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Improving the quality with desired functions of natural starch through agronomic practice will meet the increasing need of people for natural, functional foods. A one-off application of slow-release fertilizer is a simple and efficient practice in maize production, though its influence on the starch quality is scarce. In the present study, the structural and functional properties of the starch of normal maize under two fertilization modes (one-off application of slow-release fertilizer at the sowing time (SF), and three applications of conventional fertilizer at the sowing time, and topdressing at the jointing and flowering stages (CF)) under the same fertilization level (N/P2O5/K2O = 405/135/135 kg/ha) were studied using Jiangyu877 (JY877) and Suyu30 (SY30) as materials. The observed results indicate that the size of starch granules was enlarged by fertilization and the size was the largest under CF in both hybrids. The amylose content was unaffected by CF and reduced by SF in both hybrids. In comparison to no fertilizer (0F), the peak 1/peak 2 ratio was decreased by CF in both hybrids, whereas the ratio under SF was unaffected in JY877 and decreased in SY30. The amylopectin average chain-length was reduced by fertilization and the reduction was higher under CF in JY877. The relative crystallinity was increased by CF in both hybrids and the value under SF was unaffected in SY30 and increased in JY877. The peak, trough, and final viscosities of starch were increased by fertilization in both hybrids. The starch thermal characteristics in response to fertilization modes were dependent on hybrids. The retrogradation enthalpy and percentage were increased by CF in both hybrids, whereas those two parameters under SF were increased in SY30 and decreased in JY877. In conclusion, starch with similar granule size, higher peak 1/peak 2 ratio, and lower relative crystallinity was obtained under SF than under CF for both hybrids. Longer amylopectin chain-length was observed in JY877, which induced lower pasting viscosities in SY30 and lower retrogradation characteristics in JY877. [ABSTRACT FROM AUTHOR]

Waterlogging frequently occurs in Southern China in summer and significantly affects waxy maize growth. This study investigated the physicochemical properties of starch from six waxy maize varieties exposed to waterlogging for 1–7 days after pollination. Waterlogging decreased the starch granule size. Starch maximum absorption wavelength, iodine-binding capacity, crystallinity, and peak intensities in response to waterlogging depended on varieties. Swelling power and solubility in response to waterlogging increased in Wannuo5 and decreased in the other five varieties. Gelatinization and pasting temperatures were only slightly affected by waterlogging. Gelatinization enthalpy was unaffected in Nongkeyu301, increased in Guangbainuo5, and decreased in the other four varieties. Peak and breakdown viscosities decreased and retrogradation percentage increased when plants were subjected to waterlogging after pollination. In conclusion, waterlogging decreased starch granule size, crystallinity, swelling power, and solubility, resulting in deteriorated starch quality (i.e., low swelling, less sticky and easy to retrograde). [ABSTRACT FROM AUTHOR]

BACKGROUND Waxy maize is consumed as a vegetable when harvested at fresh stage (23-26 days after pollination) in China. Fresh waxy maize is normally grown under rain-fed conditions and suffers drought frequently during plant growth. The effect of drought on grain development of fresh waxy maize is not known. RESULTS Two years of pot trials showed that drought decreased fresh grain number and weight, which consequently reduced fresh ear and grain yields, especially in Yunuo7. Moisture and starch contents in grains were not affected but protein content was increased under drought treatment in both varieties. Grain soluble sugar content response to drought was not affected in Suyunuo5 but was decreased in Yunuo7. Pasting and gelatinization temperatures, trough viscosity, final viscosity, setback viscosity, gelatinization enthalpy and springiness of grain were little affected by drought. Drought decreased peak viscosity, breakdown viscosity and adhesiveness (absolute value), whereas it increased hardness. The retrogradation percentage was increased in both varieties in both years. CONCLUSION Drought after pollination decreased the fresh waxy maize yield. Grain quality was reduced through decreased peak viscosity and adhesiveness (absolute value), while its hardness and retrogradation percentage were increased, which might be due to the increased protein content. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Waxy maize is grown in South China, where high temperatures frequently prevail. The effect of high-temperature stress on grain development of waxy maize is not known. RESULTS High temperature decreased the grain fresh weight and volume, and lowered the grain dry weight and water content after 22 days after pollination (DAP). Plants exposed to high temperature had low starch content, and high protein and soluble sugar contents at maturity. Starch iodine binding capacity and granule size were increased by heat stress at all grain-filling stages. The former parameter decreased, while the latter parameter increased gradually with grain development. High temperature increased the peak and breakdown viscosity before 30 DAP, but the value decreased at maturity. Pasting and gelatinization temperatures at different stages were increased by heat stress and gradually decreased with grain development under both high-temperature and control conditions. Gelatinization enthalpy increased initially but decreased after peaking at 22 DAP under both control and heat stress conditions. High temperature decreased gelatinization enthalpy after 10 DAP. Retrogradation percentage value increased with high temperature throughout grain development. CONCLUSION High temperature after pollination changes the dynamics of grain filling of waxy maize, which may underlie the observed changes in its pasting and thermal properties. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Highlights: [•] Heat stress increased starch granule size and made their surface more uneven or pitting. [•] Heat stress decreased the swell power of waxy maize starch. [•] X-ray diffraction peak intensities in response to heat stress were variety dependent. [•] Heat stress did not affect the gelatinization enthalpy. [•] Heat stress increased the gelatinisation temperature and retrogradation tendency. [ABSTRACT FROM AUTHOR]

Abstract: The effects of high temperature during different grain filling stages (1–15d and 16–30d after pollination) on the physicochemical properties of four varieties of waxy maize grain were studied. Heat stress during grain filling decreased grain weight and starch deposition, while it increased protein content, starch granule size, abnormal granule numbers and iodine binding capacity. These effects were more severe when heat stress was introduced at early development stage than at late grain filling stage. The peak intensities and crystallinities were decreased when plants were exposed to high temperature at early development stage. By contrast, responses to high temperature at late development stage were variety-dependent. High temperature during grain filling decreased the peak and breakdown viscosities and increased the gelatinization temperature and enthalpy, and retrogradation percentage of flours, especially during early development stage. In conclusion, high temperature during grain filling changed the grain proximate and starch structure, resulting in the deterioration of pasting and thermal properties. [Copyright &y& Elsevier]

The effects of protein removal on the physicochemical properties of waxy maize flours were investigated. Protein removal caused significant reduction in the P and S contents of starches. Starch granules had a smoother surface and low protein content (<6 g/kg) compared with the flours. Both flours and starches had a typical A-type X-ray diffraction pattern, with a crystallinity range of 29.8-32.2% and 27.7-30.6%, respectively. Flours had higher swelling power and solubility, and lower light transmittance than starches. The gelatinization enthalpy and onset temperature of starches were higher compared with those of their counterpart flours. The retrogradation of flours was significantly greater compared with that of starches. Protein removal increased the peak viscosity, trough viscosity, final viscosity, and breakdown, whereas it decreased the setback and pasting temperature. Genotypic differences in those maize were related to the physicochemical characteristics of the flours and starches. [ABSTRACT FROM AUTHOR]

BACKGROUND Slow‐release fertilizer is widely used in cereal crop production because it is ecofriendly and laborsaving. Effects of different application stages (zero‐, three‐, and six‐leaf stages, denoted as SN0, SN3, and SN6, respectively) of slow‐release (N/P2O5/K2O = 225/75/75 kg ha−1) fertilizer on physicochemical properties of starch from spring‐sown waxy maize were investigated in 2018 and 2019. Application of traditional fertilizer (NCK, compound fertilizer; N/P2O5/K2O = 75/75/75 kg ha−1) at sowing time and urea (N = 150 kg ha−1) at six‐leaf stage was designated as the control. RESULTS: In comparison to the NCK, SN0 reduced grain starch content by 4.9%. Meanwhile, SN3 and SN6 did not affect this parameter. Nevertheless, all treatments, particularly SN6, increased average starch granule size. The slow‐release fertilizer reduced proportion of chains with degree of polymerization (DP) > 24. Relative to NCK, SN6 increased starch crystallinity in both years, whereas SN0 and SN3 increased it in 2018 but reduced it in 2019. SN0 reduced peak, trough, and final viscosities, whereas SN3 and SN6 produced similar starch viscosities to those produced by NCK. No fertilizer mode affected gelatinization parameters, but SN6 produced a low retrogradation percentage. In comparison to data for 2018, starch produced in 2019 showed a small granule size, and a high proportion of short amylopectin chains. These properties endowed starch with high viscosity and low retrogradation percentage. CONCLUSION: In spring‐sown waxy maize production, applying slow‐release fertilizer at the six‐leaf stage produced starch with high viscosity and low retrogradation tendency by enlarging granule size, increasing crystallinity, and reducing the proportion of long chains. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Background: In the context of climate change, maize is facing unprecedented heat stress (HS) threats during grain filling. Understanding how HS affects yield is the key to reducing the impact of climate change on maize production. Suyunuo5 (SYN5) and Yunuo7 (YN7) were used as materials, and four temperature gradients of 28℃ (day)/20℃ (night; T0, control), 32 °C/24°C (T1, mild HS), 36 °C/28°C (T2, moderate HS), and 40 °C/32°C (T3, severe HS) were set up during grain filling to explore the physiological mechanism of different degrees HS affecting photosynthetic characteristics of leaves in this study. Results: Results showed that HS accelerated the degradation of chlorophyll, disturbed the metabolism of reactive oxygen species, reduced the activity of antioxidant enzymes, and caused leaf damage. Heat stress induced the down-regulation of photosynthesis-related genes, which results in the decrease of enzymatic activities involved in photosynthesis, thereby inhibiting photosynthesis and reducing yield. Integrated analysis showed that the degree of the negative influence of three HS types during grain filling on leaves and yield was T3 > T2 > T1. The increase in HS disturbed leaf physiological activities and grain filling. Meanwhile, this study observed that the YN7 was more heat tolerance than SYN5 and thus it was recommended to use YN7 in waxy maize planting areas with frequent high temperatures. Conclusions: Heat stress during grain filling caused premature senescence of the leaves by inhibiting the ability of leaves to photosynthesize and accelerating the oxidative damage of cells, thereby affecting the waxy maize yield. Our study helped to simulate the productivity of waxy maize under high temperatures and provided assistance for a stable yield of waxy maize under future climate warming. [ABSTRACT FROM AUTHOR]

Low temperature (LT) during the grain-filling stage is an important factor that affects the source–sink relationship and leads to yield loss in maize (Zea mays L). In this study, field and pot trials were conducted to investigate the effects of LT during the grain-filling stage on leaf photosynthesis, antioxidant system, hormones, and grain yield of waxy maize cultivars Suyunuo 5 (S5) and Yunuo 7 (Y7). The results showed that LT treatment inhibited the chlorophyll biosynthesis and reduced the photosynthetic pigment levels during grain-filling stage. Ribulose-1,5-bisphosphate carboxylase and phosphoenolpyruvate carboxylase activities, photosynthetic rate, transpiration rate, and stomatal conductance decreased under LT treatment during the grain-filling stage. Furthermore, LT treatment increased the contents of malondialdehyde and reactive oxygen species, and decreased the activities of catalase, superoxide dismutase, peroxidase, and ascorbate peroxidase in the ear leaves, which accelerated the oxidative damage of leaf. The LT treatment also raised abscisic acid content and reduced indole acetic acid content in the ear leaves during grain-filling stage. The results of field and pot trials were verified by each other, but the field effect was greater than that of pot. Overall, LT treatment reduced the waxy maize dry matter accumulation after silking by affecting the physiological and biochemical processes of leaves, and ultimately decreased grain yield. Low temperature (LT) is an important abiotic stress that seriously affects the production and development of maize (Zea mays L). In this study, two waxy maize hybrids were selected and planted in two experimental environments to determine the dynamic changes in leaf photosynthesis, antioxidant system, hormones, and grain yield under post-silking LT stress. This study can be used as a reference for waxy maize to develop adaptation strategies under future climate conditions. [ABSTRACT FROM AUTHOR]

Background: Salicylic acid (SA) is a phytohormone which works to regulate the abiotic stress response of plants. However, the molecular mechanism by which SA mediates heat tolerance in waxy maize (Zea mays L. sinsensis Kulesh) remains unknown. Results: Two varieties of waxy maize seedlings, heat-tolerant 'Yunuo7' (Y7) and heat-sensitive 'Suyunuo5' (S5), were pretreated with SA prior to heat stress (HTS). After treatment, physiological and transcriptomic changes were analyzed. Compared with HTS, the exogenous application of SA enhanced the shoot dry weight, the activities of antioxidant enzymes (e.g., SOD, POD, CAT and APX), and the concentration of endogenous phytohormones (e.g., SA, ABA, IAA, GA3), while decreased the MDA content. Transcriptome analysis showed that the number of differentially expressed genes (DEGs) identified in the control (CK) vs HTS and HTS vs HTS + SA comparisons were more in S5 than in Y7. HTS induced the downregulation of genes involved in photosynthesis and the upregulation of genes encoding heat shock transcription factors (HSFs) and heat shock proteins (HSPs). Compared with HTS, SA pretreatment reversed the expression of 5 photosynthesis-related genes, 26 phytohormone-related genes, and all genes encoding HSFs and HSPs in S5. Furthermore, the number of alternative splicing (AS) events increased under HTS treatment for both varieties, while decreased under SA pretreatment of S5. Differentially spliced genes (DSGs) showed little overlap with DEGs, and DEGs and DSGs differed significantly in functional enrichment. Conclusions: Physiological and transcriptional together indicated that HTS and SA pretreatment had a greater effect on S5 than Y7. Additionally, it appears that transcriptional regulation and AS work synergistically to enhance thermotolerance in heat-sensitive waxy maize. Our study revealed the regulatory effects and underlying molecular mechanisms of SA on waxy maize seedling under HTS. [ABSTRACT FROM AUTHOR]

Heat stress (HS) during grain filling is an extreme environmental factor and affects plant growth and development. Foliar application of exogenous brassinolide (BR) is an effective practice to relieve HS injuries, but the influence on the accumulation and remobilization of biomass and nitrogen is still unclear. In the present study, the effect of foliar BR application at the silking stage on the accumulation and remobilization of biomass and nitrogen in fresh waxy maize under ambient (28/20 °C) and high (35/27 °C) temperatures during grain filling were studied in a phytotron using heat-sensitive Yunuo7 (YN7) and heat-tolerant Jingkenuo2000 (JKN2000) as materials. HS reduced the fresh ear yield by 21.8% and 19.8% in YN7 and JKN2000, respectively, but fresh grain yield was only reduced in the heat-sensitive hybrid (6.9%) and unaffected in the heat-tolerant hybrid. BR application improved the yields of fresh ears (11.3% and 10.9% in YN7 and JKN2000, respectively) and grains (19.9% and 13.2% in YN7 and JKN2000, respectively) under HS, and the increases were higher in YN7. HS decreased the post-silking biomass accumulation by 67.3% and 51.8%, and nitrogen deposition by 61.9% and 50.5%, in YN7 and JKN2000, respectively. The remobilization of pre- and post-silking biomass and nitrogen were increased and decreased by HS in YN7, respectively, but both were unaffected in JKN2000. Under HS, BR application increased the remobilization of post-silking biomass and nitrogen in both hybrids. The grain nitrogen concentration was increased by HS but decreased by BR application in both hybrids. The harvest index of biomass and nitrogen was increased by HS, and it was improved in YN7 and unaffected in JKN2000 by BR application under HS. In conclusion, BR application at the silking stage can relieve HS injuries on fresh waxy maize yields by improving the remobilization of biomass and nitrogen to grain and increasing the harvest index, especially in the heat-sensitive hybrid. Therefore, foliar BR application is a simple, feasible, efficient practice in fresh waxy maize production and is worth popularizing, especially under warmer climates. [ABSTRACT FROM AUTHOR]

Heat stress (HS) is a major environmental constraint in sustaining global waxy maize production under future climate condition. Starch physicochemical properties under 5‐day (HS5) and 10‐day (HS10) postsilking HS were investigated using two waxy maize hybrids (Suyunuo5 and Yunuo7) as materials. Ambient and high temperatures were 28°C/20℃ and 35°C/27℃, respectively. Starch granules were enlarged and exhibited additional pitting or cellular structures, increased amylopectin chain length, increased relative crystallinity, and increased 1047/1022 cm−1 ratio under HS. This finding indicated the stable and ordered structure of starch granules, especially under HS10. Pasting viscosities of Yunuo7 reduced by HS, and the change was the same under both HS5 and HS10. Peak viscosity of Suyunuo5 was unaffected and breakdown viscosity increased with HS5 although both characteristics decreased with HS10. HS increased gelatinization temperatures and retrogradation percentage. Results showed that HS enlarges starch granules with stable structure, reduces starch viscosities, and increases retrograde tendency, with severe detrimental effect under long HS durations. [ABSTRACT FROM AUTHOR]

Insufficient light radiation is one of the main factors limiting maize yield in southern China. The plum rainy season overlaps with grain filling stage, and intermittent cloudy and rainy weather results in weak-light stress restricting the yield improvement of fresh waxy maize. This study was to assess the impact of weak-light stress at different grain filling stages on yield and leaf carbon (C) and nitrogen (N) metabolism in fresh waxy maize. Suyunuo5 (SYN5) and Jingkenuo2000 (JKN2000) were used to investigate the effects of weak-light at different stages after pollination (1–7, 8–14, 15–21 and 1–21 days, recorded as Z1, Z2, Z3 and Z4) on yield, dry matter and nitrogen (N) accumulation, C and N metabolism in leaf of fresh waxy maize from 2021 to 2022. Compared with CK (natural light treatment), weak-light decreased the fresh ear and grain yield, post-silking dry matter and N accumulation, and the decrease was maximum in Z4, followed by Z1. The decrease in JKN2000 was greater than SYN5. RUBPCase and PEPCase activities, net photosynthetic rate, transpiration rate and stomatal conductance of ear leaves decreased under weak-light, and those were lowest in Z4, followed by Z1. Furthermore, weak-light stress significantly decreased the activities of nitrate reductase, glutamine synthetase, glutamate synthase, and post-silking N accumulation. The highest decrease was found in Z4, followed by Z1. Weak-light stress also downregulated the activities of superoxide dismutase, catalase, peroxidase and raised MDA content in ear leaves during grain filling stage, which accelerated leaf senescence process. Weak-light stress after pollination decreased maize yield by affecting leaf C and N metabolism and antioxidant system, and the stress occurred in first week after pollination had a more severe impact than those in middle and later stages, and JKN2000 was more sensitive to weak-light than SYN5. Our results contributed to understanding how weak-light stress could reduce the yield of fresh waxy maize by affecting leaf C and N metabolism, and offered theoretical support for implementing measures to alleviate weak-light conditions in the planting areas of fresh waxy maize. • Weak-light stress at post-silking stage decreased maize yield. • Weak-light stress decreased maize yield by affecting leaf C and N metabolism and antioxidant system. • Weak-light stress occurred at 1–7 DAP had a more severe impact on maize than 8–14 and 15–21 DAP. [ABSTRACT FROM AUTHOR]

The sexual compatibility between genetically modified (GM) glyphosate-resistant rapeseed variety Q3 (Brasska napus L.) and 5 cruciferous weeds is studied through the observation of fluorescence microscopy and cross-fertility after manual pollination. The results indicated that Q3 (as male) was highly incompatible with Thiaspi arvense L. , Capsella bursa-pastoris (L. ) Medic, Cardamine hirsuta L. and Rorippa palustris (L. ) Besser (as female). Fluorescence microscopic observation showed that growing of pollen tubes terminated on the stigma surface or at the upper 1/3 part of the style. However, B. juncea X Q3 was compatible, and the compatibility index was 1.65. Under the neighboring growth and natural pollination conditions, the rates of gene flow from Q3 to T. aroense, C. bursa-pastoris, C. hirsute and R. palustris were all 0, while it was 0.86% for B. Juncea. These results indicate that there is difference in the rate of gene flow between GM rapeseed and cruciferous wild weeds, and frequency of gene flow is highly correlated with sexual compatibility. [ABSTRACT FROM AUTHOR]

Low temperature (LT) at late growth stages is an important abiotic stress that affects the grain end–use quality of summer maize. In the present work, two experiments were conducted to study the effects of LT on the structural and functional properties of starches using two waxy maize hybrids ('Suyunuo5' and 'Yunuo7'). In field trial, the plants were sown on July 1 (normal sowing date) and August 1 (late sowing date). In pot trial, the plants were sown on July 1, grown at natural environment till silking, and suffered two post–silking temperatures (normal temperature and LT were set as 28/20 and 23/15 °C, respectively). The result showed that the starch was composed of more small granules with oval polytope when sown late (August 1) or subjected to LT post–silking. The LT–stressed starch presented high proportion of short amylopectin chains and low relative crystallinity (RC). LT reduced the pasting viscosity, gelatinization enthalpy, and gelatinization temperatures but increased the retrogradation tendency. In conclusion, the low pasting viscosity and high retrogradation tendency under LT condition were caused by the decreased granule size, amylopectin chain length, and RC. • Starch physicochemical properties of waxy maize under two temperatures were investigated. • Starch granule size and amylopectin chain length were reduced by post-silking low temperature. • Relative crystallinity was decreased by post-silking low temperature. • Reduced viscosity and increased retrogradation under LT were caused by changed starch structure. [ABSTRACT FROM AUTHOR]

Understanding the adaptive changes in maize kernels under high-temperature stress during grain formation stage is critical for developing strategies to alleviate the negative effects on yield and quality. In this study, we subjected waxy maize (Zea mays L. sinensis Kulesh) to four different temperature regimes from 1–15 d after pollination (DAP), namely normal day/normal night (control), hot day/normal night, normal day/hot night, and hot day/hot night. Compared to the control, the three high-temperature treatments inhibited kernel development and starch deposition. To understand how the kernels responded to high-temperature stress, their transcriptomes, proteomes, and metabolomes were studied at 10 DAP and 25 DAP. This showed that genes and proteins related to kernel development and starch deposition were up- and down-regulated, respectively, at 10 DAP, but this pattern was reversed at 25 DAP. Metabolome profiling under high-temperature stress showed that the accumulation patterns of metabolites at 10 DAP and 25 DAP were inversely related. Our multiomics analyses indicated that the response to high-temperature stress of signaling pathways mediated by auxin, abscisic acid, and salicylic acid was more active at 10 DAP than at 25 DAP. These results confirmed that high-temperature stress during early kernel development has a carry-over effect on later development. Taken together, our multiomics profiles of developing kernels under high-temperature stress provide insights into the processes that underlie maize yield and quality under high-temperature conditions. [ABSTRACT FROM AUTHOR]

Background: Kernel development and starch formation are the primary determinants of maize yield and quality, which are considerably influenced by drought stress. To clarify the response of maize kernel to drought stress, we established well-watered (WW) and water-stressed (WS) conditions at 1–30 days after pollination (dap) on waxy maize (Zea mays L. sinensis Kulesh). Results: Kernel development, starch accumulation, and activities of starch biosynthetic enzymes were significantly reduced by drought stress. The morphology of starch granules changed, whereas the grain filling rate was accelerated. A comparative proteomics approach was applied to analyze the proteome change in kernels under two treatments at 10 dap and 25 dap. Under the WS conditions, 487 and 465 differentially accumulated proteins (DAPs) were identified at 10 dap and 25 dap, respectively. Drought induced the downregulation of proteins involved in the oxidation–reduction process and oxidoreductase, peroxidase, catalase, glutamine synthetase, abscisic acid stress ripening 1, and lipoxygenase, which might be an important reason for the effect of drought stress on kernel development. Notably, several proteins involved in waxy maize endosperm and starch biosynthesis were upregulated at early-kernel stage under WS conditions, which might have accelerated endosperm development and starch synthesis. Additionally, 17 and 11 common DAPs were sustained in the upregulated and downregulated DAP groups, respectively, at 10 dap and 25 dap. Among these 28 proteins, four maize homologs (i.e., A0A1D6H543, B4FTP0, B6SLJ0, and A0A1D6H5J5) were considered as candidate proteins that affected kernel development and drought stress response by comparing with the rice genome. Conclusions: The proteomic changes caused by drought were highly correlated with kernel development and starch accumulation, which were closely related to the final yield and quality of waxy maize. Our results provided a foundation for the enhanced understanding of kernel development and starch formation in response to drought stress in waxy maize. [ABSTRACT FROM AUTHOR]

Sweet–waxy maize is a special type of maize with recessive mutations of waxy gene and a gene disturbed sugar‐starch transition, and its starch is composed of nearly pure amylopectin. The starch physicochemical properties of four inbred lines and six hybrids of sweet–waxy maize are studied. The starch granules are irregular and large in hybrids and oval and small in inbred lines. The chain length, molecular weight, and crystallinity are significantly different among the samples. However, no distinct difference is observed between hybrids and inbred lines. The branching degree of hybrids (except THN2000) is significantly higher than that of inbred lines. The pasting, gelatinization, retrogradation temperatures, peak and breakdown viscosities, retrogradation enthalpy, and percentage are lower in inbred lines than in hybrids. By contrast, trough, final, and setback viscosities and gelatinization enthalpy are indistinctly different between the hybrids and inbred lines. Among the six hybrids, HTN2 is suitable to make glutinous food due to its high viscosity, whereas MTN2 may enable the production of food with minimal retrogradation. The high viscosity of JH1501 and the low retrogradation percentage of JSW15525 among the four inbred lines endow different advantages on quality breeding. [ABSTRACT FROM AUTHOR]

BACKGROUND Maize is frequently subjected to simultaneous water (drought or waterlogging) and heat (HS) stresses during grain formation in southern China. This work examined the effect of high temperature combined with drought (HD) or waterlogging (HW) during grain formation on the starch physicochemical properties of two waxy maize hybrids, namely Suyunnuo5 (SYN5) and Yunuo7 (YN7). RESULTS: Heat stress enlarged the starch granule size, and water stresses aggravated this effect. Heat stress reduced the ratio of small molecular weight fractions for both hybrids, and HD aggravated this reduction only in SYN5. Relative crystallinity in SYN5 was increased by stresses but in YN7 it was unaffected by HD, reduced by HS, and increased by HW. Fourier‐transform infrared (FTIR) spectrometry results showed that the 1045/1022 cm−1 ratio in SYN5 was not influenced by HW but was increased by other stresses, and that in YN7 it was increased by all stresses, with the highest value induced by HW. Peak viscosity was decreased, whereas gelatinization temperatures and retrogradation percentage were increased by all of these stresses. These effects were exacerbated by combined heat and water stresses. The maximum decomposition rate was severely increased by HW. CONCLUSION: Drought or waterlogging at grain formation stage aggravated the detrimental effects of HS on the starch physicochemical properties of waxy maize. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Sweet-waxy is a new type of maize with waxy and sugary double recessive genes. This study aims to clarify starch structural and functional properties of this maize type. Grains with sweet-waxy and waxy phenotypes were separated from an ear using the two sweet-waxy maize hybrids of ATN and NKY as materials. Compared with waxy maize starch, the sweet-waxy maize starch mainly comprises small-sized round granules despite the typical waxy character of both starches. Mw, Mn, and relative crystallinity of sweet-waxy starch were higher than those of waxy starch in both hybrids. The average chain length of waxy starch was higher in ATN but lower in NKY compared with that of sweet-waxy starch. However, polydispersity (Mw/Mn) and F1 fraction were high in sweet-waxy and waxy starches in ATN and NKY, respectively. Breakdown viscosity, gelatinization enthalpy and temperatures of both hybrids were low in sweet-waxy starch. Peak viscosity was higher in waxy starch in NKY and similar between sweet-waxy and waxy starches in ATN. Retrogradation percentage was high and low for sweet-waxy starches in ATN and NKY, respectively. • The sweet-waxy maize starch mainly comprised round granules with small granule sizes. • The Mw, Mn, and relative crystallinity were higher in sweet-waxy starch than that of waxy starch. • The gelatinization enthalpy and temperatures were low in sweet-waxy starch. [ABSTRACT FROM AUTHOR]

Waxy maize starch serves as a pivotal component in global food processing and industrial applications, while high temperature (HT) during the grain-filling stage seriously affects its quality. Salicylic acid (SA) has been recognized for its role in enhancing plant heat resistance. Nonetheless, its regulatory effect on the quality of waxy maize starch under HT conditions remains unclear. In this study, two waxy maize varieties, JKN2000 (heat-tolerant) and SYN5 (heat-sensitive) were treated with SA after pollination and then subjected to HT during the grain-filling stage to explore the effect of SA on grain yield and starch quality. The results indicate that exogenous SA under HT treatment led to an increase in kernel weight and starch content in both varieties. Moreover, SA reduced the HT-induced holes on the surfaces of starch granules, enlarged the starch granule size, elevated the amylopectin branching degree, and reduced amylopectin average chain length. Consequently, improvements of pasting viscosity and the decrease of retrogradation percentage of starch were observed with SA under HT. Exogenous SA reduced HT-induced rapidly digestible starch content in SYN5, but had no significant effect on that in JKN2000. In summary, SA pretreatment effectively alleviated the detrimental effects of HT on starch pasting and thermal properties of waxy maize. • HT destroyed the starch structure, and changed the physicochemical properties and digestibility. • SA ensured the integrity of starch granules and enlarged the granule size under HT. • SA decreased the average chain length and increased the branching degree of amylopectin under HT. • SA improved the pasting and thermal properties and vitro digestibility of starch under HT. [ABSTRACT FROM AUTHOR]

Plant growth regulators (PGR) can be used to alleviate heat injury on the starch quality of crops. In this study, two waxy maize hybrids with exogenous cytokinin or spermine at silking stage were exposed to post-silking ambient temperature (AT; 28/20 °C) and high temperature (HT; 35/27 °C) during grain filling. Results indicated that spraying exogenous cytokinin or spermine increased the grain weight and starch content at both temperature regimes. The starch granule size, amylopectin chain length, and relative crystallinity differed between two hybrids and were affected by PGRs and temperatures. Peak viscosity decreased at HT, unaffected by cytokinin, and increased by spermine at both temperature regimes. The retrogradation percentage at HT with PGR was lower than that without PGR in both hybrids. In conclusion, spraying exogenous cytokinin or spermine at silking stage can increase peak viscosity and reduce retrogradation percentage at HT, thereby alleviating the detrimental effects of post-silking heat injury. Image 1 • Exogenous cytokinin or spermine increased the grain starch content under heat stress. • Exogenous hormones changed starch granule size and amylopectin chain length. • Retrogradation percentage at heat stress was decreased by exogenous hormones. • Spraying cytokinin or spermine alleviated the post-silking heat injury. [ABSTRACT FROM AUTHOR]

Rational plant density and fertilizer application are important crop management practices to improve maize grain yield. A two-year field experiment with maize varieties Suyu29 (SY29) and Suyu30 (SY30) was conducted with three plant densities (Low density, LD-6.0; Medium density, MD-7.5, and High density, HD-9.0 plants m−2) and three fertilization methods (no fertilizer, 0 F; one-off application of slow-released fertilizer, SF; and conventional fertilizer application, CF). Results indicated that the grain number and weight decreased with increasing plant density, and the grain yield initially increased and then decreased. The grain yields under SF with MD were the highest, being significantly higher than that under CF. The pre- and post-silking biomass accumulation and biomass remobilization from stems and leaves under SF were significantly higher than CF, thereby increasing its contribution to the grain and boosting grain yield. The grain-leaf ratios under SF and CF were similar across the three densities, and their source-sink ratios (SSRs) were similar at LD and HD. However, the SSR under SF increased by 8.4% for SY29 and 6.8% for SY30 relative to that under CF at MD. Our results showed that SF promoted biomass accumulation and remobilization to grain post-silking compared with CF at medium seeding density and delayed leaf senescence in the later stage, which increased the grain-leaf ratio, SSR, and harvest index and ultimately increased the grain yield. Consequently, selecting the appropriate density of 7.5 plants m−2 combined with one-off application of slow-released fertilizer is recommended to increase grain yield in the area under study. [ABSTRACT FROM AUTHOR]

• Waterlogging decreased starch granule size. • Waterlogging increased the proportion of long-chains and high-molecular-weight molecules in amylopectin. • Ordered structure of waterlogged starch decreased peak and breakdown viscosities. The grain formation stage is a critical stage that affects grain starch quality and frequently overlaps the rainy season in southern China for waxy maize production. Two waxy maize varieties were grown under control and waterlogging conditions during grain formation (1–15 days after pollination) to probe the effects of oversaturated soil moisture on starch structural and functional characteristics. Results indicated that waterlogging during grain formation decreased the size of starch granule, proportion of large granule (d > 15 μm) and ratio of medium-length chains (DP 10–24) in amylopectin, whereas the percentage of high-molecular-weight molecules were increased. Compared with the control, the percentage of ordered starch was increased by waterlogging for both varieties. The changes in starch internal structure under waterlogging had no influence on thermal stability, increased the maximum thermal decomposition ratio and pasting temperatures, and reduced pasting viscosity characteristics in both varieties. [ABSTRACT FROM AUTHOR]

Timely and fitting nitrogen (N) application decreases costs and pollution risk in maize cultivation. To explore the accumulation and remobilization of dry matter (DM), N, phosphorus (P), and potassium (K) in waxy maize under various N topdressings (0 kg ha−1, LN; 150 kg ha−1, MN; 300 kg ha−1, HN) at the jointing stage, a field trial involving two waxy maize varieties (Suyunuo 5 and Yunuo 7) was conducted in 2013-2016. The highest grain yield was obtained under MN mainly due to the highest grain numbers and grain weight. The increase in grain yield under MN was mainly due to the high DM accumulation post-silking, as well as high N, P, and K accumulation and remobilization pre-silking. Generally, the plants had high harvest index (HI) of DM (N, P, and K), partial N fertilizer productivity, and moderate N utilization efficiency (NUE) under MN. [ABSTRACT FROM AUTHOR]

Highlights • Light deprivation reduces starch and amylose content. • Shading increases the sizes of starch granules and the proportion of long chains in amylopectin. • Shading increases starch crystallinity. • Shading reduces pasting and gelatinization temperatures. • Shading increases starch viscosity and retrogradation percentage. Abstract The grain development of normal maize in Southern China is affected by decreases in sunlight intensity over the period of mid-June to mid-July. This study examined the starch structure and function of four normal maize varieties that had been exposed to weak-light stress (50% light deprivation; ambient light conditions served as the control) during grain filling. In all tested varieties, light deprivation decreased the contents of starch and amylose, and increased the size of starch granules and the proportion of long chains in amylopectin. Shading increased the relative crystallinity and ordered-to-amorphous ratio of starch. Shading decreased the gelatinization and retrogradation enthalpies and pasting and gelatinization temperatures of starches but increased retrogradation percentage and pasting viscosities. In conclusion, weak-light stress during grain filling increases starch viscosity and retrogradation tendency and decreases thermal stability by reducing amylose content, increasing the sizes of starch granules and the proportion of long chains in amylopectin, and improving the relative crystallinity. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Waxy maize (Zea mays L. sinensis Kulesh) suffers short‐term exposure to high temperature during grain filling in southern China. The effects of such exposure are poorly understood. RESULTS: Starch granule size was increased by 5 days' short‐term heat stress (35.0 °C) and the increase was higher when the stress was introduced early. Heat stress increased the iodine binding capacity of starches and no difference was observed among the three stages. Starch relative crystallinity was increased and swelling power was decreased only when heat stress was introduced early. Heat stress also increased the pasting viscosity, and this effect became more pronounced with later applications of stress. Heat stress reduced starch gelatinization enthalpy, and the reduction gradually increased with later exposures. Heat stress increased the gelatinization temperature and retrogradation enthalpy and percentage of the samples, with the increases being largest with earlier introduction of high temperature. CONCLUSION: Heat stress increased the pasting viscosities and retrogradation percentage of starch by causing change in granule size, amylopectin chain length distribution and crystallinity, and the effects observed were more severe with earlier introduction of heat stress after pollination. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Cross-pollination and high cross-compatibility are frequently found in many cruciferous plants, which implies that there might be potential risk of alien gene flow among crucifers. In this work, the alien glyphosate-resistant gene flow between GM (Genetically modified) rapeseed variety Q3 (Brassica napus) and 6 varieties from 5 cruciferous species was assessed by sexual compatibility through aniline blue fluorescence observation, manual cross, mentor pollination with the mixture pollen and DNA identification. The results indicated that the compatibility indices of two B. napus varieties, B. juncea var. multiceps Tsen et Lee and Chinese cabbage (B. chinensis) (as female) with Q3 (as male) were 16.15, 12.77, 2.345 and 0.85, respectively. F1 plants were examined by PCR and all of these samples were confirmed as positive. Crossing between Orychophragmus violaceus, Descurainia sophia (as female) and Q3 (as male) expressed high cross-incompatibility. Fluorescence microscope observation indicated that growing of pollen tube terminated at the upper 1/3 part of the style of O. violaceus and on the stigma surface of D. sophia. The mentor plants were further analyzed by PCR and all were shown to be negative. Under the neighboring growth and natural pollination conditions, the rates of gene flow to two B. napus varieties were 2.3278% and 2.1487%, respectively, B. juncea var. multiceps Tsen et Lee and Chinese cabbage were 1.0157% and 0.9236%, respectively. No gene flow was observed in O. violaceus and D. sophia. Frequency of gene flow was highly correlated with sexual compatibility. Due to possible alien gene flow among crucifers, special consideration and care should be taken to grow GM rapeseed. [ABSTRACT FROM AUTHOR]

Appropriate nitrogen fertilization is essential for improving grain yield and starch quality, while reducing N fertilizer costs. The starch physicochemical properties of two waxy maize hybrids, namely, Suyunuo5 (SYN5) and Yunuo7 (YN7), under N rates of 0 (zero N application [N0]), 150 (low N rate [LN]), 225 (moderate N rate [MN]), and 300 (high N rate [HN]) kg ha–1 are elucidated. Grain starch content initially increases, peaks at MN, and decreases as N rate is increased. N fertilization reduces the starch granule size of YN7. The starch granule size of SYN5 increases under MN. SYN5 exhibits high short/long amylopectin chain ratios under LN and MN. The short/long amylopectin chain ratio of YN7 is unaffected by MN but is increases by LN and HN. The swelling power of YN7 is similar among different N levels, whereas that of SYN5 increases under N fertilization. N fertilization changes starch pasting and thermal properties. Starch with large granules exhibit high trough, final, and setback viscosities and gelatinization temperatures. Starch with high long‐chain ratios is susceptible to retrogradation. In conclusion, appropriate N application (225 kg ha–1 for SYN5 and 150 kg ha–1 for YN7) favors starch accumulation, and starch has high viscosity and low retrogradation tendency. [ABSTRACT FROM AUTHOR]

High temperature (temperature over 35 °C) is an extremely important environmental factor that affects the maize grain quality in Southern China. The effects of heat stress after pollination on grain protein and starch deposition and activities of involved enzymes were studied in a pot trail in 2014 and 2015. Results showed that grain dry weight reductions at maturity were 19.8% and 19.1%, whereas starch contents (mg g−1) were reduced by 3.0% and 3.3%, and starch accumulation (mg grain−1) were reduced 22.2% and 21.8% in 2014 and 2015, respectively. Protein content was decreased by heat stress before 15 DAP and increased thereafter. At maturity, protein contents (mg g−1) were increased by 24.5% and 25.3% in 2014 and 2015, while protein accumulation (mg grain−1) were not affected by heat stress. In response to heat stress, glutamate synthase activity was enhanced by 29.1-82.9% in 2014 and 2.0-141.8% in 2015, whereas glutamine synthetase activity was reduced by 1.9-43.5% in 2014 and 0.1-27.4% in 2015 throughout the grain filling. The activities of sucrose phosphate synthase were decreased by heat stress at 10-25DAP (12.7-32.0%) in 2014 and 15-20 DAP (23.2-27.5%) in 2015, and activities of sucrose synthase were decreased by heat stress at 5-15 DAP (20.0-45.0%) in 2014 and 15 DAP (22.0%) in 2015, repectively. The activities of enyzmes that involved in starch synthessis were all suppressed by heat stress during grain filling, and the reduction of adenosine diphosphate-glucose pyrophosphorylase, soluble starch synthase, and starch branching enzyme were decreased by 21.3-43.1%, 19.1-29.2%, and 7.0-45.6% in 2014 and 1.8-78.5%, 21.4-51.2%, and 11.0-48.0% in 2015, respectively. Conclusively, grain weight and starch deposition were suppressed by heat stress due to the decreased activities of enzymes involved in starch synthesis, and the increased protein content was due to the enhanced activity of glutamate synthase. [ABSTRACT FROM AUTHOR]