Construction of Genetic Linkage Map and Mapping QTL Specific to Leaf Anthocyanin Colouration in Mapping Population ‘Allahabad Safeda’ × ‘Purple Guava (Local)’ of Guava (Psidium guajava L.)

Abstract

In the present investigation, F1 hybrids were developed in guava (Psidium guajava L.) by crossing high leaf-anthocyanin reflective-index (ARI1) content cultivars purple guava (local) ‘PG’, ‘CISH G-1’ and low leaf-ARI1 content cultivar Seedless ‘SL’ with Allahabad Safeda ‘AS’. On the basis of phenotypic observations, high ARI1 content was observed in the cross ‘AS’ × ‘PG’ (0.214). Further, an SSR-markers-based genetic linkage map was developed from a mapping population of 238 F1 individuals derived from cross ‘AS’ × ‘PG’. The linkage map comprised 11 linkage groups (LGs), spanning 1601.7 cM with an average marker interval distance of 29.61 cM between adjacent markers. Five anthocyanin-content related gene-specific markers from apple were tested for parental polymorphism in the genotypes ‘AS’ and ‘PG’. Subsequently, a marker, viz., ‘MdMYB10F1′, revealed a strong association with leaf anthocyanin content in the guava mapping population. QTL (qARI-6-1) on LG6 explains much of the variation (PVE = 11.51% with LOD = 4.67) in levels of leaf anthocyanin colouration. This is the first report of amplification/utilization of apple anthocyanin-related genes in guava. The genotypic data generated from the genetic map can be further exploited in future for the enrichment of linkage maps and for identification of complex quantitative trait loci (QTLs) governing economically important fruit quality traits in guava.

A high-density linkage map construction in guava (Psidium guajava L.) using genotyping by sequencing and identification of QTLs for leaf, peel, and pulp color in an intervarietal mapping population

“…Similar results were observed by Zhang et al, (2019) in Brassica rapa L. for the visual color scores and color space values, as they were able to identify the same QTL regions for seed coat color. In contrast to our results, Sohi et al. (2022) identified one major and two minor QTLs for anthocyanin reflective index of guava leaves in LG3, LG6 and LG8 as the presence of anthocyanin is well known to render leaves with purple color ( Shiva et al., 2017 ).…”

“…The map has markers that are placed at short distances with the highest density of 3.9 markers/cM in LG1 and the lowest density in LG10 with 1.3 markers/cM. When compared to other published maps of guava that had an average marker distance between 3.2 and 29.6 ( Padmakar et al., 2016 and Sohi et al., 2022 ), we were able to construct the linkage map with the average marker interval at 1.8 cM. Further, the map has been constructed with a LOD value between 16 and 20 and incorporated 1426 SNPs which is also high compared to the previously reported linkage maps ( Table 4 ).…”

“…However, these studies have very low coverage and less number of markers on LGs. Interestingly, QTLs linked to the color variations in leaf, fruit peel and pulp remain unexplored as yet in guava except for a recent work on leaf anthocyanin reflective index by Sohi et al. (2022) .…”

Discovery and exploration of genes related to important agronomic traits in fruit trees

“…For the continual genetic improvement of guava, diversity at the genomic level is required (Ritter, 2012;Singh et al, 2018). Hybridization breeding enables the exploitation and transference of alleles from different genetic backgrounds for the development of better recombinants (Sohi et al, 2022). The traditional breeding of fruit crops is expensive, time consuming, and constrained by a long juvenile phase (Longhi et al, 2013).…”

“…Due to the abundance of microsatellites throughout all the genomic components of eukaryotic organisms (Kalia et al, 2011), and features such as their multiallelic nature, automation, ease of detection, reproducibility, co-dominance, and capability for high-throughput genotyping (Liu S et al, 2013;Kumar et al, 2020), SSRs are still the chosen markers in most of the marker-assisted breeding programs in horticultural crops (Ritter, 2012;Nimisha et al, 2013). Guava is still considered an orphan crop with reference to its genomic and /or genetic information (Mittal et al, 2020;Sohi et al, 2022). Recent advancements in next-generation sequencing (NGS) have considerably accelerated the discovery of SSRs, short insertions and deletions (InDels), and single-nucleotide polymorphism (SNP) as PCR-ready genome-wide markers through comparative transcriptomics in guava (Thakur et al, 2021).…”