Identification of a second linkage group carrying genes controlling resistance to downy mildew ( Plasmopara halstedii ) in sunflower ( Helianthus annuus L.) (original) (raw)
Related papers
Euphytica, 2008
Quantitative resistance to sunXower downy mildew was studied on inbred lines and hybrids not carrying eYcient major gene resistance, in Weld trials in one to four sites over 3 years. Hybrids from factorial crosses showed that inheritance is under additive control and comparison with reactions of parental inbred lines gave narrow sense heritabilities of 27-57%. Analysis of a polymorphic recombinant inbred line population without eYcient major gene resistance indicated that two highly signiWcant Quantitative Trait Loci (QTL) explained 42% of variation in Weld reaction to downy mildew. These QTL were mapped on linkage groups 8 and 10, and do not appear related to any of the known major resistance gene clusters. Possible bases of this type of resistance and its use in breeding are discussed.
Theoretical and Applied Genetics, 2003
The resistance of sunflower, Helianthus annuus L., to downy mildew, caused by Plasmopara halstedii, is conferred by major genes denoted by Pl. Using degenerate and specific primers, 16 different resistance gene analogs (RGAs) have been cloned and sequenced. Sequence comparison and Southern-blot analysis distinguished six classes of RGA. Two of these classes correspond to TIR-NBS-LRR sequences while the remaining four classes correspond to the non-TIR-NBS-LRR type of resistance genes. The genetic mapping of these RGAs on two segregating F2 populations showed that the non-TIR-NBS-LRR RGAs are clustered and linked to the Pl5/Pl8 locus for resistance to downy mildew in sunflower. These and other results indicate that different Pl loci conferring resistance to the same pathogen races may contain different sequences.
Sunflower downy mildew (DM) is considered to be the most destructive foliar disease that has spread to every major sunflower-growing country of the world, except Australia. A new dominant downy mildew resistance gene (Pl18) transferred from wild Helianthus argophyllus (PI 494573) into cultivated sunflower was mapped to linkage group (LG) 2 of the sunflower genome using bulked segregant analysis with 869 simple sequence repeat (SSR) markers. Phenotyping 142 BC1F2:3 families derived from the cross of HA 89 and H. argophyllus confirmed the single genic inheritance of resistance. Since no other Pl gene has been mapped to LG2, this gene was novel and designated as Pl18. SSR markers CRT214 and ORS203 flanked Pl18 at a genetic distance of 1.1 and 0.4 cM, respectively. Forty-six single nucleotide polymorphism (SNP) markers that cover the Pl18 region were surveyed for saturation mapping of the region. Six co-segregating SNP markers were 1.2 cM distal to Pl18, and another four co-segregating SNP markers were 0.9 cM proximal to Pl18. The new BC2F4-derived germplasm, HA-DM1, carrying Pl18 has been released to the public. This new line is highly resistant to all P. halstedii races identified in the USA providing breeders with an effective new source of resistance against downy mildew in sunflower. The molecular markers that were developed will be especially useful in marker-assisted selection and pyramiding of Pl resistance genes because of their close proximity to the gene and the availability of high-throughput SNP detection assays.
Molecular Markers as a Tool in Breeding for Resistance Against Sunflower Downy Mildew
2005
Sunflower production is endangered by several diseases, necessitating a sophisticated disease management. Downy mildew of sunflower incited by Plasmopara halstedii belongs to the major sunflower diseases. Recent reports of pathotypes resistant to metalaxyl showed the necessity to breed for durable resistance of future hybrids. In order to develop molecular markers for different resistance genes, bulks and near isogenic lines were analysed employing RAPD and AFLP techniques. Segregation analysis of disease resistance was performed using the whole seedling immersion method. Markers useful in indirect selection for resistance genes Pl 2 (e.g. RHA325), Pl 6 (HA335), and Pl arg (ARG1575-2) were identified. Crosses between several resistant genotypes were used in segregation and marker analyses to study the genetics of the genes involved. These experiments confirm the allelic relationship of loci Pl 2 Pl 6 and Pl 7 , whereas Pl 6 and Pl arg as well as Pl 6 and Pl 5 seem to be inherited independently. Pyramiding of the different resistance genes may result in an extended useful lifetime of the individual genes. Therefore, the markers are now employed in marker assisted selection experiments to combine for instance genes Pl 6 and Pl arg , both giving resistance to all known races so far. But also the combination of already defeated genes (like Pl 1 or Pl 2) with one of those genes giving multiple resistances may provide more durable resistance than this complex loci alone. Hence, the management of resistance against downy mildew in sunflower should employ different combinations of Pl genes, even if some of them seem to be not very effective at the moment.
Inheritance of the wide-range downy mildew resistance in the sunflower line RHA 419
Helia, 2003
Downy mildew resistance in the USDA inbred sunflower line RHA 419 was studied in F 2 and test cross progenies from crosses with a susceptible line and with lines carrying known resistance genes. RHA 419 gives resistance to all races known at present, of type II, with frequent sporulation on cotyledons in seedling tests. The cross with a susceptible line indicated that one dominant gene imparted resistance to races 304 and 710. The progenies from crosses with lines carrying Pl5, Pl6 and Pl8 all showed segregation when tested with races 304, 710 and 730,generally agreeing with the hypothesis of two independent genes. It was concluded that RHA 419 provides a diversification of resistance and its use in breeding is discussed.
Origins of major genes for downy mildew resistance in sunflower
2008
New sources of major gene resistance to sunflower downy mildew were compared with known resistance genes. All genes appear to come from crosses with wild Helianthus, and most frequently from wild H. annuus. The gene Pl6 has been found in many different ecotypes but resistances which segregate independently from this gene have also been obtained. Genes considered as different may be the result of intra-cluster recombinations. Only 1 or perhaps 2 genes have been obtained from H. argophyllus. Identification of genes from H. tuberosus, is not complete, possibly because these sources show downy mildew sporulation on cotyledons. Some other annual species also show major gene type resistances. It is concluded that knowledge of these sources is important, both for their use in breeding and also to distinguish between major gene and quantitative resistance.
Plant Breeding, 2007
The inheritance of the reaction of sunflower to downy mildew was investigated using resistant and susceptible near isogenic lines (NILs) and their F 3 families. Resistance to race 730 was evaluated using the whole seedling inoculation technique. Seventy-three F 3 families were inoculated, among which 54 families were resistant and 19 susceptible, fitting a 3 : 1 segregation ratio. F 3 families were also studied using several PCR markers. Ten markers at the Pl6 locus, specific for the resistant line, also segregated in F 3 families with a 3 : 1 ratio. The same segregation ratio occurred for microsatellite haplotypes that resembled the resistant parent, and were amplified with ORS 166 and ORS 1043. The only common fragment that was observed between resistant and susceptible parental lines was one of the TIR-NBS-LRR resistance gene analogue markers, having a restriction site. Two co-dominant cleaved amplified polymorphic sequence (CAPS) markers were obtained. The mapping data indicate that several dominant markers and two CAPS markers, developed here, completely co-segregate with the Pl6 gene conferring resistance to race 730. CAPS markers will facilitate efficient marker-assisted selection for sunflower resistance to downy mildew race 730.
TAG Theoretical and Applied Genetics, 2002
Resistance of sunflower to the obligate parasite Plasmopara halstedii is conferred by specific dominant genes, denoted Pl. The Pl6 locus confers resistance to all races of P. halstedii except one, and must contain at least 11 tightly linked genes each giving resistance to different downy mildew races. Specific primers were designed and used to amplify 13 markers covering a genetic distance of about 3 cM centred on the Pl6 locus. Cloning and sequence analysis of these 13 markers indicate that Pl6 contains conserved genes belonging to the TIR-NBS-LRR class of plant resistance genes.
Quantitative resistance to downy mildew (Plasmopara halstedii) in sunflower (Helianthus annuus)
Euphytica, 2008
Downy mildew of sunXower, caused by the Oomycete, Plasmopara halstedii is at present controlled by major resistance genes. However, the pathogen has shown a considerable capacity for changes in virulence and these resistance genes are overcome only a few years after they have been introduced into new sunXower varieties. This paper presents research for quantitative, non-race-speciWc resistance independent of major genes. The reaction of cultivated sunXower genotypes to Weld attack by downy mildew was studied over 4 years in several environments and in the presence of the two most common races in France: 703 and 710. An experimental protocol with pre-emergence irrigation was developed, making it possible to observe downy mildew reaction whatever the weather conditions. SigniWcant levels of partial resistance were observed in about 50 inbred sunXower lines among the 800 observed. These results suggest that it should be possible to select for non-race-speciWc downy mildew resistance and to include it in modern varieties. However, since this non-speciWc resistance is partial, it may be necessary to combine it with major gene resistance. Possible strategies are discussed to obtain durable resistance to downy mildew.
Theoretical and Applied Genetics, 2012
Major gene resistance to sunflower downy mildew (Plasmopara halstedii) races 304 and 314 was found to segregate independently from the resistance to races 334, 307 and 304 determined by the gene Pl2, already positioned on Linkage Group (LG) 8 of sunflower molecular maps. Using a consensus SSR-SNP map constructed from the INEDI RIL population and a new RIL population FU 9 PAZ2, the positions of Pl2 and Pl5 were confirmed and the new gene, denoted Pl21, was mapped on LG13, at 8 cM from Pl5. The two RIL populations were observed for their quantitative resistance to downy mildew in the field and both indicated the existence of a QTL on LG8 at 20-40 cM from the major resistance gene cluster. In addition, for the INEDI population, a strong QTL on LG10, reported previously, was confirmed and a third QTL was mapped on LG7. A growth chamber test methodology, significantly correlated with field results, also revealed the major QTL on LG10, explaining 65 % of variability. This QTL mapped in the same area as a gene involved in stomatal opening and root growth, which may be suggested as a possible candidate to explain the control of this character.