ADAPTATION OF VESICULAR-ARBUSCULAR MYCORRHIZAE TO EDAPHIC FACTORS*

Transcription

1 Sea Phytol. (1980) 85, ADAPTATION OF VESICULAR-ARBUSCULAR MYCORRHIZAE TO EDAPHIC FACTORS* BY D.H.LAMBERT Laboratory for Environmental Studies, Ohio Agricultural Research and Development Center, Wooster, OH H. COLEJR.t AND D.E. BAKERJ Departments of Plant Pathology f and Agronomy,% The Pennsylvania State University, University Park, PA 16802, U.S.A. SUMMARY In threefieldsoils, birdsfoot trefoil {Lotus cormculatus L.) transplants infected with mycorrhizal fungi from 42 soils showed no clear superiority of strains from these individual soils after a year's growth. Differences among strains decreased with time and were only significant for all three soils at the first cutting. There were Jow-level correlations between yield and various chemical properties of the soils from which the cultures were derived. In the greenhouse, with sterilized soils low in P, trefoil yield was always greatest when the inoculum used was indigenous to the soil in which the plants were grown as compared to inocula from five different soils. These results suggest that indigenous strains of mycorrhizal fxingi ma.y possess an adaptation to edaphic factors and that the performance and persistence of strains otherwise more efficient in nutrient uptake may be limited hy their lack of adaptation. INTRODUCTION Interest in field-scale inoculation of plants with endomycorrhizal fungi has centred on the establishment of mycorrhizae in mineral wastes (Lambert, 1979) and fumigated soil (Hattit^h and Gerdemann, 1975), or on improvement of the quality or quantity of inoculum in low-phosphorus soils having an existing mycorrhiza! flora. Plants may respond differently to differing fungal species (Powell, 1975), and fungi interact differentially with soil types (Mosse, 1972; Mosse, 1975). Mycorrhizal fungi also vary in their response to ph (Mosse, 1972; Mosse, Hayman and Arnold, 1973; Green, Graham and Schenck, 1976; Lambert, 1979), temperature (Schenck, Graham and Green, 1975), high phosphorus (Powell and Daniel, 1978), and plant species (Bevege and Bowen, 1975; Powell, 1977 c). Any other factor, such as Zn or Mn availability (Hepper and Smith, 1976) which is deleterious to fungi might similarly affect some fungal species or strains more than others. Adaptability to edaphic factors can affect the performance of fungi introduced into soils where mycorrhizal inoculum is absent or has been eliminated, but adaptation is crucial if introduced strains are to compete successfully with indigenous strains already present in the soil. Economic justification for inoculation with mycorrhizal fungi requires a sustained improvement in plant performance so that it is superior to and more persistent than that obtained by phosphorus fertilization. This study compares the performance of indigenous and non-indigenous mycorrhizal fungi in sterilized soils, and assesses differences in top Contribution No. 1088, Departmeat of Plant Pathology, The Pennsylvania Agricultural Experiment Sution. Authorized for publication 19 July, 1979 as Jounial Series Paper No X/80/ I-08 $02.00/ The New Phytoiogist

2 514 D.H.LAMBERT, H. COLE, JR. AND D.E.BAKER dry wt over a 1-year period of field-grown plants inoculated with mycorrhizal fungi from a number of different soils. MATERIALS AND METHODS Three soils were used; a poorly drained Andover sandy loam derived from sandstone with a ph of 5-7, 7 mg P per kg soil (extracted with a 0-03 N NH4F and 0-25 N HCl solution), 0-2, 1-7, 4-2, and ll-2mequiv. loog^^k, Mg, Ca, and cation exchange capacity (CEC) respectively; a well-drained Hagerstown clay loam derived from limestone havingaph of 7-2,4mgK-iextractableP,andO-2,0-6,15-O,andl5-9mequiv. 100 g-' of K, Mg, Ca and CEC; and a droughty, shallow Edom-Weikert gravelly loam derived from shale with a ph of 7-5, 6 n:^ extractable P, and 0-29, 0-3, 15'0, and 15-7 mequiv.loo g"*^ of K, Mg, Ca and CEC. The vegetation at these sites was mostly grass-legume with weeds typical of old fields but without birdsfoot trefoil {Lottis comiculatus L.). In addition to these three soils, 39 other U.S. soils, mostly from the Mid-Atlantic and Northern Great Plains areas, were collected for use as sources of mycorrhizal fungi. The phs of these ranged from 3-8 to 8-1, the extractable P's from 3 to 130 mg K-^ and the vegetation types from humid forest to sagebrush. All soils were analysed by Baker's new soil test (Baker, 1973) for Ca, Mg, K, Na, and DTPAextractable amounts of Zn, Cu, Fe, Mn, and Al. With this test, results are reported as extractable amounts and as calculated availabilities expressed as negative logarithms. Adaptation in steriuzed soils To obtain seedlings inoculated with different sources of mycorrhizal fungi, birdsfoot trefoil seeds were germinated and grown in six soils mixed v«th vermiculite, including the Andover, Hagerstown, and Edom-Weikert, an alluvial Basher soil (ph 7-0, 19 mg K~^ extractable P, clover-grass vegetation), a Hagerstown-Morrison sou derived from limestone and sandstone (ph 6-0, 20 mg K~^ P, mixed hardwood vegetation), and a sodic mollisol (Chernozem) from Montana (ph 8-1, 5-1 n^ K~^ P, wheat and grass vegetation). A seventh set of seedlings was included as a nonmycorrhizal control. All seedlings were inoculated with the appropriate Rkizobium strains for trefoil. The three main (potting) soils were steam-sterilized and fertilized with either 0 or 100 mg P as ground monocalcium phosphate per kg of soil. Three seedlings each were transplanted into 4-litre pots in a 3 (soil) x 7 (inoculum) X 2 (P) factorial design replicated five times. The trefoil foliage was cut at a height of 5 cm after 60 days and at a height of 1 cm after an additional 50 da3rs and dry wts of the cuts were determined. The dry wt data for the two cuttings were combined and subjected to anal]7sis of variance (AOV). Because the productivity of the three soils varied, the weight of each pot's cuttings was divided by the average weight of all plants growing in the same soil with the same level of P. These data were analysed for mean differences with Duncan's modified least significant difference (DMLSD) test. In addition, the yields of the six inoculation treatments within each soi!-p level combination were ranked, and the rankings of those three combinations with the same source of inoculum as potting soil were averaged for each of the two P levels. The percentile rankings of these combinations having their indigenous strains of mycorrhizal fungi were then determined, based on the distribution curve for the 216 (6*) possible rank combinations for the three soils.

3 VA mycorrhizae and edaphic factors 515 Adaptation in non-sterilized field soils Mycorrhizal inoculum was prepared from 42 soils by wet-sieving and retaining a 50 to 250 ^m fraction which contained fine sand and mycorrhizal spores. This procedure was used to concentrate the mycorrhizal spores, to reduce the numbers of other organisms, and to avoid nutrient carry-over. The sand containing spores was packed into several 10 cm plastic straws and seeded with sweet clover {Melilotus alba Desr.). The infected seedlings and inoculum were subsequently transferred into 1-litre pots of sterilized soil which were seeded with sudangrass {Sorghum bicolor (L.) Moench), on which additional mycorrhizal spores developed. This soil was then placed in corrugated foam flats (test tube shipping containers) and a seedlii^ of birdsfoot trefoil previously inoculated -with Rhizobium was placed in each hollow. A nonmycorrhizal control, grown in sterilized soil -without inoculum, was also included. After 1 month, each seedling's roots in its cylinder of soil was wrapped in porous tissue paper. At this time (early June), these seedlings were space-planted 25 cm apart at random with ten replications in Andover, Hagerstown, and Edom- Weikert field plots which had been sprayed 2 weeks earlier with 2-11 ha""- glyphosate to suppress the existing vegetation. In late July, late September, and the following June, each plant was cut at a height of 5 cm above the groimd and its dry wt was recorded. These data were analysed by AOV and DMLSD test. Correlations were also determined between individual cutting yields for each soil and the various chemical parameters of the soils used as inoculum sources. RESULTS Adaptation in sterilized soqs In the low-p treatments, the highest yields for each soil were obtained when the trefoil was infected with the mycorrhizal fungi from the same soil, i.e. the indigenous strains (Table 1). The probability of the indigenous strains ranking first in all three soils by chance is < (1/216). Certain treatment means were significantly greater than those of others in the same soil or with the same inoculum. Inoculum 1 performed significantly better in soil 1 than in the other soils and inoculum 6 did well only in soil 2. The soil x inoculum, P x soil, and P x soil x inoculum interactions were all significant (Table 2). Dry -wt yields and certain parameters of the soils from which the fungal cultures were derived were correlated in three instances. Yield was directly correlated with available Mn and poor drainage in the Andover soil treatments, and negatively correlated with poor drainage in the Hagerstown soil treatments. Although all soils were watered uniformly in the greenhouse, less water was lost to drainage in the Andover soil, simulating its poorer drainage in the field. Available Mn in the Andover soil in the greenhouse was high enough to induce Mn toxicity symptoms. In the high-p treatments, where trefoil grew well without mycorrhizae, the highest dry -wts were not associated with the indigenous strains although no other combinations were significantly better and the average rank of the indigenous strains fell at the 79th percentile. There were few significant differences among the soil-inoculum combinations although the soil x inoculum interaction was significant (P = 0-01) for the high P treatments analysed separately.

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5 VA mycorrhizae and edaphic factors 517 Table 2. Analysis of variance table for the top dry wu of birdsfoot trefoilgroum in three soils leitk mycorrhizal inoculum from six soils {pbis a non-inoculated control) at two rates of phosphorus fertilization Sourcef if. Mean squares Blocks P Soils Inocula P X Soils P X Inocula Soils X Inocula P X Soils X Inocula Residual 4 i " *»» 3825" "* **» 13-64* 6-86 In an independent analysis, the interactions of blocks with other effects were not significant at the 005 level. f Blocks and soils analysed as random eflfects, inocula and P as fixed effects., and indicate statistical significance at the 0 05, 0 01, and levels of probability. Adaptation in non-sterilized field soil In the field, where competing indigenous fungi were present, there were significant difi^erences among inoculum treatments for all soils at the first cutting (Table 3). The yields of trefoil inoculated with indigenous strains in the Andover and Hagerstown soils were significantly lower than the highest means in this cutting but not in subsequent cuttings. In general, the performance of plants inoculated with mycorrhizal fungi from the same soil or a soil of the same series was only average (Table 3). There were no significant differences between means of the inocuia for two of the three soils at the second and third cuttings. Although a wide range in treatment means persisted, variation among plants within means was also large. With the exception of the third Andover cutting, all F test values declined with time, i.e. differences among treatments decreased progressively. Non-inoculated seedlings, which were stunted at planting time, continued to grow poorly into the second year, although they presumably developed mycorrhizae. In eight of the nine soil-cutting combinations the two poorest treatments were the non-inoculated control and that with inoculum from the most acidic soil, which had very little mycorrhizal infection at the time of transplanting. No single inoculum did well in all soils over the entire period of the experiment. The two best treatments in the first cutting, with average ranks in the three soils of 2-3 and 5-3, declined in rank to 19-0 and 12-7 by the third cuttbg. The probability of the random occurrence of an average rank < 10-0 = 0-05, < 6-0 = 0-01, and < 3-0 = The soil x inoculum interaction was significant for the first cutting {P = Q-OOI) but not for later cuttings (P > 0-5). There were low level correlations (< 0-05 but > 0-01) between shoot yield and various chemical parameters of the 42 soils from which the mycorrhizal inocula were obtained (Table 3). Such correlations were not constant with time, and few could be related to specific properties of the field soils in which the trefoil was grown. Associations with Na, Al and the transition metals occurred in the three field soils where their ranks were intermediate, ranking from 12th to 32nd among the 42 soils. There were associations with extreme properties of the Andover field soil, which had the

6 D. H. LAMBERT, H. COLE, JR. AND D, E. BAKER Table 3. Top dry wu of birdsfoot trefoilgrotm in ttfree field soils andpre-inoadated with mycorrhisial fungi from 42 soils and the correlations of these tots with edaphic parameters of the 42 culture soils Soil Andover Hagerstown Edom-Weikert Cutting 1st 2nd 3rd lst 2nd 3rd let 2nd 3rd Range of mean dry wts g/p!ant Characterization of indigenoiis (or similar) inoculum treatments Dry wt t-% 8-8S Ranks 32»t (4) m 41 ns (25) ns 32 ns (14) ns n«37 ns 20 ns (1) ns 22 ns (5) ns 27 ns (6) ns Ftest valuest for differences among inocula 1-90 " 1-25 ns 1-57* 2-34! ns ns 0-89 ns Edaphic parameters correlated with yield (P = 0-05) pzn(-). Zn( + ) i ph(-), pal(-) Cu(-I-) P(-), pk(-h), Cu(+) Fe(-(-), pcu(-), pzn(-) Na{-) f The ratio of treatment mean squares (41 d.f.) to residua] mean squares (332 to 355 d.f.). j *, **, * and ns indicate significance at the 0-05, 0-01, and 0-05 levels of non-significance of the F value or for differences between the mean dry wts of the indigenous inoculum and the inoculum ranking first for the particular saii and cutting combination. 4 Thefirstfigureis for inoculum from the samefieldplot. Thefigure in parentheses is for inoculum from a soil of the same soil series located elsewhere. (1 indicates the highest ranking dry wt). I H- or indicate that the correlation of the parameter with top dry wt is direct or inverse. sixth lowest ph, and the Hagerstown soil, for which available K and P were first and second lowest of the 42 soils. (Note that the signs of the parameters expressed with the negative logarithm p are the inverse of the actual concentration's coefficients). DISCUSSION Mycorrhizal efficiency, the net benefit to the host plant of infection by mycorrhiza] fungi, is a function of a particular set of soil and environmental conditions. Competitive ability and fitness are attributes ^sessed only by the benefit to the fui^s, although they may be affected by the same environmental and host factors as efficiency. Relative aggressiveness, reproductive ability, persistance, etc. are also important. An isoiate's efficiency may be beneficial to the fungus if host vigor is improved, but may also be unrelated or inversely related if extensive growth and spore production occur at the expense of external hyphal growth or result in an excessive drain on host metabolites. Competitive ability may be determined when the species of fungi involved are morphologically distinct {Mosse, 1977; Powell, 1977 b), but is otherwise difficult to quantify. The practical effects of competition between native and introduced strains of mycorrhizal fui^i may be refiected in changes in efficiency (plant yield) over time, although the apparent efficiency of individual isolates might also change with time, e.g. if soil P is being depleted (Powell, 1977c). Results of the greenhouse experiment with sterilized soil are a further indication that a strain's efficiency is dependent on its environment. This experiment also

7 VA mycorrhizae and edaphic factors 519 demonstrates adaptation of indigenous strains to their soils in terms of the strain's ability to benefit the host plant. With competing (indigenous) fungi in the field plots, the performance of plants preinoculated with indigenous strains was not generally superior. The better initial growtii of certain inoculum treatments was ephemeral. Other authors have reported the improved performance of plants inoculated with pure strains of mycorrhizal fungi in comparison to those inoculated with indigenous ones (Mosse, Hayman and Ida, 1%9; Mosse and Hayman, 1971; Jackson, Franklin and Miller, 1972; Mosse, 1972, 1975, 1977; Khan, 1975; Powell, 1976, 1977a, b, c; Powell and Sithamparanathan, 1977; Powell and Daniel, 1978), although in most instances the experiments involved either differences in amounts of inoculum, beneficial effects due to early inoculation with the introduced strains, or alterations of the soil's native temperature, moisture regime, ph or fertility. Likewise, competition between introduced and native strains occurred only for a short time or the performance of strains were determined in physically separate treatments. In Powell's papers, mycorrhizal fungi indigenous to certain soils were sometimes inferior to introduced isolates, depending on the particular combination of host plant, fungal species, soil, site, and fertility. These results were attributable to the fact that the indigenous mycorrhizal flora had developed under forest vegetation in infertile soils and had not adapted to pasture species and improved fertility. No single basis for adaptation of mycorrhizal fungi was evident from this study, and it is most probable that numerous factors affect strains differentially, varying in importance with the intensity of the respective stress in any given soil. In the greenhouse, indigenous strains did well although the potting soils were removed from the field and steam sterilized. In this case, increasing P eliminated the advantage of the indigenous strains, either because these indigenous strains were less adapted to high P (Powell and Daniel, 1978) or because the fertilized plants were less sensitive indicators of P deficiency. In the field, initial growth of plants in the low-p, low-k Hagerstown soil was associated with fungal strains from soiis which were also low in these elements. The factors most frequently correlated with yields were Cu and Zn concentrations and availabilities. Excess Zn is toxic to mycorrhizal fungi (Hepper and Smith, 1976; Mcllveen, 1977) and high levels of Cu prevent the establishment of ectomycorrhizae (Harris and Jurgensen, 1977), although smaller addition of Cus appear not to aflect endomycorrhizal citrus (L. W. Timmer, pers. comm.). Ojala, Jarrell and Menge (1978) have reported that response to mycorrhizae is greater in soils having lower amounts of Zn, Cu, Fe and Mn. These elements, as well as Al, which were all correlated with yield (Table 3), vary in their availability with ph, and their concentrations may be of equal or greater importance than H+ per se in the effect of soil acidity on mycorrhizae. With multiple factors conditioning the adaptation of mycorrhizal fungi to soils, interactions between inocula and soils, (and some differential responses to host species), it seems unlikely that a particular strain could improve plant yield in most soils with indigenous mycorrhizal fungi. This generalization may not apply where land renovation has resulted in a change of vegetation, soil ph, or fertility, altering the factors to which native mycorrhizal fungi were adapted. Further investigations of the bases of specificity could be useful in the selection and application of isolates for fumigated or otherwise nonmycorrhizal soils, particularly in those situations where tnycorrhizae establishment or improvement is economically adventageous.

8 52O D. H. LAMBERT, H. COLE, JR. AND D. E. BAKER REFERENCES BAEBR, D. E. (J973). A new approach to soil testing- II. Ionic equilibria involving H, K, Ca, Mg, Mn, Fe, Cu, Zn, Na and S. SoU Science Society of America Proceedings, BEVEGE, D- I. & BOWEN, G. W. (1975). Bndogone strain and host plant differences in development of vesiculai^-arbuscular mycorrhizas. In Endomycorrhizas (Ed. by F. E. Sanders, B. Mosse & P. B. Tinker), pp Academic Press, London. GREEN, N. E., GRAHAM, S. O. & SCHENCK, N. C. (1976). The influence of ph on the germination of vesicular-arbuscular mycorrhizal spores. Mycologio, 68, HARRIS, M. M. & JDHGENSEN, M. F. (1977). Development of Salix and PopuAumycorrhizae in metallic mine tailings. Plant and Soil, 47, HATTINGH & GERDEMAKN (1975). Inoculation of Brazilian sour orange seed with an endomycorrhizal fungus. Phytopathology, 65, HEPPER, C. M. & SMITH, G. A. (1976). Observations on the germination of Endogone spores. Trantactions of the British mycologicat Society, 66, JACKSON, N. E., FRANKUN, R. E. & MILLER, R. H. (1972). Effects of vesicular-arbuscular mycorrhizae on growth and phosphorus content of three agronomic crops. Sot! Science Society of America Proceedings, 36, KHAN, A. G. (1975). Growth effects of veaicular-arbuscuiar mycorrhiza on crops in the field. In Endomycorritiaias (Ed. by F. E. Sanders, B. Mosse & P. B. Tinker), pp Academic Press, London. LAMBERT, D. H. (1979). Mycorrhizae establishment for strip mine revegetation. Ph.D. Thesis, The Pennsylvania State University, University Park, PA. MC1L\'EEN, W. D. (1977). The influence of zinc on the development of vesiculai^arbuscular mycorrhizae in soybean. Ph.D. Thesis, The Pennsylvania State University, University Park, PA. MOSSE, B. (1972). The influence of soil type and Endogcne strain on the growth of mycorrhizal plants in phosphate deficient soils. Review d'ecologie et de Biologie du Sol, 9, MOSSE, B. (1975). Specificity of vesicular-arbuscular mycorrhizas. In Endomycorrhisas (Ed. by F. E. Sanders, B. Mosse & P. B. Tinker), pp Academic Press, London. MOSSE, B. (1977). Plant growth responses to vesicular-arbuscular mycorrhiza. X. Response of Stylosanihes and maize to inoculation in unsterile soils. New Phytologist, 78, MOSSE, B. & HAYMAN, D. S. (1971). Plant growth responses to vesicular-arbuscular mj'corrhiza. II. In unsterilized field soils. Netv Phytologist, 70, MOSSE, B., HAYMAN, D. S. & ARNOLD, D. J. (1973). Plant growth responses to vesicular-arbuscular mycorrhiza. V. Phosphate uptake by three plant spedes from phosphate-deficient soils labelled with «P. New Phytologist, 72, MOSSE, B., HAYMAN, D. S. & IDE, G. J. (1969). Growth responses of plants in unsterilized soil to inoculation with vesicular-arbuscular mycorrhiza. Nature, London, 224, OjALA, J. C, JARRELL, W. M. & MENGE, J. A. (1978). Soil factors affecting the response of Citrus sinensis inoculated with Glomus fasdculatus endomycorrhizae. Agronomy Abstracts ASA/CSSAl SSSA Annual Meetings, Chicago, Dec. 3-8, POWELL, C. LL. (1975). Plant growth response to vesicular-arbuscular mycorrhiza. VIII. Uptake of P by onion and clover infected with different Endogone spore types in ""P labelled soils. New Pkytotogist, 75, POWELL, C. LL. (1976). Mycorrhizal fungi stimulate clover growth in New Zealand hill country soils. Nature, London, 264, 43fr-*38. POWELL, C. LL. (1977a). Mycorrhizas in hill country soils. 11. Effect of several mycorrhizal fungi on clover growth in sterilized soils. New Zealand Journal of Agricultural Research, 20, POWELL, C. LL. (1977b). Mycorrhizas in hill country soils. III. Effect of inoculation on clover growth in unsterile soils. New Zealand youmal of Agricultural Research, 20, POWELL, C. LL. (1977c). Mycorrhizas in hill country soils. V. Growth respionses in ryegrass. Nevi Zealand Journal of Agricultural Research, 20, POWELL, C. LL. & DANIEL, J. (1978). Mycorrhizal fungi stimulate uptake of soluble and insoluble phosphate fertilizer from a phosphate deficient soil. Neui Phytologist, 80, POWELL, C. LL. & SITHAMPARANATHAK, J. (1977). Mycorrhizas in hill country soils. IV. Infection rate in grass and legume species by indigenous mycorrhizal fungi under field conditions. Nev> Zealand Journal of Agricultural Research, 20, SCHENCK, N. C, GRAHAM, S. O. & GREEN, N. E. (1975). Temperature and light effects on contamination and spore germination of vesiculai^-arbuscular mycorrhizal fungi. Mycohgia, 67,

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