JOURNAL OF NEMATOLOGY VOLUME 12 JANUARY 1980 NUMBER 1 Population Response to Temperature in the Subfamily Tylenchorhynchinae ~ R. B. Malek 2 Abstract: The effects of temperature on population development of 11 species of stunt nem- atodes in the subfamily Tylenchorhynchinae were compared on red clover or Kentucky bluegrass in constant-temperature tanks at 5-degree intervals from I0 to 35 C. The optimum temperature for population increase on red clover in 90 days was 30 C for Tylenchorhynchus agri, T. nudus, T. martini, and T. clarus, 25 C for T. sylvaticus and 7". dubius, and 20 C for T. canalis, Merlinius brevidens, and Quinisulcius capitatus. The optimum was 30 C for T. robustoides and 25 C for T. maximus on Kentucky bluegrass. The temperature range for population increase was 20-35 C for T. agri, T. nudus, T. martini, and T. clarus, 20-30 C for T. sylvaticus and T. robustoides, 15-25 C for T. maximus, 10-25 C for T. dubius, and 10-20 C for M. brevidens and Q. capitatus. T. canalis increased only at 20 C. All species were recovered in numbers near their inoculum level at 10 C. There was no survival of T. sylvaticus, T. dubius, T. canalis, T. robustoides, T. maximus, M. brevidens, and Q. capitatus at 35 C, or of the last three of these species at 30 C. Temperature had no effect on sex ratio in final populations. Population increase was greatest in T. martini and least in T. canalis. Key Words: stunt nematodes, Tylenchorhynchus, Merlinius, Quinisulcius, red clover, Kentucky bluegrass, population development. Numerous species of stunt nematodes in tional differences are unknown, although the subfamily Tylenchorhynchinae occur in differences in soil temperature regimes be- soils of the North Central region of the tween crop types may be partially responsi- United States (14, 21). Little attention has ble. been given to the host-parasite relationships Temperature requirements among stunt and ecological requirements of these nem- nematodes are known only for certain pop- atodes, although certain species are fre- ulations of Tylenchorhynchus clarus (13), quently encountered in abundance and in T. claytoni (I1), T. dubius (3, 15) and T. polyspecific communities in the rhizosphere nudus (18, 20). This paper presents results o1 herbaceous plants. of studies of the temperature preferences of While most of the native species of stunt I I species of stunt nematodes apparently nematodes are easily cultured on several indigenous to all or part of the North Cen- mutual hosts, marked population fluctua- tral United States. tions that vary with the species and season of the year have been noted by the author MATERIALS AND METHODS during attempts at increasing greenhouse populations for biological studies. More- Species of stunt nematodes studied, and over, in Illinois certain species that are com- their original sources, were: Tylenchorhyn- mon associates of herbaceous perennials, chus agri Ferris, soybean (Glycines max such as turfgrasses and clovers, are seldom [L.] Merr.), Marion County, Illinois; T. encountered on the major annual row crops canalis Thorne and Malek, western wheat- corn and soybeans, which are suitable hosts grass (Agropyron smithii Rydb.), Penning- under greenhouse conditions. Other species ton Co., South Dakota; T. clarus Allen, are frequent associates of both crop types. creeping bentgrass (Agrostis palustris The reasons for those interspecific distribu- Huds.), Hamilton Co., Ohio; T. dubius Bfitschli, Kentucky bluegrass (Poa praten- sis L.), Champaign Co., Ill.; T. martini Received for publication 31 July 1978. Fielding, oats (Arena sativa L.), Champaign aResearch supported in part by funds from the Illinois Agricultural Experiment Station. Co., Ill.; T. maximus Allen, Kentucky blue- 2Associate Professor of Nematology, Department of Plant grass, Champaign Co., Ill.; Allen, Pathology, University of Illinois at Urbana-Champaign, T. nudus Urbana, Illinois 61801. soybean, Brookings Co., S. Dak.; T. robus- The JOURNAL OF NEMATOLOGY for October (11: 293-403) was issued 18 December 1979. 2 Journal o] Nematotogy, Volume 12, No. 1, January 1980 toides Thorne and Malek, western wheat- Numbers/pot were estimated from counts grass, Pennington Co., S. Dak.; T. sylvaticus of replicated one-ml aliquots of a 200-ml Ferris, sugar maple (.4cer saccharum extract suspension or counted in toto when Marsh), Champaign Co., Ill.; Merlinius numbers were low. Plant shoots and root brevidens (Allen) Sidiqi, corn (Zea mays systems were over-dried at 80 C for 3 days L.), Pope Co., Ill.; and Quinisulcius capi- and weighed for comparison of growth tatus (Allen) Siddiqi, Kentucky bluegrass, among temperatures. Champaign Co., Ill. All but two species were cultured on 'Kenland' red clover RESULTS (Trifolium pratense L.) in a greenhouse and There were distinct differences among tested on that host. T. maximus and T. the species in response to temperature and robustoides were studied on 'Newport' Ken- ability to utilize red clover as a host (Fig. tucky bluegrass, because they failed to in- 1). Temperature-related differences in pop- crease on red clover in repeated tests. ulation development included optimum for Plants were grown in 10-cm-diam plastic reproduction, range for reproduction, and pots containing 500 cm ~ of Sparta loamy survival at upper extremes. fine sand. A 15-ml centrifuge tube was Maximum population increases of T. pressed 5 cm into the soil in the center of agri, T. nudus, T. martini, T. clarus, and each pot at planting. Clover seeds were T. robustoides occurred at 30 C. There was planted in soil infested with commercial little difference in final populations of T. Rhizobium inoculant, and the seedlings robustoides between 25 and 30 C, indicating were later thinned to four/pot. Pots for that its optimum may lie between those bluegrass were sown with 100 seeds apiece. temperatures. Increases were greatest at 25 C Nematodes for inoculation were ex- in T. sylvaticus, T. dubius, and T. max- tracted by a modification of the method o[ imus, and at 20 C in T. canalis, M. brevi- Christie and Perry (6). Two weeks after dens,, and Q. capitatus. seeding, a 25-ml suspension of 200 nem- T. agri, T. nudus, T. martini, and T. atodes of the appropriate species in all de- clarus increased in population over a range velopmental stages was poured into the hole of 20-35 C, whereas T. sylvaticus and T. resulting from removal of the tube. The robustoides increased only between 20 and hole was filled with moist soil, and the pot 30 C. Final populations were relatively low was watered gently. The pots were arranged at 20 C in these species. In contrast, M. randomly on a greenhouse bench where brevidens and Q. capitatus reproduced ambient temperatures averaged 25 C. within the relatively low temperature range Three days after inoculation, each pot of 10-20 C. T. dubius and T. maximus re- was placed in an impervious plastic con- quired an intermediate range of 15-25 C, tainer. The rim of the pot was 2 cm below though the former increased in numbers that of the container and flush with its side. slightly at 10 C. T. canalis, for which clover Four replications for each nematode species was a poor host, increased only at 20 C. were placed randomly in each of six Cornell- All species survived temperatures as low type constant-temperature tanks (10) so as 10 C, but populations increased at that that the soil line was 2 cm below the water temperature only in T. dubius, M. brevi- level. The tanks were maintained at I0, 15, dens, and Q. capitatus. Populations of T. 20, 25, 30, or 35 -4- 1 C. The pots received agri, T. nudus, T. martini, and T. clarus 50 ml of a 23% N-19% P20~-17% K20 increased substantially at the relatively high fertilizer solution at days 0 and 45 and 100 temperature of 35 C. The last three of these ml of distilled water when the soil surface species increased as well at that temperature became dry. Natural lighting was supple- as at 25 C. None of the other species sur- mented with fluorescent to provide a 14-hr vived at 35 C, where examination of sieve day length. residues following extraction revealed only Tests of individual species were initiated a few dead nematodes. At 30 C, there was consecutively so that they could be termi- little survival of T. canalis and T. dubius, nated at intervals of 3-4 days. Nematodes and none of T. maximus, M. brevidens, and were extracted 90 days after inoculation by Q. capitatus. the same method used to obtain inoculum. Temperature had no significant effect on Temperature Response in Tylenchorhynchinae: Malek 3 '5 4 i "4 m "3 ID ..... OOI • I I I I0 15 20 :'~ 30 38 I0 15 20253035 tO 15 20 28 30 35 I0 15 20 25 30 3,5 ogrl nudus mortlni clorus o o m '4 Q. n m o '3 =E .**.°, 2 0 Z I I0 15 20 25 30 35 I0 15 20 25 30lr 35 I0 15 20253038 I0 15 2025 30 lm sylvoticus dublus moximus robustolclls mm m ,....° ...... Inoculum level I0 18 20 25 30 38 io m 2o253ou lo m 2o as3o38 I~revldens copltotu| canolis TEMPERATURE (C) FIG. 1. Effect of temperature on population development of Tylenchorhynchus agrl, T. canalis, T. clarus, T. dubius, T. martini, T. nudus, T. sylvaticus, Merlinius brevidens, and Quinisulcius capitatus on red clover, and of T. maximus and T. robustoides on Kentucky bluegrass. 4 Journal of Nematology, Volume 12, No. 1, January 1980 the final adult population sex ratio, which cus were exceptions to the morphological- was similar to that in the inoculum. The physiological correlation. Although they female:male ratio at the optimum tempera- are most similar to species in the first group, ture for each bisexual species was: T.