CONICET | Buscador de Institutos y Recursos Humanos

Sipha maydis (Passerini) is a new aphid pest of cereals and cultivated and wild grasses that was recently introduced into America. This species was first reported in Argentina in 2002 in Mendoza province, close to the Andes and currently it is widespread in the main cereal producing area. This aphid damages mature cereal plants in late spring by reducing leaf area and inhibiting ear expansion. The young leaves of infested wheat become chlorotic, which results in reduced plant growth and flag leaf expansion with consequent decrease in yield. Since there are none previous report of resistance against this new pest in Argentinean bread wheat varieties, the aim of this research was to assess the defence strategies of 47 commercial cultivars. The antixenosis, antibiosis and tolerance mechanisms of plant resistance were determined by traditional tests. It was used a population of S maydis, collected from 2004 to 2010, with a wide genetic variability. Antixenotic type of resistance was identified in 24% of the cultivars. Only four varieties, with the same genetic background, showed a high antibiotic level that did not allow the aphid survivorship. One half of the cultivars had an intermediate level of tolerance and the rest showed significant losses in aerial biomass, dry weight and chlorophyll contents, when subjected to infestation. The scarce resistance found in commercial cultivars and the wide range of climatic conditions this species is adapted to is likely to make the control of this pest very difficult. An adequate level of resistance was identified in only a few varieties, their use would enable the breeding of new wheat lines by crossing with genotypes carrying other desirable genes affecting the aphid cycle, and/or conferring tolerance to S.maydis to broaden aphid resistance breeding.