New Disease Reports (2006) 13, 38.

First report of Puccinia heucherae on Heuchera spp. in the UK

B. Henricot 1*, G. Denton 1 and C. Lane 2

*beatricehenricot@rhs.org.uk

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Accepted: 21 Jun 2006

Heuchera spp. (Saxifragaceae) are hardy perennials, principally native to North America. In July 2004, June and November 2005, samples of ornamental Heuchera spp. and the variety ‘Leuchtkäfer’ showing typical symptoms of rust disease were received at the RHS. These originated from private gardens in the English counties of Surrey, Kent and Hampshire. In July 2005, CSL also identified an outbreak of the same disease on a range of cultivars (‘Hollywood’, ‘Monet’, ‘Cherries Jubilee’ and ‘Persian Carpet’ ) at a nursery in southern England.

In the USA, Puccinia heucherae is a common rust on Heuchera and other members of the Saxifragaceae ( Farr et al ., 1995 ). This disease has also been recorded in East Asia (Savile, 1954). In Europe, P. saxifragae is a common disease on Saxifragaceae and has been reported in the UK on the genus Saxifraga (Wilson & Henderson, 1966). In the USA, this species has also been found on Heuchera (Farr et al ., 1995). Therefore the possibility was considered that the Heuchera samples were infected by one of these two rust pathogens.

Morphological and molecular comparisons were carried out with herbarium samples of both species deposited at the Royal Botanical Gardens, Kew, UK. In all the samples received, the teliospores were dark brown, two-celled with a pale conical papilla. Spore morphology was not useful for distinction between P. heucherae and P. saxifragae , as the sizes of the teliospores were very similar. According to Savile (1954), the main distinction between P. heucherae and P. saxifragae is the presence of striations on the spore walls of P. saxifragae. However, the striations of the spores are not always present (Wilson & Henderson, 1966). This character was not apparent in our samples.

For DNA analysis, the 5’end of the large ribosomal subunit (LSU) was amplified and sequenced using the primers NL1/NL4 (Maier et al. , 2003). The sequences of the two Puccinia species differ at six positions, which is enough to distinguish one species from another. The LSU sequences of the RHS and CSL samples (GenBank Acc. No. DQ359701-DQ359706) were identical to that of P. heucherae ( K(M)129792, DQ359700 ).

This is the first record of Puccinia heucherae in the UK. It is likely that it has been imported from the USA on infected plants. At the nursery outbreak, the cultivar ‘Hollywood’ came from the USA as plugs in March 2005 and was growing in close proximity to the other three cultivars, that all originated from the UK.

Acknowledgments We would like to acknowledge Dr Brian Spooner from RBG Kew for lending herbarium material of P. heucherae and P. saxifragae , and also the Defra PHSI Inspector Andrew McFarlane.

Figure1+
Figure 1: : Symptoms of rust on Heuchera spp. (RHS5296/05)
Figure 1: : Symptoms of rust on Heuchera spp. (RHS5296/05)
Figure2a+Figure2b+Figure2c+
Figure 2: : Teliospores of a) P. saxifragae on Saxifraga stellaris K(M)129794; b) P. heucherae on Heuchera sp. RHS5296/05; c) P. heucherae on Heuchera micrantha K(M)129792; d) P. heucherae on Heuchera ‘Hollywood’CSL20511420. Bar = 10 µm. K(M): Royal Botanic Gardens, Kew, UK, RHS: Royal Horticultural Society, Wisley, UK, CSL: Central Science Laboratory, York, UK
Figure 2: : Teliospores of a) P. saxifragae on Saxifraga stellaris K(M)129794; b) P. heucherae on Heuchera sp. RHS5296/05; c) P. heucherae on Heuchera micrantha K(M)129792; d) P. heucherae on Heuchera ‘Hollywood’CSL20511420. Bar = 10 µm. K(M): Royal Botanic Gardens, Kew, UK, RHS: Royal Horticultural Society, Wisley, UK, CSL: Central Science Laboratory, York, UK
Figure3+
Figure 3: : One of the 828143 most parsimonious trees recovered using the large subunit ribosomal RNA based on Eocronartium muscicola (AF426194), Herpobasidium filicinum (AF426193) , Septobasidium carestianum (L20289) , Melampsora euphorbiae (AF426195), M. helioscopiae (AF426197) and M. hypericorum as outgroups. Phylogenetic analyses were performed using PAUP version 4.0b8. Heuristic searches using maximum parsimony with 10 random addition sequence replicates, TBR branch swapping, MULPARS, and steepest descent options were conducted in PAUP for all data sets. To evaluate clade support, Jackknife analysis (in PAUP) with 30% deletion and fast stepwise addition was calculated for 10,000 replicates. Groups were retained that appeared in 50% or more of the trees. Dashed lines indicate branches that collapsed in the strict consensus tree. Plain figures indicate branch lengths and figures in brackets show the Jackknife support value. Accession numbers in GenBank are in parentheses.
Figure 3: : One of the 828143 most parsimonious trees recovered using the large subunit ribosomal RNA based on Eocronartium muscicola (AF426194), Herpobasidium filicinum (AF426193) , Septobasidium carestianum (L20289) , Melampsora euphorbiae (AF426195), M. helioscopiae (AF426197) and M. hypericorum as outgroups. Phylogenetic analyses were performed using PAUP version 4.0b8. Heuristic searches using maximum parsimony with 10 random addition sequence replicates, TBR branch swapping, MULPARS, and steepest descent options were conducted in PAUP for all data sets. To evaluate clade support, Jackknife analysis (in PAUP) with 30% deletion and fast stepwise addition was calculated for 10,000 replicates. Groups were retained that appeared in 50% or more of the trees. Dashed lines indicate branches that collapsed in the strict consensus tree. Plain figures indicate branch lengths and figures in brackets show the Jackknife support value. Accession numbers in GenBank are in parentheses.

References

  1. Farr DF, Bills GF, Chamuris GP, Rossman AY, 1995. Fungi on plants and plant products in the United States . St Paul, MN, USA: APS Press. Maier W, Begerow D, Weiß M, Oberwinkler F, 2003. Phylogeny of the rust fungi: an approach using nuclear large subunit ribosomal DNA sequences. Canadian Journal of Botany 81 , 12-23. Savile DBO, 1954. Taxonomy, phylogeny, host relationship, and phytogeography of the microcyclic rusts of Saxifragaceae. Canadian Journal of Botany 32 , 400-425. Wilson M, Henderson DM, 1966. British Rust Fungi . Cambridge, UK: Cambridge University Press.

This report was formally published in Plant Pathology

©2006 The Authors