Pertanika J. Trap. Agric. Sci. 17(1): 33-42(1994) ISSN: 0126-6128© Universiti Pertanian Malaysia Press

Role of Edaphic Factors on VAM Fungal Colonization andSpore Populations in Certain Tropical Wild Legumes

T. MUTHUKUMAR, K UDAIYAN and S. MANIANMicrobiology Laboratory, Department of Botany

Bharathiar University, Coimbatore 641046Tamil Nadu, India

Keywords: VAM fungi, nodulating legumes, root colonization, spore number, edaphic factors

ABSTRAK

Empat hekacangpembintilan tahunan tropika iaituAlysicarpus monilifer, Desmodium triflorum, Indigoferalinnaei dan Tephrosia purpurea daripada tiga kawasan yang berbeza di Western Ghats ekosistem dikaji untukmenilai status mikoriza mereka. Tindakbalas pendudukan akar mikoriza vesihel-arbuskular (VAM) dan bilanganspora terhadapfaktorfaktor edafi seperti helern1Japan tanah, pHdan N serta P telah dikaji. Walaupun bilangan sporaberbeza di dalam dan di antara kawasan, pendudukan akar yangsetara didapati pada semua tumbuhan di dalamkajian ini. Bilangan spora yang direkodkan adalah tinggi, iaitu antara 15 hingga 165 spora gl tanah. Spora 16spesis kulat VAMyang tergolong dalam heluarga Acaulospora, Glomus dan Scutellospora diasingkan daripada tanahrizosfera.

Secara umum, kelembapan tanah mempunyai kesan positif terhadap pendudukan VAM dan pensporaanhecuali terhadap I. linnaei. pH pula mempunyai perkaitan negatif dengan jangkitan akar pada I. linnaei danT. purperea, tetapi ia tidak mempengaruhi dua spesis lain. Kesan 2-pH he atas pensporaan berbeza berdasarkanspesis induk dan kawasan. Tiada perkaitan umum wujud di antara khasiat tanah, pendudukan akar danbilangan spora tetapi pengaruh N dan P adalah kaunteraktif he atas jangkitan VAM. Kajian ini menunjukkantindakbalas pendudukan akar dan bilangan spora terhadap faktorfaktor edafi adalah lebih merupakan suatufenomena bertumpu dan tidak menyeluruh.

ABSTRACT

Four nodulating annual tropical wild legumes, viz., Alysicarpus monilifer, Desmodium triflorum, Indigoferalinnaei and Tephrosia purpurea from three different regions in the Western Ghats ecosystem were investigated toassess their mycorrhizal status. The response ofvesicular-arbuscular mycorrhizal (VAM) root colonization and sporenumber to edaphicfactors such as soil moisture, pH and available Nand P was analysed. Though the spore numbervaried significantly both within and between sites, a uniformly high degree ofroot colonization was observed for allthe plants in the present study. The spore number recorded was high, rangingfrom 15 to 165 spores gl soil. Sporesof sixteen VAM fungal species belonging to Acaulospora, Glomus and Scutellospora were isolated from therhizosphere soils.

Soil moisture generally had a positive influence on VAM colonization and sporulation except in I. linnaei.The pH correlated negatively with root infection in I. linnaei and T. purpurea, but had no influence in the othertwo species. The effect of 2-pH on sporulation varied with host species and sites. No general correlation existedbetween available soil nutrients, root colonization and spore number but the influence ofNand P was counteractiveon VAM infection. The present study indicates that the response of root colonization and spore number to edaphicfactors is a localised rather than a generalised phenomenon.

INTRODUCTION

Vesicular-arbuscular mycorrhizal (VAM) fungiare ubiquitous and are an important factor inregulating and cycling of nutrients in most natu­ral ecosystems. Information is lacking on how

the composition and distribution of these fungiare affected by climatic and edaphic conditions.Researches in the past were directed mainly tounderstanding the general phenomenon of themycorrhizal symbiosis such as differences in

T. MUTHUKUMAR, K. UDAIYAN AND S. MANIAN

their distribution, effect on host plants and theirability to colonize roots and sporulate. Suchstudies have demonstrated the sensitivity ofindividual species/isolates of VAM fungi to soiland environmental conditions (Mosse et al.1981) .

Spore germination, colonization ofhost rootsand the ability of VAM fungi to influence thegrowth and physiology of the host are affectedby edaphic factors (Daniels Hetrick 1984). Mostof these studies were conducted in potexperiments under simulated field conditions,which have a limited predictive value undernatural conditions although they provide a basicunderstanding of the physiology and ecology ofthe VAM systems (Bethlenfalvay el al. 1982). Theintricacy of various interacting factors in naturalecosystems makes it difficult to assess therelationship between the host plant and its VAMendophyte (Bowen and Bevege 1976; Ross andGillam 1973). Even as the distribution andabundance ofVAM fungi are known to vary withclimatic and edaphic environments, the factorswhich control their actual distribution are poorlyunderstood (Azizah Chulan and Omar 1991).Our ability to manipulate mycorrhizal symbiosisfor agricultural benefits would be limited withouta clear understanding of the role of edaphicfactors on VAM fungal colonization andsporulation.

In the present study, four annual nodulatinglegumes from three different regions in the West­ern Ghats ecosystem were selected for assessmentof their mycorrhizal status and the response ofVAM system to edaphic conditions. Since theresponse of VAM fungi may vary with host age,season etc., it seemed worthwhile to determinethe response of VAM fungi in these annual le­gumes which are available for a short period dur­ing the monsoon. The aims of the present studyare to: 1) assess the mycorrhizal status of the le­gumes under investigation, 2) find out the rela­tionship between edaphic factors and VAM fun­gal root colonization and spore density and 3)use the results from this study as a reference forthe introduction of exotic VAM fungal species infuture experimental studies.

MATERIALS AND METHODS

Study Area and Plants Investigated

The studies were conducted at three differentregions in Western Ghats. Site A, an Acacia domi-

nated jungle of Maruthamalai forest, is locatedat 76og3'N and 11°4'E. It is an offshoot of West­ern Ghats. Site B is Cymbo pogoncaesius dominatedgrassland at the foot of Maruthamalai hills. SiteC, a Teciona grandis dominated dry deciduous for­est at Siruvani, is a part of Nilgiri Biological Re­serve, located at 76°37'N and 100 58'E.

Four annual nodulating legumes Alysicarpusmonilifer DC., Desmodium triflorum W. & A.,Indigofera linnaei Ali and Tephrosia purpurea Pers.,were examined for VAM association and theirrhizosphere soils examined for VAM spores. Soilsamples were collected at 550m, 426.72m and500m MSL from the respective study sites. Totalannual rainfall during the study period was134.6mm at sites A and Band 238mm at site C.

Collection ofSamples

Roots and rhizosphere soil samples werecollected from the three sites between Augustand October 1991, during the monsoon whenthe plants were plentiful. An average of fivesamples for each species were sampled. Plantroots were dug out, washed thoroughly to removethe adhering soil particles and fixed in FAA (5mlformalin, 5ml glacial acetic acid and 90ml 70%ethanol). Rhizosphere soil samples of therespective plant species (collected from differentindividuals) were thoroughly mixed to form acomposite soil sample. The composite sampleswere packed individually in polyethylene bagsfor transport to the laboratory and stored at 4°Cfor future analyses.

Analysis ofSoil Physiochemical Properties

The soil moisture (dried 24h at 105°C) and pH(1: 1, soil: water) were determined soon afterthe soil samples were brought to the laboratory.The available nutrients, nitrogen and phospho­rus were analysed using standard procedures ofJackson (1958) and Misra (1968).

Determination of Mycorrhizal Status

Clearing and Staining ofRoots

The root samples of each species were gentlywashed free of FAA and cut into approximately 1cm long segments. The root segments of the in­dividuals of a species were mixed to form a com­posite sample. The composite sample wascleared by boiling in 10% KOH and the boilingtime varied according to the thickness of the root

34 PERTANlKAJ. TROP. AGRIC. SCI. VOL. 17 NO.1, 1994

ROLE OF EDAPHIC FACfORS ON VAM FUNGAL COLONIZATION AND SPORE POPULATIONS

segments. Cleared roots were acidified (5NHel) and stained with 0.05% trypan blue inlactophenol (Phillips and Hayman 1970). Fiftyroot segments from each composite sample wereexamined for the presence of VAM structures.The percentage root colonization by VAM fungiwas estimated using the root-slide technique ofRead el al. (1976).

VAM Fungal Spore Enumeration

VAM fungal spores were recovered from soil bya slight modification of the wet sieving and de­canting technique of Gerdemann and Nicolson(1963). One hundred grams of soil from eachcomposite sample were dispersed in 500 ml ofwater to form a uniform suspension. The heaviersoil particles were allowed to settle for 10-20 min.The suspension was then passed through a se­ries of sieves ranging from 710-38m. The resi­dues from the sieves were washed into beakers.After the settling of the heavier particles, the sus­pension was filtered through a Whatman No. Ifilter paper. To make spore count easier, lines ata distance of 2 mm were drawn on the filter pa­per and the intact spores were counted under ap­propriate magnification (x100).

Isolation and Identification of VAM Fungal Spores

Intact spores were picked up using a wet needleand mounted in lactophenol for identification.The species ofVAM fungi were identified accord­ing to the sporocarpic and spore characters suchas spore size, colour, spore walls, hyphal attach­ments and other morphological characters(Morton 1988; Schenck and Perez 1987).

Statistical Analyses

Two factor analysis of variance was used to com­pare the variation of root colonization and sporenumber between and within sites. Pearson's co­efficient correlation was used to determine thedegree of association between root colonizationand spore number with edaphic factors. Data onroot colonization and spore number were sub­jected to linear regression analysis (Zar 1984)

RESULTS

The soil at sites A and B was clayey loam and thatat site C was sandy loam. The soils at all the studysites were low in available nutrients especiallyphosphorus (P) (Table 1). The soil pH ranged

TABLE 1Soil characteristics of the sites surveyed in this study

Soil moisture pH

(%)

Site A

Aug.

Sept.Oct.

Mean

Site BAug.Sept.Oct.Mean

Site CAug.Sept.Oct.Mean

SE in parantheses

16.86

20.1327.85

21.61 (1.66)

17.2819.9027.2021.46(2.42)

20.7519.7031.2723.91 (3.01)

8.3

7.77.3

7.8(0.39)

7.47.48.07.6(0.12)

8.08.17.37.8(0.53)

Phosphorus Nitrogen

(mgkg-1) (mgkg-1

)

0.60 9.80

0.50 13.000.60 3.40

0.57(0.04) 8.73(1.83)

1.30 7.400.50 11.100.40 11.600.73(0.22) 10.03(0.99)

2.3 12.601.9 13.900.9 12.601.7(0.47) 13.03(0.53)

PERTANIKAJ. TROP. AGRIe. SCI. VOL. 17 NO.1, 1994 35

T. MUTHUKUMAR, K. UDANAN AND S. MANIAN

from 7.3 to 8.3 and the soil moisture ranged be­tween 16.86 to 31.27% (Table 1).

All the four legumes investigated showed ahigh degree of root colonization under variededapho-climatic conditions (Fig. 2). Rootcolonization showed no variation both within andbetween sites except for A. monilifer whichexhibited a significant variation (P< 0.05) betweensites (Table 2). VAM structures mainly consistedof hyphae and vesicles with arbuscules restrictedto younger regions of the root. The vesicles wereterminal, spherical and/or oval (Fig. 1)

The spore number in the rhizosphere soilranged from 15-165 spores g-l dry soil (Fig. 2).The average spore number recorded were109.78,64.44 and 78.56 spores g-l dry soil at sitesA, Band C respectively. Spore density variedsignificantly both between (P<O.Ol) and withinsites (P<O.Ol) except for 1. linnaei, where thevariation was significant (P<0.05) only betweensites. No variation was observed in T. purpurea(Table 2).

(a)

180

Fig. 1: (a) Arbuscules and distributive hyphae inIndigoferalinnaei; (b) Vesicles in Tephrosiapurpurea; pores of (c) Glomus constirctum; (d)G. monporum with peridial(asterisk) remains;(e)Acauospora scrobiculata; if) Glomu aggregatum.Bars = 50

(c)

..... 160

i~l40~ ~120

.~ j 100

'8 c 80

§ j 60

40

20

(ill A S 0SITE A

o Root colonization

~ Spore mJliler

(b)

..... 140

~j 120

~ ~ 100

~!il

o Root colonization

~ Spore number

S 0SITE C

(d)

o Root colonization

&:':I Spore number

180

160 o Root colonization...-- e 140 &:J Spore IlUlI'berc_e.

120.,

~i100 r+

....,....

0 .... r+.,~l 60

0

~ ~Or(bl A S S S

SITE A SITE 8 SITE CS 0

SITE AS 0

SITE 8S 0

SITE C

Fig. 2: Mean values for the spore number and VAM infection of A. monilifer (a); D. triflorm (b); I.linnaei (c) T.purpurea (d) at different sites during the study period (A, August; S. September; 0, October). Vertical linesindicate ± SE of the mean

36 PERTANIKAJ. TRap. AGRIe. SCI. VOL. 17 NO.1, 1994

ROLE OF EDAPHIC FACTORS ON VAM FUNGAL COLONIZATION AND SPORE POPULATIONS

TABLE 2F values from two-way analysis ofvariance on VAM root colonization and spore number both within and in

between sites. A. monilifer (A.m); D. triflorum (D.t); L linnaei (1.1); T. purpurea (T.p).

Root colonization

Among sitesWithin sites

Am

3.54*1.50

D.t

2.621.13

1.1

0.160.05

T.p

1.551.01

Spore density

Am D.t 1.1 T.p

12.00** 6.91* 4.76* 1.336.70** 7.00** 0.35 0.28

Significant at p=:0.05 and 0.01, respectively

160,--------------,A significant positive correlation (P<O.05)

was established between spore number and rootcolonization in A. monilifer but not in the others.However, the degree and nature of correlationvaried between plant species (Fig. 3).

140,...

120 ,...

Y - 55.24 - 0.216 Xr --0.101 (NS)

o o

(c)

180,--------------,

...80 t- °e /

C1l

fJ::::lc:C1l 6Of- L::c.8- zio<I) . j..~40 t-

20 t-

I I I I I

(a) 20 40 60 80 100 120Root colonization (X)

(d)

120

ot::.

IlO 60 80 100Root colonization (X)

o

I

20

l00Ir---------,-----,

Y - 77.51 - 0. 353X t::.r --0.19'l (NS)

( C)

.~ 100""I

~ so-

(a)

oo

Y - 94. 34 + 1. 60 Xr a 0.473*

160 t­

150 f­13(ff-

_ 120-

80~

t::.-60>-~O ° "0

190 (b) gY - 44.78 + 0.438 X • -;

2170 r - 0.238 (NS) ...

~"150 • ~

4(~c

120.,8- ()~.

~~ 100

<I)

20~ t::.~

... 80 •"~ 0•• • I I I I Ic:

60 ( d) 20 40 60 80 100 120~0 t::. Root colonization (X)a.<I)

40 L::c.L::c.L::c.

20

( b) w ~ 60 M 100 120Root colonization (X)

Fig. 3: Relationship between root colonization and sporenumber in A. monilifer (a); D. triflorm (b) I. lin­naei (c) and T. purpurea (d). Symbols representthe replicates for Site A (0) Site B (0) and Site C( ..*). Significant at P < 0.05, NS Not significant

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 17 NO.1, 1994 37

T. MUTHUKUMAR, K. UDAIYAN AND S. MANIAN

VAM spores belonging to 16 species assignableto Acaulospora (5 spp.), Glomus (10 spp.) and

Scutellospora (I sp.) were isolated from the rhizo­sphere soils (Fig.l; Table 3).

Host plant

TABLE 3Vesicular arbuscular mycorrhizal fungal species isolated from the soils of study sites

VAM fungal species*

Alysicarpus monilifer

Desmodium triflorum

Indigofera linnaei

Tephrosia purpurea

* Collection area: aSite A; bSite B; eSite C.

Soil moisture, pH and nutrient levels influ­enced root colonization and spore density. Asignificant positive correlation (P<0.05) was es­tablished between root colonization and soilmoisture under D. triflorum, while the sporenumber exhibited a highly significant (P<O.Ol)association with soil moisture and P (Table 4).The spore number under T. purpureasignificantly and positively correlated (P<0.05)with soil nitrogen (N), while a highly significantnegative correlation (P<O.Ol) was observed withsoil pH. In general the response of root coloni­zation and spore number to edaphic factorsvaried between sites and host species (Table 4).

DISCUSSION

Tropical soils are characterized by low availablenutrients especially P (Kang and Wilson 1987).

Acaulospora bireticulata Rothwell & Trappe,b,eA. nicolsonii Walker, Reed & Sandersb

Glomus ambisporum Smith & Schencka

G. microcarpum Tul. & Tul."G. monosporum Gerdemann & Trappea,b,e

Acaulospora bireliculata Rothwell & Trappe,b,eGlomus constriclum Trappea,bG. diaphanum Morton & Walker",bG. fasciculatum(Thaxter) Gerd. & Trappe

emnd. Walker & Kos keb

G. multicaule Gerdemann & Bakshia

Acaulospora bireticulata Rothwell & Trappea,b,eA. sporocarpia Bercha,b,eGlomus aggregatum Schenck & Smith emend.

Koskea

G. ambisporum Smith & Schencka

G. diaphanum Morton & WalkerG. mosseae (Nicol. & Gerd.) Gerdemann &

Trappeb

Acaulospora foveata Trappe &Jan0Sa,b,eA. scrobiculata Trappea,b,eGlomus hoi Berch & Trappe,b,eG. fasciculatum (Thaxter) Gerd.& Trappe emend.

Walker & Koske,bScutellospora pellucida (Nicol.& Schenck)

Walker& Sanderse

Nodulating legumes generally require a largeamount of P for optimum growth, nodulationand nitrogen fixation (Hayman 1986). In spiteof having less extensive root systems, legumesare able to fulfil their nutritional requirementsdepending on colonization by native VAM fungi(Bethlenfalvay and Newton 1991). A high inci­dence of root infection in the present investiga­tion supports the fact that the nodulating le­gumes are mycorrhizal dependent.

Phosphorus (P) in the plant has often beenconsidered the only factor controlling mycor­rhizal infection (Menge et at. 1978). Under lowphosphorus nutrition, low P content of plantscould correlate with a decrease in phospholipidlevels; and an increase in root membrane per­meability would favour mycorrhizal infection(Graham et al. 1981; Ratnayake el al. 1978). The

38 PERTANIKAJ. TRap. AGRIC. SCI. VOL. 17 NO.1, 1994

ROLE OF EDAPHIC FACTORS ON VAM FUNGAL COLONIZATION AND SPORE POPULATIONS

TABLE 4Pearson's correlation coefficient (r) for VAM fungal status (Root colonization - RC, Spore number- SN) and soil

characteristics of the legumes at different sites (n = 4) and in general (n = 16).

Site Soil moisture pH Phosphorus Nitrogen

RC SN RC SN RC SN RC SN

A. monilifer A -0.781 -0.682 +0.525 +0.045 -0.785 -0.991 *** +0.999*** +0.664B +0.922** +0.556 +0.792 +0.719 -0.958** -0.287 +0.961 ** +0.212C +0.581 +0.874* -0.549 +0.636 -0.832* -0.885* +0.339 0.240

(+0.328) (-0.010) (+0.328) (+0.008) (-0.248) (-0.306) (+0.498) (+0.126)

D. triJlorum A +0.907* +0.979*** +0.435 -0.853* -0.248 +0.419 -0.447 -0.912*B +0.704 +0.986*** +0.499 +0.996*** -0.994*** -0.655 +0.994** +0.887*C +0.396 +0.975*** -0.303 -0.967** +0.468 -0.475 -0.945** -0.372

(+0.551*) (+0.620**) (-0.417) (-0.122) (+0.019) (+0.620**) (+0.453) (-0.210)

I. linnaei A +0.529 +0.722 +0.447 -0.302 +0.945*** +0.509 -0.928*** -0.177B -0.937** -0.985*** -0.995***-0.996*** -0.503 +0.653 -0.509 -0.659

C +0.512 -0.879* -0.484 +0.863* -0.684 +0.991 *** +0.414 +0.109(+0.070) (+0.140) (+0.070) (-0.189) (-0.215) (+0.346) (+0.446) (-0.420)

T.purpurea A +0.510 +0.599 -0.334 -0.834* +0.898* -0.643 -0.967** -0.015B +0.489 -0.674 +0.252 -0.834* -0.932** +0.057 +0.927** -0.065C +0.999*** +0.045 -0.850* +0.078 -0.791 +0.313 -0.492 -0.258

(+0.437) (+0.140) (+0.192) (-0.647**) (+0.257) (+0.070) (+0.509*) (-0.046)

*,**,*** Correlations are significant at p = 0.05, 0.01 and .001 respectivelyGiven in the parentheses are the general response (combined response of all sites).

low soil P in the study soils and high P require­ment of legumes may explain the high VAMinfection.

The spore number recorded in the presentstudy is many times greater than the previouslyreported numbers from tropics (Al-Garni andDeft 1990; Jasper et al. 1990; Khan 1974; Neerajet al. 1991; Parvathi et al. 1984) which contradictsthe view that perennial ecosystems contain fewerspores than fields subjected to annual distur­bance (Hayman 1982). Louis (1988) also re­ported a high spore number of 64-160 sporesg-l soil from the tropical rain forests in Singapore.The high spore number may be either due toconducive edaphic conditions for sporulationlike low nutrient status, high aeration andoptimum moisture or the undisturbedconditions of the soils, which allowed sufficienttime for the build up of mycorrhizal spores(Azizah Chulan and Omar 1991). The sporenumber varied within and between sites in thepresent study. Spore density is influenced by a

wide range of soil, climatic, fungal and host fac­tors (Anderson et al. 1983- Howerer et al. 1987).

VAM fungal spore number in naturalecosystems is not necessarily related to the abun­dance of VAM infection (Hetrick and Bloom1986). In the present study a significant positivecorrelation was observed only in A. monilifer, butnot in others. Root colonization and subsequentsporulation are reported to vary depending onthe host and fungal species and edaphic factors(Khalil et al. 1992).

Soil moisture, pH and available nutrients (Nand P) had varied influence on VAM fungal in­fection and spore number (Table 4). Soil mois­ture positively correlated with root colonizationin D. triflorum, A. monilifer and T. purpurea. Asimilar influence was found on spore number.Generally VAM fungi are sensitive to soil mois­ture and the optimum moisture for plant growthis also suitable for VAM infection and sporula­tion (Redhead 1975). However, soil moisture hada negative influence on VAM root infection and

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 17 NO.1, 1994 39

T. MUTHUKUMAR, K UDANAN AND S. MANIAN

spore number in 1. linnaei. It is known that spe­cies and strains of VAM fungi differ in their sen­sitivity to soil moisture due to their non-adapt­ability to changing 02 tension (Mosse el al. 1981).

Soil pH had a negative influence on root colo­nization in 1. linnaei and T. purpurea at sites Band C respectively, while its influence was not sig­nificant in others. This not in conformity withthe earlier report that soil pH had no markedeffects on mycorrhizal infection in natural veg­etation (Abbott and Robson 1991). Varying soilpH may affect the development and functioningof VA mycorrhizas (Abbott and Robson 1985;Hayman and Tavares 1985) by altering the con­centration of many nutrients and toxic ions insoil solutions as well as hydrogen ions (Russell1973). The spore number on the other hand wasboth positively and negatively influenced by soilpH in D. triflorum and 1. linnaei at different sites.However, they negatively correlated in T. purpureaand no correlation existed in A. monilifer. Theresponse of VAM fungi to soil pH may dependon the species and strains constituting the in­digenous VAM flora (Robson and Abbott 1989).The variation in response can also be attributedto the host mediated changes of the rhizospherepH. The nitrate reduction process of the mycor­rhizal host changes the pH of the root exudate,which in tum alters the rhizosphere pH, affect­ing pH sensitive micro-organisms includingVAM fungi (Smith and Gianinazzi Pearson1988). The species of Glomus constituted 63%of the total species recorded (Table 3). A neutralto alkaline soil has been reported to favour thepredominance of Glomus species by early workers(Abbott and Robson 1977; Mosse et al. 1981).

No general correlation existed between thesoil P on one hand and the root colonizationand spore number on the other. Soil P had anegative influence on root infection and sporenumber in A. monilifer while it was positive in 1.linnaei. In D. triflorum and T. purpurea, the soil Pnegatively correlated with root infection at siteB, but a positive correlation was evident in thelatter species at site A. However, soil P had noinfluence on the spore number in both thespecies. Previous studies have shown a negativeassociation between the amount of extractablesoil phosphate and the abundance of VAMinfection (Bolgiano et al. 1983; Morita andKonishi 1989) and spore number (Sylvia andNeal 1990). Variations in the response of root

colonization and spore number to soil P can beattributed to a number of factors such asa) VAM fungal species colonizing the roots,

since species and strains vary in their sensi­tivity to P (Trouvelot et al. 1987)

b) the varied host root growth response to chang­ing P levels (Smith 1982) or

c) changes in the cell membrane permeabilityto varying cellular P concentrations, whichaffect the degree of mycorrhizal colonizationand sporulation (Daniels Hetrick 1984).

The response of root colonization and sporenumber to soil N also varied. The influence ofsoil N on root colonization was positive andnegative respectively in A. monilifer and 1. linnaeibut in D. triflorum and T. purpurea, the responsevaried from site to site. Generally, soil N had noinfluence on spore number of these wildlegumes but in D. triflorum the spore numbercorrelated positively with soil N at site A andnegatively at site B . There are reports that N canstimulate or suppress root colonization andspore production through modifications of soilpH (Sylvia and Neal 1990, Thompson 1986).Results of our study also reflect the same trend(Table 4).

An interesting phenomenon observed in thepresent study was the counteractive influence ofsoil P and N on VAM colonization. When thesoil P vs root colonization correlated negatively,it was positive for soil N vs root colonization andvice versa (Table 4). Thus, our results clearlyindicate the decisive influence of soil P and Ninteraction on VAM colonization. It has alreadybeen reported that VAM fungal infection was notaffected by increasing P when plants were Ndeficient, but when N was sufficient P additionssuppressed root colonization (Sylvia and Neal1990) .

The findings of this study emphasize theneed for an understanding of the ecology ofVAMfungi in various ecosystems and soils for the suc­cessful selection and introduction of VAM fun­gal species and strains for a particularenvironment.

REFERENCES

ABBOTI, L.KandA. D. ROBSoN. 1977. The distributionand abundance of vesicular arbuscularendophytesinsome Western Australian soils.Aust. J Bot. 25: 515-522.

40 PERTANIKAJ. TROP. AGRIC. SCI. VOL. 17 NO.1, 1994

ROLE OF EDAPHIC FACTORS ON VAM FUNGAL COLONIZATION AND SPORE POPULATIONS

ARBon, L. K and A D. ROBSON. 1985. The effect ofsoil pH on the formation of VA mycorrhizas bytwo species of Glomus. Aust. J Soil Res. 23: 253­261.

ARBon, L. KandA D. ROBSON. 1991. Factors influenc­ing the occurrence ofvesicular-arbuscular myc­orrhizas. Agri. Ecosystems Environ. 35: 121-150.

AL-GARNI, S.M and MJ. DAFT. 1990. Occurrence andeffectiveness of vesicular-arbuscular mycorrhi­zas in agricultural soils from Saudi Arabia. Biol.Agric. Hortic. 7: 69-80.

ANDERSON, RC., AE. LIBERTA., LA. DICKMAN and A j.KATZ. 1983. Spatial variation in vesicular­arbuscular mycorrhiza spore density. Bull. TorreyBot. Club 110: 519-525.

AzIZAH CHULAN, Hand M. OMAR. 1991. Incidence ofVAM spores in some Malaysian soils. Pertanika14: 133-137.

BETHLENFALVAY, G. j and W. E. NEWTON. 1991.Agroecological aspects of the mycorrhizal,nitrogen-fixing legume symbiosis. In TheRhizosphere and plant Growth, ed. D.L. Keisterand P.B.Cregan, p.349-354. Netherlands: KluwerAcademic Publishers.

BETHLENFALVAY, G. j., R S. PACOVSKY., M. S. BROWNand G. FULLER. 1982. Mycotrophic growth andmutualistic development of host plant and fun­gal endophyte in an endomycorrhizal symbiosis.Plant Soil 68: 43-54.

BOLGIANO, N.C., G.R SAFIR and D.D. WARNCKE. 1983.Mycorrhizal infection and growth of onion inthe field in relation to phosphorus and wateravailability. J Am. Soc. Hortic. Sci. 108: 819-825.

BOWEN, G. D and D. 1. BEVEGE. 1976. Micro-organisms,the third dimension in phosphate nutrition andecology. In Prospectsfor ImprovingEfficiency ofPhos­phorus Utilization, ed. GJ. Blair, p.103-112. Aus­tralia: New England Press.

DANIELS HETRICK, B. 1984. Ecology ofVA mycorrhizalfungi. In VA Mycorrhiza, ed. C. Li. Powell andDJ.Bagyaraj, p. 36-55. Boca Raton, Florida:CRC Press, Inc.

GERDEMANN,j. W. and T. H. NICOLSON. 1963. Spores ofmycorrhizal Endogone extracted from soil by wetsieving and decanting. Trans. Br. Mycol. Soc. 46:235-244.

GRAHAM, j.H., R.T. LEONARD and J.A MENGE. 1981.Membranemediated decrease in root exudationresponsible for phosphorus inhibition ofvesicu­lar-arbuscular mycorrhiza formation. Plant

Physiol. 68: 549-552.

HAYMAN, D. S. 1982. Influence of soils and fertilityon activity and survival of vesicular-arbuscularmycorrhizal fungi. Phytopathology 72: 1119-1125.

HAYMAN, D. S. 1986. Mycorrhizae of nitrogen­fixing legumes. MIRCENJ Appl. Microbiol. Biotech.2: 121-145.

HAYMAN, D.S and M. TAVARES 1985. Plant growthreponses to vesicular arbuscular mycorrhiza.Xv. Influence of soil pH on the symbiotic effi­ciency ofdifferent endophytes. New Phytol. 100:367-377.

HETRICK, B.AD and j. BLOOM. 1986. The influenceof host plant on production and colonizationability of vesicular-arbuscular mycorrhizalspores. Mycologia 78: 32-36.

HOWELER, RH., E. SIEVERDING and S. SAIF. 1987. Practi­cal aspects of mycorrhizal technology in sometropical crops and pastures. Plant Soil 100: 249­283.

JACKSON, N. L. 1958. Soil Chemical Analysis. NewDelhi: Prentice Hall of India Pvt. Ltd.

JASPER, D.A, L.K ARBon and AD. ROBSON. 1990.The effect of soil disturbance on vesicular­arbuscular mycorrhizal fungi in soils from dif­ferent vegetation types. New Phytol. 118: 417­476.

KANG, B. Tand G. F. WILSON. 1987. The developmentofalley farming as a promising agroforestry tech­nology. In Agroforestry: A Decade ofDevelopment,ed. H.A Steppler and P.KR Nair, p. 227-243.Nairobi, Kenya: ICRAF.

KHALIL, S., T. E. LOYNACHAN and H. S. MCNABBJR. 1992.Colonization of soybean by mycorrhizal fungiand spore populations in Iowa soils. Agron. J84: 832-836.

KHAN, AG. 1974. The occurrence ofmycorrhizas inhalophytes, hydrophytes and xerophytes, andof Endogone spores in adjacent soils. J Gen.Microbiol. 81: 7-14.

Louis, I. 1988. Status of mycorrhizal research inSingapore. In Mycorrhizae for Green Asia. Pro­ceedings ofthe First Asian Conference on mycorrhiza,ed. A Mahadevan, N. Raman and K Natarajan,p.22-23. Madras, India.

MENGE,j.A, D. STERILE., DJ. BAGRAYAj., E.L.V.joHNSOand RT. LEONARD. 1978. Phosphorus concen­trations in plants responsible for inhibition ofmycorrhizal infection. New Phytol. 80: 575-578.

MISRA, R 1968. Ecology Work Book. India: Oxford andIBH publishing Co. Pvt. Ltd.

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 17 NO.1, 1994 41

T. MUTHUKUMAR, K. UDANAN AND S. MANIAN

MORITA, A and S. KONISHI. 1989. Relationship betweenvesicular-arbuscular mycorrhizal infectionandsoil phosphorus concentration in tea fields.Soil Sci. Plant Nutr. 35: 139-143.

MORTON,]. B. 1988. Taxonomy of VA mycorrhizalfungi: classification, nomenclature and identifi­cation. Mycotaxon 32: 267-324.

MOOSE, B., D. B. STRIBLEYand F. LE TACON. 1981. Ecol­ogy ofmycorrhizae and mycorrhizal fungi. Adv.Microb. Ecol. 5: 137-210.

NEERA], A, SJ. MATHEW and AVARMA. 1991. Occur­rence of vesicular-arbuscular mycorrhizaewith Amaranthaceae in soils of the Indian semi­arid region. Biol. Fertil. Soils 11: 140-144.

PARVATHI, K, K. VENKATESWARLU and AS. RAo. 1984.Occurrence of VA mycorrhizas on different le­gumes in a laterite soil. Cun: Sci. 53: 1254-1255.

PHILLIPS,].M and D.S. HAYMAN. 1970. Improved pro­cedures for clearing roots and staining para­sitic and VAM fungi for rapid assessment of in­fection. Trans. Br. Mycol. Soc. 55: 158-161.

RATNAYAKE, M., R.T. LEONARD and].A MENGE. 1978.Root exudation in relation to supply ofphosporus and its possible relevance to mycor­rhizal formation. New Phytol. 81: 543-552.

READ, D], H.K KOUCHEKI and]. HODGSON. 1976. Ve­sicular arbuscular mycorrhiza in natural veg­etation systems. I. Occurrence of infection. NewPhytol. 77: 641-653.

REDHEAD,]. F.1975. Endotrophic mycorrhiza in Ni­geria: Some aspects of the ecology of the en­dotrophic mycorrhizal association of Khayagrandiflora C.D.C. In Endomycorrhizas, ed. F. E.Sanders, B. Mosse and P.B.Tinker, p. 447-460.New York: Academic Press.

ROBSON, A D. and L. K ABBOTT. 1989. The effect ofsoil acidity on microbial activity in soils. In SoilAcidity and Plant Growth, ed. AD. Robson, p. 139­165. Sydney: Academic Press.

Ross,]. P and]. W. GILLAM. 1973. Effect ofEndogonemycorrhiza on phosphorus uptake by soybeansfrom inorganic phosphates. Soil Sci. Soc. Am.Proc. 37: 237-239.

RUSSEL, E.W. 1973. Soil conditions andplant growth. Lon­don: Longman.

SCHENK, N. C and Y. PEREZ. 1987. Manual for theidentification of VA mycorrhizal fungi. Florida:University ofFlorida, Gainsville.

SMITH, S. E. 1982. Inflow of phosphate into mycor­rhizal and non-mycorrhizal plants of Trifoliumsubterraneum at different levels ofsoil phosphate.New Phytol. 90: 293-303.

SMITH, S. E. and V. GIANINAZZI-PEARSON. 1988. Physi­ological interactions between syrnbionts in ve­sicular-arbuscular mycorrhizal plants. Ann. Rev.PlantPhysiol. 39: 221-224.

SYLVIA, D. M. and L. H. NEAL. 1990. Nitrogen affectsthe phosphorus responses of VA mycorrhiza.New Phytol. 115: 303-310.

THOMPSON, J. P. 1986. Soilless culture of vesicular­arbuscular mycorrhizas ofcereals: effects of nu­trient concentration and nitrogen source. Can.J Bot. 64: 2282-2294.

TRoUVELoT, A, S. GIANINAZZI and V. GIANINAZZI-PEARsO .1987. Screening of VAM fungi for phosphatetolerance under simulated field conditions. InMycorrhizae in the Next Decade. Proceedings ofthe 7th North American Conference on Mycorrhiza,ed, D.M. Sylvia, L.L. Hung and].H. Graham, p.39. University of Florida, Gainesville, Florida:IFAS.

ZAR,]. H. 1984. Biostatistical Analysis. New Jersey:Englewood Cliffs, Prentice-Hall Inc.

(Received 7July 1993)

42 PERTANlKAJ. TROP. AGRIC. SCI. VOL. 17 NO.1, 1994