Endophyte Fungi as Indicators of Soil Health in Continuous Cropping Systems. Case Study Peach Tree and Horticultural Crops.

Europexs fruit trees are concentrated in Spain, Italy, France, Portugal and Greece accounting for 93% of the Community's fruit growing areas. Spain and Italy are the most important producers of stone fruits, however a reduction of total surface of peach has been observed since 1996 in Italy. Biotic and abiotic components of replant problems are the technical reasons of that. Soil borne pathogens represent the main biotic component of replant problems; therefore a study was carried out in an intensively cultivated area of southern Italy. The objective was to investigate on the possibility of planting new peach orchards on soils cultivated with horticultural crops, to avoid either fumigation or a fallow period.

A greenhouse bioassay was performed using vitroplants of peach rootstock GF677. They were transplanted to soil samples collected from five replant orchards and five horticultural crops (winter-spring crops) close to the orchards. Plants were grown in greenhouse; root endophytic fungal communities were assessed.

GF677 plants showed a growth reduction significantly higher on horticultural soils than on peach soil. Infection frequency of endophytic fungi did not differ, however, according with analysis of similarity test, community composition widely differed among peach and horticultural sites. Saprophytic fungi prevailed in peach orchards, while Cylindrocarpon destructans and Thielaviopsis basicola were the most abundant species in horticultural soil. These soil borne fungi resulted highly aggressive on peach rootstock after further pathogenicity tests.

The results of this study suggest that peach rootstock can be attacked by the typical soil borne pathogens of horticultural crops. Replanted peach orchards in this study did not seem affected by biotic components of replant. In case of replant of new fruit tree orchards in intensively cultivated areas with continuous crops, greenhouse bioassay with target crop and evaluation of root endophyte fungal communities may help in deciding the best soil use.