Cinética da secagem de amostras de pera com geometrias distintas em secador solar (Pyrus L. ) / Drying kinetics of pear samples with different geometries in solar dryer

O objetivo do estudo foi realizar a desidratação de amostras de pera através da secagem solar e obter as respectivas curvas de secagem. As amostras foram submetidas à desidratação em dois tipos de geometrias, circulares com 1cm de espessura e em cubos com 1cm de comprimento. Os dados experimentais das curvas de secagem para as duas condições foram ajustados ao modelo matemático de secagem baseado na Segunda Lei de Fick. Os resultados mostram que a umidade do fruto é de aproximadamente 85%. As amostras apresentaram peso constante a partir de 18 horas de experimento para a geometria plana e a partir de 30 horas para a geometria cilíndrica. O coeficiente difusivo, obtido através da aplicação da Segunda Lei de Fick, para geometria plana foi de 6,4 x 10(-4)m2/s e para a geometria cilíndrica de 3,35 x 10(-4) m2/s.

BBX16, a B-box protein, positively regulates light-induced anthocyanin accumulation by activating MYB10 in red pear.

The red coloration of pear (Pyrus pyrifolia) results from anthocyanin accumulation in the fruit peel. Light is required for anthocyanin biosynthesis in pear. A pear homolog of Arabidopsis thaliana BBX22, PpBBX16, was differentially expressed after fruits were removed from bags and may be involved in anthocyanin biosynthesis. Here, the expression and function of PpBBX16 were analysed. PpBBX16's expression was highly induced by white-light irradiation, as was anthocyanin accumulation. PpBBX16's ectopic expression in Arabidopsis increased anthocyanin biosynthesis in the hypocotyls and tops of flower stalks. PpBBX16 was localized in the nucleus and showed trans-activity in yeast cells. Although PpBBX16 could not directly bind to the promoter of PpMYB10 or PpCHS in yeast one-hybrid assays, the complex of PpBBX16/PpHY5 strongly trans-activated anthocyanin pathway genes in tobacco. PpBBX16's overexpression in pear calli enhanced the red coloration during light treatments. Additionally, PpBBX16's transient overexpression in pear peel increased anthocyanin accumulation, while virus-induced gene silencing of PpBBX16 decreased anthocyanin accumulation. The expression patterns of pear BBX family members were analysed, and six additional BBX genes, which were differentially expressed during light-induced anthocyanin biosynthesis, were identified. Thus, PpBBX16 is a positive regulator of light-induced anthocyanin accumulation, but it could not directly induce the expression of the anthocyanin biosynthesis-related genes by itself but needed PpHY5 to gain full function. Our work uncovered regulatory modes for PpBBX16 and suggested the potential functions of other pear BBX genes in the regulation of anthocyanin accumulation, thereby providing target genes for further studies on anthocyanin biosynthesis.

Ethylene response factors Pp4ERF24 and Pp12ERF96 regulate blue light-induced anthocyanin biosynthesis in 'Red Zaosu' pear fruits by interacting with MYB114.

KEY MESSAGE: Pp4ERF24 and Pp12ERF96 fine tune blue light-induced anthocyanin biosynthesis via interacting with PpMYB114 and promoting the interaction between PpMYB114 and PpbHLH3, which enhances the expression of PpMYB114-induced PpUFGT. The red coloration of pear fruit is attributed to anthocyanin accumulation, which is transcriptionally regulated by the MYB-bHLH-WD40 complex. A number of ethylene response factors (ERF) have been identified to regulate anthocyanin biosynthesis in different plants. In pear, several ERF transcription factor genes were identified to be potentially involved in the light-induced anthocyanin biosynthesis according to transcriptome data. But the molecular mechanism of these ERFs underlying the regulation of anthocyanin accumulation is unknown. In this study, exposure of 'Red Zaosu' pear, a mutant of 'Zaosu' pear, to blue light significantly induced the anthocyanin accumulation by increasing the expression levels of anthocyanin biosynthetic genes. Gene expression analysis confirmed that the expression of Pp4ERF24 and Pp12ERF96 genes were up-regulated in the process of blue light-induced anthocyanin biosynthesis. Yeast two-hybrid and bimolecular fluorescence complementation assay revealed that Pp4ERF24 and Pp12ERF96 interacted with PpMYB114, but not with PpMYB10. Bimolecular fluorescence complementation assay demonstrated that the interaction between these two ERFs and PpMYB114 enhanced the interaction between PpMYB114 and PpbHLH3. Further analysis by dual luciferase assay verified that these two ERFs increased the up-regulation of PpMYB114-mediated PpUFGT expression. Furthermore, co-transformation of Pp12ERF96 with PpMYB114 and PpbHLH3 in tobacco leaves led to enhanced anthocyanin accumulation. Transient overexpression of Pp4ERF24 or Pp12ERF96 alone in 'Red Zaosu' pear fruit also induced anthocyanin biosynthesis in pear peel. Our findings provide insights into a mechanism involving the synergistic interaction of ERFs with PpMYB114 to regulate light-dependent coloration and anthocyanin biosynthesis in pear fruits.

The blue light signal transduction pathway is involved in anthocyanin accumulation in 'Red Zaosu' pear.

MAIN CONCLUSION: A conserved blue light sensing and transduction pathway contributes to blue light-induced anthocyanin accumulation in the peel of red pear. Peel color is an economically important characteristic that influences the appearance quality of red pear, whose red color is due to anthocyanin accumulation. The process of coloration in the fruit peel is strongly influenced by light. However, how light quality influences color development remains unclear. In this study, we analyzed the effects of different light qualities on color development in the red pear 'Red Zaosu', a mutant of the hybrid cultivar 'Zaosu' of Pyrus pyrifolia and P. communis. The results showed that blue light increased anthocyanin accumulation after 72 h of light treatment, while red light had almost no effect. The expression of anthocyanin biosynthesis-related genes showed a similar trend to the anthocyanin accumulation. To clarify the mechanism of blue-light induced coloration, PpCRYs, PpCOP1 and PpHY5 genes were cloned. Gene expression analysis showed that their transcript abundance did not correlate with the expression of anthocyanin-related genes or anthocyanin content, but the yeast two-hybrid system revealed conserved physical interactions among these proteins. In addition, PpHY5 directly bound to the promoters of the anthocyanin biosynthesis genes PpCHS, PpDFR, PpANS and PpMYB10, and activated the transcription of PpCHS in a Nicotiana benthamiana-based dual-luciferase assay. In summary, our results preliminarily revealed that the conserved blue light signal transduction module CRY-COP1-HY5 contributed to the anthocyanin biosynthesis induced by blue light in red pear. However, our results did not provide evidence for why red light had no effect on anthocyanin accumulation, which needs further study.

Transcriptome analysis of bagging-treated red Chinese sand pear peels reveals light-responsive pathway functions in anthocyanin accumulation.

Bagging is an efficient method to improve fruit colour development. This work reported a transcriptome analysis using bagging-treated red Chinese sand pear peels. In total, 8,870 differentially expressed genes were further analysed by a weighted gene co-expression network analysis and early-, middle- and late light-responsive genes were identified. An annotation analysis revealed several pathways involved in the different responsive stages. The presence of LONG HYPOCOTLY 5, CRY-DASH and a CONSTANS-like transcription factors among the early light-responsive genes indicated the pivotal role of light, especially blue light, in the biological changes that occurred after bag removal. Other light-responsive transcription factors were also identified from the three light-responsive stages. In addition, the light-responsive pattern of anthocyanin biosynthetic genes differed among the biosynthetic steps. Although yeast-one hybrid assay showed that most of the structural genes were regulated by PpMYB10, their different temporal expressive pattern suggested that besides PpMYB10, other light-responsive transcriptional factors were also involved in the regulation of anthocyanin biosynthesis. In summary, our transcriptome analysis provides knowledge of the transcriptional regulatory network operating during light responses, which results in anthocyanin accumulation and other significant physiological changes in red Chinese sand pear peels after bag removal.

Characterization of virus-derived small interfering RNAs in Apple stem grooving virus-infected in vitro-cultured Pyrus pyrifolia shoot tips in response to high temperature treatment.

BACKGROUND: Heat treatment (known as thermotherapy) together with in vitro culture of shoot meristem tips is a commonly used technology to obtain virus-free germplasm for the effective control of virus diseases in fruit trees. RNA silencing as an antiviral defense mechanism has been implicated in this process. To understand if high temperature-mediated acceleration of the host antiviral gene silencing system in the meristem tip facilitates virus-derived small interfering RNAs (vsiRNA) accumulation to reduce the viral RNA titer in the fruit tree meristem tip cells, we used the Apple stem grooving virus (ASGV)-Pyrus pyrifolia pathosystem to explore the possible roles of vsiRNA in thermotherapy. RESULTS: At first we determined the full-length genome sequence of the ASGV-Js2 isolate and then profiled vsiRNAs in the meristem tip of in vitro-grown pear (cv. 'Jinshui no. 2') shoots infected by ASGV-Js2 and cultured at 24 and 37 °C. A total of 7,495 and 7,949 small RNA reads were obtained from the tips of pear shoots cultured at 24 and 37 °C, respectively. Mapping of the vsiRNAs to the ASGV-Js2 genome revealed that they were unevenly distributed along the ASGV-Js2 genome, and that 21- and 22-nt vsiRNAs preferentially accumulated at both temperatures. The 5'-terminal nucleotides of ASGV-specific siRNAs in the tips cultured under different temperatures had a similar distribution pattern, and the nucleotide U was the most frequent. RT-qPCR analyses suggested that viral genome accumulation was drastically compromised at 37 °C compared to 24 °C, which was accompanied with the elevated levels of vsiRNAs at 37 °C. As plant Dicer-like proteins (DCLs), Argonaute proteins (AGOs), and RNA-dependent RNA polymerases (RDRs) are implicated in vsiRNA biogenesis, we also cloned the partial sequences of PpDCL2,4, PpAGO1,2,4 and PpRDR1 genes, and found their expression levels were up-regulated in the ASGV-infected pear shoots at 37 °C. CONCLUSIONS: Collectively, these results showed that upon high temperature treatment, the ASGV-infected meristem shoot tips up-regulated the expression of key genes in the RNA silencing pathway, induced the biogenesis of vsiRNAs and inhibited viral RNA accumulation. This study represents the first report on the characterization of the vsiRNA population in pear plants infected by ASGV-Js2, in response to high temperature treatment.

Comparison of phenolic metabolism and primary metabolism between green 'Anjou' pear and its bud mutation, red 'Anjou'.

Green 'Anjou' pear and its bud mutation, red 'Anjou' were compared to understand their differences in phenolic metabolism and its effect on primary metabolism. In the flesh of the two cultivars, no difference was detected in the concentration of any phenolic compound, the transcript level of MYB10 or the transcript levels or activities of key enzymes involved in anthocyanin synthesis. Compared with green 'Anjou', the shaded peel of red 'Anjou' had higher anthocyanin concentrations, higher transcript levels of MYB10 and higher activity of UDP-glucose:flavonoid 3-O-glycosyltransferase (UFGT), suggesting that MYB10 regulates UFGT to control anthocyanin synthesis in red 'Anjou' peel. In the sun-exposed peel, activities of phenylalanine ammonia lyase, dihydroflavonol reductase, flavonol synthase and anthocyanidin synthase as well as UFGT were higher in red 'Anjou' than in green 'Anjou'. The peel of red 'Anjou' had higher activities of sorbitol dehydrogenase, raffinose synthase and sucrose synthase and higher levels of raffinose, myo-inositol and starch, indicating that sorbitol metabolism, raffinose synthesis and starch synthesis were upregulated in red 'Anjou'. The flesh of red 'Anjou' had higher concentrations of glucose, but lower activities of ATP-dependent phosphofructokinase, pyruvate kinase and glucose-6-phosphate dehydrogenase and lower dark respiration. The peel of red 'Anjou' had higher activities of glutaminase, asparagine synthetase and asparaginase, and higher concentrations of asparagine, aspartate, alanine, valine, threonine and isoleucine. The effects of anthocyanin synthesis on primary metabolism in fruit peel are discussed.

The effect of gamma irradiation as a phytosanitary treatment on physicochemical and sensory properties of bartlett pears.

A major concern in exporting agricultural commodities is the introduction or spread of exotic quarantine pests to the new area. To prevent spread of insect pests, various phytosanitary measures are used. Worldwide commercial use of irradiation as a phytosanitary treatment has increased greatly in recent years; however, trade has been limited to tropical fruits. Bartlett pear is a major summer variety of California pears with great potential and market for export. In this study, the effect of gamma irradiation at dose levels of 400, 600, and 800 Gy on physicochemical properties and sensory attributes of early and late harvest Bartlett pears was investigated. Firmness and color changes indicate that irradiation delayed the ripening of pears by 1 d. For the early harvest pears, scarring, bruising, and off flavor were significantly increased at the highest irradiation dose (800 Gy). The appearance of early harvest 800 Gy irradiated pears was the only attribute that received significantly (P ≤ 0.05) lower scores than the control in consumer testing. For the late harvest pears, the 400 Gy fruit had lowest levels of scarring and bruising as rated by trained panelist but consumers did not score the control and 800 Gy fruit differently for any attribute. Titratable acidity, total soluble solids, and chroma were significantly (P ≤ 0.05) decreased and hue increased by irradiation for the early harvest pears. These results suggest that there was a difference in radiotolerance of early and late harvest pears, but in both cases, irradiation at 400 to 600 Gy seemed to maintain best quality.

Compositional changes in 'Bartlett' pear ( Pyrus communis L.) cell wall polysaccharides as affected by sunlight conditions.

Preharvest conditions can have a great impact on fruit quality attributes and postharvest responses. Firmness is an important quality attribute in pear, and excessive softening increases susceptibility to bruising and decay, thus limiting fruit postharvest life. Textural characteristics of fruits are determined at least in part by cell wall structure and disassembly. Few studies have analyzed the influence of fruit preharvest environment in softening, cell wall composition, and degradation. In the current work 'Bartlett' pears grown either facing the sun (S) or in the shade (H) were harvested and stored for 13 days at 20 °C. An evaluation of fruit soluble solids, acidity, color, starch degradation, firmness, cell wall yield, pectin and matrix glycan solubilization, depolymerization, and monosaccharide composition was carried out. Sun-exposed pears showed more advanced color development and similar levels of starch degradation, sugars, and acids than shaded fruit. Sunlight-grown pears were at harvest firmer than shade-grown pears. Both fruit groups softened during storage at 20 °C, but even after ripening, sun-exposed pears remained firmer. Sunlight exposure did not have a great impact on pectin molecular weight. Instead, at harvest a higher proportion of water-solubilized uronic acids and alkali-solubilized neutral sugars and a larger mean molecular size of tightly bound glycans was found in sun-exposed pears. During ripening cell wall catabolism took place in both sun- and shade-grown pears, but pectin solubilization was clearly delayed in sun-exposed fruit. This was associated with decreased removal of RG I-arabinan side chains rather than with reduced depolymerization.

The properties of terrestrial laser system intensity for measuring leaf geometries: a case study with Conference Pear trees (Pyrus communis).

Light Detection and Ranging (LiDAR) technology can be a valuable tool for describing and quantifying vegetation structure. However, because of their size, extraction of leaf geometries remains complicated. In this study, the intensity data produced by the Terrestrial Laser System (TLS) FARO LS880 is corrected for the distance effect and its relationship with the angle of incidence between the laser beam and the surface of the leaf of a Conference Pear tree (Pyrus commmunis) is established. The results demonstrate that with only intensity, this relationship has a potential for determining the angle of incidence with the leaves surface with a precision of ±5° for an angle of incidence smaller than 60°, whereas it is more variable for an angle of incidence larger than 60°. It appears that TLS beam footprint, leaf curvatures and leaf wrinkles have an impact on the relationship between intensity and angle of incidence, though, this analysis shows that the intensity of scanned leaves has a potential to eliminate ghost points and to improve their meshing.

Use of UV-C treatment to inhibit the microbial growth and maintain the quality of Yali pear.

UNLABELLED: The effects of UV-C radiation on microbial growth in vitro (Monilinia fruticola) and in inoculated Yali pears (Pyrus bretschneideri Rehd.) were investigated. Moreover, postharvest quality and the activities of defense and antioxidant enzymes were analyzed after the pears were exposed to UV-C irradiation at an energy level of 5 kJ m⁻².The results showed that spore germination of M. fructicola was significantly inhibited by each of the 3 doses (1, 5, and 10 kJ m⁻²) in vitro. In the in vivo assays, lesion diameter on the fruit being inoculated before or after the UV-C treatment was both significantly lower than that on the fruit of control. Meanwhile, the activities of phenylalanine ammonia lyase, ß-1,3-glucanase, superoxide dismutase, catalase, and glutathione reductase were induced to high levels by UV-C treatment. We conclude that UV-C treatment could reduce postharvest disease by the germicidal and induced effects and maintain the quality by enhancing the antioxidant enzyme activities. PRACTICAL APPLICATION: UV-C radiation has recently been proposed as a new technology to avoid chemical fungicides. However, there are few studies regarding the effect of UV-C treatment on Yali pear. In this study, we found that 5 kJ m⁻² UV-C irradiation can control postharvest disease and maintain the quality of Yali pear. This method may be applied to reduce the decay of Yali pears during exporting and storage.

Evidence for a photoprotective function of low-temperature-induced anthocyanin accumulation in apple and pear peel.

The light requirement and low-temperature stimulation of anthocyanin synthesis in peel of apple (Malus domestica) and pears (Pyrus communis) and the presence of anthocyanins in immature fruits are not congruent with a visual function in dispersal. We hypothesized that anthocyanins afford photoprotection to peel during low-temperature-induced light stress and that the protection is not a fortuitous side-effect of light absorption by anthocyanin. The extent of photoinhibition at harvest and after light stress treatment in pear cultivars differing in redness decreased with increasing red color on the sun-exposed sides of fruits. Green-shaded sides of the pears showed comparable levels of photoinhibition indicating that pears did not differ in their inherent photosensitivity. Apple and pear peel show considerable short-term fluctuation in redness in response to temperature, with red color increasing rapidly in response to low temperature and just as quickly fading in response to high temperature. Briefly, shading pears and apples during cold conditions for 2 days reduced the accumulation of anthocyanin and increased the photosensitivity of peel. Subsequent shading during warm conditions did not affect the accumulation of anthocyanin or the photosensitivity of peel indicating that the response at low temperature was not due to shade adaptation. The assessment of photosystem II (PSII) efficiency and quenching of chlorophyll fluorescence between 16 and 40 degrees C indicated that 'Forelle' pear peel was particularly sensitive to photostress at low temperature. The photosynthetic system in mature 'Forelle' leaves was comparatively much less sensitive to light stress at low temperature. Results support the view that anthocyanins are adaptable light screens deployed to modulate light absorption in sensitive tissues such as fruit peel in response to environmental triggers such as cold front snaps.

Red 'Anjou' pear has a higher photoprotective capacity than green 'Anjou'.

Photoprotective function of anthocyanins along with xanthophyll cycle and antioxidant system in fruit peel was investigated in red 'Anjou' vs green 'Anjou' pear (Pyrus communis) during fruit development and in response to short-term exposure to high light. The sun-exposed peel of red 'Anjou' had higher maximum quantum yield of photosystem II (F(V)/F(M)) than that of green 'Anjou' and both the sun-exposed peel and the shaded peel of red 'Anjou' had smaller decreases in F(V)/F(M) after 2-h high light (photon flux density of 1500 mumol m(-2) s(-1)) treatment than those of green 'Anjou'. At the middle and late developmental stages, the xanthophyll cycle pool size on a chlorophyll basis, the activity of superoxide dismutase, ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) and the level of reduced ascorbate and total ascorbate pool in the sun-exposed peel were either the same or lower in red 'Anjou' than in green 'Anjou', whereas the xanthophyll cycle pool size on a chlorophyll basis and the activity of APX, catalase, MDAR, DHAR and GR in the shaded peel were higher in red 'Anjou' than in green 'Anjou'. It is concluded that red 'Anjou' has a higher photoprotective capacity in both the sun-exposed peel and the shaded peel than green 'Anjou'. While the higher anthocyanin concentration along with the larger xanthophyll cycle pool size and the higher activity of some antioxidant enzymes may collectively contribute to the higher photoprotective capacity in the shaded peel of red 'Anjou', the higher photoprotective capacity in the sun-exposed peel of red 'Anjou' is mainly attributed to its higher anthocyanin concentration.