Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi, is the main disease affecting soybean production in Brazil. The plant introduction PI 594756 is a resistance source that has been employed in breeding for resistance to ASR in this country. This study aimed at investigating the resistance of the PI 594756 to a panel of P. pachyrhizi isolates and mapping its resistance in populations derived from the cross with the susceptible PI 594891. The PI 594756 and resistant varieties were inoculated with seven ASR monosporic isolates. F 2 and F 2:3 populations were tested against ASR in a greenhouse and used to map a resistance gene to a likely genomic location by means of bulked segregant analysis. Bulks were genotyped with In nium BeadChips and the genomic region identi ed was saturated with target GBS (tGBS). PI 594756 presented a unique resistance pro le compared to the differential varieties, being resistant to six isolates and immune to one. The resistance was visually monogenic dominant; however, it was classi ed as incompletely dominant when quantitatively studied. Genetic and QTL mapping placed the PI 594756 gene between chromosome (chr) 18 55, 863,741 and 56,123,516. This position is slightly upstream mapping positionsof Rpp1 (PI 200492) and Rpp1-b (PI 594538A). Finally, we performed a haplotype analysis of a panel composed of Brazilian historical germplasm, sources of Rpp genes and resistant varieties and found SNPs that can successfully differentiated the new allele from PI 594756 from Rpp1 and Rpp1-b sources. The haplotype identi ed can be used as a tool for marker assisted selection.
As plantas daninhas são causa do encarecimento das lavouras, entre elas está Conyza spp, conhecida como buva. Marcadores moleculares vem sendo utilizados para complementar sua caracterização. A técnica AFLP (Amplified Fragment Length Polymorphism) é adaptada para diversas análises genéticas, fornecendo alta cobertura do genoma. Com objetivo de caracterizar molecularmente morfotipos de buva, foram coletadas 60 plantas da UENP – Bandeirantes/PR. A análise molecular com AFLP seguiu etapas de digestão, ligação de adaptadores, amplificação pré-seletiva e seletiva, utilizando combinação de seis pares de primers AFLP. Os fragmentos foram separados em gel de poliacrilamida 8% e corados com AgNo3. Dos 218 loci, 97 foram polimórficos sendo 53 específicos para um morfotipo e 44 para o outro. A matriz de distância genética, a porcentagem de locos polimórficos, diversidade gênica de Nei (1978), e a distância genética foram obtidas utilizando o programa TFPGA (Tools For Population Genetcs Analyses). Os resultados da AMOVA mostram que a variação entre as populações é de 85,18% e dentro das populações é de 14,82% indicando que os morfotipos sejam espécies diferentes. Através das análises moleculares e principais características morfológicas demonstrou se que os morfotipos são espécies distintas, o morfotipo A é Conyza sumatrensis e o morfotipo B Conyza bonariensis.
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