Identification of the Er1 resistence gene and RNase S-alleles in Malus prunifolia var. ringo rootstock

Woolly apple aphid (WAA; Eriosoma lanigerum Hausm.) is a major insect pest that has significant economic impact on apple growers worldwide. Modern breeding technologies rely on several molecular tools to help breeders select genetic determinants for traits of interest. Consequently, there is a need for specific markers linked to the genes of interest. Apple scions and rootstocks have an additional barrier to the introduction of pest resistance genes due to the presence of self-incompatibility S-RNase alleles. The genetic characterization and early identification of these alleles can amplify the contribution of a breeding program to the selection of resistant genitors that are as compatible as possible. In this study, we identified the Er1 gene involved in the resistance to WAA in Malus prunifolia var. ringo, also known as Maruba Kaido rootstock, and we analyzed the inheritance pattern of the WAA resistance Er1 gene in a segregant population derived from Malus pumila M.9 and Maruba Kaido rootstocks. The self-incompatibility of S-RNase alleles S6S26 of Maruba Kaido were also identified along with their inheritance pattern. We also confirmed the identification of the S1S3 alleles in the M.9 rootstock. To the best of our knowledge, this is the first study to characterize WAA resistance and RNase S-alleles in Maruba Kaido. Furthermore, we discuss the potential use of the genetic markers for these genes and their potential impact on apple breeding programs.(AU)

Identification of the Er1 resistence gene and RNase S-alleles in Malus prunifolia var. ringo rootstock

Woolly apple aphid (WAA; Eriosoma lanigerum Hausm.) is a major insect pest that has significant economic impact on apple growers worldwide. Modern breeding technologies rely on several molecular tools to help breeders select genetic determinants for traits of interest. Consequently, there is a need for specific markers linked to the genes of interest. Apple scions and rootstocks have an additional barrier to the introduction of pest resistance genes due to the presence of self-incompatibility S-RNase alleles. The genetic characterization and early identification of these alleles can amplify the contribution of a breeding program to the selection of resistant genitors that are as compatible as possible. In this study, we identified the Er1 gene involved in the resistance to WAA in Malus prunifolia var. ringo, also known as Maruba Kaido rootstock, and we analyzed the inheritance pattern of the WAA resistance Er1 gene in a segregant population derived from Malus pumila M.9 and Maruba Kaido rootstocks. The self-incompatibility of S-RNase alleles S6S26 of Maruba Kaido were also identified along with their inheritance pattern. We also confirmed the identification of the S1S3 alleles in the M.9 rootstock. To the best of our knowledge, this is the first study to characterize WAA resistance and RNase S-alleles in Maruba Kaido. Furthermore, we discuss the potential use of the genetic markers for these genes and their potential impact on apple breeding programs.

ITS-rDNA phylogeny of Colletotrichum spp. causal agent of apple Glomerella leaf spot / Filogenia por ITS-rDNA de Colletotrichum spp., agente causal da mancha foliar da Gala em macieira

Several diseases have affected apple production, among them there is Glomerella leaf spot (GLS) caused by Colletotrichum spp. The first report of this disease in apple was in plants nearby citrus orchards in São Paulo State, Brazil. The origin of this disease is still not clear, and studies based on the molecular phylogeny could relate the organisms evolutionarily and characterize possible mechanisms of divergent evolution. The amplification of 5.8S-ITS (Internal Transcribed Spacer) of rDNA of 51 pathogenic Colletotrichum spp. isolates from apples, pineapple guava and citrus produced one fragment of approximately 600 bases pairs (bp) for all the isolates analyzed. The amplified fragments were cleaved with restriction enzymes, and fragments from 90 to 500bp were obtained. The sequencing of this region allowed the generation of a phylogenetic tree, regardless of their hosts, and 5 isolated groups were obtained. From the "in silico" comparison, it was possible to verify a variation from 93 to 100 percent of similarity between the sequences studied and the Genbank data base. The causal agent of GLS is nearly related (clustered) to isolates of pineapple guava and to the citrus isolates used as control.

A produção de maçã vem sendo comprometida pela ocorrência de muitas doenças, entre as quais se destaca a Mancha Foliar de Glomerella (MFG), causada por Colletotrichum spp. O primeiro relato dessa doença em maçã foi registrado em plantas próximas a pomares de citrus no Estado de São Paulo, Brasil. A origem da MFG ainda não está bem clara, e estudos baseados na filogenia permitirão relacionar o organismo evolutivamente, possibilitando caracterizar possíveis mecanismos divergentes de evolução. A amplificação da região 5.8S-ITS (espaçador interno transcrito) do rDNA de 51 isolados de Colletotrichum patogênicos em de maçã, goiabeira serrana e citrus produziu um fragmento de aproximadamente 600 pares de bases (pb) para todos os isolados analisados. Os fragmentos amplificados foram digeridos por enzimas de restrição, sendo obtidos fragmentos de 90 a 500pb. O sequenciamento dessa região permitiu a construção de uma árvore filogenética com a distribuição dos isolados em cinco grupos, independentemente de seus hospedeiros. A partir da comparação in silico, foi possível verificar uma variação de 93 a 100 por cento de similaridade entre as sequências estudadas e o banco de dados do GenBank. O agente causal da MFG está relacionado (agrupado) a isolados de goiabeira serrana e aos isolados padrões de citrus.

Transference of microsatellite markers from Eucalyptus spp to Acca sellowiana and the successful use of this technique in genetic characterization

The pineapple guava (Acca sellowiana), known in portuguese as the goiabeira-serrana or "Feijoa", is a native fruit tree from southern Brazil and northern Uruguay that has commercial potential due to the quality and unique flavor of its fruits. Knowledge of genetic variability is an important tool in various steps of a breeding program, which can be facilitated by the use of molecular markers. The conservation of repeated sequences among related species permits the transferability of microsatellite markers from Eucalyptus spp. to A. sellowiana for testing. We used primers developed for Eucalyptus to characterize A. sellowiana accessions. Out of 404 primers tested, 180 amplified visible products and 38 were polymorphic. A total of 48 alleles were detected with ten Eucalyptus primer pairs against DNA from 119 A. sellowiana accessions. The mean expected heterozygosity among accessions was 0.64 and the mean observed heterozygosity 0.55. A high level of genetic diversity was also observed in the dendrogram, where the degree of genetic dissimilarity ranged from 0 to 65 percent among the 119 genotypes tested. This study demonstrates the possibility of transferring microsatellite markers between species of different genera in addition to evaluating the extent of genetic variability among plant accessions.