O fungo Podosphaera xanthii afeta a cultura do meloeiro, apresenta diversas raças e é controlado por genes de resistência raça-específica. O acesso PI414723 é resistente às raças 1, 3 e 5 e é uma fonte adequada de genes de resistência. A herança da resistência a essas raças foi analisada em 87 plantas F2 do cruzamento PI414723 × Védrantais. A resistência às três raças pode ser explicada pela segregação de um gene dominante, embora um modelo digênico também possa ser aceito. Um mapa genético foi obtido com 206 marcadores e análise de co-segregação de fenótipos resistentes indicou a existência de dois locos ligados, posicionados no grupo de ligação II, um conferindo resistência às raças 1 e 5 (denominado Pm-x1,5) e o segundo à raça 3 (denominado Pm-x3), localizado a 5,1cM. Este estudo relata pela primeira vez a existência de Pm-x3 e as localizações genéticas desses genes de resistência de PI414723.

The fungus Podosphaera xanthii affects melon crops and presents several races controlled by race-specific resistance genes. The accession PI 414723 is resistant to races 1, 3 and 5 and it is a suitable source of resistance genes. The inheritance of resistance to these races was analyzed on 87 F2 plants from the cross of PI 414723 × Védrantais, and resistance to all three races could be explained by the segregation of a single dominant gene, although a digenic model could also be accepted. A genetic map was assembled with 206 markers, and co-segregation analysis of resistance phenotypes indicated the existence of two linked loci in linkage group II, one conferring resistance to races 1 and 5 (denominated Pm-x1,5), and the second to race 3 (denominated Pm-x3), located 5.1 cM apart. This study reports for the first time the existence of Pm-x3 and the genetic locations of these resistance genes from PI 414723.

Alu-PCR is a relatively simple technique that can be used to investigate genomic instability in cancer. This technique allows identification of the loss, gain or amplification of gene sequences based on the analysis of segments between two Alu elements coupled with quantitative and qualitative analyses of the profiles obtained from tumor samples, surgical margins and blood. In this work, we used Alu-PCR to identify gene alterations in ten patients with invasive ductal breast cancer. Several deletions and insertions were identified, indicating genomic instability in the tumor and adjacent normal tissue. Although not associated with specific genes, the alterations, which involved chromosomal bands 1p36.23, 1q41, 11q14.3, 13q14.2, occurred in areas of well-known genomic instability in breast and other types of cancer. These results indicate the potential usefulness of Alu-PCR in identifying altered gene sequences in breast cancer. However, caution is required in its application since the Alu primer can produce non-specific amplification.