35 (3), 119-123 (1996)

Lime-induced chlorosis of grapevine as affected by and root infection with arbuscular mycorrhiza and Pseudomonas fluorescens

by

L. BAVAREsco 1) and C. FoGHER2)

1 ) Istituto di Frutti-Viticoltura and 2) Istituto di Botanica e Genetica Vegetale, Universita Cattolica Sacro Cuore, Piacenza, Italia

S u m m a r y : Grapevine cuttings ( L. cv. Pinot blanc, clone VCR 5), grafted on 3309 C, a lime-susceptible rootstock, SO 4, a medium lime-tolerant rootstock and 41 B, a lime-tolerant rootstock, were grown in pots containing unsterilized calcareous soil. Before potting, the roots of the grafted were inoculated with a suspension of a mutant of Pseudomonas fluorescens and with the vesicular-arbuscu1ar mycorrhizal (VAM) fungus Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, in order to investigate the effect of these microorganisms on the severity of lime-induced chlorosis. The most significant findings were: a) Pseudomonas fluorescens and Glomus mosseae treatments increased Fe and concentrations in the leaves and thus lime tolerance in plants grafted on 3309 C and 41 B; b) the positive effect of VAM treatment was associated with increased levels of root infection and lower root growth; c) the bacterial treatment improved the establishment of VAM fungi; d) fruit quality of the susceptible graft combination raised to the level of untreated Pinot blanc/SO 4 vines due to the root treatments.

Key words : iron chlorosis, grapevine, rootstock, Pseudomonas fluorescens, Glomus mosseae, VAM fungi.

Introduction hydroxamate siderophores under iron stress conditions (BAKKER et al. 1988), the lower availability of iron for Vitis species differ in their degree of susceptibility to pathogenic microorganisms (KLOEPPER et al. 1980) and the lime-induced chlorosis (e.g. BAVAREsco et al. 1994). Vitis supply of iron to the roots (REID et al. 1986). Recent vinifera L. is ranked as lime-tolerant, but with a range of results of BAR-NESS et al. (1992) and WALTER et al. (1994) variation within the varieties (BRANAS 1974). In modern do not fully support this latter statement. Other results , V. vinifera is normally grafted on interspecific (W ASCHKIES et al. 1994) suggest a direct or indirect role of , with a wide range of adaptation to adverse soil fluorescent pseudomonads in the "replant disease" of grape­ conditions. Rootstock tolerance to increasing levels of lime vine. It is therefore evident that lime tolerance of field­ and IPC (index of chlorosis power) has been reported by grown plants, including grapevine, is not only related to GALET (1947), quoted by JUSTE and MENCH (1992), and the plant genome but also to its interaction with rhizosphere PouaET and JusTE (1972); resistance to iron-chloro'sis is re­ microorganisms (MozAFAR et al. 1992). ferred to "Strategy I" response mechanisms at the root level (MARSCHNER 1978; BAVARESCO et al.1991; BRANCADORO et al. 1995). Materials and methods Grapevines growing on calcareous soils can benefit from application with vesicular-arbuscular mycorrhizal (VAM) C u 1 t i vat i o n o f t h e g rap e s : Vitis vinifera fungi and with siderophore-producing pseudomon-ads cv. Pinot blanc, clone VCR 5, was grafted on different root­ (BAVARESCO and FoaHER 1992, 1996 a and b; BAVARESCO et stocks, inducing an increasing degree of lime tolerance: al. 1995). VAM fungi affect the growth of responsive plants 3309 C (V. riparia MICHX. X V. rupestris SCHEELE), SO 4 in different ways; the most important is by increasing the (V. berlandieri PLANCH. x V. riparia MicHx.) and 41 B uptake of some , especially phosphorus, in soils (V. vinifera L. x V. berlandieri PLANCH.). The plants were with low level (GEBBING et al. 1977; BoLAN 1991; grown in pots (9 1) with calcareous soil collected in a vine­ LI et al. 1991; KoTHARI et al. 1991; GEORGE et al. 1994; yard a few days before. The main soil characteristics were: KARAGIANNIDIS et al. 1995), due to a mycorrhizal phosphate­ sandy-silt texture; pH 8.9; carbonates 80 %; active lime uptake transporter (HARRISON and voN BuuREN 1995). Other 32 %; organic matter 0.19 %; P 6 mg kg· 1 soil (Olsen causes for improved growth are changes of the hormonal method); IPC (indice de pouvoir chlorosant or chlorosis balance, of the plant water relations and the suppression of index, according to PouaET and JusTE 1972) 45. 3309 C root pathogens (MARSCHNER 1995; MORANDI et al. 1984). and SO 4 rootstocks are referred to be susceptible to lime, The plant growth-promoting activity of fluorescent while 41 B is ranked tolerant (FREGONI 1980). Before pot­ pseudomonads in the rizosphere is well documented ting, the roots of 6 plants per graft combination were in­ (KLOEPPER and ScHROTII 1981 ); it is related to many fac­ fected by a suspension of a mutant of Pseudomonas tors, including the ability to produce plant hormones such fluorescens, and by an inoculum of the vesicular-arbuscular as IAA (DuBEIKOVSKI et al. 1993), the production of mycorrhizal (VAM) fungus Glomus mosseae (Nicol. &

Correspondence to: Dr. L. BAVARESCO, Universita Cattolica del Sacro Cuore, Facolta di Agraria, Istituto di Frutti-Viticoltura, Via Emilia Parmense, 84, I-29100 Piacenza, Italy. Fax: (0523) 599268. 120 L. BAVAREsco and C. FooHER

Gerd.) Gerd. & Trappe; in addition 6 uninoculated (control) !·Control !loores:ens *G. mosseae plants per rootstock were cultivated. The soil was not steri­ +P. 11 lLso (p 100 ! bud burst the plants were with 2 g N/pot as calcium nitrate, 0.44 g P/pot as liquid , 2.5 g K/pot as potassium 8s;; (/) nitrate and trace elements without iron. 50 Preparation of the bacterial inoculum: Strain EM4 RS of Pseudomonas jluorescens, a spontane­ ous rifampicin- and streptomycin- resistant mutant produc­ ing fluorescent pigments, was isolated from roots of maize as used for the experiment by PouNELLI et al. ( 1991 ). The 200 strain was grown on a nutrient medium (VtVADER 1967) at Pinot b. 1S04 28 oc for 48 h to a density of about 9.5 x 109 colony form­ ing units (CFU)/ml. The root system of the plant to be in­ 150 oculated was dipped in the bacterial suspension for a few E seconds just before potting. 2- Preparation of the mycorrhizal ;; i n o c u 1 u m : The stock culture was prepared by mixing g' 100 ! sterilized soil, sand and peat ( 1: 1: 1), the pH corrected to 0 6.8 by . 0 CaC03 Inoculation was done with isolated spores of .r:. Glomus mosseae (original supply: Dr. J. M. BAREA, Estacion (/) 50 Experimental del Zaidin, Granada, Spain; FooHER et al. tMineral element 1986). Spores, mycelium and infected root fragments from + analysis stock culture on tomato were used as inoculum, adding ea. IChi analysis 60 ml of culture for each pot underneath the roots. Le a f sa m pI in g: The 3rd and 4th leaf (from the 200 shoot tip) were sampled 40 and 110 d after bud burst (1st 41 and 3rd sampling respectively), while leaves of the same Pi not b. 1 B age (20 d after unfolding) were sampled 70 d after bud burst, i.e. at fruit set (2nd sampling). The latter leaves were 150 not located at the same position along the shoot because E 2- of different growth rates induced by the rootstocks, but they ;S were all located at the median Cl third of the shoot: one leaf ~ 100 per shoot was sampled. 0 C h 1 or o ph y 11: The young leaves sampled at the 0 s;; lst and 3rd date were analyzed (/) for chlorophyll (Chi) con­ .... tChl analysis tent using the portable Chlorophyll 50 Meter SPAD 502 1~ineral element (Minolta). SPAD units were transformed into Chi values + analysis (mg/g DW) using the equation given by BAVAREsco (1995). IChi analysis M i n e r a I e I e m e n t s : After wet digestion oL-~ __ _L__ _L __ J_ __ L_~--~--~ macronutrients (N, P, K, Ca and Mg) and some trace ele­ 0 40 60 00 100 12) 140 160 ments (Fe, Mn, Zn and B) were analyzed in leaves of the days after bud burst 2nd sampling by flame photometry (K and Ca), atomic absorption spectrometry (Mg, Fe, Mn and Zn) and Figure: Shoot growth of Pinot blanc vines as affected by root­ colorimetry (total N, P and B). stock variety and treatment (LSD only for the final lengths). Berry sa m pI in g: At berry ripening, 140 d after bud burst, clusters were sampled and berry juice was M y c o r r h i z a 1 i n f e c t i o n : Before drying, thin analyzed for soluble solids (0 Brix). lateral roots (0 < 1 mm), cut into ea. 2 cm segments, were R o o t d r y w e i g h t : At the end of the analyzed for VA mycorrhizal infection by the slide length experiment (in October) the soil was washed off the roots, method of GtoVANNETII and MossE ( 1980). After initial clean­ and the roots of three plants/treatment were oven-dried for ing in 10 % KOH they were staind with trypan blue in acidic 48 h at 80 oc and weighed. glycerol solution, according to WASCHKIES et al. (1994). Chlorosis affected by rootstocks, mycorrhiza and pseudomonads 121

Rh i z o s ph ere p s e u d o m o n ad s u r v e y : Soil ance of the rootstock genotypes, from 3309 C to 41 B. of the rhizosphere was collected at the end of the experi­ The mycorrhizal inoculation increased root infection of ment and pseudomonad cells were counted on nutrient me­ 3309 C and 41 B, but not of SO 4. The Pseudomonas dium KMB at pH 7.2, after 48 hat 37 °C (KING et al. 1954). treatment had a positive effect on VAM infection of all In order to isolate the P. fluorescens strain EM4 RS, the rootstocks. KMB medium was added with 50 mgll rifampicin and 100 No P. fluorescens colony was found in the microbio­ mg/1 streptomycin. The colony forming units (CFU) were logical survey, but other Pseudomonas spp. occurred. The calculated on the basis of 1 g of soil dried overnight at room EM4 RS strain added as inoculum was not recovered ei­ temperature. ther. The data presented in Tab. 1 therefore show no main­ S tat i s t i c a l an a l y s i s : A two-way ANOVA tenance of P. fluorescens inoculation, at least in the investi­ with interaction was used, the means were compared by gated rhizosphere under our experimental conditions. using the LSD test (5 % level). Percent mycorrhizal coloni­ The chlorophyll content was lowest in plants grafted zation data were submitted to angular transformation. to the lime-susceptible rootstock 3309 C, in particular at the 3rd sampling date, and highest in plants on the lime­ tolerant rootstock 41 B (Tab. 2). An inoculation either with Results P. fluoescens or G. mosseae resulted in significantly higher chlorophyll concentrations in plants on both rootstocks 41 B Shoot growth of Pinot blanc vines was lowest with the and 3309 C, while with 3309 C no plant regreening oc­ lime-tolerant rootstock 41 B and highest with the lime-sus­ curred. No significant effects were observed with the vines ceptible rootstock 3309 C. In tendency, mycorrhizal inocu­ grafted on SO 4. lation increased shoot growth with all three rootstock com­ Potassium, manganese, zinc and boron were not sig­ binations, but significantly for plants on SO 4 and 41 B root­ nificantly affected by the treatments (Tab. 3). Correspond­ stocks (Figure). ing to the enhanced chlorophyll content due to inoculation Root dry weight of control plants was not significantly with P. fluorescens and G. mosseae also the Fe concentra­ different between rootstocks (Tab. 1). Root systems of tions were enhanced, in particular in plants grafted on the 3309 C and 41 B were reduced by the mycorrhizal inoculum rootstock 3309 C. The same was true for phosphorus. It is by 21 and 40 %, resp. Morphological changes of the roots interesting to note that plants on the rootstock SO 4 had a were not investigated. The natural VAM infection of much higher Ca content in the shoots (+ 40-50%) than plants uninoculated plants increased, according to the lime toler- on the other rootstocks.

Table 1 Effect of rootstock and root treatment on root dry weight, root YAM infection, rhizosphere Pseudomonas and soluble solids of the fruit at the end of the vegetation period

Pinot b./3309 C Pinot b./S04 Pinot b./418 LSD

Control P. jluorescens G. mosseae Control P. jluorescens G. mosseae Control P. jluorescens G. mosseae (p<0.05)

Root dry weight 53 59 42 51 56 53 52 46 31 15 .2 (g/plant)

Root VAM 12.0 20.3 37.9 14. 5 17.6 12.2 17.2 20.7 27.3 2.4 infection(%)

Rhiwsphere 8 5 8 33 6 4 15 33 31 17 Pseudomonas (CFUxl01/g soil)

Fruit soluble 20.9 23.3 24.1 23 .3 20. 2 24.6 26.1 22.3 25.4 solids (0 8rix)

Table 2 Chlorophyll (mg/g DW) of leaves as affected by rootstock and root treatment

Pinot b./3309 C Pinot b./S0 4 Pinot b./418 LSD ---·· - Control P. jluorescens G. mosseae Control P. jluorescens G. mos.~eae Control P. jluorescens G. mosseae (p<0.05)

1" sampling 1.77 2. 17 2.01 2.14 2.3 8 2.26 2.84 3. 11 3. 19 0.27

3'd sampling 1.06 1.99 1.59 2.43 2.41 2.49 2.48 2.62 2.8 1 0.33 122 L. BAVARESco and C. FOGHER

Corresponding to the different chlorophyll content in FOGHER (1992 and 1996 b) and BAVARESCO et al. (1995) in­ the shoot, plants on the most lime-tolerant rootstock (41 B) dicating differences due to the rootstock genotype. In fact, had the highest level of soluble solids in the berries while microorganisms can stimulate, inhibit, or can be without plants on the most lime-susceptible rootstock (3309 C) had effect on root growth, depending on many factors including the lowest. But in the latter plants, treatments with the genotype (DUBEIKOVSKY et al. 1993; MARSCHNER 1995). P. fluoescens and G. mosseaecaused the highest increase Both, rootstock genotype and root treatment affected of soluble solids in the berries (Tab. 1). the chlorophyll content of young leaves; the rootstocks be­ haved according to their known degree of lime tolerance and chlorosis symptoms of the susceptible rootstock/plant Discussion combination (Pinot blanc/3309 C) increased during the veg­ etation period, as has been reported earlier (BAVAREsco et Shoot growth was strongly affected by the rootstock al. 1993; BAVARESCO and FOGHER 1996 b). In a late stage of genotype and, to a lower extent, by root treatments. The growth the effect of the root infection on plants grafted on lime tolerance of Pinot blanc/41 B is related to a slow veg­ 3309 C was evident: reduction of the severity of chlorosis etative growth; it seems that the plants under stress condi­ without regreening and higher rate of Fe uptake. Neverthe­ tions reduce growth of vegetative organs which have to be less, the partial recovery from chlorosis was sufficient to supplied with nutrients, while sugar accumulation in the enhance grape ripening and to increase sugar concentration fruit is increased. The positive effect of mycorrhizal treat­ in berries ( + 11 %) for Pseudomonas treatment, and + 15 % ment on plant growth confirms previous findings with for the mycorrhizal treatment. The lack of a positive effect grapevine (SCHUBERT et al. 1988; LOVATO et al. 1992; of the VAM treatment on plants grafted on SO 4 may be due I

Table 3 Effect of root treatments on leaf mineral composition and dry matter, 2nd sampling

Pinot b./3309 C Pinotb./S04 Pinot b./41B LSD - Control P. fluorescens G. mosseae Control P. fluorescens G. mosseae Control P. fluorescens G. mosseae (p<0.05)

N(%) 2.41 2.72 3.07 2.44 2.62 2.68 2.65 2.43 2.62 0.35

P(%) 0.25 0.34 0.34 0.27 0.35 0.30 0.27 0.31 0.29 0.05

K(%) 1.47 1.51 1.63 1.53 1.60 1.55 1.45 1.30 1.36 0.24

Ca(%) 0.49 0.56 0.43 0.67 0.62 0.65 0.45 0.48 0.48 0.18

Mg(%) 0.24 0.24 0.24 0.23 0.25 0.25 0.29 0.51 0.40 0.12

Fe (mg/Kg) 87 135 141 103 120 129 93 123 122 32.7

Mn(mg/Kg) 28 26 25 26 26 30 25 24 28 5.3

Zn(mg/Kg) 18 17 21 17 24 21 21 20 20 5.6

B(mg/Kg) 9 17 13 13 14 11 13 12 16 6.7

Dry matter(%) 24.2 23 .3 21.8 24.2 23.3 23 .5 25 .9 26.7 26.3 2.00 Chlorosis affected by rootstocks, mycorrhiza and pseudomonads 123

or to a complete endophytic habitus, which can not be iden­ J. A., CROWLEY, D. E.; LuSTER, D. G. (Eds.): Biochemistry of Metal tified in a rhizosphere survey. The second hypothesis is more in the Rhizosphere, 93-109. Lewis Pub!., Boca Raton. GIOVANNEITI, M.; MossE, B.; 1980: An evaluation of techniques for likely, since an appreciable effect of the infection was evi­ meas­ uring vesicular-arbuscular mycorrhizal infection in roots. New Phytol. dent. 84, 489-500. HARRISON, M. J.; VAN BuUREN M. L.; 1995: A phosphate transporter from mycorrhizal fungus Glomus versiforme. Nature 378, 626-629. JusTE, C.; MENCH, M.; 1992: Le pouvoir chlorosant des sols. C.R. Acad. Acknowledgements Agric. Franc. 78, 57-69. KARAGIANNIDIS, N.; NIKOLAOU, N.; MAITHEOU, A.; 1995: Wirkung dreier VA-Mykorrhizapilze auf Ertrag und Nahrstoffaufnahme von drei The authors want to thank G. BRUZZI (viticulturallab crew) Unterlagen und einer Tafeltraubensorte. Vitis 34, 85-89. and M. DI PARDO (graduate student) for their contribution to this KINo, E. 0 .; WARD, W. K. ;RANEY, D. E.; 1954: Two simple media for the project. demonstration of pycyanin and fluorescein. J. Lab. Cin. Med. 44, 301-307. KLOEPPER, J. W.; LEONG, J.; TEINZE, M.; ScHROTH, M. N.; 1980: Enhanced References plant growth by siderophore produced by plant growth-promoting rhizobacteria. Nature 286, 885-886. BAKKER, P.A. H. M.; WEISBEEK, P. J.; ScHJPPERS, B.; 1988: Siderophore pro­ - -; ScHROTH, M. N.; 1981 : Plant growth-promoting rhizobacteria and plant duction by plant growth-promoting Pseudomonas spp. J. Plant Nutr. growth under gnotobiotic conditions. Phytopathology 71, 642-644. 11, 925-933. KoTHARI, S. K; MARSCHNER, H.; ROMHELD, V.; 1991 : Contribution of the BAR-NESS, E.; HADAR, Y.; CHEN, Y.; ROMHELD, V. ; MARSCHNER, H.; 1992: VA mycorrhizal hyphae in acquisition of phosphorus and zinc by Short-term effects of rhizosphere microorganisms on Fe uptake from maize grown in calcareous soil. Plant Soi1131, 177-185. microbial siderophores by maize and oat. Plant Physiol. 100, 451- LI, X. L.; GEORGE, E.; MARSCHNER, H.; 1991: Extension of the phosphorus 456. depletion zone in VA-mycorrhizal white clover in a calcareous soil. BAVAR ESCo, L.; 1995: Utilisation d'un compteur non destructif pour Plant Soil136, 41-48. determiner la concentration de chlorophylle dans les feuilles de vigne. LovAro, P.; Gu!LLEMIN, J. P.; GIANINAzzi, S.; 1992: Application of commer­ Bull. O.I.V. 68, 404-414. cial arbuscular endomycorrhizal fungal inoculants to the establish­ - -; FOGHER, C.; 1992: Effect of root infection with Pseudomonas jluorescens ment of micropropagated grapevine rootstock and pineapple plants. and Glomus mosseae in improving Fe-efficiency of grapevine Agronomie 12, 873-880. ungrafted rootstocks. Vitis 31, 163-168. MARSCHNER, H.; 1978: Beziehung zwischen der Eisenversorgung von Wein­ - -;- -; 1996 a: Lime-chlorosis occurrence and leaf mineral composition of reben und dem pH-Verlauf in der Niihrlosung. Vitis 17, 152-160. grapevine treated by root micro-organisms. J. Plant Nutr. 19, 87-98. - -; 1995: Mineral nutrition of higher plants. 2nd Edition. Academic Press, - -, - -; 1996 b: Effect of root infection with Pseudomonas jluorescens and London. Glomus mosseae on severity oflime-induced chlorosis in Vitis vinifera MoRANDI, D.; BAILEY, J. A.; GIANINAZZI-PEARSON, V. ; 1984: Isoflavonoid L. cv. 'Pinot blanc'. J. PlantNutr. (in press.) accumulation in soybean roots infected with vesicular-arbuscular - -; FRASCHINI, P.; PERINO, A.; 1993: Effect of the rootstock on the occur­ mycorrhizal fungi. Physiol. Plant Pathol. 24, 357-364. rence of lime-induced chlorosis of potted Vitis vinifera L. cv. 'Pinot MossE, B.; HAYMAN, D. S.; IoE, G. J.; 1969: Growth response of plants in blanc'. Plant Soil157, 305-311. unsterilized soil to inoculation with vesicular-arbuscular mycorrhiza. - -; FREGONI, M; FooHER, C.; 1995: Effect of some biological methods to Nature 224, 1031-1032. improve Fe-efficiency in grafted grapevine. In: ABADIA, J. (Ed.): Iron MozAFAR, A.; Duss, F.; 0ERTLI, J. J.; 1992: Effect of Pseudomonas Nutrition in Soils and Plants, 83-89. Kluwer Acad. Pub!., Dordrecht. jluorescens on the root exudates of two tomato mutants differently - -; - -; FRASCHINI, P.; 1991: Investigations on iron uptake and reduction by sensitive to Fe chlorosis. Plant Soi1144, 167-176. excised roots of different grapevine rootstocks and a V. vinifera PouNELLI, E.; CIVARDI, L. ; FooHER, C.; 1991: Endophytic pseudomonas in cultivar. Plant Soil130, I 09-113. maize. In: Pseudomonas 1991, Third Intern. Symp. on Pseudomonas - -; - - ; PERINO, A. ; 1994: Physiological aspects of lime-induced chlorosis Biology and Biotechnology, 116 Abstr. Miramare-Grignano, Trieste. in some Vitis species. !. Pot trial on calcareous soil. Vitis 33, 123-126. PouoET, R. ; JuSTE, C.; 1972: Le choix de porte-greffes de la vigne pour les BOLAN, N. S.; 1991: A critical review on the role of mycorrhizal fungi in sols calcaires. Connaiss. Vigne Vin 6, 357-364. the uptake of phosphorus by plants. Plant Soil134, 189-207. RAJAPAKSE, S.; MILLER jr., J.C.; 1987: Intraspecific variability for VA BRANAS, J.; 1974: Viticulture. Dehan, Montpellier, France. mycorrhizal symbiosis in cowpea (Vigna unguiculata L. Walp.). In: BRANCADORo, L. ; RAsorr1, G.; SciENZA,A.; ZoccHI, G.; 1995: Mechanisms GABELMAN, H. W.; LouoHMAN, B. C. (Eds.): Genetic Aspects of Plant of Fe-efficiency in roots of Vitis spp. in response to iron deficiency Mineral Nutrition, 523-536. Martinus Nijhoff Pub!., Dordrecht. stress. Plant Soi1171, 229-234. REID, C. P. P.; SzANISZLO, P. J.; CROWLEY, D. E.; 1986: Siderophore involve­ DuBEIKOVSKY, A. N.; MoRDUKHOVA, E. A. ; KocHETKov, V. V.; PouKARPOVA, ment in plant iron nutrition. In: SwiNBURNE, T.R. (Ed.): Iron, Sidero­ F. Y. ; BoRONIN, A. M.; 1993; Growth promotion of blackcurrant phore, and Plant Diseases, 29-42. Plenum Pub!. Corp., New York. softwood cuttings by recombinant strain Pseudomonas jluorescens ScHONBECK, F.; RASCHEN, I.; 1995: Symbioses: Mycorrhizae. Progr. Bot. BPS53a synthesizing an increased amount of indole-3-acetic acid. 56, 457-471. Soil Bioi. Biochem. 25, 1277-1281. ScHUBERT, A.; CAMMARATA, S.; EYNARD, 1.; 1988: Growth and root coloniza­ FOGHER, C.; MAGGIONI , L.; CORTI, C.; 1986: Effetti dell'inoculo con Glomus tion of grapevines inoculated with different mycorrhizal endophytes. mosseae sulla radicazione di piantine di aglio (Allium sativum L.) HortScience 23, 302-303. rigenerate da callo. Ann. Fac. Agr. Univ. Cattolica S.C., Milano 26, VIVADER, A. K.; 1967: Synthetic and complex media for rapid detection of 9-14. fluorescence of phytopathogenic pseudomonads: Effect of the car­ FoRTUNA, P.; CITERNESI, S.; MoRINI, S.; GIOVANNEITI, M.; LoRETI, F. ; 1992: bon source. Appl. Microbial. 15, 1523-1524. Infectivity and effectiveness of different species of arbuscular W ALTER, A.; ROMHELD, V. ; MARSCHNER, H.; CROWLEY, D. E.; 1994: Iron nu­ mycorrhizal fungi in micro propagated plants of Mr S 2/5 plum root­ trition of cucumber and maize: Effect of Pseudomonas putida YC 3 stock. Agronomie 12, 825-829. and its siderophore. Soil Bioi. Biochem. 26, 1023-1031. FREGONI, M.; 1980: Nutrizione e Fertilizzazione della Vite. Edagricole, W ASCHKIES, C.; ScHROPP, A.; MARSCHNER, H. ; 1994: Relations between grape­ Bologna. vine replant disease and root colonization of grapevine (Vitis sp.) by GEBBING, H.; ScHwAB,A.;ALLEWELDT, G.; 1977: MykorrhizaderRebe. Vitis fluorescent pseudomonads and endomycorrhizal fungi. Plant Soil162, 16, 279-285. 219-227. GEORGE, E.; ROMHELD, V. ; MARSCHNER, H.; 1994: Contribution of Mycorrhizal Fungi to Uptake by Plants. In: MANTHEY Received April18, 1996