Inheritance of Potato virus Y tolerance introgressed from Nicotiana africana to cultivated tobacco

Abstract

Potato virus Y (PVY) is an important pathogen of to- bacco. Growing resistant cultivars is the best way to prevent si- gnificant losses of the crop caused by this virus. However, the protection given by the commonly used resistance factor, called va gene, can be overcome by the highly virulent PVY strains. Therefore, tobacco breeding for resistance will benefit from intro- ducing additional PVY resistance/tolerance factors. BPA is a to- bacco breeding line with introgressed PVY tolerance from a wild species N. africana. This trait is effective against a wide range of PVY isolates, including the ones that overcome va resistance. Here, we describe the inheritance of PVY tolerance of BPA. We obtained F1 and F2 plants from reciprocal crosses between BPA and a susceptible tobacco cultivar BP-210. Then we performed me- chanical inoculation tests using sap from PVY infected leaves on both generations of plants. Four weeks later we recorded disease symptoms and subjected all experimental plants to DAS-ELISA tests. All F1 plants developed vein necrosis which confirmed their susceptibility to the virus. The proportion of susceptible and tole- rant plants in the F2 fitted 3:1 ratio which was expected under the assumption that the tolerance is determined by a single, recessive gene. Moreover, the proportion of the susceptible and tolerant in- dividuals did not differ between two F2 populations derived from crosses where BPA was used as a maternal plant or a pollen do- nor, hence cytoplasmic factors do not influence the tolerance of that breeding line