The major objective in this study was to find a interspecific hybrid that has a high level of resistance to both leafminers (LM) and greenhouse whiteflies (GW). Interspecific hybrids were used rather than straight species accessions because we felt the level of resistance in the hybrid would probably be closer to the level of resistance possible in a commercial cultivar. In addition, we were able to rank highly resistant accessions and examine insect response to different levels of resistance. In both the LM and GW experiments a choice and no choice test was conducted and 12 different genotypes were evaluated.
In the LM experiment the following plant material was evaluated: ICR.13 (Lycopersicon esculentum); ICR.13 x LA94 (L. hirsutum); ICR.13 x LA1401 (L. cheesmanii); 'Flora-Dade' LnG (hairy mutant gene) (L. esculentum); ICR.13 x LA121 (L. pimpinellifolium); LA1716 (L. pariflorium); ICR.13 x LA716 (L. pennellii); ICR.13 x LA1958 (L. chilense); Tropic x PI127826 (L. hirsutum); Tropic x PI126449 (L. hirsutum f. galabratum); ICR.13 x LA1735 (L. pennellii); and ICR.13 x LA1421 (L. esculentum var cerasiforme). In the no choice test, 12 clones of each entry were infested with 50 adult leafminers and after one week data on number and length of mines were recorded. In the choice test, the plants infested in the no choice test were placed in ground beds and these plants were grown for 12 weeks using standard greenhouse production practices. After transplanting the plants were re-infested with 670 adult LM and with 1100 pupae on 8/31, 9/19 and 10/10. At the end of the experiment data was collected on number of leaves with mines and % reduction in leaf area/leaflet. In the no choice test: ICR13 x LA1401, ICR.13 x LA716 and ICR.13 x LA1735 had the lowest percentage of mined leaves and the least amount of mines per leaflet and plant. In the choice test: ICR.13 x LA716 and ICR.13 x LA1735 had the lowest percentage of mined leaves and the lowest % reduction in leaf area/leaflet. The entries that were intermediate in all characteristics followed were: ICR.13 x LA94, Tropic x PI127826, Tropic x PI126449 and LA1716. ICR.13 x LA121 was preferred more often than ICR.13 or 'Flora-Dade' but in the no choice test the L. esculentum entries were the most susceptible.
In the GW experiments, 'Flora-Dade' and LA1716 were replaced with ICR.13 x LA1500 (L. chmielewskii) and ICR.13 x LA1627 (L. cheesmanii). The GW experiments were conducted using either a fully mature and expanded leaf containing only 4 leaflets and an 11 cm stem section sitting in a bottle of weak nutrient solution (detached leaf experiment, DLE) or an 8 week old rooted cutting that was topped and pruned to 3 leaves and 4 leaflets/leaf (whole plant experiment, WPE). In the DLE, 21 day larvae counts were used to establish preference and small clip-on cages containing 5-10 adult GW were used to determine adult mortality, larvae development and production of a second generation. In the WPE, egg counts after 48 hours were used to indicate preference and small clip-on cages containing 5-10 adult GW were used to study larvae survival. ICR.13 x LA1735 exhibited the most adult and larvae antibiosis and non-preference, supported the lowest amount of eggs and larvae and developed the smallest second generation of adults. For all the characteristics examined except non-preference, ICR.13 was grouped with the most susceptible entries. In the 2 choice tests, ICR.13 x LA94 was preferred more often than ICR.13. All the entries in these experiments were able to support all the GW developmental stages. There were differences in the amount of antibiosis to larvae and adults and the amount of non-preference for egg laying. However, even the hybrids that exhibited the highest amount of adult antibiosis were still be able to support a second generation of adults.
The genotype that exhibited a high level of resistance to both pests was ICR.13 x LA1735. Other interesting genotypes were ICR.13 x LA94 because it was intermediate in resistance to LM and the most preferred by GW and ICR.13 x LA1401 because it had a high level of resistance to LM and was susceptible to GW.