In the first part of this thesis, the developmental strategies of the two contrasting barley leaf rusts, <I>Puccinia striformis</I> f. sp. <I>hordei</I> (barley yellow rust, BYR) and <I>P. hordei</I> (barley brown rust, BBR) were compared during infection of the susceptible cultivar Golden Promise. The techniques of fluorescence microscopy and low-temperature scanning microscopy were used correlatively to provide complementary information on the temporal and spatial development of these rusts within the host. These studies revealed many differences between the two rusts, including: (1) the germ tubes of BYR were long and unbranched whilst those of BBR were short and branched. (2) Only BBR produced appressoria. (3) The spread from the substomatal cavity into surrounding leaf tissue was delayed in BYR but not BBR. (4) BYR formed large, aseptate, invasive runner hyphae prior to reproduction after which they became septate. BBR lacked runner hyphae. (5) BYR exhibited semi-systemic growth during the colonisation of leaf tissue whilst BBR colonised leaf tissue only around the site of penetration. (6) BYR produced morphologically distinct hyphae involved in uredinal bed formation whilst BBR did not. (7) Primary uredina were formed some distance from the site of penetration by BYR whilst in BBR, uredinia formed at the site of penetration. In the second part of this study, quantitative comparisons were made of the contrasting infection strategies of the two rusts in their respective optimum conditions for development. This study revealed for the first time that the semi-systemic infection strategy employed by BYR was more efficient than the localised infection strategy exemplified by BBR. The final part of the investigation involved a study of the role of contact sensing in the induction of appressorium formation by <I>P. hordei</I> and <I>P. graminis</I> f. sp. <I>tritici</I> (wheat stem rust). Polystyrene replicas of microfabricated silicon wafers, bearing precisely defined topographies, were used as artificial substrata for growing these cereal rust <I>in vitro</I>.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:642533 |
| Date | January 1994 |
| Creators | Kellock, Lesley |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12344 |
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