Redefinition of the map position and validation of a major quantitative trait locus for fire blight resistance of the pear cultivar ‘Harrow Sweet’ (Pyrus communis L.)

In a previous study, a QTL analysis was conducted on a pear F1 progeny derived from a cross ‘Passe Crassane’ (PC) × ‘Harrow Sweet’ (HS). Four genomic regions associated with fire blight resistance were identified, including two main QTL located on linkage groups (LGs), 2A and 4 of ‘Harrow Sweet’ (HS02A and HS04). In the present study, we report the combination of LGs HS02A and HS02B into a single LG by mapping additional SSR loci from Malus or Pyrus spp. We could thereby precisely identify a single major QTL on LG HS02. We also confirm a putative QTL on LG HS04 by including new SSR markers to the pre-existing LG HS04. Based on SSR marker analysis of ‘Harrow Sweet’ pedigree, the major HS02 QTL is presumed to originate from the cultivar ‘Early Sweet’, while the HS04 QTL was traced from ‘Harrow Sweet’ back to ‘Bartlett’. We also describe the validation of the major HS02 QTL for the fire blight severity trait in a second F1 progeny derived from a cross ‘Angelys’ × ‘Harrow Sweet’

The complete sequence of the Acacia ligulata chloroplast genome reveals a highly divergent clpP1 gene

Legumes are a highly diverse angiosperm family that include many agriculturally important species. To date, 21 complete chloroplast genomes have been sequenced from legume crops confined to the Papilionoideae subfamily. Here we report the first chloroplast genome from the Mimosoideae, Acacia ligulata, and compare it to the previously sequenced legume genomes. The A. ligulata chloroplast genome is 158,724 bp in size, comprising inverted repeats of 25,925 bp and single-copy regions of 88,576 bp and 18,298 bp. Acacia ligulata lacks the inversion present in many of the Papilionoideae, but is not otherwise significantly different in terms of gene and repeat content. The key feature is its highly divergent clpP1 gene, normally considered essential in chloroplast genomes. In A. ligulata, although transcribed and spliced, it probably encodes a catalytically inactive protein. This study provides a significant resource for further genetic research into Acacia and the Mimosoideae. The divergent clpP1 gene suggests that Acacia will provide an interesting source of information on the evolution and functional diversity of the chloroplast Clp protease comple

Genetic mapping and pyramiding of two new pear scab resistance QTLs

Scab is one of the major fungal diseases infecting pear trees, causing the greatest economic losses. Identifying and pyramiding scab resistance factors should help in breeding new resistant pear cultivars. We have identified and mapped two new pear resistance loci against the fungal pathogen Venturia pirina. The first locus, mapped both as a major gene and as a QTL, is located on linkage group (LG) 01 of the hybrid P3480, deriving from the European pear cultivar ‘Wilder.’ It colocalizes with the Vnk resistance gene found in the Asian pear cultivar ‘Kinchaku’ against Venturia nashicola. A second locus, mapped as a QTL, is located on LG04 of the interspecific cultivar ‘Euras.’ In a small ‘Euras’ × P3480 progeny, seven seedlings carrying the resistant alleles at both loci have been selected using SSR markers

Redefinition of the map position and validation of a major quantitative trait locus for fire blight resistance of the pear cultivar ‘Harrow Sweet’ (Pyrus communis L).

In a previous study, a QTL analysis was conducted on a pear F1 progeny derived from a cross Passe Crassane (PC) · Harrow Sweet (HS). Four genomic regions associated with fire blight resistance were identified, including two main QTL located on linkage groups (LGs), 2A and 4 of Harrow Sweet (HS02A and HS04). In the present study, we report the combination of LGs HS02A and HS02B into a single LG by mapping additional SSR loci from Malus or Pyrus spp. We could thereby precisely identify a single major QTL on LG HS02. We also confirm a putative QTL on LG HS04 by including new SSR markers to the pre-existing LG HS04. Based on SSR marker analysis of Harrow Sweet pedigree, the major HS02 QTL is presumed to originate from the cultivar Early Sweet, while the HS04 QTL was traced from Harrow Sweet back to Bartlett. We also describe the validation of the major HS02 QTL for the fire blight severity trait in a second F1 progeny derived from a cross Angelys · Harrow Sweet