RESUMO
Quince familias de papa (824 genotipos) provenientes de cruzas inter-específicas entre especies de Solanum stenotomum, S. goniocalyx y S. phureja fueron genotipadas, con el objetivo de asociar seis marcadores moleculares (GP94, HC, Nl25, Gro 1-4, RYSC3 y CP60) con genes mayores de resistencia para tizón tardío (Phytophthora infestans), verruga (Synchytrium endobioticum), nematodo - quiste (Globodera pallida y G. rostochiensis) y virus PVY y PVX. Los resultados mostraron que cinco de los marcadores aplicados fueron polimórficos y amplificaron en más del 80% de las familias. El marcador RYSC3 que co-localiza con el gen Ry adg no amplificó en ninguna de las familias evaluadas. La familia 8 amplificó la banda para tres marcadores (CP60, GP94 y NL25) en la totalidad de sus clones. La prueba de χ² se utilizó para determinar el ajuste de las proporciones de segregación de cada familia para cada marcador y genotipar los progenitores. Nueve caracteres agronómicos y morfológicos fueron evaluados en la cosecha. Mediante agrupamiento cluster fueron seleccionados 107 clones con resistencia a PVX, P. infestans, G. rostochiensis y S. endobioticum, alto rendimiento y volumen de tubérculos, elevado número de tubérculos y ojos superficiales. Sobre la base de estos resultados, aspectos prácticos para la aplicación eficiente de la selección asistida por marcadores moleculares son discutidos en este artículo.
Fefteen families of potato (824 genotypes) originated from inter-specific crosses among Solanum stenotomum, S. goniocalyx and S. phureja were genotyped in order to associate six molecular markers (GP94, HC, Nl25, Gro 1-4, RYSC3 y CP60). These molecular markers are linked to major genes for resistance to late blight (Phytophthora infestans), wart (Synchytrium endobioticum), root cyst nematode (Globodera pallida and G. rostochiensis) and viruses PVY and PVX. Results showed that five of six molecular markers were polymorphic and primers amplified in more than 80 % of the families. Molecular marker RYSC3 that is linked to Rya dg gene did not amplify in any family. All individuals in Family 8 scored positive for three markers (CP60, GP94, and NL25). χ² test was used to determine the significance of the segregation ratios of each marker in every single family; so to the possible genotype of its parents was inferred. Nine morphological and agronomical characters were assessed during the harvest. Cluster analysis classified and selected 107 genotypes by putative resistance to PVX, P. infestans, G. rostochiensis and S. endobioticum, high yield, tuber volume and tuber number and shallow eyes. According to our results, practical aspects of efficient use of marker assisted selection in potato are discussed in this paper.
RESUMO
Asian soybean rust (ASR), caused by the phytopathogenic fungi Phakopsora pachyrhizi, has caused large reductions in soybean (Glycine max) yield in most locations in Brazil where it has occurred since it was first reported in May 2001. Primary efforts to combat the disease involve the development of resistant cultivars, and four dominant major genes (Rpp1, Rpp2, Rpp3 and Rpp4) controlling resistance to ASR have been reported in the literature. To develop new long-lasting soybean ASR resistance genes, we used field experiments to assess ASR leaf lesion type in 11 soybean genotypes (BR01-18437, BRS 184, BRS 231, BRS 232, BRSGO Chapadões, DM 339, Embrapa 48, PI 200487, PI 230970, PI 459025-A and PI 200526) and the 55 F2 generations derived from their biparental diallel crosses. The results indicated that PI 200487 and PI 200526 carry different dominant resistance major genes which are both different from Rpp2 through Rpp4. Furthermore, resistance to ASR in BR01-18437 is controlled by a single recessive major gene, also different from Rpp1 through Rpp4 and different from the genes in PI 200487 and PI 200526.