Denis Griffin

Development of diagnostic markers for use in breeding potatoes resistant to Globodera pallida pathotype Pa2/3 using germplasm derived from Solanum tuberosum ssp. andigena CPC 2802

Quantitative resistance to Globodera pallida pathotype Pa2/3, originally derived from Solanum tuberosum ssp. andigena Commonwealth Potato Collection (CPC) accession 2802, is present in several potato cultivars and advanced breeding lines. One genetic component of this resistance, a large effect quantitative trait locus (QTL) on linkage group IV (which we have renamed GpaIVadgs) has previously been mapped in the tetraploid breeding line 12601ab1. In this study, we show that GpaIVadgs is also present in a breeding line called C1992/31 via genetic mapping in an F1 population produced by crossing C1992/31 with the G. pallida susceptible cultivar Record. C1992/31 is relatively divergent from 12601ab1, confirming that GpaIVadgs is an ideal target for marker-assisted selection in currently available germplasm. To generate markers exhibiting diagnostic potential for GpaIVadgs, three bacterial artificial chromosome clones were isolated from the QTL region, sequenced, and used to develop 15 primer sets generating single-copy amplicons, which were examined for polymorphisms exhibiting linkage to GpaIVadgs in C1992/31. Eight such polymorphisms were found. Subsequently, one insertion/deletion polymorphism, three single nucleotide polymorphisms and a specific allele of the microsatellite marker STM3016 were shown to exhibit diagnostic potential for the QTL in a panel of 37 potato genotypes, 12 with and 25 without accession CPC2082 in their pedigrees. STM3016 and one of the SNP polymorphisms, C237(119), were assayed in 178 potato genotypes, arising from crosses between C1992/31 and 16 G. pallida susceptible genotypes, undergoing selection in a commercial breeding programme. The results suggest that the diagnostic markers would most effectively be employed in MAS-based approaches to pyramid different resistance loci to develop cultivars exhibiting strong, durable resistance to G. pallida pathotype Pa2/3.

DNA fingerprinting, metalaxyl resistance and mating type determination of thePhytophthora infestans population in the Republic of Ireland

SummaryDuring the period 1995–1999 one hundred and sixty three isolates of P. infestans were collected in Ireland. The majority (150) were from the 1996 population. Isolates were analysed for mating type and sensitivity to metalaxyl, and subsets were also genotyped for mitochondrial haplotype (124) and RG-57 fingerprint (114). Four of the isolates tested were of the A2 mating-type. Of four haplotypes known, only two were detected in the Irish population. RG-57 probe analysis determined that there were 12 genotypes present. However, clustering analysis demonstrated close relationships between many of the strains found. Metalaxyl resistance was predominantly associated with two closely-related genotypes. All A2 isolates shared the same genotype. Due to the low population diversity, especially of A2, sexual reproduction does not appear to be a factor in disease epidemiology.

The effect of pyramiding two potato cyst nematode resistance loci to Globodera pallida Pa2/3 in potato

Globodera pallida is a major nematode pest causing severe constraints in many potato production regions worldwide. The most prevalent G. pallida pathotypes are Pa2 and Pa3, which exist in mixed populations referred to as Pa2/3. Due to heterogeneity for avirulence genes within these nematode populations, so far, breeders have failed to identify a single resistance gene source which offers complete resistance. Currently, there are two quantitative trait loci (QTL) available,

Molecular characterization of Ralstonia solanacearum strains from Ethiopia and tracing potential source of bacterial wilt disease outbreak in seed potatoes

GpaIV_{adg}^{s}

A disease resistance locus on potato and tomato chromosome 4 exhibits a conserved multipartite structure displaying different rates of evolution in different lineages.

and Gpa5, conferring partial levels of resistance to G. pallida pathotype Pa2/3. The objective of this research was to pyramid

Roles of shoots and roots in cadmium uptake and distribution in tubers of potato (Solanum tuberosum L)

GpaIV_{adg}^{s}