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Glandular trichomes from some Solanum species have suppressed infestation by insects including green peach aphid, which is a main vector of potato virus Y (PVY) and potato leaf roll virus (PLRV), both of which contribute to a serious loss in potato production. Eight Solanum phureja Juz. et Buk.-S. stenotomum Juz. (Phu-Stn), three S. berthaultii Hawkes (Ber), nine F₁ [(Phu-Stn) × Ber], fifteen backcross (BC) [(Phu-Stn) × F₁], and seventeen reciprocal BC (BC_R) [F₁ × (Phu-Stn)] families were evaluated to determine the genetic variability and heritability of A and B glandular trichome density and polyphenol oxidase (PPO) activity. Experiments were carried out in completely randomized and randomized complete-block designs in the greenhouse. Genetic analysis was done using half-sib family and parent-offspring regression analysis. Phu-Stn showed a higher density of A trichomes than Ber and F₁, while the BC and BC_R had densities of A trichomes similar to Phu-Stn. B trichomes were not observed in Phu-Stn. Ber showed a high B trichome density, which was transmitted to the F₁. In the BC, B trichomes were almost absent, but, in the BC_R, the density of B trichomes was higher than that of BC. Ber and F₁ had similar or higher PPO activity than Phu-Stn. PPO activity decreased in the BC, but, in the BC_R, it was high and similar to Ber and F₁. Broad-sense heritability estimates for A and B trichome density and PPO activity were from medium to high (0.48 to 0.77) in Phu-Stn, Ber, and F₁. Narrow-sense heritability estimates for A and B trichome density and PPO activity were very low (0.04 to 0.24) in BC and BC_R. In the BC families, additive genetic variance was very low for A and B trichome density and PPO activity. Half-sib family selection based on progeny testing and combined with BCs to Phu-Stn in subsequent generations would be a suggested breeding procedure to improve these traits. Phenotypic correlations between A and B trichome densities were 0.26 (F₁) and 0.44 (BC_R), between A trichome density and PPO activity 0.20 (F₁) and 0.31 (BC_R), and between B trichome density and PPO activity 0.04 (F₁) and 0.27(BC_R. Positive associations found between traits might facilitate simultaneous improvement for high levels of A and B trichome density and PPO activity.

Prostrate growth habit (PGH) in tomato (Lycopersicon esculentum Mill.) lines derived from breeding material developed at the Agriculture Canada Research Station, Beaverlodge, Alberta, was the subject of a quantitative inheritance study. Plants with PGH have an increased lateral branch angle, relative to upright plants, and crown-set fruit supported above the soil surface making hand harvest easier. Genetic parameters were estimated in two families (20G and 53G), each containing PGH and upright-habit parental lines, F₁, F₂, and backcrosses to each parent. Field-grown plants were subjectively rated twice during the growing season. Broad-sense heritability of PGH in family 20G was estimated to be 0.65 and 0.71 for ratings of plant growth habit 6 and 9 weeks after transplanting, respectively, and 0.71 and 0.68 for those of family 53G. Narrow-sense heritability was estimated to be 0.83 and 1.05 for the two ratings in the 20G family and 0.77 and 0.78 in the 53G family. F₁ and F₂ means were not different from mid-parent values. The genetic variance was entirely additive and expression was influenced by the environment. The data did not support the hypothesis that PGH was controlled by a single gene.