Search Results (6)

Peaches are a fruit crop with global importance due to their economic value. Fruit quality (e.g., weight, soluble solids content (SSC)) and phenology traits (e.g., maturity date) are essential for generating novel varieties. Nevertheless, modern germplasm’s narrow genetic diversity hampers breeding efforts to enhance these traits. To identify genetic markers helpful for marker-assisted breeding, this work leveraged a diverse panel of 140 peach commercial cultivars and advanced breeding lines phenotyped across three harvest seasons for the maturity date (MD), chlorophyll absorbance (IAD), SSC, and fruit weight (FW). Genotypic data were generated via ddRADseq, identifying 5861 SNPs. A rapid linkage disequilibrium decay (critical r² = 0.308 at 950 kb) was determined, and a population structure analysis revealed two admixed genetic clusters, with phenotypic distributions influenced by seasonal environmental factors. A total of 599 marker–trait associations were detected by using single and multi-year analysis, and for each trait the surrounding genomic regions explored to identify potential candidate genes annotated with functions related to the trait under study, and expressed in peach fruits. This study highlights multiple loci potentially responsible for phenotypic variations in plant phenology and fruit quality, and provides molecular markers to assist peach breeding for fruit quality. Full article

Fruit quality and skin color are key determinants of apple marketability. This study investigated the effect of fruit maturity and 1-methylcyclopropene (1-MCP) treatment on quality attributes and chlorophyll (Chl) degradation in ‘Golden Ball’ apples during long-term cold storage. Apples were harvested at two maturity stages—low maturity (LM, starch pattern index [SPI] 6) and high maturity (HM, SPI 8)—based on Cornell’s SPI method, and subsequently treated with 1-MCP (LM+1-MCP and HM+1-MCP) before storage. At harvest, HM fruits exhibited significantly higher soluble solid content (SSC), titratable acidity (TA), red coloration (a*), index of absorbance difference (I_AD), and respiration rate compared to LM fruits, although ethylene production, internal ethylene concentration (IEC), and firmness were not affected by maturity stage. During storage, HM fruits showed a more rapid decline in firmness, SSC, and TA, along with increased IEC, respiration rate, and a* value, and reduced I_AD and Chl contents. Consistently, expression levels of genes associated with ethylene biosynthesis and Chl degradation were also higher in HM fruits. However, application of 1-MCP effectively suppressed ethylene production and respiration, thereby slowing the deterioration of fruit quality and Chl degradation in both maturity groups. Notably, the LM+1-MCP group demonstrated stronger ethylene inhibition and retained higher Chl levels than the HM+1-MCP group. Overall, the findings demonstrate that applying 1-MCP at the LM stage is a superior strategy for maintaining the postharvest quality of the apples. Full article

A new non-destructive index of absorbance difference (I_AD), calculated with different wavelengths as references, near the chlorophyll absorbance peak or that for anthocyanin, has been used to determine the fruit ripening of several fruit species using portable devices such as Standard DA-Meter^® and Kiwi-Meter^®. In this study, for the first time, the application of the I_AD was evaluated on single, intact olives of the Leccino cultivar, as a single non-destructive maturity index to follow ripening in the field, directly on the tree. The I_AD determined by both devices was found to be useful for monitoring the olive ripening, however, better performance was achieved with the Kiwi-Meter^®. In fact, the I_AD determined by this device was more effective at measuring all the studied olive ripening parameters in the calibration and validation datasets with acceptable accuracy. Specifically, better performance of the I_DA by Kiwi-Meter^® was observed in estimation of the color index (R² = 0.817, DRMSEC = 0.404 and RPIQ = 3.863 for calibration and R² = 0.752, DRMSECV = 0.574 and RPIQ = 3.244 for validation), confirming its potential for evaluating the degree of olive ripeness. This novel index has significant applicative possibilities, since it would allow rapid, on-site screening of the best harvesting time to improve the olive production in terms of both yield and quality. Full article

Traditional destructive fruit assessment methodologies are currently being replaced by non-destructive alternatives. The Kiwi-Meter™ is promoted as a non-destructive device for assessment of kiwifruit maturation and ripening. In this study, three trials evaluated the feasibility of using the Kiwi-Meter and its I_AD™ index data for monitoring maturation, ripening, and quality of Actinidia chinensis var. chinensis ‘Donghong’ kiwifruit. The findings from the trials suggest that the Kiwi-Meter provides a non-destructive tool for measuring the color or chlorophyll content of the outer tissues of ‘Donghong’ kiwifruit. Since the timing of harvest of kiwifruit is not determined solely by flesh color, the utility of the Kiwi-Meter in any wider evaluation of fruit maturation (or ripening or quality) is dependent on there being a strong association between other fruit characteristics of interest with flesh color. The ‘Donghong’ fruit used in this trial degreened fully before ripening and thus the Kiwi-Meter could not provide a measure of maturation, ripening, or fruit quality. It is concluded that the Kiwi-Meter can assess fruit for flesh color, although even for this purpose, it must be considered that the I_AD measurement may be limited to only the outer area of the fruit flesh. Full article

Fruit skin colour is one of the most important visual fruit quality parameters driving consumer preferences. Proximal sensors such as machine vision cameras can be used to detect skin colour in fruit visible in collected images, but their accuracy in variable orchard light conditions remains a practical challenge. This work aimed to derive a new fruit skin colour attribute—namely a Colour Development Index (CDI), ranging from 0 to 1, that intuitively increases as fruit becomes redder—to assess colour development in peach and nectarine fruit skin. CDI measurements were generated from high-resolution images collected on both east and west sides of the canopies of three peach and one nectarine cultivars using the commercial mobile platform Cartographer (Green Atlas). Fruit colour (RGB values) was extracted from the central pixels of detected fruit and converted into a CDI. The repeatability of CDI measurements under different light environments was tested by scanning orchards at different times of the day. The effects of cultivar and canopy side on CDI were also determined. CDI data was related to the index of absorbance difference (I_AD)—an index of chlorophyll degradation that was correlated with ethylene emission—and its response to time from harvest was modelled. The CDI was only significantly altered when measurements were taken in the middle of the morning or in the middle of the afternoon, when the presence of the sun in the image caused significant alteration of the image brightness. The CDI was tightly related to I_AD, and CDI values plateaued (0.833 ± 0.009) at I_AD ≤ 1.20 (climacteric onset) in ‘Majestic Pearl’ nectarine, suggesting that CDI thresholds show potential to be used for harvest time decisions and to support logistics. In order to obtain comparable CDI datasets to study colour development or forecast harvest time, it is recommended to scan peach and nectarine orchards at night, in the early morning, solar noon, or late afternoon. This study found that the CDI can serve as a standardised and objective skin colour index for peaches and nectarines. Full article

The decline of relative chlorophyll contents during fruit ripening is considered to be an important indicator of fruit physiological condition. The recent availability of low-cost portable visible spectrum (VIS) spectrometers has spurred research interest towards optical sensing of chlorophyll changes in intact fruit, with many scientists attempting to link the shifts in optical signals, attributed to chlorophyll changes, to different maturity and quality parameters. One of the widely available portable devices for non-destructive estimation of relative chlorophyll contents is the DA meter, which provides a maturity index that is calculated as a difference between absorption at 670 nm (near the chlorophyll-a absorption peak) and 720 nm (background of the spectrum), abbreviated as IAD. In the present study, the evolution of IAD and its relation to starch pattern index (SPI) and fruit flesh firmness (FFF) was monitored in fruit of two cv. ‘Gala’ clones during maturation and storage, aiming to identify a potential existence of a usable IAD range for the assessment and prediction of the optimal harvest window and storage potential. In both clones, canopy positions, fruit sides, and seasons IAD, SPI, and FFF generally changed in a linear fashion over time, but with partially very different slopes, i.e., they were changing at different rates. What all of these parameters had in common was the presence of a very high biological variability, which is typical of apple fruit. Significantly powerful estimations of SPI (r² > 0.7, p < 0.005) and pre- and post-storage FFF (r² > 0.6, p < 0.005) were achieved. However, the very large biological variability could not be neutralized, which means that the predictions always included large confidence intervals of up to 0.46–0.59 units for SPI and 0.82–1.1 kgF FFF, which ultimately makes them unusable for practical applications. Experiments done under real-life conditions in a commercial fruit storage facility on several different fruit batches confirmed that IAD measured at harvest cannot be used indiscriminately for predicting post-storage FFF of cv. ‘Gala’ originating from different orchards. Nevertheless, mean IAD values that were obtained at optimal maturity from samples of the same orchards remained stable over seasons (0.8–1.2), which strongly suggests that, provided that the calibrations and validations are not only cultivar, but also orchard-specific, IAD has a potential for estimating maturity and storability of apple fruit. In this case, IAD could replace standard maturity indices, otherwise it would be suited for use as a supplementary index for determining fruits physiological maturity status. Full article