Proof of concept of Bayesian integrated QTL analyses across pedigree-related families from breeding programs of an outbreeding species. Results include QTL confidence intervals, individuals' genotype probabilities and genomic breeding values. Bayesian QTL linkage mapping approaches offer the flexibility to study multiple full sib families with known pedigrees simultaneously. Such a joint analysis increases the probability of detecting these quantitative trait loci (QTL) and provide insight of the magnitude of QTL across different genetic backgrounds. Here, we present an improved Bayesian multi-QTL pedigree-based approach on an outcrossing species using progenies with different (complex) genetic relationships. Different modeling assumptions were studied in the QTL analyses, i.e., the a priori expected number of QTL varied and polygenic effects were considered. The inferences include number of QTL, additive QTL effect sizes and supporting credible intervals, posterior probabilities of QTL genotypes for all individuals in the dataset, and QTL-based as well as genome-wide breeding values. All these features have been implemented in the FlexQTL(™) software. We analyzed fruit firmness in a large apple dataset that comprised 1,347 individuals forming 27 full sib families and their known ancestral pedigrees, with genotypes for 87 SSR markers on 17 chromosomes. We report strong or positive evidence for 14 QTL for fruit firmness on eight chromosomes, validating our approach as several of these QTL were reported previously, though dispersed over a series of studies based on single mapping populations. Interpretation of linked QTL was possible via individuals' QTL genotypes. The correlation between the genomic breeding values and phenotypes was on average 90 %, but varied with the number of detected QTL in a family. The detailed posterior knowledge on QTL of potential parents is critical for the efficiency of marker-assisted breeding.
Powdery mildew (Blumeria graminis f. sp. tritici) is one of the major diseases of wheat (Triticum aestivum). Adult plant resistance (APR) to powdery mildew is considered more durable than resistance conferred by major race-specific resistance genes. The objective of the present study was a better understanding of the genetic basis of APR in RE714 by means of QTL analysis of several resistance scores along the growing season. A population of 160 recombinant inbred lines obtained from the cross between RE714 and Hardi (susceptible) was assessed for APR under natural infection conditions during 3 years and a genetic map with whole genome coverage was developed with microsatellite and AFLP markers in this population. Two major QTL on chromosomes 5D and 6A were detected each year, and 6 minor QTL were detected only in 1 or 2 years. The QTL on chromosome 5D was detected during all the growing season each year and its R 2 value varied between 8.5 and 56.3%, whereas the QTL on chromosome 6A was detected at 1-4 scoring dates in the 3 years, and its R 2 value varied between 6.1 and 20.5%. The two QTL explained between 24.4 and 52.1% of the phenotypic variance for AUDPC, depending on the year. The models including QTL and cofactors in the composite interval mapping explained between 29 and 72% of the variance. The molecular markers linked to the two major QTL could be used in marker-assisted selection for adult plant resistance to powdery mildew.
On the basis of the fresh weight of apple fruit and its peel and the concentration of bioactive compounds, the total quantity of L-cysteine, glutathione, ascorbate, flavonols, and anthocyanins as well as phenolics was evaluated in a wide range of cultivars and two growing seasons. Apple peel as a contributor to the entire apple quantity of the examined components considerably differed in relation to the investigated compounds and was also highly cultivar dependent. A great amount of flavonols was found in apple peel (approximately 40%), followed by ascorbate (approximately 30%) and total phenolics (approximately 20%), while the lowest contribution was assessed for thiols (approximately 11% and 14% for L-cysteine and total quantity of glutathione, respectively), based on average values for both years. Seasonal variations in the quantity of antioxidants was more pronounced in apple peel, whereas the contribution of apple peel to the whole fruit was predominantly affected by the genotype. A very high positive correlation existed between apple peel and the whole fruit quantity of antioxidants.
Postharvest treatment by 1-methylcyclopropene (1-MCP) for ‘Szampion’ cultivar apples inhibits ripening of climacteric fruit by blocking ethylene receptors, preventing ethylene from binding and eliciting its action. It is also possible to apply 1-MCP preharvest, which so far has not been studied for the ‘Szampion’ cultivar. The aim of this study was to assess the effects of preharvest 1-MCP treatment on the fruit quality parameters of cold-stored ‘Szampion’ cultivar apples in a Polish experiment. Two identical groups of apple trees (6 years, experimental orchard in Warsaw) were included, to obtain studied apples (preharvest 1-MCP treatment with HarvistaTM, 150 g/ha, 7 days before the optimum harvesting window, OHW) and control apples (1-MCP not applied). Apples for the studied group were harvested twice—on 28 September (OHW) and 24 October (delayed harvesting)—and for control group once—on 28 September, as before 24 October the majority of apples fell from trees. Afterwards, apples were stored in an Ultra Low Oxygen chamber (1.2% CO2, 1.2% O2). Apples were assessed in the preharvest period (weekly, six measurements for the studied group, and five measurements for the control group) and postharvest period (monthly, three measurements separately for each harvest time for the studied group and control group). The following parameters were assessed: internal ethylene content (IEC), firmness, total soluble solids (TSS) content, starch index, Streif index, titratable acidity (TA), and color for blush. For the preharvest period, statistically significant differences between the studied group and the control group were observed for IEC, the a* coordinate of color (p < 0.05; for apples treated with 1-MCP lower results), firmness, Streif index, TA (p < 0.05; higher results), and starch index (p < 0.05; no defined trend). For the postharvest period, statistically significant differences between the studied group and the control group were observed for apples harvested in the OHW for firmness (p < 0.05; for apples treated with 1-MCP higher results) and IEC (p < 0.05; no defined trend), while for delayed harvesting the differences were only minor. It may be concluded, that preharvest 1-MCP application makes it possible not only to obtain better results for ‘Szampion’ cultivar apples’ quality parameters, but also allows delayed harvesting without deterioration in quality.
Antioxidant Capacity, Anthocyanin Content Profile in ‘Bluecrop’ Blueberry Fruit Mature ‘Bluecrop’ berries, with no visible damage on the fruit surface, were picked by hand and placed in a common cold storage (as control) and under CA conditions consisting of 8 different CO2:O2 ratios (12:1.5, 12:3, 12:6, 12:12 and 18:1.5, 18:3, 18:6, 18:12) at 0°C. HPLC was used to separate and determine individual anthocyanin compounds in blueberry fruit. ‘Bluecrop’ blueberries contained 14 anthocyanins: glycosides of delphinidin, cyanidin, peonidin, petunidin and malvidin all with sugar bound at the 3-position. Generally, the content of anthocyanin compounds in fruit was the highest after 2 or 4-week storage. Total anthocyanin content was significantly higher in berries stored under CA condition, especially under low oxygen concentration, as compared with those placed in common cold storage, and CO2 concentration does not have any effect. Antioxidant activity strongly correlated with total anthocyanin content, delphinidin-3-glucoside, delphinidin-3-galactoside, delphinidin-3-arabinoside, petunidin-3-glucoside, petunidin-3-galactoside and with firmness, but slightly correlated with soluble solids and titratable acidity.
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