JOURNAL OF NEMATOLOGY VOLUME 12 JANUARY 1980 NUMBER 1

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1 JOURNAL OF NEMATOLOGY VOLUME 12 JANUARY 1980 NUMBER 1 Population Response to Teperature in the Subfaily Tylenchorhynchinae ~ R. B. Malek 2 Abstract: The effects of teperature on population developent of 11 species of stunt neatodes in the subfaily Tylenchorhynchinae were copared on red clover or Kentucky bluegrass in constant-teperature tanks at 5-degree intervals fro I0 to 35 C. The optiu teperature for population increase on red clover in 90 days was 30 C for Tylenchorhynchus agri, T. nudus, T. artini, and T. clarus, 25 C for T. sylvaticus and 7". dubius, and 20 C for T. canalis, Merlinius brevidens, and Quinisulcius capitatus. The optiu was 30 C for T. robustoides and 25 C for T. axius on Kentucky bluegrass. The teperature range for population increase was C for T. agri, T. nudus, T. artini, and T. clarus, C for T. sylvaticus and T. robustoides, C for T. axius, C for T. dubius, and C for M. brevidens and Q. capitatus. T. canalis increased only at 20 C. All species were recovered in nubers near their inoculu level at 10 C. There was no survival of T. sylvaticus, T. dubius, T. canalis, T. robustoides, T. axius, M. brevidens, and Q. capitatus at 35 C, or of the last three of these species at 30 C. Teperature had no effect on sex ratio in final populations. Population increase was greatest in T. artini and least in T. canalis. Key Words: stunt neatodes, Tylenchorhynchus, Merlinius, Quinisulcius, red clover, Kentucky bluegrass, population developent. Nuerous species of stunt neatodes in the subfaily Tylenchorhynchinae occur in soils of the North Central region of the United States (14, 21). Little attention has been given to the host-parasite relationships and ecological requireents of these neatodes, although certain species are frequently encountered in abundance and in polyspecific counities in the rhizosphere o1 herbaceous plants. While ost of the native species of stunt neatodes are easily cultured on several utual hosts, arked population fluctuations that vary with the species and season of the year have been noted by the author during attepts at increasing greenhouse populations for biological studies. Moreover, in Illinois certain species that are coon associates of herbaceous perennials, such as turfgrasses and clovers, are seldo encountered on the ajor annual row crops corn and soybeans, which are suitable hosts under greenhouse conditions. Other species are frequent associates of both crop types. The reasons for those interspecific distribu- Received for publication 31 July aresearch supported in part by funds fro the Illinois Agricultural Experient Station. 2Associate Professor of Neatology, Departent of Plant Pathology, University of Illinois at Urbana-Chapaign, Urbana, Illinois tional differences are unknown, although differences in soil teperature regies between crop types ay be partially responsible. Teperature requireents aong stunt neatodes are known only for certain populations of Tylenchorhynchus clarus (13), T. claytoni (I1), T. dubius (3, 15) and T. nudus (18, 20). This paper presents results of studies of the teperature preferences of I I species of stunt neatodes apparently indigenous to all or part of the North Central United States. MATERIALS AND METHODS Species of stunt neatodes studied, and their original sources, were: Tylenchorhynchus agri Ferris, soybean (Glycines ax [L.] Merr.), Marion County, Illinois; T. canalis Thorne and Malek, western wheatgrass (Agropyron sithii Rydb.), Pennington Co., South Dakota; T. clarus Allen, creeping bentgrass (Agrostis palustris Huds.), Hailton Co., Ohio; T. dubius Bfitschli, Kentucky bluegrass (Poa pratensis L.), Chapaign Co., Ill.; T. artini Fielding, oats (Arena sativa L.), Chapaign Co., Ill.; T. axius Allen, Kentucky bluegrass, Chapaign Co., Ill.; T. nudus Allen, soybean, Brookings Co., S. Dak.; T. robus- The JOURNAL OF NEMATOLOGY for October (11: ) was issued 18 Deceber 1979.

2 2 Journal o] Neatotogy, Volue 12, No. 1, January 1980 toides Thorne and Malek, western wheatgrass, Pennington Co., S. Dak.; T. sylvaticus Ferris, sugar aple (.4cer saccharu Marsh), Chapaign Co., Ill.; Merlinius brevidens (Allen) Sidiqi, corn (Zea ays L.), Pope Co., Ill.; and Quinisulcius capitatus (Allen) Siddiqi, Kentucky bluegrass, Chapaign Co., Ill. All but two species were cultured on 'Kenland' red clover (Trifoliu pratense L.) in a greenhouse and tested on that host. T. axius and T. robustoides were studied on 'Newport' Kentucky bluegrass, because they failed to increase on red clover in repeated tests. Plants were grown in 10-c-dia plastic pots containing 500 c ~ of Sparta loay fine sand. A 15-l centrifuge tube was pressed 5 c into the soil in the center of each pot at planting. Clover seeds were planted in soil infested with coercial Rhizobiu inoculant, and the seedlings were later thinned to four/pot. Pots for bluegrass were sown with 100 seeds apiece. Neatodes for inoculation were extracted by a odification of the ethod o[ Christie and Perry (6). Two weeks after seeding, a 25-l suspension of 200 neatodes of the appropriate species in all developental stages was poured into the hole resulting fro reoval of the tube. The hole was filled with oist soil, and the pot was watered gently. The pots were arranged randoly on a greenhouse bench where abient teperatures averaged 25 C. Three days after inoculation, each pot was placed in an ipervious plastic container. The ri of the pot was 2 c below that of the container and flush with its side. Four replications for each neatode species were placed randoly in each of six Cornell- type constant-teperature tanks (10) so that the soil line was 2 c below the water level. The tanks were aintained at I0, 15, 20, 25, 30, or C. The pots received 50 l of a 23% N-19% P20~-17% K20 fertilizer solution at days 0 and 45 and 100 l of distilled water when the soil surface becae dry. Natural lighting was suppleented with fluorescent to provide a 14-hr day length. Tests of individual species were initiated consecutively so that they could be terinated at intervals of 3-4 days. Neatodes were extracted 90 days after inoculation by the sae ethod used to obtain inoculu. Nubers/pot were estiated fro counts of replicated one-l aliquots of a 200-l extract suspension or counted in toto when nubers were low. Plant shoots and root systes were over-dried at 80 C for 3 days and weighed for coparison of growth aong teperatures. RESULTS There were distinct differences aong the species in response to teperature and ability to utilize red clover as a host (Fig. 1). Teperature-related differences in population developent included optiu for reproduction, range for reproduction, and survival at upper extrees. Maxiu population increases of T. agri, T. nudus, T. artini, T. clarus, and T. robustoides occurred at 30 C. There was little difference in final populations of T. robustoides between 25 and 30 C, indicating that its optiu ay lie between those teperatures. Increases were greatest at 25 C in T. sylvaticus, T. dubius, and T. axius, and at 20 C in T. canalis, M. brevidens,, and Q. capitatus. T. agri, T. nudus, T. artini, and T. clarus increased in population over a range of C, whereas T. sylvaticus and T. robustoides increased only between 20 and 30 C. Final populations were relatively low at 20 C in these species. In contrast, M. brevidens and Q. capitatus reproduced within the relatively low teperature range of C. T. dubius and T. axius required an interediate range of C, though the forer increased in nubers slightly at 10 C. T. canalis, for which clover was a poor host, increased only at 20 C. All species survived teperatures as low as 10 C, but populations increased at that teperature only in T. dubius, M. brevidens, and Q. capitatus. Populations of T. agri, T. nudus, T. artini, and T. clarus increased substantially at the relatively high teperature of 35 C. The last three of these species increased as well at that teperature as at 25 C. None of the other species survived at 35 C, where exaination of sieve residues following extraction revealed only a few dead neatodes. At 30 C, there was little survival of T. canalis and T. dubius, and none of T. axius, M. brevidens, and Q. capitatus. Teperature had no significant effect on

3 Teperature Response in Tylenchorhynchinae: Malek 3 '5 4 i "4 "3 ID..... OOI I :'~ ogrl I nudus I I to ortlni I ,5 clorus I o Q. '4 n o =E 0 Z I sylvoticus lr I dublus I oxius '3.**., 2 I I l robustolclls, Inoculu level I I~revldens io 2o253ou copltotu lo 2o as3o38 canolis TEMPERATURE (C) FIG. 1. Effect of teperature on population developent of Tylenchorhynchus agrl, T. canalis, T. clarus, T. dubius, T. artini, T. nudus, T. sylvaticus, Merlinius brevidens, and Quinisulcius capitatus on red clover, and of T. axius and T. robustoides on Kentucky bluegrass.

4 4 Journal of Neatology, Volue 12, No. 1, January 1980 the final adult population sex ratio, which was siilar to that in the inoculu. The feale:ale ratio at the optiu teperature for each bisexual species was: T. agri, 2.0; T. nudus, 2.6; T. sylvaticus, 0.9; T. dubius, 1.0; T. robustoides, 1.1; T. canalis, 5.8; and Q. capitatus, 1.1. One ale of T. rnaxius was noted at 20 C and two of M. brevidens at 10 C, but none were found at other teperatures or anywhere in the reaining onosexual species. Populations of ost species increased rapidly at and near their optiu teperatures. T. artini reached the highest level (125,000) of any species and T. canalis the lowest (475). Increases of the different species at their optia on red clover were: T. artini, 625 ; T. agri, 430 ; M. brevidens, 418 ; T. nudus, 157 ; T. clarus, 136 ; Q. capitatus, 121 ; T. dubius, 92 ; T. sylvaticus, 9 ; and T. canalis, 2. T. robustoides and T. rnaxius populations respectively increased 171 and 65 on Kentucky bluegrass. Shoot and root weights of red clover were highest at 20 C in all neatode treatents. Weights of Kentucky bluegrass were greatest at 25 C for shoots and at 20 C for roots. The optiu teperature for population developent of T. agri, T. nudus, T. artini, and T. clarus was well above the optiu for plant growth. The optiu for other species was the sae or only slightly above that for the host. DISCUSSION There was a relatively wide range of teperature preferences aong the species of stunt neatodes, as well as soe correlation between orphology and response to teperature. The group containing T. agri, T. nudus, T. artini, and T. clarus, which have sooth feale tail tips, required relatively high teperatures for axiu reproduction. The optia for those species ay be higher than 30 C, and the upper liit for reproduction appears to be above 35 C. Poor plant growth above 30 C, however, probably restricted feeding sites and thus the degree of population developent. A second group, consisting of T. dubius, T. axirnus, and T. canalis, with annulated feale tail tips, preferred an interediate teperature and could not survive high teperatures. T. robustoides and T. sylvati- cus were exceptions to the orphologicalphysiological correlation. Although they are ost siilar to species in the first group, their teperature responses resebled those of the second group. M. brevidens and Q. capitatus, which differ fro the Tylenchorhynchus spp. in having ore than four lateral lines, required relatively low teperatures for reproduction and could not survive at or above 30 C. Those species appear to have a threshold for reproduction slightly below the 10 C liit of testing. This distinct physiological difference fro the other species biologically supports the division of the genus Tylenchorhynchus sensu taro into the genera proposed by Siddiqi (16, 17). The teperature requireents for population developent of T. nudus and T. dubius were siilar to those reported by other workers. Solik (18) and Solik and Malek (20) found that the optiu for the sae population of T. nudus used in this study is also 30 C on sorghu (Sorghu bicolor Pers.) and spring wheat (Triticurn aestivu L.). Shara (15) reported that 25 C was the preferred teperature for a Netherlands population of T. dubius on ryegrass (Loliu perenne L.). Brzeski (3) indicated that 20 C was the optiu for a Polish population on cabbage (Brassica oleracea L.), a response that was probably related to the cool teperature requireents of the host. The reaction of the Ohio isolate of T. clarus to teperatures below 30 C was siilar to that recorded for a California population of the species on alfalfa (Medicago sativa L.) by Noel and Lownsbery (13), whose upper liit of study was 27 C. Results of this study appear to explain the difficulties encountered in increasing and aintaining cultures of any of these species in the greenhouse, where seasonal teperature fluctuations are often extree. Several years of culturing at this laboratory have shown that species in the T. agri group increase very little during the winter, when soil teperatures often cannot be aintained above 20 C. In suer, these species can be increased rapidly to high population levels. Tile converse is true of M. brevidens and Q. capitatus. Large nubers can be obtained in winter, whereas populations drop to low levels during the suer when daily

5 Teperature Response in Tylenchorhynchinae: Malek 5 soil teperatures frequently rise above S0 C. Little difficulty has been encountered with the other species, although T. canalis and T. sylvaticus have been slow to increase on all of the several hosts tested earlier. The differences aong the species in response to teperature ephasize the need for adequate teperature control in biological studies of these neatodes, particularly in obtaining a true picture of their reproductive potentials and pathogenic capabilities. Suboptiu teperatures, at which population increase was slow and/or plants were tolerant of parasitis, ay have been ajor factors in the inability of past research to deonstrate pathogenicity of species in the T. agri group on red clover (1, 2, 4). Relatively low teperatures ay also have been a factor in soe cases of neatode-induced stiulation of plant growth noted by several workers (1, 2, 5, 7, 12). The results indicate also that differences in soil teperature regies aong crop types is a factor controlling intraregional distribution patterns of soe species of stunt neatodes, particularly in darkcolored soils. The infrequent row-crop association of the low-teperature-requiring M. brevidens and Q. capitatus and other species that cannot withstand high teperatures ay be due to the lack of insulation of the soil surface and upper levels of the profile during early stages of crop growth. Tile effect oe insolation on uch of the profile is enhanced by planting preparation and cultivation of fields before canopy foration in row crops. Mebers of the T. agri group apparently can withstand, and in fact see in prefer, the high teperatures of this environent. Routine analysis of turf saples in Illinois have shown that these species seldo reach the population levels encountered in row crops in this area by the author and Ferris and Bernard (8, 9). Soil teperatures beneath turf in Illinois rarely rise above 25 C, which is suboptiu for reproduction of these species. Stunt neatode populations beneath this and other perennial cover crops are frequently doinated by T. dubius, T. rnaxius, and Q. capitatus, which prefer cooler soils. In eastern South Dakota, however, where teperatures beneath turf are soewhat higher in suer, the therophilic T. nudus is an abundant associate of turfgrasses (19). LITERATURE CITED 1. AMOSU. J. o., and D. P. TAYLOR Interaction of Meloidogyne hapla, Pratylenchus penetrans and Tylenchorhynchus agri on Kenland red clover, Trlfoliu pratense. Indian J. Neatol. 4: AMOSU, J. o., and D. P. TAYLOR Stiulation of growth of red clover by Tylenchorhynchus agri. Indian J. Neatol. 4: BRZESKI, M. W The effect of teperature on developent of Heterodera schachtii Sch. and Tylenchorhynchus dubius Brit. (Neatoda, Tylenchida). Roczn. Nauk Roln., Ser. E, 1(1): CHAPMAN, R. A Developent of Pratylenchus penetrans and Tylenchorhynchus artini on red clover and alfalfa. Phytopathology 49: CHAPMAN, R. A Population developent of Meloidogyne arenaria in red clover. Proc. Helinthol. Soc. Wash. 30: CHRISTIE, J. R., and V. G. PERRY Reoving neatodes fro soil. Proc. Helinthol. Soc. Wash. 18: COURSEN, B. W Biology and hostparasite relationships of the neatode Paratylenchus projectus. M.S. Thesis, Univ. Md., 41 p. 8. FERRIS, V. R., and R. L. BERNARD Seasonal variations of neatode populations in soybean field soil. Plant Dis. Rep. 45: FERRIS, V. R., and R. L. BERNARD Crop rotation effects on population densities of ectoparasitic neatodes. J. Neatol. 3: FERRIS, J. M., B. LEAR, A. W. DIMOCK, and W. F. MAI A description of Cornell teperature tanks. Plant Dis. Rep. 39: ll. KRUSBERG, L. R Investigations on the life cycle, reproduction, feeding habits and host range of Tylenchorhynchus claytoni Steiner. Neatologica 4: MALEK, R. B., and W. R. JENKINS Aspects of the host-parasite relationships of neatodes and hairy vetch. N. J. Agr. Exp. Sta. Bull. 813, 31 p. 13. NOEL, G. R., and B. F. LOWNSBERY Effects of teperature on the pathogenicity of Tylenchorhynchus clarus to alfalfa and observations on feeding. J. Neatol. 10: NORTON, D. C., O. J. DICKERSON, and J. M. FERRIS Neatology in the North Central region, N. C. Reg. Res. Public. 187, 20 p. 15. SHARMA, R. D Studies on the plant parasitic neatode Tylenchorhynchus dubius. Meded. Landbouwhog. Wageningen 71(1): SIDDIQI, M. R On the plant-parasitic neatode genera Merlinius gen. n. and Tylenchorhynchus Cobb and the classification of the failies Dolichodoridae and Belonolaiidae n. rank. Proc. Helinthol. Soc. Wash. 37: SIDDIQI, M. R Structure of the oesophagus in the classification of the superfaily

6 6 Journal o[ Neatology, Volue 12, No. 1, January 1980 Tylenchoidea (Neatoda). Indian J. Neatol. I: SMOLIK, J. D Effects of Trichodorus allius and Tylenchorhynchus nudus on growth o~ sorghu. Plant Dis. Rep. 61: SMOLIK, J. D., and R. B. MALEK Tylenchorhynchus nudus and other neatodes associated with Kentucky bluegrass turf in South Dakota. Plant Dis. Rep. 56: SMOLIK, J. D., and R. B. MALEK Teperature and host suitability studies on Tylenchorhynchus nudus. Proc. S. Dak. Acad. Sci. 51: THORNE, G., and R. B. MALEK Neatodes of the northern Great Plains. I. Tylenchida (Neata: Secernentea). S. Dak, Agr. Exp. Sta. Tech. Bull. 31, 111 p.