Ramirez, CC (reprint author), Univ Talca, Inst Biol Vegetal & Biotecnol, Talca, Chile.In the last few years an increasing interest on species and hybrids of the genus Populus has occurred in Chile. However, such plantations are strongly affected by pest and diseases. With the aim to identify potentially resistant (or less susceptible) hybrids of the genus Populus, the susceptibility of some poplar hybrids growing in experimental nurseries in Southern-Center Chile to the aphid Chaitophorus leucomelas Koch and to the rust Melampsora spp. was assessed. Results showed that aphid abundance was higher in the month of March, particularly in Coinco (O'Higgins Region) and lower in Pillanlelbun (Los Rios Regions) and Yumbel (Biobio Region). In Pillanlelbun the most susceptible hybrid to aphids was TDxTD [(P. trichocarpa x P. deltoides) x (P. trichocarpa x P. deltoides)], and the less susceptible ones were TDxD [(P. trichocarpa x P. deltoides) x P. deltoides], TxN (P. trichocarpa x P. nigra), TMxTM [(P. trichocarpa x P. maximowitzii) x (P. trichocarpa x P. maximowitzii)] and TDxT [(P. trichocarpa x P. deltoides) x P. trichocarpa]. Hybrid TxN (P. trichocarpa x P. nigra) was the most susceptible to rust in all testing sites, while the less susceptible hybrids were TDxT [(P. trichocarpa x P. deltoides) x P. trichocarpa], TDxD [(P. trichocarpa x P. deltoides) x P. trichocarpa] and TDxT [(P. trichocarpa x P. deltoides) x P. trichocarpa]. These susceptibilities varied among localities, particularly on aphids. Genetic and environmental factors accounting for by these results are discussed
