Using soil bed cultivations as controls and under two temperature regimes (maximum/minimum ≈20/4 °C and 25/10 °C), effects of container volume (16-, 10-, and 3-L pots) on in vitro germination, in vivo tube growth, acetocarmine staining, and quantity of pollen of tomato [Lycopersicon esculentum Mill. `Moneymaker', L. pennellii (Corr.) D'Arcy accession PE-45, and of the corresponding F1 hybrid] were studied. Under the 20/4 °C regime, in comparison with soil-bed cultivated control plants, the cold sensitive cultivar, Moneymaker, grown in the two smaller pots showed significant increases of in vitro pollen germination, acetocarmine staining, and number of pollen grains produced per flower. Similar results were observed with the F1 except for the number of pollen grains which were not significantly different. Pollen of accession PE-45 was unaffected by cold and no container effect was detected. Results of in vivo pollen tube growth in `Moneymaker' at the 20/4 °C regime showed that fruit set was only possible in 3-L pots. Reduction of the negative effects of cold on pollen from plants grown in the 3-L pots may be explained in part by the daytime rise of root-zone temperatures that did not occur in the 10- or 16-L pots or in the soil bed. Therefore, fruit production of tomato plants grown under low temperatures in small pots may not be a valid predictor of commercial winter fruit production of plants cultivated in soil beds.
Eva Domínguez, Jesús Cuartero, and Rafael Fernández-Muñoz
Rafael Fernández-Muñoz, María Salinas, Marta Álvarez, and Jesús Cuartero
Genetics of resistance to Tetranychus urticae Koch and of glandular trichomes of Lycopersicon pimpinellifolium accession TO-937 in a cross between susceptible L. esculentum Mill. `Moneymaker' and resistant TO-937 was studied in a greenhouse experiment. Parents, F1, F2, and two BC1 generations, interspersed with susceptible tomato plants to avoid negative interplot interference, were artificially infested. Mite susceptibility was evaluated by a rating based on plant capacity to support mite reproduction. TO-937, BC1 to TO-937, and F1 were resistant, `Moneymaker' susceptible, and the F2 and the BC1 to `Moneymaker' segregated. Resistance was controlled by a single dominant major locus, but modulated by unknown minor loci. TO-937 presented type IV glandular trichomes, their presence governed by two dominant unlinked loci. Type IV trichome density correlated to resistance; however, a causal relationship between type IV trichomes and mite resistance could not be definitively established. The relatively simple inheritance mode will favor successful introgression of resistance into commercial tomatoes from the close relative L. pimpinellifolium.