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  • Author or Editor: Rong Zhang x
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‘Korla’ fragrant pear (Pyrus sinkiangensis T.T. Yu) variety has shown severe coarse skin in recent years. The intrinsic quality of its coarse fruit shows an increase in the number of stone cells and poor taste. In this study, stone cells and the cell wall of coarse pear (CP) and normal pear (NP) during various development stages were compared using paraffin-sectioning and transmission electron microscopy (TEM), and the relationships between lignin-related genes and stone cell formation and cell wall thickening were also analyzed. Our results show that giant stone cells are formed and distributed in the core of pear, whereas many of these crack 60 days after flowering (DAF). The period of stone cell fragmentation occurs later in CP fruits than in NP fruits. Parenchyma cell wall development in CP and NP fruits varies from 120 DAF to maturity. The parenchyma cell wall of CP fruits thickens, whereas that of NP fruits is thinner during the same period. The expression pattern of five genes (Pp4CL1-l, PpHCT-l, Pp4CL2-l, PpPOD4, and PpPOD25) coincides with changes in stone cell content in the pulp. Correlation analysis demonstrates a significant correlation between stone cell content and the expression level of the five genes (ρ < 0.05). In addition, the expression of those five genes and PpCCR1 genes in CP fruits significantly increases during maturation and is highly correlated with the thickness of the parenchyma cell wall. The aim of this work is to provide insights into the mechanism of stone cell and parenchyma cell wall development in pear fruits and identify important candidate genes to regulate the quality of fruit texture using bioengineering methods.

Open Access

Bearded iris (Iris ×hybrida Hort.) is a large horticultural hybrid complex in the Iris genus, and the lack of understanding about its inheritance laws has seriously hindered the breeding process. From parental bearded iris ‘Indian Chief’ and ‘Sugar Blues’, four hybrid populations—including F1, F2, BC1P1, and BC1P2—were generated through hybridization. Fifteen key phenotypic traits, including plant height (PH), scape height (SH), length of fall (LF), width of fall (WF), length of standard (LS), width of standard (WS), and so on, were measured, and several genetic parameters (e.g., trait variation, heritability, trait correlation, distribution of flower color) were analyzed. The variation of phenotypic traits indicated that the F1 generation could produce larger flowers and a greater number of blooming stems than other generations, whereas backcrossing was beneficial at producing more flowers on one scape in the offspring of ‘Indian Chief’ and ‘Sugar Blues’. WF had the greatest broad-sense heritability (73.91%) among the 15 phenotypic traits, whereas the broad-sense heritability of SH was the lowest (2.06%). The correlation between a vegetative trait (PH) and a reproductive trait (WS) provided a path to early selection of germplasm. Furthermore, four important floral traits (LF, WF, LS, and WS) also correlated significantly to each other, thus simplifying the selection of larger flowers. Genes regulating fuchsia flower color were dominant over those for bluish purple flowers. Genetic effects of flower color in recurrent parents could be reinforced by backcrossing, thereby providing a potential way to modify flower color through hybridization.

Free access

Potassium (K+) is an essential nutrient element for the growth and development of sweetpotato [Ipomoea batatas (L.) Lam.]. To investigate growth and physiological responses to K+ deficiency during early growth stage of sweetpotato, two representative cultivars with different tolerance to K+ deficiency were chosen. The seedlings of ‘Xushu 32’ (tolerance to K+ deficiency) and ‘Ningzishu 1’ (sensitive to K+ deficiency) were cultured in three different K+ concentrations (K0: 0 mmol·L−1 K+; K1: 5 mmol·L−1 K+; and K2: 20 mmol·L−1 K+, the control) of nutrient solution. Results showed that the extreme K+ deficiency (K0) significantly reduced the total dry weight, leaf number, root length, and chlorophyll content (CCI) compared with K2. However, the growth traits of ‘Xushu 32’ were less suppressed than those of ‘Ningzishu 1’. The net photosynthetic rate (P n), stomatal conductance (g S), and transpiration rate (T r) of ‘Ningzishu 1’ were significantly decreased in K0 and K1 (low K+), whereas ‘Xushu 32’ showed no significant change in K1 treatment. Increasing minimal fluorensence (F 0) of ‘Ningzishu 1’ comes with decreased maximum quantum efficiency of photosystem II (PSII) photochemistry (F v/F m) and photochemical quenching (q P) at K0 treatment. However, all the chlorophyll fluorescence parameters in ‘Xushu 32’ were nonsignificantly changed by K+ deficiency (K0 and K1). These results suggest that ‘Xushu 32’ could maintain a better growth state to adapt to K+ deficiency stress, which may be mainly because of a lighter affected photosynthesis and a less damaged PSII reaction center.

Free access

The study here aimed to investigate the effects of pre-winter ditching and freezing-thawing on soil microbial structure in different soil layers of old apple orchards. A total of 30 samples were obtained from 3 Nov. 2016 to 9 Mar. 2017. The relative abundance, alpha diversity, community structure of fungi, and the relationship between environmental factors and microbial community structure were analyzed, and the greenhouse experiments were used for further verification. Results showed that the number of actinomycete and total bacterial colonies decreased, whereas the number of fungi sustained decreased, resulting in a higher bacteria/fungi ratio. The percentage of Fusarium initially decreased, then later increased by 11.38%, 3.469%, 2.35%, 2.29%, and 3.09%. However, Fusarium levels were still 9% lower on 9 Mar. 2017 that on 3 Nov. 2016. Both the abundance and diversity of the community were higher in the upper soil than in the lower. The main environmental factor contributing to the percentage of Fusarium change was average temperature (AT), although highest temperature (HT) and water content (WC) also had an impact. The Malus hupehensis Rehd. seedlings growing in lower soil were more vigorous than that in upper soil. In sum, pre-winter ditching and freezing-thawing in old apple orchards can reduce the abundance percentage of harmful Fusarium and promote the growth of M. hupehensis Rehd. seedlings.

Open Access

A pot experiment was performed to investigate the effects of Trichoderma harzianum on the root morphology of Malus hupehensis Rehd. seedlings and their soil environment under replant conditions. The experiment consisted of four treatments: continuously cropped soil (CK1), methyl bromide fumigation (CK2), carrier substrate control (T1), and T. harzianum fertilizer (T2). Plant growth parameters, soil phenolic acid content, abundance of soil microorganisms, and root respiration rate were measured. Compared with CK1, plant height, basal diameter, and fresh weight were 34.58%, 27.55%, and 32.91% greater in T2; 11.35%, 12.10%, and 18.33% greater in T1; and 54.34%, 57.64%, and 45.74% greater in CK2. These metrics were significantly higher in the CK2 treatment than in the other treatments. The second highest values were recorded in the T2 treatment. Differences in root architecture were consistent with differences in biomass. Application of T. harzianum fertilizer was associated with increases of 45.45%, 120.06%, 86.44%, and 268.29% in the activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), respectively, and there was little difference between T2 and CK2. The contents of phlorizin and phloretin were 39.39% and 51.70% less in T2, respectively, and 17.85% and 18.14% less in T1, respectively, compared with CK1. Trichoderma harzianum fertilizer increased the abundance of bacteria and actinomycetes while decreasing that of fungi. The gene copy numbers of Fusarium oxysporum and Fusarium moniliforme were 64.30% and 49.35% less, respectively, in the T2 treatment. The fungus population and the gene copy number of Fusarium oxysporum and Fusarium moniliforme was the least in CK2 because of the good sterilization effect. The T. harzianum fertilizer showed satisfactory effects in promoting the root growth of M. hupehensis, increasing the root resistance, decreasing the soil phenolic acid content, and significantly reducing the gene copy number of F. oxysporum and F. moniliforme. In summary, T. harzianum fertilizer is an effective and green alternative for the prevention and control of apple replant disease (ARD).

Open Access

Broccoli (Brassica oleracea var. italica) is an important vegetable crop rich in vitamins and sulforaphane. However, the floral heads of broccoli experience rapid postharvest senescence. Here we found that hydrogen sulfide (H2S) treatment alleviated dark-promoted senescence in broccoli florets. H2S delayed the symptoms of senescence and maintained higher levels of chlorophyll and Rubisco and lower protease activity compared with water control. Gene expression analysis showed that H2S down-regulated the expression of chlorophyll degradation-related genes BoSGR, BoNYC, BoCLH1, BoPPH, and BoRCCR. Expression of lipoxygenase gene BoLOX1 and the genes involved in the ethylene synthesis pathway, BoACS2 and BoACS3, were also down-regulated by H2S. The reduced expression level in cysteine protease gene BoCP3 and aspartic protease gene BoLSC807 suggested the role of H2S in alleviating protein degradation during broccoli senescence. H2S up-regulated the expression of sulfur metabolism genes BoSR and BoOASTL, and the antioxidant gene BoCAT. These results show that H2S plays a vital role in alleviating broccoli senescence through a broad regulation on gene expression of reactive oxygen species (ROS) metabolism genes, ethylene synthesis genes, and protease genes.

Free access

Dendrobium officinale Kimura et Migo is a famous traditional Chinese medicinal plant. It produces various phytochemicals, particularly polysaccharides, which have nutraceutical and pharmaceutical values. To increase its biomass production and polysaccharide content, our breeding program has generated a series of polyploid cultivars through colchicine treatment of protocorm-like bodies (PLBs). The present study compared two tetraploid cultivars, 201-1-T1 and 201-1-T2, with their diploid parental cultivar, 201-1, in an established in vitro culture system. Tetraploid ‘201-1-T1’ and ‘201-1-T2’ had shorter leaves and shorter and thicker stems and roots, and they produced higher biomass compared with the diploid cultivar. The length and width of stomata significantly increased, but stomatal density decreased in tetraploid cultivars. The PLB induction rates from the stem node explants of the tetraploid cultivars were significantly higher than those of diploid. However, the PLB proliferation of tetraploids was lower than that of the diploid. The mean number of plantlets regenerated from tetraploid PLBs was also lower than that of the diploid after 4 months of culture. Polysaccharide contents in stems, leaves, and roots of 6-month-old tetraploid plantlets were significantly higher than those of diploids. The polysaccharide content in the stem of ‘201-1-T1’ was 12.70%, which was a 2-fold increase compared with the diploid cultivar. Our results showed that chromosome doubling could be a viable way of improving D. officinale in biomass and polysaccharide production.

Free access

Kiwifruit (Actinidia deliciosa) is a typical climacteric fruit, and its ripening is closely associated with ethylene. In this study, we present evidence that H2S alleviated ethylene-induced ripening and senescence of kiwifruit. Kiwifruit were fumigated with ethylene released from 0.4 g·L−1 ethephon solution or H2S with 1 mm sodium hydrosulfide (NaHS) as the donor or in combination. Fumigation with ethylene was found to accelerate kiwifruit ripening and H2S treatment effectively alleviated ethylene-induced fruit softening in parallel with attenuated activity of polygalacturonase (PG) and amylase. Ethylene + H2S treatment also maintained higher levels of ascorbic acid, titratable acid, starch, soluble protein, and reducing sugar compared with ethylene group, whereas suppressed the increase in chlorophyll and carotenoid. Kiwifruit ripening and senescence under ethylene treatment was accompanied by elevation in reactive oxygen species (ROS) levels, including H2O2 and superoxide anion and malondialdehyde (MDA), but combined treatment of ethylene plus H2S alleviated oxidative stress in fruit. Furthermore, the activities of antioxidative enzymes catalase (CAT) and ascorbate peroxidase (APX) were increased by ethylene + H2S treatment in comparison with ethylene alone, whereas the activities of lipoxygenase (LOX) and polyphenol oxidase (PPO) were attenuated by H2S treatment. Further investigations showed that H2S repressed the expression of ethylene synthesis-related genes AdSAM, AdACS1, AdACS2, AdACO2, and AdACO3 and cysteine protease genes, such as AdCP1 and AdCP3. Taken together, our findings suggest that H2S alleviates kiwifruit ripening and senescence by antagonizing the effect of ethylene through reduction of oxidative stress and inhibition of ethylene synthesis pathway.

Free access

The relationship between soil texture and the degree of apple replant disease (ARD) was analyzed from the perspective of the microbial community structure and diversity within the rhizosphere soil of Malus hupehensis Rehd. seedlings. Three different textured soils were taken from different apple orchards in Laizhou, Yantai. The soils were divided into two parts, one was kept in replanted conditions, and the other was fumigated with methyl bromide to act as a high standard control. The strength of ARD occurrence was examined by measuring fresh and dry weight suppression (%) of the M. hupehensis seedlings. Differences in the fungal community structure (especially in Fusarium) among the three soil texture types were analyzed using high-throughput sequencing. The results showed that replanted loam clay soil had the highest fungal diversity, followed by sandy loam soil and finally loam soil. The richness of fungi between soil textures, however, was not significantly different. At the genus level, the relative abundance of Fusarium was 1.96%, 0.78%, and 10.89% in replanted sandy loam, replanted loam soil, and replanted loam clay soil, respectively. Moreover, the gene copy number of Fusarium oxysporum, Fusarium solani, and the inhibition rate of fresh weight of M. hupehensis seedlings were the same in the three soil textures. The plant height, photosynthesis (net) (Pn), and stomatal conductance (g S) of the M. hupehensis seedlings were significantly less in the replanted soil compared with the control treatments, with the overall difference being greatest in replanted loam clay soil, followed by replanted sandy loam and then replanted loam soil.

Open Access

Chinese cymbidiums are important flowering ornamental plants. Traditional propagation via seed or division cannot satisfy growers’ demand for commercialization of new cultivars, and in vitro propagation has a low micropropagation efficiency due to the browning of rhizomes. In this study, rhizomes of Cymbidium ‘14-16-13’ and ‘14-16-5’ were cultured on half-strength Murashige and Skoog (MS) medium supplemented with 6-benzyl aminopurine (BAP), NAA (α-napthaleneacetic acid), or BAP with NAA under either the dark or light. The degree of browning was read, and rhizome proliferation or sprouting (sprout numbers) was evaluated. Results showed that there was significant difference in browning grade of rhizomes between ‘14-16-13’ and ‘14-16-5’ regardless of dark and light culture. Dark culture induced rhizome proliferation but failed to induce sprouts. Light culture slightly elevated the degree of browning but induced sprouting. Among the growth regulators evaluated, BAP was more effective for sprout induction. As rhizome browning appeared to be inevitable in micropropagation of the cymbidiums, a compromise between browning and sprout production could be a realistic approach. Our study showed that rhizomes cultured on half-strength MS medium supplemented with 1.5 mg·L−1 BAP were able to produce more than 16 sprouts per vessel even though browning occurred in the rhizomes. Thus, culturing rhizomes in this medium could be a practical solution for in vitro propagation of Chinese cymbidiums.

Open Access