Genetic mapping of ovary colour and quantitative trait loci for carotenoid content in the fruit of Cucurbita maxima Duchesne

Abstract

The high content of carotenoids, sugars, dry matter, vitamins and minerals makes the fruit of winter squash (Cucurbita maxima Duchesne) a valuable fresh-market vegetable and an interesting material for the food industry. Due to their nutritional value, long shelf-life and health protective properties, winter squash fruits have gained increased interest from researchers in recent years. Despite these advantages, the genetic and genomic resources available for C. maxima are still limited. The aim of this study was to use the genetic mapping approach to map the ovary colour locus and to identify the quantitative trait loci (QTLs) for high carotenoid content and flesh colour. An F6 recombinant inbred line (RIL) mapping population was developed and used for evaluations of ovary colour, carotenoid content and fruit flesh colour. SSR markers and DArTseq genotyping-by-sequencing were used to construct an advanced genetic map that consisted of 1824 molecular markers distributed across linkage groups corresponding to 20 chromosomes of C. maxima. Total map length was 2208 cM and the average distance between markers was 1.21 cM. The locus affecting ovary colour was mapped at the end of chromosome 14. The identified QTLs for carotenoid content in the fruit and fruit flesh colour shared locations on chromosomes 2, 4 and 14. QTLs on chromosomes 2 and 4 were the most meaningful. A correlation was clearly confirmed between fruit flesh colour as described by the chroma value and carotenoid content in the fruit. A high-density genetic map of C. maxima with mapped loci for important fruit quality traits is a valuable resource for winter squash improvement programmes.Electronic supplementary materialThe online version of this article (10.1007/s11032-018-0869-z) contains supplementary material, which is available to authorized users.

Identification of Fruit-Associated QTLs in Winter Squash (Cucurbita maxima Duchesne) Using Recombinant Inbred Lines

“…In this region, major-effect QTLs were also mapped for fruit yield, diameter, flesh thickness and sucrose and dry matter contents. In the same region, major-effect QTLs for fruit color and carotenoid content were identified [20]. Co-localization of major-effect QTLs for fruit characteristics in a single region at the end of chromosome 4 could be explained by C. maxima diversification and/or domestication processes.…”

“…The genetic map was constructed using 802 × 801 F 6 RILs and consisted of 1824 markers-34 simple sequence repeat markers (SSRs), 1094 single-nucleotide polymorphism markers (SNPs) and 694 in silico DArTSeq markers (silicoDArTs) distributed across the 20 chromosomes of C. maxima [20]. A separate QTL analysis was conducted for each season's data.…”

“…RILs showed the variability of fruit phenotypes (Figure 1; Figure 2). This RILs population has been used in a previous study for QTL mapping of fruit flesh color and carotenoid content [20].…”

“…Despite biological and horticultural interest in C. maxima, knowledge of its genetics and genomic resources is limited in comparison with other economically important cucurbit crops. Recently, the first detailed genetic maps were developed for C. maxima [2,[19][20][21]. Additionally, the nuclear genome of C. maxima cv.…”

“…For C. maxima, the genetic bases of fruit-associated traits are largely unknown [4]. The only QTLs described so far for C. maxima have been for a dwarf vine identified in an F 2 population [19], seed-related traits using an F 2:3 population [21] and fruit flesh color and carotenoid content-identified using F 6 RILs [20].…”