Organic amendments on the control of Fusarium Crown and root rot of asparagus and Fusarium wilt of tomato.

Fusarium crown and root rot (FCRR) of asparagus (Asparagus officinalis L.), with a complex etiology including several Fusarium spp., and Fusarium wilt (FW) of tomato (Solanum lycopersicum L.), caused by Fusarium oxysporum f. sp. lycopersici (Fol), occur in most growing areas of the world and can cause serious economic losses. Its control is difficult due to the long survival of pathogens in the soil and their easy spreading by propagation material. In addition, asparagus cultivars available often have low resistance levels and, due to the wide genetic diversity within species of Fusarium pathogenic of asparagus, implementation of resistance is difficult to develop. On the other hand, tomato cultivars resistant to Fusarium have been available for decades and provide a certain degree of control, but the emergence and development of new pathogenic races is a constant problem. In fact, commercially acceptable varieties of tomato with complete resistance are not frequent. Therefore, there are few chemical control options available for the management of these diseases. A sustainable and environmentally friendly alternative is the use of organic soil amendments that can greatly reduce the impact of soilborne plant pathogens (Lazarovits, 2001; Noble y Coventry, 2005; Bonanomi et al., 2007; Melero-Vara et al., 2011). This work has been conducted in the framework of organic farming since organic by-products from agricultural and fishing industries in the area (poultry manure, commercial pellet of poultry manure, olive residue compost and fish emulsion) have been tested as organic soil amendments aiming disease control for the pathosystems Fusarium spp./asparagus and Fusarium oxysporum f. sp. lycopersici / tomato.La Podredumbre de raíces y corona (PRC) del espárrago (Asparagus officinalis L.), de etiología compleja, incluyendo varias especies de Fusarium, y la Fusariosis vascular (FV) del tomate (Solanum lycopersicum L.) ocasionada por Fusarium oxysporum f. sp. lycopersici (Fol), están presentes en la mayoría de las zonas de cultivo del mundo y causan graves pérdidas económicas. Su control es difícil debido a la prolongada supervivencia de los patógenos en el suelo y su fácil diseminación con el material de propagación. Además, los cultivares de espárrago suelen tener escasa resistencia, que es difícil de implementar por la amplia diversidad genética dentro de las especies de Fusarium patogénicas de espárrago y, aunque los cultivares de tomate resistentes a la Fusariosis han estado disponibles desde hace décadas y proporcionan un cierto grado de control, la aparición y desarrollo de nuevas razas patogénicas supone un problema constante. De hecho, no existen variedades de tomate comercialmente aceptables con una resistencia suficiente. Para el manejo de estas enfermedades hay pocas opciones de control químico disponibles. Una alternativa sostenible y ecológica es el uso de enmiendas orgánicas de suelo, que pueden reducir el impacto de hongos de suelo fitopatógenos (Lazarovits, 2001; Noble y Coventry, 2005; Bonanomi et al., 2007; Melero-Vara et al., 2011). Este trabajo se ha realizado en el marco de una agricultura ecológica, utilizándose residuos orgánicos de la industria agrícola y pesquera de la zona (gallinaza, pellet comercial de gallinaza, compost de alpeorujo y emulsión de pescado) como enmiendas orgánicas de suelo en ambos patosistemas Fusarium spp./espárrago y Fusarium oxysporum f. sp. lycopersici / tomate.Dirigida por Dr. José María Melero Vara (IAS Córdoba CSIC) y Dra. Mª José Basallote Ureba (IFAPA "Las Torres-Tomejil).

Characterization of Fusarium isolates from asparagus fields in southwestern Ontario and influence of soil organic amendments on Fusarium crown and root rot

Fusarium crown and root rot (FCRR) of asparagus has a complex etiology with several soilborne Fusarium spp. as causal agents. Ninetythree Fusarium isolates, obtained from plant and soil samples collected from commercial asparagus fields in southwestern Ontario with a history of FCRR, were identified as Fusarium oxysporum (65.5%), F. proliferatum (18.3%), F. solani (6.4%), F. acuminatum (6.4%), and F. redolens (3.2%) based on morphological or cultural characteristics and polymerase chain reaction (PCR) analysis with species-specific primers. The intersimple- sequence repeat PCR analysis of the field isolates revealed considerable variability among the isolates belonging to different Fusarium spp. In the in vitro pathogenicity screening tests, 50% of the field isolates were pathogenic to asparagus, and 22% of the isolates caused the most severe symptoms on asparagus. The management of FCRR with soil organic amendments of pelleted poultry manure (PPM), olive residue compost, and fish emulsion was evaluated in a greenhouse using three asparagus cultivars of different susceptibility in soils infested with two of the pathogenic isolates (F. oxysporum Fo-1.5 and F. solani Fs-1.12). Lower FCRR symptom severity and higher plant weights were observed for most treatments on 'Jersey Giant' and 'Grande' but not on 'Mary Washington'. On all three cultivars, 1% PPM consistently reduced FCRR severity by 42 to 96% and increased plant weights by 77 to 152% compared with the Fusarium control treatment. Populations of Fusarium and total bacteria were enumerated after 1, 3, 7, and 14 days of soil amendment. In amended soils, the population of Fusarium spp. gradually decreased while the population of total culturable bacteria increased. These results indicate that soil organic amendments, especially PPM, can decrease disease severity and promote plant growth, possibly by decreasing pathogen population and enhancing bacterial activity in the soil. © 2014 The American Phytopathological Society.This research was funded by Agriculture and Agri-Food Canada, by a JAEPredoc-CSIC grant to A. Borrego-Benjumea, and by projects INIA RTA 2006-00045 (Ministerio de Agricultura, Alimentación y Medio Ambiente, Spain) and P06-AGR-02313 (Consejería de Economía, Innovación y Ciencia, Junta de Andalucía).Peer Reviewe