Temperature Effects on Tuber Production and Carbohydrates Partitioning in Different Cultivars During Consecutive Stages of Potato (Solanum tuberosum L.) Growth

The main objective of this study was to assess responses of mid-early (Spunta) and mid-late (Bellini) potato cultivars to different temperature regimes during subsequent stages of potato growth. The impact of high temperature (25/22°C day/night), low temperature (18/16°C day/night) and intermediate temperature (20/18°C day/night) was evaluated for different growth stages. Data were obtained for photosynthesis, carbohydrates in leaves, stems and tubers as well as production parameters. Enzyme activities were determined for sucrose-phosphate synthase in leaves, acid invertase in stems and acid and neutral invertases in tubers. Gene expression levels of relevant sugar metabolizing enzymes was quantified.A detailed correlation analysis revealed a strong impact of the expression level of sugar metabolizing enzymes in leaves on the final number of tubers per plant.Whereas total tuber yield increases with temperature, the number of tubers per plant was highest under low temperature conditions. Our data suggest an important role of the temperature on the length of the different growth stages.

Genome sequencing and population resequencing provide insights into the genetic basis of domestication and diversity of vegetable soybean

Vegetable soybean is one of the most important vegetables in China, and the demand for this vegetable has markedly increased worldwide over the past two decades. Here, we present a high-quality de novo genome assembly of the vegetable soybean cultivar Zhenong 6 (ZN6), which is one of the most popular cultivars in China. The 20 pseudochromosomes cover 94.57% of the total 1.01 Gb assembly size, with contig N50 of 3.84 Mb and scaffold N50 of 48.41 Mb. A total of 55 517 protein-coding genes were annotated. Approximately 54.85% of the assembled genome was annotated as repetitive sequences, with the most abundant long terminal repeat transposable elements. Comparative genomic and phylogenetic analyses with grain soybean Williams 82, six other Fabaceae species and Arabidopsis thaliana genomes highlight the difference of ZN6 with other species. Furthermore, we resequenced 60 vegetable soybean accessions. Alongside 103 previously resequenced wild soybean and 155 previously resequenced grain soybean accessions, we performed analyses of population structure and selective sweep of vegetable, grain, and wild soybean. They were clearly divided into three clades. We found 1112 and 1047 genes under selection in the vegetable soybean and grain soybean populations compared with the wild soybean population, respectively. Among them, we identified 134 selected genes shared between vegetable soybean and grain soybean populations. Additionally, we report four sucrose synthase genes, one sucrose-phosphate synthase gene, and four sugar transport genes as candidate genes related to important traits such as seed sweetness and seed size in vegetable soybean. This study provides essential genomic resources to promote evolutionary and functional genomics studies and genomically informed breeding for vegetable soybean.

A Vacuolar Invertase CsVI2 Regulates Sucrose Metabolism and Increases Drought Tolerance in Cucumis sativus L.

Vacuolar invertase (VI) can irreversibly degrade sucrose into glucose and fructose and involve in plants abiotic-stress-tolerance. Cucumber (Cucumis sativus L.) is susceptible to drought stress, especially during the seedling stage. To date, the involvement of VI in drought tolerance in cucumber seedlings is in urgent need of exploration. In the present study, a cucumber vacuolar invertase gene, CsVI2, was isolated and functionally characterized. The results showed that (1) CsVI2 showed vacuolar invertase activity both in vivo and in vitro; (2) the transcript level of CsVI2, along with VI activity, was significantly induced by drought stress. Moreover, the expression of sucrose synthase 3 (CsSUS3) was increased and that of sucrose phosphate synthase 1 (CsSPS1) was decreased after exposure to drought stress, which was followed by an increase in sucrose synthase activity and a decrease in sucrose phosphate synthase activity; (3) CsVI2-overexpressing transformed cucumber seedlings showed enhanced vacuolar invertase activity and drought tolerance and 4) protein–protein interaction modelling indicated that a cucumber invertase inhibitor, CsINVINH3, can interact with CsVI2. In summary, the results indicate that CsVI2 as an invertase can regulate sucrose metabolism and enhance drought stress in cucumber seedlings.

The difference in temperature between day and night affects the strawberry soluble sugar content by influencing the photosynthesis, respiration and sucrose phosphatase synthase

Plenty of studies have demonstrated that DIF has an effect on the fruit growth. To study the effects of day and night temperature differences on the strawberry sugar quality, an experiment using climate chambers was conducted. Five different differences between the day and night temperatures (DIF) were set, which were 6 °C (28 °C/22 °C, day/night temperature), 8 °C (29 °C/21 °C), 10 °C (30 °C/20 °C), 12 °C (31 °C/19 °C), 14 °C (32 °C/18 °C). The results showed the following indices peaked with a DIF of 12 °C, including the photosynthesis rate, glucose content, fructose content, sucrose content, soluble sugar content and sugar metabolic enzyme activity. The respiration rate increased with the DIF during the day and decreased with the DIF at night. The root dry weight peaked at a DIF of 10 °C, the stolon dry weight peaked at a DIF of 8 °C and the leaf dry weight peaked at a DIF of 6 °C; however, the fruit dry weight reached maximum values at a DIF of 12 °C. The Grey correlation analysis showed that the most important factor in our experiment affecting the fructose content was the sucrose phosphate synthase; however, for the sucrose, glucose, and soluble sugars, the most important factor was the photosynthesis. We found that a DIF of 12 °C (31 °C/19 °C, day/night temperature) was the most suitable for strawberry growth, especially for the sugar content accumulation.

Genotypic variation in root morphology, cotton subtending leaf physiology and fiber quality against nitrogen

Background Nitrogen (N) is important for improving various morphological and physiological processes of cotton but their contribution to fiber quality is still lacking. Aims The current study aimed to explore the relationship between root morphology, subtending leaf physiology, and fiber quality of contrasting N-efficient cotton genotypes in response to N. Methods We analyzed the above parameters of CCRI 69 (N-efficient) and Xinluzao-30 (XLZ-30, N-inefficient) under control (2.5 mmol·L−1) and high N (5 mmol·L−1) conditions. Results The results showed that root morphological traits were increased in CCRI-69 under control conditions than high N. Subtending leaf morphology, chlorophyll and carotenoid contents, free amino acids, and soluble proteins were higher under high N as compared with the control. However, soluble sugars, fructose, sucrose contents, and sucrose phosphate synthase were higher under control conditions than high N across the growth stages. Irrespective of the N conditions, all morphological and physiological traits of cotton subtending leaf were higher in CCRI-69 than XLZ-30. Except for fiber uniformity, fiber quality traits like fiber length, strength, micronaire, and elongation were improved under control conditions than high N. Between the genotypes, CCRI-69 had significantly higher fiber length, strength, micronaire, and elongation as compared with XLZ-30. Strong positive correlations were found between root morphology, soluble sugars, sucrose content, and sucrose phosphate synthase activity with fiber quality traits, respectively. Conclusions These findings suggest that CCRI-69 performed better in terms of growth and fiber quality under relatively low N condition, which will help to reduce fertilizer use, the cost of production, and environmental pollution.

The Involvement of Glucose in Hydrogen Gas-Medicated Adventitious Rooting in Cucumber

Hydrogen gas (H2) and glucose (Glc) have been reported as novel antioxidants and signal molecules involved in multiple biological processes in plants. However, the physiological roles and relationships of H2 and Glc in adventitious rooting are less clear. Here, we showed that the effects of different concentrations Glc (0, 0.01, 0.05, 0.10, 0.50 and 1.00 mM) on adventitious rooting in cucumber were dose-dependent, with a maximal biological response at 0.10 mM. While, the positive roles of hydrogen rich water (HRW, a H2 donor)-regulated adventitious rooting were blocked by a specific Glc inhibitor glucosamine (GlcN), suggesting that Glc might be responsible for H2-regulated adventitious root development. HRW increased glucose, sucrose, starch and total sugar contents. Glucose-6-phosphate (G6P), fructose-6-phosphate (F6P) and glucose-1-phosphate (G1P) contents were also increased by HRW. Meanwhile, the activities of sucrose-related enzymes incorporating sucrose synthase (SS) and sucrose phosphate synthase (SPS) and glucose-related enzymes including hexokinase (HK), pyruvate kinase (PK) and adenosine 5′-diphosphate pyrophosphorylase (AGPase) were increased by HRW. Moreover, HRW upregulated the expression levels of sucrose or glucose metabolism-related genes including CsSuSy1, CsSuSy6, CsHK1, CsHK3, CsUDP1, CsUDP1-like, CsG6P1 and CsG6P1-like. However, these positive roles were all inhibited by GlcN. Together, H2 might regulate adventitious rooting by promoting glucose metabolism.

Effects of Seaweed Extracts on the Growth, Physiological Activity, Cane Yield and Sucrose Content of Sugarcane in China

Seaweed extracts (SEs) have been widely used as biostimulants in crop management due to their growth-promoting and stress-resistant effects. To date, there are few reports of the effect of SEs on sucrose content and cane yield. Here, we conducted field experiments for three consecutive growth seasons (2017∼2019) in two areas (Suixi and Wengyuan) of China, to investigate the yield and sugar content of sugarcane in response to SE treatment at different growth stages. The results showed that spraying SEs once at seedling (S), early elongation (E), and early mature (M) stages, respectively, once at S and E stages, respectively, or once at the S stage increased the cane yield by 9.23, 9.01, and 3.33%, respectively, implying that SEs application at the early elongation stage played a vital role in promoting sugarcane growth. Photosynthetic parameters and nutrient efficiency analysis showed that spraying SEs at S and E stages enhanced the net photosynthetic rate, transpiration rate, and water use efficiency, and increased N, P, or K utilization efficiency, compared with those of the control. Notably, cane yield increasing rate of SEs in 2017 and 2018 were higher than those in 2019 in Wengyuan but lower than those in 2019 in Suixi. Interestingly, the total rainfall and monthly average rainfall in 2017 and 2018 were lower than those in 2019 in Wengyuan but higher than those in 2019 in Suixi. The results suggested that the yield increasing rate of SEs on sugarcane was better in less rainfall years. The sucrose content of sugarcane showed no difference between spraying SEs at the M stage alone or at the three growth stages but was higher than those of SE treatments at S and/or E stages. Enzyme activity analysis showed that spraying SEs at the M stage increased the activity of sucrose phosphate synthase activity by 9.14% in leaves and 15.16% in stems, and decreased soluble acid invertase activity in stems by 16.52%, which contributed to the sucrose increase of 5.00%. The above results suggested that SEs could increase cane yield and promote sucrose accumulation in sugarcane. The yield increasing effect was more obvious under conditions of drought stress.

EFFECT OF SALT (NaCl) ON PHOTOSYNTHESIS AND CARBOHYDRATES IN LEAVES OF TWO RAGI (ELEUSINE CORACANA (L.) GAERTN) VARIETIES

Salinity is one of the most widespread environmental threats to global crop production, especially in arid and semi-arid regions. Photosynthesis and carbohydrates were determined in two ragi (Eleusine coracana (L.) Gaertn) varieties (CO13 and PAIYUR-1), subjected to salt stress of different concentrations (0, 40, 80 and 120mM). Salinity was given as a basal dose and sampling was done in leaves on 30th Days. After Treatment (DAT). There was a marked variation in the photosynthetic rates and ribulose-1, 5-bisphosphate carboxylase activity between the two ragi varieties subjected to salt stress. Photosystem II (PSII) and sucrose phosphate synthase activities were also significantly reduced as measured by salt stressed conditions. The quantity of glucose and sucrose decreased with increasing salt stress while starch showed a reverse trend under salt-stressed conditions. The results revealed that CO-13 exhibits higher photosynthetic rates and activities of ribulose-1,5-bisphosphate carboxylase, sucrose phosphate synthase with photochemical efficiency of PSII compared to PAIYUR-1