Identificação e dosagem alélica de marcadores moleculares associados a resistência ao vírus PVY em batata

Abstract

Potato is the third main food crop in the world, and is one of the most promising crop to suppress hunger in developing countries. From the 40 viruses which infect potato growing fields, Potato virus Y (PVY) is currently considered the most important one. PVY is transmitted by several ways, all of them with limited control, begin genetic resistance the main way to control this important disease controlled by Ry genes. Molecular markers, which amplify the region containing Ry gene have been developed and are available to be used by potato breeding. This work was developed with the aim of increasing the efficiency of potato breeding programs for resistance to PVY making use of molecular assisted selection. The dissertation is divided into two chapters. In the first chapter, in order to estimate allelic dosage of Ry genes in clones used as genitors in the breeding program, progenies from seven families were genotyped with the markers RYSC3 and M45. For Ryadg gene, based on the marker RYSC, from the five PVY resistant parents analysed, four are simplex, C1883-22-97, C2372-02-02, C2388-01-02 and MB9846-1, and one is duplex, C2389- 01-02. For Rysto gene, based on the marker M45, both parents, C2388-01-02 and MB9846-1, are simplex, and the parent C2389-01-02 is duplex. For the C1883-22-97 and C2372-02-02, it was not possible to estimate the allelic dosage of the Rysto gene. In the second chapter, in order to identify germplasm with extreme resistance to PVY associated to desirable agronomic traits, clones carrying the Ry gene, belonging from eight different genetic combinations, were evaluated for characteres related to tuber appearance and yield. The genetic combinations C2389-01-02 x Asterix and BRS Ana x C1883-22-97 showed good potential to be exploited in order to add resistance to virus Y to traits related to yield and tuber appearance. The correlation between traits indicates very strong and direct association between tuber general appearance and roughness of tuber; strong and direct association of the intensity of the periderm color and tuber general appearance; between number of tubers per plant and average tuber weight; between average tuber weight and intensity of the periderm color and between the total mass of tubers per plant and total number of tubers per plant. Also, strong and inverse associations between tuber shape and flesh color and between periderm color and average tuber weight were detected. The results of our study showed that the molecular markers RYSC3 and M45 are important tools to be used by potato breeding programs to accelerate the development of cultivars with resistance to PVY.