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QTL Mapping Through Pedigree-Based Analysis for Six Phenological and Quality Traits in Peach
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Three studies were conducted on peaches Prunus persica (L.) Batsch]. The first was to identify QTLs and SNP haplotypes linked to the predictive SNP marker(s) for six traits. The second was to assess peaches for postharvest durability, and the third was to screen peach seedlings for susceptibility to bacterial leaf spot (BLS). To identify QTLs, seven F1 peach families were phenotyped for bloom date (BD), ripe date (RD), fruit development period (FDP), blush (BL), soluble solids content (SSC), and titratable acidity (TA) over two years in Texas and California and genotyped with the 9K SNP Illumina array. One QTL for RD and FDP was co-localized at the central part of LG4 (40 – 44 cM) with ~35 % phenotypic variance explained (PVE). Three QTLs were discovered for DB on LG1 (88 – 92 cM), LG4 (48 – 50 cM), and LG7 (40 – 44 cM), with 17 - 94%, 11 - 55%, and 11 - 18% PVE, respectively. One QTL on the central part of LG4 was found for BL (42 – 44 cM) with ~20 % PVE. A major QTL for TA co-localized with the D-locus at the proximal end of LG5 (0 - 0 cM) with ~60 % PVE. A QTL at the distal end of LG5 (52 - 62 cM) was associated with both TA and SSC with ~15 % PVE. Unique SNP haplotypes associated with the predictive SNP marker(s) of desired QTL alleles along with their original sources were identified. Thirty-five peach and nectarine genotypes grown in Texas were assessed for internal breakdown over three years (2016 - 2018) by measuring expressible juice, mealiness, and texture. Mealiness developed in TX3C394N, ‘Royal Zest Two’, ‘Texstar’, ‘Royal Zest Three’, TX3B376LWP and ‘Harvester’ fruits after storing them for two weeks at 5° C, whereas ‘Flavorrich’, ‘White Delight One’, and TX2D357LW genotypes performed well in storage. Expressible juice, mealiness, and texture were well correlated. Bacterial leaf spot incidence assessed using field evaluation and lab assessments indicated that the seven peach families were susceptible to BLS. The disease severity in the field was greatest in years with more total and more frequent rains.
Rawandoozi, Zena Jameel (2019). QTL Mapping Through Pedigree-Based Analysis for Six Phenological and Quality Traits in Peach. Doctoral dissertation, Texas A & M University. Available electronically from