New Zealand Journal of Botany abstracts

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Ultrastructural studies of the telial, basidial, and spermatial stages of the willow rust fungus Melampsora coleosporioides in New Zealand

A. G. SPIERS

Soil Conservation Centre, Aokautere
DSIR, Private Bag
Palmerston North, New Zealand

D. H. HOPCROFT

Electron Microscope Laboratory
Biotechnology Division, DSIR, Private Bag
Palmerston North, New Zealand

Abstract Telia of Melampsora coleosporioides Dietel on willow leaves formed intra-epidermally, subepidermally, and subcuticularly from primordial cells which elongated and delimited terminal cells determinately. On maturity these cells became thick-walled and were fused laterally forming extensive cushions. Telial germination was marked by the emergence of a metabasidium (germtube) through an apical pore formed by localised dissolution of the telial wall. The metabasidium extended enteroblastically following synthesis of a new wall layer. The single diploid telial nucleus entered the metabasidium and divided meiotically, each of the four daughter nuclei becoming separated by centripetally formed, aperforate septa. Each uninucleate cell formed a sterigma and eventually a terminal basidiospore initial. The nucleus entered the basidiospore initial and later divided mitotically. The basidiospore initial was delimited from the basidium by formation of two septa, one halfway along the sterigma and the other at the base of the basidiospore initial. Cleavage at or near the uppermost septum released the basidiospore. Basidiospores of M. coleosporioides established a few spermagonia on Larix kaempferi, but despite spermatisation failed to form aecia.

Keywords Larix; willow; Melampsora; rust; basidiospore; telia

Received 3 December 1987; accepted 10 March 1988
New Zealand Journal of Botany, 1988, Vol. 26: 423-430
0028-825X/88/2603-O423$2.50/0 © Crown copyright 1988

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