Factors Affecting Germination of of Pucciniaobtegens

S. K. TURNER, Former Research Assistant, A. KWIATKOWSKI, Exchange Scientist from Poland, P. K. FAY, Associate Professor of Agronomy, Department of Plant and Soil Science, and D. C. SANDS, Associate Professor, Department of Plant Pathology, Montana State University, Bozeman 59717 by observing 250 teliospores (50 in each per ABSTRACT of five microscope fields at X100) Turner, S. K., Kwiatkowski, A., Fay, P. K., and Sands, D. C. 1986. Factors affecting germination plate. Germination from one or both of teliospores of Puccinia obtegens. Plant Disease 70:390-391. cells was recorded as one . germinated at Bozeman on 18 and roots stimulated germination when flooded over collected Extracts of Canada thistle (Cirsium arvense) Sp te mbec ted at 12,18 , Maximum percent germination was obtained in darkness at 21 C. teliospores on water agar. 30 September 1980 were tested at 12, greater after 6 than after 3 mo of storage at 4 C and varied with collection Percent germination was C. Separate extracts from root, before 15 August) and locations. 18, and 21 dates (no germination stem, and leaf tissue were prepared and The experiment was Additional key words: biological weed control, Pucciniapunctiformis tested as described. conducted twice. Germination was assessed after 72 and 96 hr of incubation. Teliospore collections from different locations were tested for germination. (Link) Tul. (2), an germination of P. carthami(9). Klisiewicz Puccinia obtegens spore lot was treated with host root on Cirsium (9-11) showed that germination of P. Each autoecious, host-specific tested two to five times is a carthami teliospores was stimulated by extract and arvense (L.) Scop. (Canada thistle), tested of tio for this host plant exudates flooded on water agar. epend potential biological control agent teliospo The objective of this research was to depending on the number of weed (13). C. arvense plants are stressed available. To determine the effect of light by systemic infection that may occur after determine if P. obtegens teliospores could on germination, teliospores were exposed infection by uredospores or basidiospores be stimulated to germinate so they could daily to white fluorescent light for 12 hr (5,12). Systemically infected shoots be used to inoculate Canada thistle. versus complete darkness. All plates contained teliospores brushed onto usuallyGermination die by August of teliospores in Montana. is poor and MATERIALS AND METHODS cnandtloprsbuhdot h erratic; therefore, they have not been used Canada thistle tissue containing medium saturated either with host root effectively as inoculum for Canada teliospores of P. obtegens was collected extract or water (for controls). Plates thistle. Germination of teliosporesC of . during the summer and fall of 1980 from were incubated at 21 C and observed for obtegens is inconsistent (5,12), resulting 19 locations in Montana. Plant material germination after 48, 72, and 96 hr. in infrequent pycnia. The importance of containing teliospores was also collected Six teliospore collections from Bozeman teliospores, the overwintering spore stage from one site at Bozeman over a period of from 29 July to 21 October 1980 were in the rust's life cycle, is unclear because 3 mo. All plant material was air-dried and tested for germination in February 1981. the fungus also overwinters as mycelium stored at room temperature until October Leaves with teliospores from each collec- in the host's root system. 1981, then refrigerated at 4 C. tion were homogenized separately and Teliospore dormancy has been reported Teliospores were obtained by com- left in the homogenate for 12 hr before leaves they were placed on water agar, saturated for P. graminis var. tritici and P. minuting dried Canada thistle water with host root extract, and incubated for carthami (7,9). Buller (5) observed (0. 5-2 g) in l00 ml of sterile distilled for 1 min. 96 hr at 21 C with 12 hr light daily. germination of P. obtegens teliospores (SDW) in a Waring Blendor through Teliospore collections from Hilger, after refrigerated storage. Menzies (12) The suspension was strained Lewistown, Winifred, and Bozeman, MT, 1% germination of P. obtegens four layers of cheesecloth and centrifuged reported were tested for germination after 3-6 mo teliospores that were stored over the at 10,000 g for 5 min. The supernatant or of storage at 4 C. Teliospores soaked in winter at 5 C, then kept moist for 6 wk at suspension was removed immediately for homogenate for 12 hr were placed on roomenvironmental temperature. conditions Cotter (7) foundsuch thatas germinationafter 12 hr, and tests teliospores at both times.were usedGermi- water agar, saturated with root extract, freezing and alternate wetting and drying nation tests were performed in 9-cm and incubated at 21 C for 96 hr in stimulated germination of dormant plastic petri plates containing 10 ml of 2% darkness. teliospores of P. graminis var. tritici. Bacto water agar on which teliospores Certain volatile compounds stimulated were spread with a camel's-hair brush. RESULTS (3,8) or inhibited (1) urediospore and Canada thistle extract was prepared by Root and stem extracts of Canada teliospore germination. Nonhost and host comminuting 10-20 g of fresh roots, thistle stimulated teliospore germination. plant exudates have stimulated teliospore stems, or leaves in 100 ml of SDW for 1 Teliospore germination, increased over mmi. The suspension was strained that of the control when spores were through four layers of cheesecloth. In treated with root or stem extract at JounalSeresape 131 fom he ontna germination tests, the extract was incubation temperatures of 15, 18, and 21 Agricultural Experiment Station. atomized uniformly on the agar medium C. The highest germination percentage in bearing teliospores until the surface was all treatments occurred at 21 C. Accepted for pubiication 4 November 1985 wet. Controls were atomized with Germination percentages were signifi- (submitted for electronic processing). distilled water. cantly different between the control and In germination tests, teliospores were root extract-treated teliospores. Germi- The publication costs ofithis article were defrayed inlpart incubated at 21 C in a controlled- nation percentages increased from 3.7 (ntaedpos)o32 at8Cad by page charge payment. This article must therefore be tpeauechabrfr9hrues utetdsoe)t 2 t1 n hereby marked "advertisement" in accordance with 18 tmeaue abrfr9 ruls U.S.C. § 1734 solely to indicate this fact. otherwise stated. Three replicate plates from 7.6 to 44% at 21 C. Water extracts of were used for each germination treat- stem tissue were less stimulatory than © 1986 The American Phytopathological Society ment. Percent germination was recorded root extracts. Germination at 18 and 21 C

390 Plant Disease/Vol. 70 No. 5 increased from 3.7 and 7.6% for the Table 1. Percent germination of Puccinia obtegens teliospores collected at four locations in control to 11.9 and 14.1% for teliospores Montana in 1980 and stored at 4 C for 3 or 6 mo treated with stem tissue extracts, respectively. Leaf extracts did not Months of Percent germinationab per collection location stimulate teliospore germination, cold storage Hilger Lewistown Winifred Bozeman In a separate experiment, teliospore 3 3.50 0.10 2.10 2.30 germination was influenced by temper- 6 14.10 8.80 16.40 63.30 ature. Teliospores treated with root LSD 0.05 4.12 2.12 3.41 6.62 extracts were incubated for 96 hr in 'Mean value of three replicates. darkness at temperatures of 12-24 C, 5Teliospores were allowed to germinate on water agar containing root extracts of Canada thistle for which increased at three-degree intervals. 96 hr at 21 C without light. Germination occurred at all temperatures tested; however, the highest germination percentages, 21.2 and 28.9, occurred at 18 in soil during late spring and summer ACKNOWLEDGMENTS and 21 C, respectively. Germination within the geographical distribution of We wish to thank Patty Turrentine, Leslie increased from 0.9% at 12 C to 12.4% at Canada thistle and P. obtegens in North Dillaway, and Bernard Sally for technical assistance. 15 C. Germination declined from 28.9 at America (6). The optimal temperature for 21 C to 0.8% at 24 C. germination of wheat races LITERATURE CITED Teliospores under a 12-hr photoperiod differs (8). Further testing of P. obtegens 1. Allen, P. J. 1957. Properties of a volatile fraction Teliospores from uredospores of Puccinia graminis var. showed significantly lower germination teliospores might disclose races that tritici affecting their germination and develop- than those incubated in complete dark- would germinate at lower soil temper- ment. I. Biological activity. Plant Physiol. ness. Germination increased from 19.7% atures. Germination at lower soil 44:385-388. in light to 32.4% in complete darkness temperatures presumably would initiate 2. Arthur, J. C. 1934. Manual of the Rusts inUnited n lStates and Canada. Purdue Research Foundation. Teliospore germination percentages infection earlier in the growing season, Lafayette, IN. 438 pp. varied among spore lots collected at which would be more conducive to 3. Binder, R. G., Klisiewicz, J. M., and Waiss, A. different sites and dates. Plant tissue widespread infection. C., Jr. 1977. Stimulation of germination of containing telia was collected from nine Percent germination was higher when Puccinia carthami teliospores by polyacetylenes from safflower. Phytopathology 67:472-474. widely separated locationsfrom5June to spores were incubated in complete 4. Blackman, J. H. 1903. On the conditions of 18 September 1980. Percent germination darkness than when subjected to light. teleutospore germination and of sporidia to 38, with germination Teliospores of P. obtegens are normally formation in the uredineae. New Phytol. 2:10-15. occurringranged from onlyinsamplescollectedon 0 15 borne on plant debris that becomes 5. Buller, A. H. R. 1950. Puccinia suaveolens and o r o i p c c plaoborneon dristhint beomess its sexual process. Pages 344-388 in: Researches August or later. A second study was initi- soilborne, providing conditions more on Fungi. Vol. 7. University of Toronto Press. ated to determine the effect of collection conducive for germination of the spores. 458 pp. date. Germination of teliospores from sys- Incorporation of teliospore inoculum 6. Canada Atmospheric Environment Service. Temperature Data. Oct./ Dec. 1979 temically infected Canada thistle leaves into soil would enhance germination. Daily Soil temicall msand Vol. 21, Nos. 1-3. collected at the same location six times Because most of the teliospore samples 7. Cotter, R. U. 1940. Unseasonable germination of from 29 July to 21 October 1980 ranged collected from separate locations did not teliospores of Puccinia graminis tritici. from 0 to 36%. The highest germination germinate, environmental conditions Phytopathology 30:689-691. percentages occurred when plant tissue during development might influence 8. French, R. C. 1961. Stimulation of uredospore p sw trmingbili.develo ectiontmighte mayalgermination in wheat stem rust by terpenes and was collected in September and October. germinability. Collection date may also related compounds. Bot. Gaz. 122:194-198. Percent germination of teliospores be an important factor. Teliospore 9. Klisiewicz, J. M. 1972. Effect of host plant from four locations was greater after 6 germination percentages increased when materials and temperature on germination of than after 3 mo of storage at 4 C (Table 1). spores were collected later in the growing 62:436-438.isporesofPucciniacarthami'Phytopathlgy Germination also increased in samples season. Waters (14)found that low light 10. Klisiewicz, J. M. 1973. Effect of volatile from the other three locations after 6 mo intensity and/or nutrient stress induced substances from safflower on germination of of cold storage. formation of P. obtegens teliospores. teliosporesofPucciniacarthami. Phytopathology Spore immaturity may explain lower 63:795. germination percentages of teliospores 11. Klisiewicz, J. M. 1977. Effect of flooding and temperature on incidence and severity of DISCUSSION from samples collected early in the safflower seedling rust and viability of Puccinia Germination of teliospores of P. growing season. carthamiteliospores. Phytopathology 67:787-790. obtegens, as with P. carthami (9), was P. obtegens teliospores can be used as 12. Menzies, B. P. 1953. Studies on the systemic stimulated by host plant extracts. inoculum for biological control of C. fugu7P:5ni51-s5o68. nn Ht Klisiewicz (10) demonstrated that a arvense if the following factors are 13. Turner, S. K.. Fay, P. K., Sharp. F. L.. and stimulatory substance in safflower considered: 1) Collection should be done Sands, D. C. 1981. Resistance of Canada thistle extract was volatile, in September and October after a period (Cirsium arvense) ecotypes to a rust pathogen Tempratretliop nflencdoe wthou aders wethe coditonssuc 14(Puccinia obtegens). Weed Sci. 29:623-624. Tempratretliopor nflencd wihoutadvrseweaherconitins uch 14.Waters, C. W. 1928. The control of teliospore germination. The optimal temperature as rain or snow. 2) Root extracts of the and urediniospore formation by experimental range for germination (18 to 21 C) occurs host plant ensure maximum germination, methods. Phytopathology 18:157-213.

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