1. PaDIL Factsheet

Scientific Name: Phymatotrichopsis omnivora (Duggar) Hennebert Basidiomycetes

Common Name Cotton rot Live link: http://www.padil.gov.au/pests-and-diseases/Pest/Main/136625

Image Library Australian Biosecurity Live link: http://www.padil.gov.au/pests-and-diseases/

Partners for Australian Biosecurity image library

Department of Agriculture, Water and the Environment https://www.awe.gov.au/ Department of Primary Industries and Regional Development, Western Australia https://dpird.wa.gov.au/ Health Australia https://www.planthealthaustralia.com.au/ Museums Victoria https://museumsvictoria.com.au/ 2. Species Information

2.1. Details Specimen Contact: Dr Jose R. Liberato - [email protected] Author: Liberato, JR Citation: Liberato, JR (2006) Cotton root rot(Phymatotrichopsis omnivora)Updated on 7/16/2016 Available online: PaDIL - http://www.padil.gov.au Image Use: Free for use under the Creative Commons Attribution-NonCommercial 4.0 International (CC BY- NC 4.0)

2.2. URL Live link: http://www.padil.gov.au/pests-and-diseases/Pest/Main/136625

2.3. Facets Status: Exotic Regulated Pest - absent from Australia Group: Fungi Commodity Overview: Field Crops and Pastures Commodity Type: Cotton & other fibres Distribution: USA and Canada, Central and South America, Africa

2.4. Other Names Phymatotrichum root rot Texas root rotPhymatotrichum root rot

2.5. Diagnostic Notes When deep-seated sclerotia contact a descending cotton root, the grows as strands toward the soil surface, entwining the root. Near the soil line, the fungus changes to a floccose growth. The upper root periderm is killed and the pathogen colonizes the inner root occluding the xylem. Foliar symptoms usually appear at time of flowering as a slight bronzing of leaves followed by a rapid wilt. apparently healthy wilt and die within 2-3 days. Leaves become desiccated but do not fall from the plant. are covered by fungal strands extending to the soil surface (Lyda 1978, Rush et al. 1985). Mycelial strands are most obvious on the roots 5-10 cm below the soil surface (Riggs 2001).

Atypical aboveground symptoms consisted of gradual wilting followed by leaf chlorosis and defoliation have been observed by Rush et al. (1985) during periods of low soil moisture availability.

The pathogen:

“Conidial stage (Phymatotrichum omnivorum). Hyphae forming a loose layer on the surface of the soil in areas where the root rot has killed the plants; fertile hyphae arising irregularly from the mycelium, simple or forked; conidia numerous, sessile, borne on the irregularly swollen clavate or subglobose short terminal or lateral branches of the hyphae or on the sides of the undifferentiated hyphae, pale ochraceous to gray in mass, appearing nearly colorless when separate, globose to ovoid 4—6 x 5 8 µm, smooth. Sterile mycelial stage (Ozonium omnivorum) mycelium thin, floccose to arachnoid, forming thin branching strands, the dirty ochraceous branches arising from these strands are thin, somewhat rigid and branch at right-angles from somewhat swollen nodes, 2 to 4 branches from a node, usually long, thin, tapering and acute” (Shear 1925). The morphology of strands and sclerotia has been presented by Neal et al. (1934) and Alderman & Stowell (1986).

Notes: According to Shear (1925), this pathogen was first tentatively referred to Ozonium auricomum Link. by Pammel in 1889. Shear, comparing this pathogen with the type of O. auricomum, found they were quite different and described a new species Ozonium omnivorum Shear in 1907 to accommodate the cotton root rot. At that time this pathogen was know only as a sterile mycelia. In 1916, its conidial state was described as Phymatotrichum omnivorum Duggar. Afterwards, Shear (1925) described the basidiomycete fungus Hydnum omnivorum Shear associated to plants dying from Phymatotrichum root rot that he believed to be the perfect state of P. omnivorum, although it was based on circumstancial evidence. According to Burdsall Jr & Nakasone (1978), H. omnivorum is not the perfect state of the cotton pathogen and was reclassified as Phanerochaete omnivorum (Shear) Burdsall Jr & Nakasone. Barnieki and Bloss (1969) observed clamp connections, basidia and basidiospores in a few cultures of P. omnivorum and stated brinkmannii (Bres.) J. Erikss. (? Trechispora brinkmannii (Bres.) D.P. Rogers & H.S. Jacks.) as the perfect state of the P. omnivorum. However, according to Dong et al. (1981) the hyphal septa ultrastructure of the two fungi suggests that they are not two stages of the same species as reported by Barnieki and Bloss (1969). Thus, so far the perfect state of P. omnivorum has not been found. Hennebert (1973) has transferred this species to the genus Phymatotrichopsis.

2.6. References Alderman SC & Stowell LJ (1986) Strand ontogeny in Phymatotrichum omnivorum. Transactions of the British Mycological Society 86:207-211. Burdsall Jr H & Nakasone KK (1978) of Phanerochaete chrysorhizon and Hydum omnivorum. Mycotaxon 7: 10-22. Baniecki JF & Bloss HE (1969) The basidial stage of Phymatotrichum omnivorum. Mycologia 61:1054-1059. Crop Protection Compendium 2005 Edition. Phymatotrichopsis omnivora (cotton root rot). CAB International, Wallingford, UK. Dong S, Bloss HE, Alcorn SM (1981) Ultrastructure and comparison of Phymatotrichum omnivorum and . Mycologia 73:321-333. Hennebert GL (1973) Botrytis and Botrytis-like genera. Persoonia 7:183-204. Kenerley CM, Jeger MJ, 1992. Fungal diseases of the root and stem. Cotton diseases [edited by Hillocks, R.J.] Wallingford, UK; CAB International, 161-190. Lyda SD (1978) Ecology of Phymatotrichum omnivorum. Annual Review of Phytopathology 16:193-209. Lyda SD & Kenerley CM (1992) Phymatotrichum. In: Singleton LL, Mihail JD, Rush CM, eds. Methods for Research on Soilborne Phytopathogenic Fungi. St. Paul, MN, USA: American Phytopathological Society Press, p.145-148. Neal DC, Wester RE & Gunn KC (1934) Morphology and life history of the cotton root-rot fungus in Texas. Journal of Agricultural Research 49:539- 548. Rogers CH, Watkins GM, 1938. Strand formation in Phymatotrichum omnivorum. American Journal of Botany, 25:244-246. Riggs JL (2001) Phymatotrichum root rot. In Kirkpatrick TL & Rothrock CS (eds) Compendium of cotton diseases. 2nd ed. St. Paul, MN, USA: APS Press. p. 31-32. Rush CM, Gerik TJ, Kenerley CM (1985) Atypical disease symptoms associated with Phymatotrichum root rot of cotton. Plant Disease 69:534-537. Shear CL (1925) The life history of the Texas root rot fungus, Ozonium omnivorum Shear. Journal of Agricultural Research 30: 475-477. Streets RB & Bloss HE (1973) Phymatotrichum Root Rot. APS Monograph No. 8. St Paul, MN, USA: APS Press.

2.7. Web Links New Mexico State University: http://www.cahe.nmsu.edu/pubs/_a/a-229.pdf The Texas A&M University System: http://plantanswers.tamu.edu/publications/cottonrootrot/cotton.html The University of Arizona: http://ag.arizona.edu/pubs/diseases/az1150.html 3. Diagnostic Images

Hyphal strand of Phymatotrichopsis Hyphal strand of Phymatotrichopsis omnivora. omnivora.

pathogen: J.R. Liberato DPI&F pathogen: J.R. Liberato DPI&F

Results Generated: Friday, September 24, 2021