection of Neotyphodium endophyte isolates representing several taxonomic groups.