A note on the occurrence of Miyagia pseudosphaeria in New Zealand

Until 1997 Miyagia pseudosphaeria was known in New Zealand from only two specimens, both with the host recorded as Sonchus oleraceus L. The first specimen (PDD 281, Palmerston North, Jun 1919, G. H. Cunningham) is, unfortunately, missing from its package within Herb. PDD. A second collection (PDD 4029, Otago, Butcher's Creek, Jan 1937, G. H. Cunningham) has had the host redetermined by A. E. Esler, Auckland, as S. asper (L.) Hill.

In October 1997, a few pustules of M. pseudosphaeria were found on a single plant of S. oleraceus growing in Mt Albert, Auckland. Within a month the rust was found on other plants in Auckland and in Northland, and by February 1998 it was observed in Nelson. The rust became very obvious on sow thistle, sometimes causing dieback, and soon independent reports of its presence were received from other parts of the country. It is now very common throughout New Zealand on S. oleraceus. Additional

specimens of M. pseudosphaeria on S. asper have been obtained from Northland, Coromandel, Bay of Plenty, and Gisborne. In December 1997, plants of the endemic species S. kirkii, originating from Otago but cultivated in Auckland in the vicinity of infected S. oleraceus, were found infected with M. pseudosphaeria. This is of some concern since S. kirkii is a species undergoing human-induced, gradual decline (Hitchmough 2002), and the rust may exacerbate loss of plants through dieback. It would be of interest to know if Embergeria grandifolia is susceptible to this rust.

Miyagia pseudosphaeria is now also noticeable on S. oleraceus in Victoria, Australia (E. McKenzie pers. obs.). It was first recorded in South Australia on S. asper (Cook & Dubé 1989). Recently, Hernández et al. (2003) reported the first occurrence (January 2002) of this rust in the Americas, on plants of S. oleraceus growing in California. It seems quite probable that a new, more virulent race of M. pseudosphaeria arose somewhere in the world. As with many other rust fungi, it is also probable that the new race of M. pseudosphaeria was carried from Australia to New Zealand, possibly on air currents (McKenzie 1998) or on passengers' clothing (Sheridan 1985, 1989).

REPRESENTATIVE SPECIMENS EXAMINED: On Sonchus asper: NORTHLAND: Kohukohu Creamery Road, R. E. Beever, 14 Sep 1998, PDD 69427 II, III. GISBORNE: Taradale, Sugar Loaf Hill, R. E. Beever, 17 Oct 1999, PDD 71690 II. On S. kirkii: AUCKLAND: Royal Oak, R. E. Beever, 11 Jan 1998, PDD 68407 II, III. On S. oleraceus: AUCKLAND: Mt Albert, E. H. C. McKenzie, 12 Oct 1997, PDD 68318 II; Whangaparaoa Peninsula, near Stanmore Bay, E. H. C. McKenzie, 20 Dec 1998, PDD 69773 II, III. WELLINGTON: Palmerston North, Massey University, E. H. C. McKenzie, 13 Feb 1999, PDD 70397 II, III. NELSON: Marybank, E. H. C. McKenzie, K. & C. Vánky, 21 Feb 1998, PDD 68511 II. CANTERBURY: Kaikoura town, B. H. Macmillan, 5 Oct 1998, PDD 69470 II; Christchurch, Addington, A. J. Healy, 7 Dec 1998, PDD 70629 II. AUSTRALIA: VICTORIA: Bright, Canyon Track, E. H. C. & A. McKenzie, 25 Dec 2001, PDD 75042 II.

ETYMOLOGY: From the host plant.

NOTES: Several rusts, including species of Coleosporium, Miyagia, and Puccinia, have been described or recorded from Sonchus, but only one rust, the widespread Miyagia pseudosphaeria (Mont.) Jørst., has been recorded in New Zealand on Sonchus (Cunningham 1924). Puccinia embergeriae is quite distinct from M. pseudosphaeria, which is distinguished by possessing a peripheral, palisadelike layer of brown, thick-walled paraphyses in both the uredinia and telia; such paraphyses are lacking in P. embergeriae. In addition, the urediniospores of M. pseudosphaeria are generally narrower, with 3- 4 germ pores. Parmelee & Savile (1981) gave an account of North American Puccinia species on members of the Lactuceae (syn. Cichorieae). Of the species treated, P. hieracii, which has been recorded in New Zealand, has a wide host range within the Lactuceae. However, the urediniospores of P. hieracii have a tonsure, or smooth area, below each germ pore, a feature not observed in P. embergeriae.

Embergeria grandifolia is a threatened plant, and is listed as a nationally endangered species i Hitchmough (2002). Puccinia embergeriae, which is an obligate parasite, probably co-exists with its host plant. However, it is also a threatened species, classified as nationally critical (Hitchmough 2002).

When viewed with the scanning electron microscope, the urediniospores of P. embergeriae appeared to be smaller than when viewed by light microscopy. Measurements were checked and it is concluded there is significant shrinking of these spores when placed in the electron microscope. At high magnification, wrinkling of the spore surface between the spines was evident.