CORKY ROOT OF TOMATO IN PORTUGAL CAUSED BY PYRENOCHAETA LYCOPERSICI

Joana M.P. Santa-Marta Instituto Superior de Agronomia Lisboa Portugal

Abstract Corky root (Brown root rot) was detected for the first time in Portu

gal during 1984, on the tomato cultivar Carmelo in greenhouses. The symptoms of the disease and morphological features of the pathogen {Pyrenochaeta Zycopers-ici Schneider and Gerlach) are described. The pathogenicity of all isolates were proved. Some control measures are suggested.

1. Introduction Since 1983, in many plastic greenhouses of Portugal, symptoms very

similar to those described as corky root or tomato brown root rot (B.R.R.) have been consistently repported in many countries of Europe (Bakariev, 1981; Cartia and Grasso, 1974; Garibaldi and Matta, 1965; Last and Ebben, 1966; Malathrakis et al., 1983; Messiaen and Lafon, 1970; Preece, 1964), North America (Manning and Vardaro, 1974; Campbell et al., 1982), Asia (Davet, 1970), and New Zeland (Laundon, 1970). The wilted and stunted tomato plants presented a marginal chlorosis on the leaves, very severe on the basis and progressing upwards. Affected leaves became necrotic,witherd and died,resulting in a premature defoliation and dwarfing of plants, particularly during periods of excessive transpiration. The root system was poorly developed. The smaller roots had numerous brown lesions and browned stubs with few if any feeder roots (Fig. 1). The larger roots have brown lesions on their surface (Fig. 2) and are corky in appearance. Sometimes numerous black dots are visible on the root system of these plants.

Isolations from corked and browned roots yielded a grey sterile fungus (G.S.F.). Since William's (1929), cultures of a grey sterile fungus have been isolated from diseased tomato roots. Richardson and Berkeley (1944) in Canada and Thermohlen (1962) in the Netherlands showed that G.S.F. was a primary parasite of tomato roots, being associated with root browning and the development of corkiness. Marion Ebben (1959) noticed in very particularly conditions that some grey fungal isolates, isolated from roots, developed pycnidia and were identified as Pyrenochaeta sp. It was in 1966, in Germany, that Schneider and Gerlach (Gerlach and Schneider, 1964; Schneider and Gerlach, 1966) have investigated the pycnidial and biological properties of G.S.F. isolates and concluded that they contribute a new specie of Pyrenochaeta, wich was designate, as Pyrenochaeta lycopersi-ci Schneider and Gerlach.

This paper repports the results of our initial studies on G.S.F. isolates, identification obteined from roots of tomato plants cultivar Carmelo with corky root symptoms and suggestions for control measures.

Acta Horticulturae, 191, 1986 Solanacea in Mild Winter

311

2. Material and methods

2.1. Isolat¿oni_identification_and_caracterization_of_isolates

The isolates were obtained from tomato roots with corky root symptoms. Fragments of tomato root were surface-sterilized for 2-3 minutes in 2.5% sodium hypochlorite solution, rinsed and blotted dry on sterile filter paper. Chips of cortical tissues, from the lesion margins, were plated aseptically on S media (Messiaen and Lafon, 1970) added with chloramphenicol (5% w/v) and incubated at 22°C with 16h photoperiod. Transfers were made to provide one or two isolates of G.S.F. from each collection of roots from an infested field.

Futher, tomato juice agar (T.J.A. Oxoid) was also used and the plates were incubated in a growthchamber at 19±1C, where 2 tubular low -pressure mercury lamps suplied U.V. radiation between 300 and 460 nm. with a maximum at 365 nm (Philips "TL" 40 w/05). The plates were placed 56 centimetres away. Cultures were stored at 6°C in a refrigerator.

2.2. Pathogenicit^_tests

The method repported by Clerjeau and Conus (1973) was followed to realise the pathogenicity tests. Young tomato seedlings cv. Carmelo with a root of 3 cm long, grown

on a moistened filter paper in Petri dishes, were inoculated on the root below the hypocotyl with 5 mm diameter pieces of 20 days growing cultures and incubated at 22°C with 16h photoperiod. Control plants were inoculated in the same way, with pieces of S

media, without any fungus. Per isolate were used four replicates with 4 plants per replicate.

3 . Re s u 11 s

3.1. Isolation^identification_and_characterization_of_isolates

A G.S.F. was consistently isolated from tomato roots with corky root. Most of the isolates were typically slow growing and grey in color. Others were lighter grey with a pink color in older mycelium observed in the reversed Petri dish. They were sterile but some of them sporuleted when young brown roots were plated out on T.J.A. under fluorescent light. In this case many pycnidia were formed in less than 15 days on the root pieces and on the surface of the culture medium.

Some isolates in old cultures produced numerous sclerotia on S media. The pycnidia are solytary, globose to sub-globose, 198-300 p diam.,

brown to black dark with an ostiole and septate setae (Fig. 4). The conidia are hyaline, unicellular, cylindrical to allantoid,

4.5-6 x 1.5 U (Fig. 5). The young mycelium is hyaline, sparsely branching with few septa,

and has a tendency to form narrow strands of closely packed paralleled hyphae. With age, it becames darker colored, coarser, and becoming very closely septated with constrictions at the septa (Fig. 3).

3.2. PathogenicitY_tests

About 10 days after the inoculation of the young seedlings with P. lycopersici a wide variation in pathogenicity among the G.S.F.

312

isolates has been noted. Some isolates caused moderate brown root rot (the area of the root

adjacent to the inoculum became light brown) and the others severe brown root rot (the area of root adjacent to the inoculum is dark brown and the young plants died when the whole root system were infected). The root system of control plants are not atacked. The new isolates from test plant lesions yielded pure cultures of P.

lyoopersici.

4. Discussion On the basis of symptomatology, morphological characteristics of the

pathogen and the pathogenical tests, it was demonstrated that the G.S.F. isolated is similar to Pyrenochaeta lyoopersici Schneider and Gerlach, the causal agent of corky root of tomatoes. In fact, the cultural and pycnidial characters of most Portuguese

G.S.F. isolates are alike those reported in literature (Table 1) like the cultural variability of G.S.F. isolates already repported by Termohlen (1962). When pathogenicity studies were finished B.R.R. symptoms were found and the new isolates from test plant lesions yielded pure cultures of P. lyoopersici. As far as we know this is the first time that the corky root is

repported in Portugal. Since the know importance of this pathogen in Solanum species (Matta,

1976; Volin and Ramos, 1980) and Cuoumis melo L. (Risser and Laugie, 1968) on glasshouse conditions, we think that is very important to repport the control measures already used. The methods often used against the corky root are both the soil

sterilization by steam and the soil desinfection by chemicals, like chloropicrin (C.P.), methyl-bromide (M.B.) C.P. + M.B., metham sodium and dazomet (Bongarra, 1980; Campbell, 1981; Clerjeau et al., 1973; Cuany et al., 1982: Lavergne et al., 1980; Malathrakis et al., 1982). Another method is the utilization of grafted sensitive plants of

tomato on Dutch interspecific-hybrid (Fi) KNVF, resistent to Pyreno-ohaeta lyoopersici, Vertioillium dahliae, Vertioillium albo-atrum, Fu-sarium oxysporum f. sp. lyoopersici (race 0), Meloidogyne sp. and Di-dymella lyoopersici (D'ercole and Nipoti, 1978- Ginoux and Dauple, 1985; Ginoux et al., 1978; Ginoux et al., 1979). Recently another rootstocks are available, like Heres (with aditional T.M.V. resistance) and Brigeor (with aditional T.M.V. resistance and F. oxys-porum f. sp. lyoopersici race 1) and both were specialy created to graft resistant varietis to the T.M.V. (Laterrot, 1983). Resistant cultivars can be used, like the French hybrid Fi Pyrella,

resistant to V. dahliae, V. albo-atrum, F. oxysporum f. sp. lycoper-sioi race 0, Meloidogyne sp. T.M.V., Cladosporium fulvum and P. lyco-persioi (Laterrot, 1983).

Soil solarization as an efficient method of control for certain soil fungy has been widely known (Katan, 1981; Katan et al., 1983; Pullmann et al., 1981) and it seems to be very promissing controling P. lycoper sici by its eficacy and low cost (Goisque et al., 1984). This piece of work aimed for a new research line, thinking on the interest of solarization on the control of P. lyoopersioi, however is too soon to present results.

313

Acknowledgement s

The author thanks to Prof. Jorge F. Pinto-Ganhâo, directeur of Labo-ratorio de Patologia Vegetal "Verissimo de Almeida", for his precious help and financial support.

References

Bakhariev, D., 1981. Effect of some factors and corky root (Py. Zyoo-persici Schn. Gerì.) of glasshouse tomato. Grad, lozar. Nauka 18: 56-60.

Bongarrà, G.S., 1980. Prove di lotta in serra contro Pyrenoohaeta lyoo persia-i su pomodoro in Sicilia. Tecn. agric. 32: 249-258.

Campbell, R.N., 1981. Soil fumigation for control of tomato corky root. Phytopathology 71: 207.

Campbell, R.N., Schweers, V.H., and Hall, D.H., 1982. Corky root of tomato in California caused by Pyrenoohaeta lyoopersioi and control by soil fumigation. Plant Disease 66: 657-661.

Cartia, G. , and Grasso, S., 1974. La presenza del "Corky root" del po-modoro nille coltivazioni in serra della Sicilia orientale. Tecn. agric. 26: 739-747.

Clerjeau, M., 1974. Etude de la fructification de Pyrenoohaeta lyooper sioi Schneider et Gerlach sur racines de tomate et de melon. Ann. Phytopath. 6: 45-54.

Clerjeau, M., and Conus, M., 1973. Méthode rapide de contamination de jeunes plantules de tomate par Pyrenoohaeta tyoopersici Schneider et Gerlach. Ann. Phytopath. 5: 143-150.

Clerjeau, M., Dauplé, P., Ginoux, G., Leroux, J.P., and d'Oleon, F., 1973. I - Efficacité comparée de divers fumigants contre le "corky--root" de la tomate dû à Pyrenoohaeta lyoopersici. Rev. hort., Pa-ris, n° 138: 25-32.

Cuany, A., Lavergne, J.C., Scotto la Massese, C., Mars, S., Blancard, D., and Lecocq, A., 1982. Essais de déterminât ion d'un rythme pra-tique d'application du bromure de methyle en cultures maraîchères de plein champ. Rev. hort., Paris, n9 232: 39-45.

Davet, P., 1970. Étude des pourritures des racines de la tomate au Li-ban et du complexe qui leur est associe. Thèse Docteur es Sciences Univ. Nancy I. 120 pp.

D'ercole, N., and Nipoti, 1978. Suberosi radicale della melanzana in coltura protetta e suggerimenti di lotta. Inform, fitopat. 10: 13--17.

Ebben, M.H., 1959. Brown root rot of tomatoes. II - The fungal flora of the rizosphera. Ann. appi. Biol. 47: 17-27.

Garibaldi, A., and Matta, A., 1965. A "corky root" del pomodoro in Liguri. Phytopath. medit. 4: 167-169.

Gerlach, W., and Schneider, R., 1964. Nachweis eines Pyrenoohaeta stadiums bei stammen des korkwurzelerregers der tomate. Phytopath. Z. 50: 262-269.

Ginoux, G., and Dauplé, P., 1985. Greffe par perforation latérale de l'aubergine et de la tomate. Rev. hort. , Paris, n? 253: 29-34.

Ginoux, G., Dauplé, P., and Lefebvre, J.M., 1978. La greffage de la toma te. Un moyen contre les parasites du sol. Rev. hort., Paris, n? 192: 33-44.

Ginoux, G., Dauplé, P., Guimbard, C., and Lefebvre, J.M., 1979. La greffage de la tomate. Un moyen de lutte contre les parasites du sol. Rev. hort., Paris, n9 194: 19-29.

314

Goisque, N.J., Louvet, H., Martin, C., Lagier, J., Davet, P., Couteau-dier, J., Louvet, J., 1984. La désinfection solaire du sol. Uu moyen de lutte contre la maladie des racines liégeuses de la tomate. Rev. hort., Paris, n? 247: 1-4.

Katan, J., 1981. Solar heating (solarization) of soil for control of soilborne pests. Annu. Rev. Phytopath. 19: 211-236.

Katan, J., Fishier, G. , and Grinstein, A. , 1983. Short-and long-term effects of soil solarization and crops sequence on Fusarium wilt and yield of cotton in Israel. Phytopathology 73: 1215-1219.

Last, F.T., and Ebben, M.H., 1966. The epidemiology of tomato brown root rot. Ann. appl. Biol. 57: 95-112.

Laterrot, H., 1983. La lutte génétique contre la maladie des racines liégeuses de la tomate. Rev. hort., France, n? 238: 23-25.

Laundon, G.F., 1970. Records of fungal plant diseases in New Zealand. N.Z.J. Bot. 8: 51-66.

Lavergne, J.C., Cuany, A., Nourrisseau, J.G., Clerjeau, M., Lecocq, A., and Jacquot, M. , 1980. Résultats d'essais de désinfection des sols pour la culture de tomate de plein champ. Rev. hort., Paris, n9 208: 29-38.

Malathrakis, N.E., Kapetanakis, G.E., and Linardakis, D.C., 1983. Brown root rot of tomato, and its control, in Crete. Ann. appl. Biol. 102: 251-256.

Manning, W.J., and Vardaro, P.M., 1974. Brown root rot of tomato in Massachusetts. Plant Dis. Reptr. 58: 483-486.

Matta, A., 1976. Dannositâ della Pyvenochaeta lycopevsioi nella coltu-ra di pomodoro in serra della riviera ligure. Coltura Protette 5: 31-33.

Messiaen, C.M., and Lafon, R. , 1970. Les maladies des plantes maraî-chères. INRA. Paris.

Preece, T.F., 1964. Observations on the corky root disease of tomatoes in England. Trans. Brit, mycol. Soc. 47: 375-379.

Pullmann, G.S., DeVay, J.E., Garber, R.H., and Weinhold, A.R., 1981. Soil solarization: Effects on Verticillium wilt of cotton and soilborne populations of Vevticillium da.hli.ae, Pytium spp. Rhizocto-nia solani and Thielaviopsis basicola. Phytopathology 71: 954-959.

Richardson, J.K., and Berkeley, G.H., 1944. Basal rot of tomato. Phytopathology 34: 615-621.

Risser, G., and Laugie, M., 1968. Mise en évidence de la sensibilité de divers cultivars de Melon ( Cucumis melo L.) à Pyrenochaeta sp. agent de la "Maladie des racines liégeuses de la tomate". Ann. Amél. Plantes 18: 75-80.

Schneider, R., and Gerlach, W., 1966. Pyrenochaeta lycopersici nov. spec., der Erreger der Korkwurzelkrankheit der tomato. Phytopathol. Z. 56: 117-122.

Sutton, B.C., 1980. The Coelomycetes. Commonwealth Mycological Institute. England.

Termohlen, G.P., 1962. On corky root of tomato and the corky root fungus. Tijdschr. PIZiekt. 68: 295-367.

Volin, R.B., Ramos, L., 1980. The association of brown root rot resistance with yield components and root weight among tomato selections grown in infested and non-infested soil in Dade county, Florida. Proc. Fla St. hort. Soc. 93:224-226.

Williams, P.H., 1929. Fungi occuring in tomato roots. Rep. Exp. Res. Stn. Cheshunt 1928: 42-45.

315

Annexes

Table 1 - Size comparison of different morphological characteristics of P. lycopersici by several authors.

Schneider and Clerjeau Sutton Portuguese Gerlach isolate

Morph. charact. (1966) (1974) (1980) (198A)

Pycnidia 150-300 y 90-260 y 175 M 198-300 y Conidia 4.5-8 x 3.2-5 x 5-7 x 4.5 x 1.5 y

x 1.5-2 y x 1.2-1.6 y x 1.5 y Setae > 120 x 7 y 100-150 y 150 x 10 y — x 7 y

Fig. 3. Old mycelium of Fig. 4. Pycnidia Fig. 5. Conidiae P. lyoop. dark colored, of P. lyoopersioi cylindrical to coarser, very closely allantoid of P. Ly-septated. oopevsioi.

Fig. 1. Brown lesions and browned stubs on the smaller roots of a plant grew in soil infested with P. lyoop.

Fig. 2. Brown and root lesions on main root infected with P. lyoop.

316