IN VITRO ANTIMICROBIC ACTIVITY OF METHYL THIOPHANATE, FLUTOLANIL AND STREPTOMYCES SPP. STRAINS AGAINST SOIL-BORNE PLANT PATHOGENS The in vitro antagonistic activity of methyl thiophanate, flutolanil, Streptomyces lydicus strain WYEC 108 and Streptomyces sp. strain AtB-42 was studied using eight soil-borne plant pathogens. Methyl thiophanate was effective in reducing mycelial growth of C. destructans (LC50=0.05 g/L, LC95=9.5 g/L), F. solani (LC50=0.006 g/L, LC95=10.0 g/L), P. lycopersici (LC50=0.01 g/L, LC95=0.1 g/L), S. sclerotiorum (LC50=0.005 g/L, LC95=0.01 g/L) and V. dahliae (LC50=0.006 g/L, LC95=5.8 g/L). Flutolanil had the best performance against R. solani (LC50 0.0006 g/Land LC95 0.007 g/L). Both fungicides were not superior to propamocarb+fosetil Al, used as reference fungicide in these experiments, in inhibiting Phytium sp. and Phythophtora sp. growth. Streptomyces strains showed wide antimicrobic range. S. lydicus WYEC 108 inhibited completely the growth of all fungal pathogens tested. Streptomyces sp. AtB-42 and S. griseoviridis K61, the latter used here as reference product, reduced significantly (at least 65% and 92%, respectively), but just in a few cases completely, the growth of fungal pathogens.

The effects of Streptomyces spp. isolates in the biological control of corky root of tomato and Verticillium wilt of eggplant was determined in in vitro, greenhouse and field trials. Twenty-six Streptomyces spp. isolates were obtained from the rhizospheres of different vegetable crops in southern Italy. In in vitro dual culture tests, mycelial radial growth of Pyrenochaeta lycopersici and Verticillium dahliae was reduced up to 18.6% and 30.1%, respectively. Radial growth of seven other fungal pathogens was variably reduced as well. The isolates StB-3, StB-6, StB-11 and StB-12 showed a good antagonistic effect against both P. lycopersici and V. dahliae, while the rest of isolates eventually showed antagonism against only one pathogen. In pot-experiments in the greenhouse three of the four above-mentioned Streptomyces spp. isolates significantly reduced corky root up to 64.9% (StB-11), and all four isolates reduced foliar symptoms of Verticillium wilt (AUDPC) up to 48.3%, but none of them reduced the severity of vascular browning. In naturally infested field trials, StB-11 significantly reduced corky root severity in tomato by 48.2%, StB-12 by 35% and StB-6 by 32.6%, but none of the isolates were effective in controlling Verticillium wilt of eggplant. The effectiveness of the streptomycete AtB-42, successfully used in previous researches, was here confirmed as it reduced corky root of tomato in the field by 33.6%. In conclusion, our research demonstrates that under field conditions corky root of tomato, but not Verticillium wilt of eggplant, can be effectively controlled by the Streptomyces spp. isolates used in this study.

EVALUATION OF EFFECTIVENESS OF METHYL THIOPHANATE FOR THE CONTROL OF SOIL-BORNE DISEASES OF TOMATO AND ARTICHOKE In greenhouse pot-experiments, the effectiveness of methyl thiophanate against soil-borne plant pathogens infecting tomato (Fusarium solani, Rhizoctonia solani and Pythium sp.) was compared to that of other fungicides (propamocarb+fosetyl-Al and flutolanil) and biological control agents (Streptomyces griseoviridis strain K61, S. lydicus strain WYEC 108 and Streptomyces sp. strain AtB-42). Moreover, three soil application strategies of methyl thiophanate were evaluated in the control of Verticillium wilt of artichoke. In tomato, treatments with thiophanate-methyl were constantly the most effective, and reduced plant death caused by Pythium sp. by 66%, and by 44-73% the disease severity of Pythium sp., F. solani and R. solani, with variable plant biomass increases. Interestingly, Streptomyces sp. AtB-42 reduced F. solani and R. solani infections by 58% and 54% respectively, thus resulting superior to S. griseoviridis K61. In artichoke, three post-transplanting treatments with 0.65 L/ha of methyl thiophanate, preceded by root-dipping into the fungicide at transplanting, proved to be the best control strategy, and reduced Verticillium wilt by 35-40% while increasing leaf fresh weight by 10%.

The globe artichoke (Cynara cardunculus L. var. scolymus (L.) Fiori (=C. scolymus L.)) (diploid, 2n = 34) is the most important botanical variety of the species, which also includes C. cardunculus L. var. altilis DC. (=C. cardunculus L. var. cardunculus), the cultivated cardoon, and C. cardunculus L. var. sylvestris (Lamk) Fiori, which comprises wild relatives. The genus Cynara, native of the Mediterranean Basin, belongs to the botanical family Asteraceae (=Compositae) and includes seven species besides C. cardunculus. It is widely accepted that C. cardunculus var. sylvestris is the ancestor of the other two varieties (55,120). Artichoke is an allogamous species that is mainly propagated vegetatively via “stumps” (basal stem pieces with attached root sections) or “ovoli” (axillary buds separated from the stumps), although a few cultivars are seed-propagated (101). More than 120,000 ha of globe artichokes are cultivated in more than 25 countries worldwide that yield approximately 1,300,000 t of buds. This hectarage represents 2.5% of the world area cultivated to vegetables (51). Italy is the leading artichoke-producing country with more than 35% of world production. Spain ranks second with 19% of world production despite a 20% hectarage reduction during the last 5 years. Similar reductions of the cultivated area and production of artichokes have occurred in France, the United States, and, less markedly, in Greece (Table 1). Conversely, the crop hectarage has expanded greatly in other countries: over a 30-fold increase in Peru, twofold increase in China and Turkey, about 60% increase in Chile and Egypt, and nearly 20% increase in Algeria, Argentina, and Morocco. Additionally, the yield per cultivated area in countries such as Algeria, China, Morocco, Peru, and Turkey has recently achieved a level comparable with that of other countries. This may be a consequence of significant improvements in artichoke cultivation technology in those countries, where artichoke plantations have been established more recently than elsewhere. An overview of world production of artichokes was published recently (80). Verticillium wilt, caused by the soilborne fungus Verticillium dahliae Kleb., is one of the main constraints for artichoke production worldwide. This disease was first reported on artichoke in Italy in the late 1920s (42,95). Subsequently, new reports were published from France (27), again in Italy (25,32,36), Spain (112), Chile (52), Greece (114), California (17), and Tunisia (67). Currently, Verticillium wilt occurs in all artichoke-growing areas. Verticillium wilt is becoming an increasing concern in artichoke production because the rapid spread of the disease to new growing areas has led to declining production. For example, in the 1980s, the disease was found affecting artichoke crops in several Italian regions such as Apulia, Campania, Lazio, Sardinia, Sicily, and Tuscany. In Apulia, which is the most important Italian area of artichoke production, problems with Verticillium wilt led to a reduction in the area cultivated to artichoke in the Bari Province, and also extended rapidly to new plantations that had been established in the provinces of Brindisi, Foggia, and Lecce (2,33). A similar decrease in artichoke cultivation due to Verticillium wilt was observed in Chile (52,53). In Spain, Armengol et al. (3) underlined the spread of Verticillium wilt in the Comunidad Valenciana region in eastern-central Spain, the main artichoke-growing area in the country. They reported over 80% disease prevalence in fields of stump- and seed-propagated artichokes sampled during 1999 to 2002, with an average wilt incidence of 53.8%.