19 research outputs found
Simple sequence repeats for the genetic analysis of apple
No full textThe development of highly informative markers, such as simple sequence repeats, for tagging genes controlling agronomic characters is essential for apple breeding. Furthermore the use of these markers is fundamental both for variety identification and for the characterisation and management of genetic resources. We have developed 16 reliable simple sequence repeat (SSR) markers that amplify all alleles from a panel of 19 Malus x domestica (Borkh.) cultivars or breeding selections and from Malus fioribunda 821. Those markers show a high level of genetic polymorphism, with on average 8.2 alleles per locus and an average heterozygosity of 0.78. Due to this high level of polymorphism, it was possible using two selected SSRs to distinguish all cultivars except Starking and Red Delicious. Ten of the markers we developed have been mapped on a RAPD linkage map, proving their Mendelian segregation as well as their random distribution in the apple genome. Finally, we discuss the importance of using co-dominant markers in outbreeding species
Molecular selection in apple for resistance to scab caused by Venturia inaequalis
No full textLarge-scale marker-assisted selection requires highly reproducible, consistent and simple markers. The use of genetic markers is important in woody plant breeding in general, and in apple in particular, because of the high level of heterozygosity present in Malus species. We present here the transformation of two RAPD markers, which we found previously to be linked to the major scab resistance gene Vf, into more reliable and reproducible markers that can be applied directly to apple breeding. We give an example of how the use of such markers can speed up selection for the introduction of scab resistance genes into the same plant, reducing labour and avoiding time- consuming test crosses. We discuss the nature and relationship of the scab resistance gene Vf to the one present in Nova Easygro, thought to be Vr
Marker-assisted selection in apple breeding
No full textApple breeding is aimed at creating varieties with high fruit quality, regular and high yields and durable disease and pest resistance. Traditional breeding is time and labour consuming. DNA markers for traits related to fruit quality, productivity and resistances will allow early and precise selection for desired characters. Within the framework of an EU apple genome project and the Swiss Science Foundation priority programme biotechnology we have focussed mainly on molecular markers related to scab and mildew resistance. CAPS and SCAR-markers were developed which allow to determine the allelic status of the Vf locus coding for scab resistance. Progeny plants obtained from crosses with two Vf-resistant parents were used. Markers for the Vbj scab resistance originating from Malus baccata jackii have been developed and will allow the combination of Vf and Vbj resistance in the same genotype in order to increase durability of resistance. The segregation for mildew resistance in the progeny Iduna x A 679-2 comprising 400 individuals was assessed. Quantitative trait loci (QTL)-analysis using the nonparametric Kruskal-Wallis test was performed. Major QTLs controlling mildew resistance were detected in the A 679-2 genome. A linkage map was constructed using a random subpopulation of 189 individuals of Iduna x A 679-2 using random amplified polymorphic DNA. The linkage map of A 679-2 contains 142 RAPD-markers and 9 microsatellites arranged in 15 linkage groups. Routine application of marker-assisted selection for scab resistance is being investigated also for economical feasibility
DNA markers linked to Malus floribunda 821 scab resistance
No full textBreeding resistant apple plants is an alternative way to control fungal pathogens reducing the environmental impact due to the use of pesticides. The breeding of apple cultivars resistant to Venturia inaequalis could be much improved by marker-assisted selection. A molecular marker closely linked to the resistance locus called Vf could replace selection based on infection studies. To find such molecular markers, DNA of progenies from crossings of a resistant and a susceptible apple tree was subject to bulked segregant analysis. Two markers were found with a genetic distance of 10.6% and 19.7% recombination frequency to the Vf locus
Molecular markers applied to apple breeding: analysis of oligogenic and single gene resistances
No full textThe use of molecular markers can dramatically improve apple breeding by increasing selection efficiency. We show two examples of how DNA markers have been successfully applied to prove that the resistance gene present in the cultivar 'Nova Easygro' (said to be Vr), is tightly linked to V f and is most probably Vf itself. We were able to detect homozygous resistant plants and showed that those plants are on average more resistant than the heterozygous ones. In a population obtained by crossing a powdery mildew resistant selection (A679-2) and a susceptible one ('Iduna') we studied the resistance to powdery mildew introgressed from Malus zumi (Pl 2). Genetic linkage maps of the two parental plants were constructed. By analysing Quantitative Trait Loci (QTL) we were able to detect two major genomic regions containing genes controlling the resistance. Several other minor regions have been detected both in the resistant and in the susceptible parents. The analysis of a larger sample and repeated observations over several years will enable a more precise localisation of the QTLs and evaluation of the importance of the genomic regions containing putative loci controlling powdery mildew resistance
Field update: scouting and seed collection: Denver Botanic Gardens
No full textPresented at the 15th symposium held on September 14, 2018 in Colorado Springs, Colorado
The use of open top chambers to understand the response of two rare alpine species to increased warming
No full textPresented at the 18th annual symposium held on September 10th, 2021 at Trinidad Jr. College in Trinidad, Colorado
Towards a marker assisted breeding for resistance against apple scab
No full textWe present the first attempts to find molecular markers (RAPDs) in the apple genome linked to the Vf gene conferring resistance to scab. The availability of genetic markers will allow selection of individuals with resistance genes in progeny. Moreover genetic markers allow us to recognise individuals with minimal linkage drag in back-crossing experiments with wild species. The feasibility of the bulk-segregant analysis to identify linked markers has been demonstrated on several occasions (Martin et al., 1991; Giovannoni et al., 1991; Michelmore et al., 1991). In this paper we report the preliminary results proving that the method could also be applied successfully in allogamous plants
Desenvolvimento de um mapa genético de ligação de macieira saturado para a região com resistência à mancha foliar de Glomerella (Coletotrichum gloeosporioides)
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Agrárias. Programa de Pós-Graduação em Recursos Genéticos Vegetais.Desde a década de 80, o cultivo da macieira no Brasil vem sofrendo grandes perdas devido à Mancha foliar de Glomerella (MFG) causada por Colletotrichum spp. Esta doença tem se espalhado pelos pomares do sul do Brasil, e recentemente também pelos pomares dos Estados Unidos. Devido aos prejuízos econômicos causados pela MFG é crescente a preocupação por parte da comunidade científica em buscar o entendimento dos mecanismos genéticos envolvidos na resistência a essa doença, uma vez que não existem medidas de controle químico que atendam às exigências da produção integrada (PIM). Neste sentido, o objetivo deste trabalho foi desenvolver um mapa genético de ligação, em macieira, saturado para a região que contém o gene de resistência à Mancha Foliar de Glomerella (Colletotrichum gloeosporioides), visando contribuir para a eficiência na geração de novas cultivares de macieira resistentes a essa doença. Foi analisada reação à MFG em três populações de mapeamento (M-13/91 x M-46/94, M-13/91 x 'Gala' e 'Pink Lady' x 'Imperatriz'). Os resultados obtidos nos bioensaios indicaram a necessidade de se fazer ajustes de metodologia para incubação da MFG em cada caso. A reação identificada nas populações em estudo aponta para uma resistência monogênica recessiva, concordando, portanto, com os resultados encontrados na literatura. Contudo, os resultados encontrados também não permitem rejeitar a hipótese de segregação de 9:7. Assim, não se descarta a hipótese de que outro gene esteja interferindo nas respostas das plantas ao Colletotricum spp. Foi também realizada a seleção de marcadores RAPD, microssatélites e AFLP, visando mapeamento genético de macieira em duas populações segregantes. Para os marcadores RAPD a estratégia de seleção de marcadores utilizada foi o BSA. Dos 195 iniciadores RAPD testados, nenhum apresentou produto de amplificação co-segregando com o gene de resistência a MFG. No caso dos marcadores microssatélites o polimorfismo encontrado foi abundante e dos 93 iniciadores testados, 63 foram utilizados no mapeamento genético da população M-13/91 x 'Gala'. Os marcadores AFLP apresentaram uma média de 13,1 e 10,5 fragmentos polimórficos entre os parentais das duas populações em estudo. Um mapa genético de ligação foi construído para a população proveniente do cruzamento M-13/91 x 'Gala' contendo 23 grupos de ligação abrangendo 1.179,7 cM com uma média de distância entre marcadores de 8,8 cM. O gene de resistência a MFG foi mapeado no grupo de ligação 15, próximo aos microssatélites NZ02b1 (2,1 cM), CH03b06 (6,8cM) e Hi03g06 (7,5 cM). O microssatélite NZ02b1 pode ser utilizado em programas de melhoramento de macieira, visando selecionar plantas resistentes a MFG, uma vez que o mesmo encontra-se ligado ao gene de resistência a essa doença. A freqüência de recombinação relativamente baixa entre eles caracteriza este como um marcador útil para seleção indireta
