Abstract
Septoria leaf spot (Septoria lycopersici) is one of the major fungal diseases of tomatoes (Solanum lycopersicum) in tropical and subtropical regions with humid climates and/or in areas cultivated under sprinkler irrigation systems. Sources of resistance have been found in accessions of Solanum (section Lycopersicon) species. However, many of the described sources are not effective under Brazilian conditions. The objective of this work was to evaluate wild and cultivated Solanum (section Lycopersicon) germplasm to S. lycopersici isolates. A collection of 124 accessions was initially evaluated under greenhouse conditions. Ten accessions were highly resistance (HR), whereas 33 were classified as having a resistant (R) response to S. lycopersici isolates. Field evaluation was also conducted with a sub-set of accessions identified as either HR or R in the greenhouse experiment. This field evaluation confirmed greenhouse tests and indicated the presence of some potential sources of rate-reducing resistance. One highly resistant and eight resistant S. habrochaites accessions were identified as being resistant under both conditions, confirming that this wild species is one of the most promising sources of resistance to S. lycopersici. Five new sources with high levels of resistance were found in S. peruvianum accessions (PI-306811, CNPH-1036, LA-1910, LA-1984 and LA-2744). One accession derived from an interspecific cross between S. lycopersicum and S. peruvianum was also found to be highly resistant and might be useful to introgress resistance factors from this wild species into cultivated tomato germplasm. However, additional breeding efforts will be necessary to introgress into the cultivated tomato the resistance factors identified in other S. peruvianum accessions due to the presence of natural crossing barriers between the two species.
Highlights
Septoria leaf spot, caused by the fungus Septoria lycopersici Speg., is one of the major fungal diseases of the cultivated tomato (Solanum lycopersicum L. section Lycopersicon [Mill.] Wettst. subsection Lycopersicon) inSci
Sources of resistance to S. lycopersici have been found in germplasm of wild tomatoes [Solanum L. subsection Lycopersicon, an autonym of Solanum section Lycopersicon (Mill.) Wettst.) (Peralta et al, 2005)] evaluated under either field conditions with natural inoculum (Barksdale, 1982; Maluf et al, 1985; Poysa & Tu, 1993) or under controlled greenhouse conditions using spore suspensions (Locke, 1949; Kurozawa & Balmer, 1977; Barksdale & Stoner, 1978; Sotirova & Rodeva, 1990; Moretto & Barreto, 1993)
The germplasm collection under evaluation (Table 1) comprised the following accessions: 42 S. lycopersicum L. (= Lycopersicon esculentum); 07 S. lycopersicum var. cerasiforme; 13 S. pimpinellifolium L. (= L. pimpinellifolium); one S. chilense (Dunal) Reiche (= L. chilense); one S. pennellii (Corr.) D’Arcy (= L. pennellii); 12 S. habrochaites Knapp & Spooner (= L. hirsutum) and 42 accessions belonging to S. peruvianum L. (Peralta et al, 2005; Spooner et al, 2005)
Summary
Septoria leaf spot, caused by the fungus Septoria lycopersici Speg., is one of the major fungal diseases of the cultivated tomato (Solanum lycopersicum L. section Lycopersicon [Mill.] Wettst. subsection Lycopersicon) inSci. Septoria leaf spot, caused by the fungus Septoria lycopersici Speg., is one of the major fungal diseases of the cultivated tomato Sources of resistance due to the presence of putative single dominant genes have been identified in accessions of S. lycopersicum ‘Targinnie Red’ (= LA-1800) (Andrus & Reynard, 1945) and S. pimpinellifolium PI422397 (Barksdale & Stoner, 1978). This resistance appears to be unstable (Andrus & Reynard, 1945). Accessions derived from these two sources were shown to have intermediate to susceptible responses to S. lycopersici isolates in Brazil (Maluf et al, 1985)
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