Contribution of arbuscular mycorrhizas to biological protection of micropropagated pineapple (,Ananas comosus (L.) Merr) against Phytophthora cinnamomi Rands Jean-Philippe Guillemin, Silvio Gianinazzi, Vivienne Gianinazzi-Pearson and Jean Marchal Guillemin, J.P. 1 , Gianinazzi, S.', Gianinazzi-Pearson, V. 1 & Marchal, J.2 1994. Contribution of endomycorrhizas to biological protection of micropropagated pineapple (Ananas comosus (L.) Mere) against Phytophthora cinnamomi Rands. Agricultural Science in Finland 3: 241-251. (‘ Laboratoire de Phytoparasitologie, INRA-CNRS, Station de Génétique et d’Amdlioration des Plantes, INRA, BV 1540, 21034 Dijon Cedex, France and 2 Laboratoire de Physiologie et Biochimie, CIRAD, FLUOR, Avenue du Vai de Montferrand, BP 5035, 34032 Montpellier Cedex 01, France.) Phytophthora cinnamomi Rands causes root rot of pineapple ( Ananas comosus (L.) Merr.) and the development of this disease is harmful for fruit production. Micro- propagated plants of two varieties, Queen Tahiti and Smooth Cayenne (clone CYO), were inoculated at transplanting from axenic conditions with an arbuscular mycor- rhizal fungus to evaluate the importance of endomycorrhiza development for bio- logical protection against P. cinnamomi. Growth and mineral nutrition of endomyc- orrhizal plants were not affected by different inoculum levels of P. cinnamomi, whilst they were reduced for non-mycorrhizal plants. Root/shoot ratio of endomyc- orrhizal plants was lower than that ofnon-mycorrhizal plants, and the pathogen did not modify this effect except at highest inoculum levels of P. cinnamomi. Endomy- corrhizal colonization was not altered by the pathogen; however symbiotic func- tioning was reduced by the highest concentration of inoculum of Pcinnamomi. Endomycorrhization is an interesting biotechnology for the production of micro- propagatedpineapple. Key words: arbuscular endomycorrhizal infection, bioprotection agent, pathogen fungus, pineapple microplant, plant growth Introduction In soil, plant roots develop in the presence of micro-organisms, some of which can have a pos- itive (e.g. arbuscular mycorrhizal fungi (AMF)) or negative (e.g. pathogen fungi) impact on plant growth. Root rot of pineapple (Ananas comosus (L.) Merr.), caused by the soilborne fungus Phy- tophthora cinnamomi Rands, is a major problem in pineapple production (Mehrlich 1936). This pathogen damages root systems, negatively in- fluences shoot development (Mehrlich 1934) causes the production of fruits without commer- cial interest (Py et al. 1984) and is able to devas- tate plantations (Anderson 1951). The disease is presently controlled by chemical applications (Pegg 1977, Rochbach and Schenck 1985) and/ or by modifying the soil environment before plant- ing (drainage, pH reduction). Several reports have indicated the bioprotec- tive effect of endomycorrhiza formation against pathogens (Gianinazzi et al. 1982, Paulitz and 241 Agricultural Science in Finland 3 (1994) https://www.c-info.fi/en/info/?token=ENMLV1TH1AEOmmL1.oWs1Na7TSkqY5JzcujNSXQ.bCJZzK1az_zUQEMpaKYBqQq5tSxNVsWViNZV8iHLveaTfb1lVSU0BJsNfWqyEF-4YHa3sUHDZnNoATL0KkIji2N5PL59sYsgRQhXe7vHpgGqP0tDnQXvEH7N4-3hEOooXbFKoXDhg8R28bU7A5UHD9iBpDd-pRTMgMywh91wKZ0145J_3zsDFLnJa1xEiPoCzoklpFQa62DUshcBYQKjVIGAxIB-JBRvlEGMC4M1uewi--ZXqpzHh0KfeKNh17JAJoBIJlGL-OrlK_b69Dy2WMa8lAWtY7VYkhblEsUvLhcbqMomD9PkFBU8q3plsBvfMnMmNIJ9z9KiFBxyz8FO9OFaNz69kCsMImyXi0hYmA Linderman 1991). However results are contra- dictory for P.cinnamomi. Whilst an important de- crease in root rot disease was observed for en- domycorrhizal plants of Chamaecyparis lawsoni- ana L. (Bärtschi et al. 1981), the impact of the disease was not modified by endomycorrhization of avocado (Matare and Hatting 1978) or citrus (Davis et al. 1978). The aim of this work was to evaluate the success of AMF as biological con- trol agents against damage by P.cinnamomi in pineapple plant production. Material and methods Two micropropagated pineapple varieties. Queen Tahiti and Smooth Cayenne (clone CYO), were used. Experiments were carried out under simu- lated tropical conditions (300(iE s -1 irr2 , 29-25°C, 12h/12h, 70-90% relative humidity). Microprop- agated plants were inoculated at transplanting from axenic conditions with root fragments of Tephro- sia ehlenbergiana infected by an isolate of Glomus sp. (LPA2I). Inoculation was performed in seed trays containing a mix (1:1, v:v) of y-irradiated (lOkGy) acid soil (Marlins, pH 5.0) and steam- sterilized gravel (Guillemin et al. 1991). Four weeks later, micropropagated plants were indi- vidually outplanted to pots containing 400 g of the soil-gravel mix. Plant were watered daily with distilled water and twice weekly 20ml of Hoag- land n0.2 nutrient solution (Hoagland and Ar- non 1950) without phosphate was supplied. P.cinnamomi (strain 50, Laboratoire de Pathol- ogic, CIRAD, FLHOR, Montpellier, France) was grown in 30ml of liquid culture at 25°C (Louvel 1975).After one week, the macerated P.cinnamomi culture was diluted in water from 10-fold to 10000-fold (levels 4 to 1). After pre-inoculation with AMF, 30ml inoculum was applied to each plant at outplanting to pots, or one month later. For the later application, only two dilution levels (1:10 (level 4) and 1 : 100 (level 3)) were used. Plant growth was evaluated by leaf area (Chau- vel 1991), shoot and root fresh weight and shoot dry weight. N, P, K, Ca and Mg contents of shoots were analysed (Warner and Jones 1967, Comité Inter Instituts pour le diagnostic foliaire 1968, 1972). Endomycorrhizal colonization was evalu- ated by the Trouvelot et al. (1986) method (in- tensity of infection in the root cortex (M%) and arbuscular frequency in the root cortex (A%)) after clearing and staining with trypan blue (Philipps and Hayman 1970) and after staining for succinate dehydrogenase (SDH) (living) (Smith and Gianinazzi-Pearson 1990) or alka- line phosphatase (ALP) (functional) (Tisserant et al. 1993) activities. Each treatment consisted of 5 replicates and all data was analysed statistically by Newman- Keuls tests. Results Development of the endomycorrhizal infection The endomycorrhizal colonization was well de- veloped in roots of both pineapple varieties. Eval- uations of infection intensity (M%) were between 83% and 91% after non vital staining with trypan blue (Fig. 1). Values of M% estimated after stain- ing for SDH and ALP activities, to evaluate liv- ing and functional infection respectively, were lower, fluctuating between 48% and 63% for the former, and between 27% and 38% for the latter (Fig. IA, 18, 2A, 2B). P.cinnamomi did not signif- icantly affect infection intensity (M%) for either inoculation time, that is at transplanting to pots (Fig. lA, 2A) or one month later (Fig. 18, 2B). Arbuscule frequency (A%) estimated by trypan blue and ALP staining was significantly reduced for the Queen Tahiti variety in presence of the highest inoculum level of P. cinnamomi at out- planting to pots (Fig. 1C). For the Smooth Cay- enne variety, reduction of A% was observed only for ALP staining and after inoculation of highest concentration of the pathogen at outplanting to pots (Fig. 2C). Development of P cinnamomi infection No necroses were observed on roots of non-myc- orrhizal and endomycorrhizal plants infected by 242 Agricultural Science in Finland 3 (1994) P. cinnamomi at any concentrations of the patho- gen inoculum. Plant growth The important development of the AMF in roots of both pineapple varieties was reflected in the better growth of endomycorrhizal plants, with or without P. cinnamomi (Tables 1,2, 3,4). Effect of P. cinnamomi at outplanting to pots P. cinnamomi significantly decreased shoot growth of non-mycorrhizal plants of the Queen Tahiti variety at all dilutions whilst such a negative ef- fect was only observed for endomycorrhizal plants at the highest inoculum level of the pathogen (Table 1). All concentrations of P. cinnamomi sig- nificantly decreased root growth of non-mycor- rhizal plants whilst root growth of endomycor- rhizal plants was only negatively influenced by the two higher levels of pathogen inoculum (Ta- ble 1). Shoot and root growth of endomycorrhiz- al plants, whether infected or not by P. cinnamo- mi, was always greater than that of non-mycor- rhizal plants. Plants of the Smooth Cayenne variety tolerat- Fig. 1. Intensity of infection (M%) (A and B) and arbuscular frequen- cy (A%) (C and D) observed after trypan blue (TB), succinate dehy- drogenase (SDH) and alkaline phosphatase (ALP) staining of roots of endomycorrhizal Queen Tahiti variety of pineapple inocu- lated with P. cinnamomi at differ- ent dilutions at outplanting to pots (A and C) and one month later (B and D). Values for each staining followed by different letters are sig- nificantly different (p = 0.05). 243 Agricultural Science in Finland 3 (1994) ed P. cinnamomi better. Only the inoculum dilu- tions of 1:100 and 1:10 affected shoot growth of non-mycorrhizal plants. For endomycorrhizal plants, shoot growth was not significantly affect- ed by the pathogen at any concentration (Table 2). However, root growth of endomycorrhizal plants was altered by higher levels of pathogen inocu- lum, but values were always greater than those of non-mycorrhizal plants, with or without the pathogen. In these experiments, root/shoot ratios (R/A) of endomycorrhizal plants were always lower than those of non-mycorrhizal plants for both pineap- pie varieties except for endomycorrhizal plants of the Queen Tahiti variety in presence of the high- est level of P. cinnamomi inoculum (Fig. 3A, 3C). In the absence of P. cinnamomi, endomycor- rhiza formation improved shoot mineral contents of the Queen Tahiti variety (Table 5). Pathogen inoculation caused a reduction in the P concen- tration of non-mycorrhizal plants. Decreases in Ca and Mg nutrition were less important for P. cinnamomi-inoculated endomycorrhizal plants. However, N and K concentrations tended to in- crease in the presence of P. cinnamomi in all plants (Table 5). Fig. 2. Intensity of infection (M%) (A and B) and arbuscular frequen- cy (A%) (C and D) observed after trypan blue (TB), succinate dehy- drogenase (SDH) and alkaline phosphatase (ALP) staining of roots of endomycorrhizal Smooth Cayenne variety of pineapple in- oculated with P. cinnamomi at different dilutions at outplanting to pots (A and C) and one month after later (B and D). Values for each staining followed by differ- ent letters are significantly differ- ent (p = 0.05). 244 Agricultural Science in Finland 3 (1994) Table 1, Leaf area (cm2 ), shoot (g) and root (g) fresh mass and shoot dry (g) mass of endomycorrhizal (M) and nonmycorrhizal (NM) Queen Tahiti variety of pineapple, inoculated at outplanting to pots with Phytophthom cinnamomi at different dilutions. Pathogen Leaf area Shoot fresh Root fresh Shoot dry dilution mass mass mass Non-inoculated NM 312.4 b 24.82 b 2.52 b 2.58 b M 482.9 a 37.52 a 3.52 a 3.99 a 1 : 10000 NM 221.5 c 16.84 c 1.78 c 1.74 c M 484.1 a 33.80 a 3.22ab 3.61 a 1 : 1000 NM 165.9 c 13.23 c 1.45 c 1.43 c M 437.1 a 32.65 a 3.09ab 3.30 a I : 100 NM 223.3 c 16.62 c I.Boc 1.72 c M 463.5 a 33.66 a 2.83 b 3.51 a I : 10 NM 240.9 c 17.75 c 1.63 c 1.85 c M 344.0 b 26.07 b 2.85 b 2.43 b Values in a column followed by different letters are significantly different (p = 0.05) Table 2. Leaf area (cm2 ), shoot (g) and root (g) fresh mass and shoot dry (g) mass of endomycorrhizal (M) and nonmycorrhizal (NM) Smooth Cayenne variety ofpineapple, inoculated at outplanting to pots with Phytophthora cinnamomi at different dilutions. Pathogen Leaf area Shoot fresh Root fresh Shoot dry dilution mass mass mass Non-inoculated NM 299.7 b 23.25 b 2.63 c 2.88 b M 640.9 a 54.87 a 5.48 a 5.02 a 1 : 10000 NM 285.5 b 22.37 b 2.42 c 2.31 b M 527.9 a 46.14 a 4.16ab 4.10 a 1 : 1000 NM 373.9 b 23.45 b 2.52 c 2.43 b M 544.3 a 45.44 a 4.35ab 4.36 a 1 : 100 NM 241.0 b 18.27 c 2.03cd 1.73 c M 479.2 a39.05ab3.64b3.43ab 1 : 10 NM 166.6 c 12.65 c 1.74 d 1.24 c M 502.2 a39.02ab 3.86 b 3.71 a Values in a column followed by different letters are significantly different (p = 0.05) Table 3. Leaf area (cm2 ), shoot (g) and root (g) fresh mass and shoot dry (g) mass of endomycorrhizal (M) and nonmycorrhizal (NM) Queen Tahiti variety of pineapple, inoculated one month after outplant- ing to pots with Phytophthora cinnamomi at different dilutions. Pathogen Leaf area Shoot fresh Root fresh Shoot dry dilution mass mass mass Non-inoculated NM 278.1 b 22.14 c 2.49 c 2.09 b M 637.0 a 49.03 a 5.04 a 4.64 a 1 : 100 NM 272.6 b 21.86 c 2.29 c 2.09 b M 590.9 a40.14ab 3.77 b 4.08 a 1 : 10 NM 230.2 c 16.99 d 1.49 d 1.59 c M 549.8 a38.14ab 4.15ab 3.94 a Values in a column followed by different letters are significantly different (p = 0.05) 245 Agricultural Science in Finland 3 (1994) Table 4. Leaf area (cm 2 ), shoot (g) and root (g) fresh mass and shoot dry (g) mass of endomycorrhizal (M) and nonmycorrhizal (NM) Smooth Cayenne variety of pineapple, inoculated one month after outplanting with Phytophlhora cinnamomi at different dilutions. Pathogen Leaf area Shoot fresh Root fresh Shoot dry dilution mass mass mass Non-inoculated NM 299.7 b 23.25 b 2.63 b 2.88 b M 640.9 a 54.87 a 5.48 a 5.02 a 1 : 100 NM 244.2 b 20.07 b 2.54 b 2.02 b M 540.6 a 46.16 a 4.40 a 4.44 a 1 : 10 NM 287.7 b 23.06 b 2.44 b 2.25 b M 523.1 a 44.22 a 4.18 a 4.01 a Values in a column followed by different letters are significantly different (p = 0.05) Fig. 3. Root/shoot ratios of non- mycorrhizal (NM) and endomyc- orrhiza! (M) Queen Tahiti (A, B) and Smooth Cayenne (C, D) vari- eties of pineapple inoculated with Phytophthora cinnamomi at differ- ent dilutions: A, C) at outplanting to pots and B, D) one month later. Values followed by different let- ters are significantly different (p = 0.05). 246 Agricultural Science in Finland 3 (1994) Table 5. Mineral concentration (% of dry mass) of shoot of nonmycorrhizal (NM) and endomycorrhizal (M) Queen Tahiti variety of pineapple inoculated with Phytophthora cinnamomi at different dilutions at outplanting to pots Pathogen dilution N P K Ca Mg Non-inoculated NM 1.72 0.10 3.83 0.83 0.33 M 1.83 0.12 3.87 0.91 0.36 I : 10000 NM 1.82 0.07 4.40 0.64 0.27 M 1.87 0.14 4.03 0.84 0.36 1 : 1000 NM 1.80 0.06 4.47 0.68 0.27 M 1.90 0.11 4.03 0.76 0.31 1 : 100 NM 2.45 0.08 4.62 0.74 0.28 M 1.89 0.11 4,10 0.83 0.34 1:10 NM 1.90 0.09 4,40 0.82 0.32 M 2.22 0.14 4.42 0.90 0.36 Table 6. Mineral concentration (% of dry mass) of shoot of nonmycorrhizal (NM) and endomycorrhizal (M) Smooth Cayenne variety of pineapple inoculated with Phytophthora cinnamomi at different dilu- tions at outplanting to pots Pathogen dilution N P K Ca Mg Non-inoculated NM 2.03 0.13 4.46 1.05 0.35 M 1.99 0.13 4.07 1.17 0.34 I : 10000 NM 2.21 0.11 4.68 1.11 0.32 M 1.99 0.17 3.81 1.19 0.35 I : 1000 NM 2.04 0.11 3.90 1.12 0.34 M 2.02 0.15 4.14 1.23 0.35 I : 100 NM 1,95 0.09 4.20 1.05 0.33 M 1.96 0.17 3.94 1.23 0.38 1 : 10 NM 2.07 0.08 4,71 1.07 0.33 M 1.99 0.17 3.68 1.18 0.37 For the Smooth Cayenne variety, positive ef- fects of endomycorrhiza on P, Ca and Mg nutri- tion was more important in presence of the path- ogen (Table 6). N and K concentrations were not modified by P. cinnamomi inoculation and were generally slightly lower for endomycorrhizal plants (Table 6). Effect ofP. cinnamomi one month after outplanting to pots In contrast to non-mycorrhizal plants, shoot growth of endomycorrhizal plants of the Queen Tahiti variety was not altered by P.cinnamomi inoculation (Table 3). However, the root growth of both endomycorrhizal or non-mycorrhizal plants of this variety was reduced by the patho- gen (Table 3). P.cinnamomi did not affect shoot or root growth of the Smooth Cayenne variety (Table 4). As could be expected, root/shoot ratios were lower in endomycorrhizal plants, with the exception of the Queen Tahiti variety in presence of the highest level of P. cinnamomi inoculum (Fig. 38, 3D). Endomycorrhization increased P, Ca and Mg 247 Agricultural Science in Finland 3 (1994) Table 7. Mineral concentration (% of dry mass) of shoot of nonmycorrhizal (NM) and endomycorrhizal (M) Queen Tahiti variety of pineapple inoculated with Phylophthora cinnamomi at different dilutions one month after outplanting to pots Pathogen dilution N P K Ca Mg Non-inoculated NM 2.21 0.09 5.12 0.80 0.27 M 1.77 0.15 3.54 1.03 0.36 1:100 NM 1.97 0.08 5.04 0.73 0.28 M 1.63 0.14 3.57 0.96 0.38 1:10 NM 2.33 0.11 5.11 0.84 0.32 M 1.75 0.15 3.95 0.99 0.37 Table 8. Mineral concentration (% of dry mass) of shoot of nonmycorrhizal (NM) and endomycorrhizal (M) Smooth Cayenne variety of pineapple inoculated with Phytophthora cinnamomi at different dilu- tions one month after outplanting to pots Pathogen dilution N P K Ca Mg Non-inoculated NM 2.03 0.13 4.46 1.05 0.35 M 1.99 0.13 4.07 1.17 0.34 I : 100 NM 2.18 0.12 4.87 1.02 0.33 M 2.27 0.15 4.28 1,24 0.35 I : 10 NM 2.19 0.08 4.66 1.18 0.33 M 1,94 0.17 3.89 1.21 0.36 nutrition of the Queen Tahiti variety with and without P cinnamomi (Table 7). However, N con- centration of endomycorrhizal plants was less (phenomenon of dilution). The effect of the sym- biotic fungus on P nutrition was more important in presence of the pathogen for the Smooth Cay- enne variety (Table 8). For both varieties, N and K contents were lower in endomycorrhizal plants and P. cinnamomi inoculation did not modify this effect (Tables 7,8). Discussion Experiments with both pineapple varieties showed that the endomycorrhizal effect on plant growth was not influenced by P cinnamomi, except for the Queen Tahiti variety in the presence of the highest concentration of pathogen, when patho- gen inoculation was carried out at outplanting to pots. The negative effect of P. cinnamomi on non- mycorrhizal plants was likewise important for the Queen Tahiti variety when inoculation was per- formed at outplanting to pots. Pathogen inocula- tion did not alter endomycorrhizal colonization of this variety roots but the highest concentration of inoculum depressed fungal activity (arbuscule formation, ALP activity and endomycorrhizal ef- fect). The reduction in endomycorrhizal plant growth could be explained by a less efficient en- domycorrhizal symbiosis in the presence of P. cinnamomi. The influence of the pathogen depends on sev- eral factors. Although root necroses were not ob- served both varieties of micropropagated pineap- ple showed varying susceptibility to negative ef- fects of P. cinnamomi. Better shoot growth of the Smooth Cayenne variety following colonization 248 Agricultural Science in Finland 3 (1994) by AMF was less affected by P. cinnamomi than that of the Queen Tahiti variety. The level of pathogen inoculum influenced plant growth in a similar way to that reported by Davis and Menge (1981) for citrus, with growth of endomycorrhiz- al pineapple being decreased at higher levels of P. cinnamomi inoculum. The protective effect of the symbiosis can also change with the AMF. Bärtschi et al. (1981) showed that it was more interesting to inoculate with a mixture of symbi- otic fungi to ensure good plant growth and a good level of tolerance towards the pathogen. Such a mixture could contain efficient fungi for both min- eral nutrition and protection, and so act synergis- tically to provide more efficient tolerance to the pathogen. It is well known that AMF positively influ- ence P nutrition of plants (Harley and Smith 1983) and increases in P nutrition have been sug- gested to decrease root membrane permeability, therefore reducing and modifying root exudation (Ratnayake et al. 1978). Root exudates of en- domycorrhizal plants have been reported to con- tain more arginine and reducing sugars (Baltrus- chat and Schönbeck 1975), and changes in exu- date composition can modify rhizosphere popu- lations and decrease pathogen activity (Graham and Menge 1982). Meyer and Linderman (1986) reported reductions in sporangia and zoospore pro- duction by P. cinnamomi in rhizosphere soil ex- tracts from endomycorrhizal roots. Better absorp- tion of P by endomycorrhizal roots could also counterbalance pathogen damage (Davis and Menge 1980), but P is probably not the only factor contributing to pathogen tolerance (Gra- ham and Egel 1988). The present study on pine- apple shows that the influence of P. cinnamomi also depends on the age of the two varieties at the time of pathogen inoculation and that this is modified by endomycorrhiza infection. Non-my- corrhizal plants were more severely affected by early inoculation with the pathogen but no such difference was observed with endomycorrhiza for- mation, indicating modifications in the physiolo- gy of the plant. Endomycorrhiza can influence other aspects of plant physiology than mineral nutrition. As could be expected, they modified biomass distribution in pineapple, root produc- tion being lower in relation to that of shoots. However, the application of the highest inoculum level of P. cinnamomi inversed this proportion for Queen Tahiti variety, suggesting that the en- domycorrhizal plants may have produced a more important root system to support the pathogen. AMF can also influence phenol metabolism and root lignification (Dehne and Schönbeck 1979), making plants better adapted to resist to patho- gen aggressions. Other micro-organisms can show a potential for biological control of Phytophthora root rot, such as antagonistic bacteria and fungi (Broad- bent and Baker 1974, Gees and Coffey 1989, Ownley and Benson 1992). Calvet et al. (1993) have reported the synergistic action of a fungal antagonist with an AMF in increasing marigold growth in the presence of Pythium ultimum. This effect may be through increases in the population of the antagonistic micro-organism under the in- fluence of AMF (Secilia and Bagyaraj 1987), and opens the possibility of using both groups of mycoflora for improving biocontrol of the root pathogen. Conclusion AMF can be considered as potential biological control agents contributing to tolerance to P cin- namomi in pineapple; the Smooth Cayenne vari- ety may be more tolerant to P. cinnamomi ag- gression. 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Manuscript received December 1993 SELOSTUS Mykorritsasienten merkitys biologisena torjuntakeinona Phytophthora cinnamomi -tautia vastaan mikrolisätyllä ananaksella (Ananas comosus (L.) Merr). Jean-Philippe Guillemin' , Silvio Gianinazzi 1 , Vivienne Gianinazzi-Pearson 1 ja Jean Marchal2 1 Laboratoire de Phytoparasitologie, INRA-CNRS, Dijon, Ranska ja 2 Laboratoire de Physiologic et Biochimie, CIRAD, FLHOR, Montpellier,Ranska Phytophthora cinnamomi Rands aiheuttaa ananaksessa sa- toa alentavaa juurilahoa. Tutkimuksessa selvitettiin arbus- kelimykorritsasienisiirrostuksen vaikutusta P. cinnamomi- sientä vastaan ananaslajikkeilla Queen Tahiti ja Smooth Cayenne. Mykorritsasieni siirrostettiin ananaksen pikku- taimiin in vitro -vaiheen jälkeen. Erisuuruiset P. cinnamo- mi -tartutemäärät eivät vaikuttaneet mykorritsallisten kas- vien kasvuun ja ravinteiden ottoon, mutta mykorritsatto- milla kasveilla P. cinnamomi alensi sekä kasvua että ra- vinteiden ottoa. Mykorritsallisten kasvien juuri/verso -suh- de oli pienempi kuin mykorritsattomien kasvien eikä P. cinnamomi vaikuttanut suhteeseen muulloin kuin käy- tettäessä suurimpia tartutemääriä. Taudinaiheuttajan vai- kutus juurten mykorritsasieni-infektioon oli vähäinen, mut- ta symbioosin toiminta heikkeni suurimmilla P. cinnamo- miin tartutemäärillä. Mykorritsasienten hyödyntäminen on mielenkiintoinen bioteknologian sovellutus mikrolisätty- jen ananastaimien tuotannossa. 251 Agricultural Science in Finland 3 (1994)