Selection and breeding of tomato for organic conditions

One of the main aims of the H2020 Framework Programme BRESOV project is the development of tomato materials specifically adapted to organic agriculture. Germplasm of potential interest for organic agriculture was assembled in a core collection (CC; 233 accessions) for pre-breeding, and in a breeding set (BS; 217 accessions) for selection and breeding. Both the CC and BS have been characterized for multiple morphological, agronomic, and quality traits under organic conditions in Italy and Spain. Also, the CC and BS, and a collection of EMS mutants have been characterized for tolerance to drought and high temperature. A wide diversity was found in the materials for most traits. Most of the cultivated tomato materials of the CC and BS were also genotyped using the high-throughput ddRAD sequencing technique revealing a high genetic diversity in the collection and allowing the detection of candidate genes and associations for relevant traits under organic conditions. The screening of BS for several diseases (Phytophthora, Fusarium, TSWV, ToMV) has allowed the identification of new sources of tolerance and resistance. A selected set of materials has been screened both in Italy and in Spain under control, drought and low N fertilization conditions, and resilient materials under these conditions have been identified. Hybrids obtained between selected materials has allowed the identification of promising hybrids heterotic for yield and with high fruit quality. In addition, several backcross programmes have been undertaken in order to introduce resistance to several diseases, and advanced backcrosses with introgressed resistances have been obtained. New intraspecific and interspecific hybrids have been developed and tested as rootstocks. Some of them outperformed control rootstocks commonly used for grafting tomato. The new improved tomato materials specifically selected for organic conditions can have a dramatic impact in the production of organically grown tomato.