Genetic, metabolite and developmental determinism of fruit friction discolouration in pear

Abstract

BackgroundThe unattractive appearance of the surface of pear fruit caused by the postharvest disorder friction discolouration (FD) is responsible for significant consumer dissatisfaction in markets, leading to lower returns to growers. Developing an understanding of the genetic control of FD is essential to enable the full application of genomics-informed breeding for the development of new pear cultivars. Biochemical constituents [phenolic compounds and ascorbic acid (AsA)], polyphenol oxidase (PPO) activity, as well as skin anatomy, have been proposed to play important roles in FD susceptibility in studies on a limited number of cultivars. However, to date there has been no investigation on the biochemical and genetic control of FD, employing segregating populations. In this study, we used 250 seedlings from two segregating populations (POP369 and POP356) derived from interspecific crosses between Asian (Pyrus pyrifolia Nakai and P. bretschneideri Rehd.) and European (P. communis) pears to identify genetic factors associated with susceptibility to FD.ResultsSingle nucleotide polymorphism (SNP)-based linkage maps suitable for QTL analysis were developed for the parents of both populations. The maps for population POP369 comprised 174 and 265 SNP markers for the male and female parent, respectively, while POP356 maps comprised 353 and 398 SNP markers for the male and female parent, respectively. Phenotypic data for 22 variables were measured over two successive years (2011 and 2012) for POP369 and one year (2011) only for POP356. A total of 221 QTLs were identified that were linked to 22 phenotyped variables, including QTLs associated with FD for both populations that were stable over the successive years. In addition, clear evidence of the influence of developmental factors (fruit maturity) on FD and other variables was also recorded.ConclusionsThe QTLs associated with fruit firmness, PPO activity, AsA concentration and concentration of polyphenol compounds as well as FD are the first reported for pear. We conclude that the postharvest disorder FD is controlled by multiple small effect QTLs and that it will be very challenging to apply marker-assisted selection based on these QTLs. However, genomic selection could be employed to select elite genotypes with lower or no susceptibility to FD early in the breeding cycle.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0241-3) contains supplementary material, which is available to authorized users.

Integrated high-density consensus genetic map ofPyrusand anchoring of the ‘Bartlett’ v1.0 (Pyrus communis) genome

“…Population: a ‘Old Home’ × ‘Louise Bon Jersey’. b ‘Bayuehong’ × ‘Dangshansuli’. c Consensus genetic map derived from five populations: ‘Old Home’ × ‘Louise Bon Jersey’, PremP003 × ‘Moonglow’ (T003xM), PEAR1 × PEAR2 (T042xT081), 9 POP369 (T052xT003), and POP356 (T052xT064) 8 …”

“…1B) with European pear genetic backgrounds were used for anchoring the ‘Bartlett’ v1.0 genome scaffolds, while other genetic maps with Asian pear ( P. bretschneideri or P. pyrifolia ) genetic backgrounds were not involved in the anchoring because of the large differences in SNPs and their low efficiency of transferability among different species. These three maps included the newly created genetic map OHxLBJ, a ‘BYH’ map extracted from the ‘BYH’ × ‘Dangshansuli’ consensus map (named BYHxDS-JXB), 10 and a European pear and interspecific Asian pear hybrid consensus genetic (PH-CG) map attained from the 10 genetic maps published by Montanari et al 23 derived from five populations, including OHxLBJ, PremP003 × ‘Moonglow’ (T003xM), PEAR1 × PEAR2 (T042xT081), 9 POP369 (T052xT003), and POP356 (T052xT064) 8 . The BYH map was a subset of BYHxDS-JXB 10 with marker names start with Pyb and Pybd, representing SNPs derived from ‘BYH’ and both parents, respectively.…”

Acceleration of Forest and Fruit Tree Domestication by Genomic Selection

“…GWAS detected two significant markers for harvest time and one for the number of spurs, but predictions based on these markers were much less accurate than GS predictions; this result suggests that the traits are determined by several minor and medium QTLs as well as the major QTLs detected by GWAS. Saeed et al (2014) also suggested a possible benefit of the application of GS to the genetic improvement of friction discolouration controlled by multiple smalleffect QTLs.…”

“…Recently, Zhang et al (2013) reported a QTL analysis of six fruit traits (soluble solids content, fruit weight, fruit length, fruit diameter, fruit shape index and fruit maturity date) using a population derived from a cross between a European  Chinese pear hybrid and Chinese pear, and detected 19 QTLs. Saeed et al (2014) performed QTL analysis for fruit friction discolouration and related traits (fruit firmness, polyphenol oxidase activity, concentrations of phenolic compounds and ascorbic acid) using two populations derived from Asian  European pears, and identified a total of 221 QTLs for 22 phenotyped variables. Yamamoto et al (2014) performed QTL mapping of seven fruit traits (harvest time, fruit skin colour, flesh firmness, fruit weight, acid content, total soluble solids content, and preharvest fruit drop) using a population derived from a Japanese pear cross, and detected 12 QTLs.…”

Genetic Research Progress of Fruit Ripening and Quality Control

“…The results showed that four regions were related to cold resistance traits and two were linked to thorn density. Saeed et al (2014) used 250 seedlings of interspecific hybrids of pear from Asian (Pyrus pyrifolia Nakai and P.bretschneideri Rehd) and Europen (P. communis) which with two shared groups (POP369 and POP356) to identify the genetic factors of pear fruit friction discolouration(FD). The result showed that the single nucleotide polymorphism (SNP) based on linkage map was suitable for the development of two separate groups of female parents by QTL analysis.…”