First Report of Cirsium arvense (Canada thistle) as a New Host of Orobanche cumana Wallr. in Xinjiang, China

Cirsium arvense (Canada thistle) is a perennial herb native to Eurasia that has been introduced to temperate regions of the world where it is considered one of the serious weeds for arable and pastoral agriculture (Schröder et al. 1993). C. arvense reproduces both clonally and sexually. The weed is highly competitive, causes yield reductions in crops such as wheat, alfalfa, sugarbeet, and can reduce forage availability and production (Wilson 1981). Canada thistle is also a harbour for plant pathogens such as plant-parasitic nematodes (Tenuta et al. 2014). Sunflower broomrape (Orobanche cumana Wallr.) is a holoparasitic plant species with a restricted range of hosts both in the wild, where it mainly parasitizes a few species of the Asteraceae, and in agricultural fields, where it is exclusively found growing on sunflower (Fernández-Martínez et al. 2015). O. cumana infection can cause up to 80% of the yield loss in sunflower, which is a serious threat for sunflower production in Xinjiang and Inner Mongolia, China (Parker 2009). In July 2019, broomrape was observed parasitizing C. arvense in the greenhouse used for sunflower resistance identification (Shihezi, 86° 3' 36" E, 44° 18' 36" N, 500 m elevation) in Xinjiang, China. Fifty percent of the plants were parasitized by broomrape in the greenhouse and the host had an average of 1-2 broomrape shoots per plant. For molecular analysis, total genomic DNA was extracted from the flowers of broomrape and the rps2, rbcL, trnL-F genes, and ribosomal DNA internal transcribed spacer (ITS) region were amplified by PCR using the primer pairs rps2F/rps2R, rbcLF/rbcLR, C/F, ITS1/ITS4, respectively (Park et al. 2007; Manen et al. 2004; Taberlet et al. 1991; Anderson et al. 2004). The ITS (659bp), rps2 (451 bp), trnL-F (914 bp), and rbcL (961 bp) gene sequences of the broomrape were deposited in GenBank, the accession numbers are MT856745, MW809407, MW809408, and MW809409. The results of BLAST analysis showed that ITS sequence shared 100% similarity with O. cumana (659/659 nucleotide identity, MK567978), the rps2 sequence shared 99% similarity with O. cumana (449/451 nucleotide identity, KT387722), trnL-F sequence shared 99% similarity with O. cumana (907/911 nucleotide identity, MT027325), rbcL sequence shared 99% similarity with O. cumana (956/964 nucleotide identity, MK577840). The morphological characteristics such as stem, inflorescence, corolla, bracts, calyx, stamens, gynoecium are consistent with O. cumana described by Pujadas-Salvá and Velasco (2000). Morphological and molecular identification strongly support that the broomrape parasitic on C. arvense belonged to the O. cumana. Greenhouse pot experiments were carried out to assess the parasitic relationship between sunflower broomrape and C. arvense (Fernández-Martínez et al. 2000). In January 2020, C. arvense roots were harvested from an extant field of C. arvense in the greenhouse at Shihezi University (Supplementary Figure S1A). The soil was dug to 30-40 cm depth and C. arvense roots were removed and carefully washed in water. The healthy and living C. arvense roots were selected and cut into 10-11 cm pieces. Four C. arvense root pieces were grown (buried at a depth of 10-12 cm) in 8-L pots containing a mixture of sand-vermiculite-compost (1:1:1 v:v:v) and O. cumana seeds (50 mg of O. cumana seeds per 1 kg of the substrate) with 5 replicates. Three non-infected plants were grown and evaluated in parallel. Approximately 80 days after planting, at the flowering stage of the O. cumana, C. arvense plants were uprooted from the soil. Compared to non-infected plants, the hosts’ symptoms were slow growth, leaf wilting, and chlorosis, and similiar to the broomrape-infected C. arvense plants observed in the greenhouse field. The roots of C. arvense and broomrape were carefully washed in water and observed the parasitism of O. cumana. The infection was confirmed by observation of the attachment of the O. cumana to the C. arvense roots (Supplementary Figure S1D). To the best of our knowledge, this is the first report of O. cumana parasitizing C. arvense in Xinjiang, China. C. arvense as a new host of O. cumana indicates that sunflower broomrape can also propagate and survive in a host such as Canada thistle grown in sunflower fields. This finding suggests that it may be more difficult to control sunflower broomrape by rotation. 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An urban wildlife habitat experiment: conservation implications of altering management regimes on animals and plants along urban and rural rights-of-way

Biodiversity along rights-of-way (ROWs) can decline due to local-scale management, including frequent urban mowing and spraying, or with increasing amount of urban infrastructure surrounding those grassy spaces. Distinguishing effects of mowing regime from effects of surrounding urban land are necessary to determine what management strategies effectively conserve wildlife in different landscapes, and to justify changes in management that could increase populations of weeds. We used a manipulative Before/After-Control/Impact (BACI) experiment in 17 transmission line ROWs during 2007–2009, along an urbanization gradient, to disentangle effects of mowing frequency and the amount of urban land (buildings, hard surfaces like concrete, asphalt) surrounding ROWs. In the BACI study, we halted mowing and spraying for 1 year in five urban ROWs, introduced two rounds of mowing per year in three rural ROWs, and compared vegetation and arthropods found within these manipulated ROWs and within three urban and six rural control ROWs. European skipper butterflies Thymelicus lineola, lepidopteran biomass in herbaceous vegetation, milkweeds (Asclepias spp.) and Canada thistle Cirsium arvense increased when mowing and spraying were halted for one year. Conversely, monarch butterflies Danaus plexippus, legume cover and dandelion Taraxacum officinale increased when mowing was introduced to rural ROWs. To increase taller butterfly resource plants while still controlling weeds within urban ROWs, we recommend reducing management frequency within the interior of ROWs while maintaining frequent management along ROW borders that are adjacent to infrastructure.