Corky root is a severe disease affecting both greenhouse and field-grown tomato all over the world. On severely affected secondary and main roots parenchyma tissues develop dark-brown, swollen and fissured corky patches which may invade the whole length of roots. Adult plants in a soil with a high inoculum level show massive root failure which causes wilting, leaf yellowing, dwarfing and dramatic yield reduction. The causal agent of this disease is Pyrenochaeta lycopersici, a soil-borne fungus which forms microsclerotia within infected cortical tissues. Corky root rot has been known as a disease of greenhouse tomato since the 1960s, but has also spread in field crops since the 1980s in California, Israel and Italy where it is considered a major cause of tomato root rot. Several control measures can be used against this disease, but the most effective and ecologically sustainable measure is the use of disease-resistant cultivars. The present research studied the response to manuring in susceptible and diversely resistant tomato germplasm grown in monosuccession over a period of 3 to 5 years. Testing was carried out in commercial greenhouses on soil naturally infested by P. lycopersici, in two different locations: Bari and Valenzano in Apulia, Southern Italy. The experimental statistical design was a "split-plot" with two blocks. Each block contained one plot treated with a mixture of horse and cow manure (70 m3 ha-1) and one untreated plot. Two susceptible cultivars, Craigella and Super Marmande, two partially resistant lines, J513 and 68808 and one resistant line, Lycopersicon peruvianum 1373-9 of tomato were used. Tomato croppings were arranged in monosuccession 5 years in Bari, and 3 years in Valenzano. Disease severity was evaluated by recording the percentage of rotted root surface at 90, 140 and 190 days after transplanting and the area under disease progress curve (AUDPC) was also calculated. Treatment with manure significantly reduced AUDPC% in both the Bari and Valenzano greenhouses. No significant interaction was detected between manure and the tomato genotypes. In the Bari and Valenzano trials, manure caused a significant reduction of AUDPC% in the two susceptible cultivars during the first two years of testing. Likewise, in the same two years manuring significantly reduced AUDPC% on the partially resistant tomato line 68808 only in the Valenzano trials. In the last three years of trial tests in Bari and in the last year of trial tests in Valenzano, manuring caused no reduction of AUDPC% in susceptible tomato cultivars. During all the years of testing, manuring never caused significant reduction of AUDPC% on the partially resistant J513 line or on the highly resistant L. peruvianum 1373-9 line. On the basis of our results, polyannual manuring did not enhance the expression of resistance in either partially resistant or highly resistant tomatoes and the effectiveness of manuring in controlling corky root is of short-term duration on susceptible tomatoes. These results, together with the consideration of the high cost and technical difficulties involved, make organic farming therefore a rather dubious method of tomato corky root control and support the need for a high type resistance for a better control of this disease.
Effect of an organic amendment on corky root susceptible and resistant tomatoes
Colella, C.;Bubici, G.;
2008
Abstract
Corky root is a severe disease affecting both greenhouse and field-grown tomato all over the world. On severely affected secondary and main roots parenchyma tissues develop dark-brown, swollen and fissured corky patches which may invade the whole length of roots. Adult plants in a soil with a high inoculum level show massive root failure which causes wilting, leaf yellowing, dwarfing and dramatic yield reduction. The causal agent of this disease is Pyrenochaeta lycopersici, a soil-borne fungus which forms microsclerotia within infected cortical tissues. Corky root rot has been known as a disease of greenhouse tomato since the 1960s, but has also spread in field crops since the 1980s in California, Israel and Italy where it is considered a major cause of tomato root rot. Several control measures can be used against this disease, but the most effective and ecologically sustainable measure is the use of disease-resistant cultivars. The present research studied the response to manuring in susceptible and diversely resistant tomato germplasm grown in monosuccession over a period of 3 to 5 years. Testing was carried out in commercial greenhouses on soil naturally infested by P. lycopersici, in two different locations: Bari and Valenzano in Apulia, Southern Italy. The experimental statistical design was a "split-plot" with two blocks. Each block contained one plot treated with a mixture of horse and cow manure (70 m3 ha-1) and one untreated plot. Two susceptible cultivars, Craigella and Super Marmande, two partially resistant lines, J513 and 68808 and one resistant line, Lycopersicon peruvianum 1373-9 of tomato were used. Tomato croppings were arranged in monosuccession 5 years in Bari, and 3 years in Valenzano. Disease severity was evaluated by recording the percentage of rotted root surface at 90, 140 and 190 days after transplanting and the area under disease progress curve (AUDPC) was also calculated. Treatment with manure significantly reduced AUDPC% in both the Bari and Valenzano greenhouses. No significant interaction was detected between manure and the tomato genotypes. In the Bari and Valenzano trials, manure caused a significant reduction of AUDPC% in the two susceptible cultivars during the first two years of testing. Likewise, in the same two years manuring significantly reduced AUDPC% on the partially resistant tomato line 68808 only in the Valenzano trials. In the last three years of trial tests in Bari and in the last year of trial tests in Valenzano, manuring caused no reduction of AUDPC% in susceptible tomato cultivars. During all the years of testing, manuring never caused significant reduction of AUDPC% on the partially resistant J513 line or on the highly resistant L. peruvianum 1373-9 line. On the basis of our results, polyannual manuring did not enhance the expression of resistance in either partially resistant or highly resistant tomatoes and the effectiveness of manuring in controlling corky root is of short-term duration on susceptible tomatoes. These results, together with the consideration of the high cost and technical difficulties involved, make organic farming therefore a rather dubious method of tomato corky root control and support the need for a high type resistance for a better control of this disease.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
