Potential susceptibility of Australian flora to a NA2 isolate of Phytophthora ramorum and pathogen sporulation potential

Abstract

infection of some species has been found to play a crucial role in transmission of the pathogen in the 76 UK (Rhododendron spp.) and California (Umbellularia californica, California Bay Laurel; and 77Notholithocarpus densiflorus, Tanoak) by providing key sources of inoculum that drive epiphytotics 78 (Goheen et al. 2002;Brasier et al. 2004; Davidson et al. 2005). Detached foliar assays have been used 79 by a number of authors to assess susceptibility and sporulation potential of a range of species to P. 80 ramorum in vitro (Parke et al. 2002;Denman et al. 2005a;Hansen et al. 2005;Denman et al. 2006a; 81 Hüberli et al. 2008). These methods have been confirmed as a good indicator of field susceptibility 82 when compared with natural infection and other methods of inoculation . 83Australian quarantine restricts the entry of all materials which fall into known host genera of P. Experimental design 97In vitro leaf inoculations of Australian native plants were used to determine potential foliar 98 susceptibility to P. ramorum and sporangia production potential in 22 experiments between April 2008 99 and October 2009 at Davis, California, USA (Table 1). Potential foliar susceptibility was tested by 100 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Branches of each individual were collected the day before inoculations were undertaken and cut 145 stems and branches were kept in deionised water overnight. Before inoculation, leaves were cut at the 146 base of the petiole from branches, rinsed with deionised water and placed on paper towels to air-dry. 147Mature, fully expanded leaves were used for all species. Juvenile-aged leaves were tested for 24 of the 148 test species, as well as for R. 'Colonel Coen'. Juvenile leaves were included to account for overall 149 susceptibility of the test plants and to test for differences in susceptibility between leaf ages. 150 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 either DiPel (Bacillus thuringiensis; Abbot Laboratories, Chicago IL, USA) at 1.6 to 3.9 ml/l of water 154 and Vegol (canola oil; Lilly Miller Brands, Clackamas OR, USA) at 3.9 to 19.5 ml/l or Sunspray Oil 155 (Paraffinic Oil; Sun Refining & Marketing Co., Philadelphia PA, USA) at 6.5 ml/l during the "summer" 156 and with Conserve SC (Spinosad; Dow Agrosciences LLC, Indianapolis IN, USA) at 1.7 ml/l and 157Bonide All Seasons Spray Oil (Petroleum Oil, Oriskany NY, USA) at 10 ml/l during the "winter" 158 inoculations. These species wer...

Combining Inferential and Deductive Approaches to Estimate the Potential Geographical Range of the Invasive Plant Pathogen, Phytophthora ramorum

“…Furthermore, in the case of P. ramorum , no infectious host implies less of a problem, as rapid expansion of the pathogen’s range has been linked to “super-sporulating” hosts such as U. californica (California bay laurel) in California [72] and L. kaempferi (Japanese larch) in the United Kingdom [2], [73]. Potential host range studies of species from areas considered to be at risk of P. ramorum invasion have indicated that susceptible and infectious hosts exist on the east coast of the USA, Asia and Australasia [2], [74], [75], [76], [77], [78]. Knowledge of these hosts combined with knowledge of the potential geographical distribution is important when concentrating efforts for early detection of the pathogen, or when attempting to uncover the origins of invasive species such as P. ramorum .…”

Potential susceptibility of Australian native plant species to branch dieback and bole canker diseases caused by Phytophthora ramorum

“…Colonel Coen leaves to maintain pathogenicity and maintained on PARP (Erwin & Ribeiro, 1996). This isolate was also used in a concurrent study of foliar susceptibility and sporulation potential (Ireland et al. , 2011).…”

“…A number of native Australian plant species have been found to be either potential or naturally infected foliar or branch hosts of P. ramorum , when planted in the UK or California (RAPRA, 2007; Hüberli et al. , 2008; Ireland et al. , 2011; USDA‐APHIS, 2010).…”

“…Correa cv. Sister Dawn, Eucalyptus regnans , Isopogon cuneatus , I. formosus , Leptospermum scoparium , L. lanigerum and Melaleuca squamea have been identified as potentially highly susceptible Australian foliar host species (Ireland et al. , 2011).…”

“…, 2011). Additionally, putative sporulating hosts have also been identified and include Agonis flexuosa , Corymbia ficifolia , Eucalyptus haemastoma , E. delegatensis and E. viminalis (Ireland et al. , 2011).…”