Root Starch Content Research Articles

The Effect of Nitrogen and Potassium Interaction on the Leaf Physiological Characteristics, Yield, and Quality of Sweet Potato

This study selected two sweet potato varieties as research subjects and conducted a field experiment using a two-factor design with two potassium (K) levels (K0 and K1) and five nitrogen (N) levels (N0–N4). The physiological changes in sweet potato leaves under different N and K treatments were measured, and nutrients such as the soluble sugar, protein, and starch content of sweet potato roots were analyzed. The results indicate that the activity of glutamine synthetase (GS) and the soluble protein content in sweet potato leaves increase first and then decrease with increasing N application, while K application can significantly increase the activity of GS and the soluble protein content. The N metabolic capacity of leaves is strongest when the fertilizer ratio is K1N2. The SPAD value of sweet potato leaves increases with increasing N application. The net photosynthetic rate, stomatal conductance, and intercellular CO2 concentration first increase and then decrease with increasing N application. K fertilizer has a significant effect on these parameters. As the N application rate increases, the starch and protein content in the tubers increase, while the soluble sugar content decreases. However, the number of tubers per plant, fresh weight of the tubers, and dry weight of the tubers increase initially and then decrease, while the vine length continuously increases. The application of K fertilizer can significantly increase the number of tubers per plant and stem thickness of sweet potato. In conclusion, the appropriate N–K combined application can promote N metabolism, enhance the photosynthetic capacity of sweet potato, increase yield, and improve quality.

Effects of cadmium stress on the growth and physiological characteristics of sweet potato

This study evaluated the responses of sweet potatoes to Cadmium (Cd) stress through pot experiments to theoretically substantiate their comprehensive applications in Cd-polluted agricultural land. The experiments included a CK treatment and three Cd stress treatments with 3, 30, and 150 mg/kg concentrations, respectively. We analyzed specified indicators of sweet potato at different growth periods, such as the individual plant growth, photosynthesis, antioxidant capacity, and carbohydrate Cd accumulation distribution. On this basis, the characteristics of the plant carbon metabolism in response to Cd stress throughout the growth cycle were explored. The results showed that T2 and T3 treatments inhibited the vine growth, leaf area expansion, stem diameter elongation, and tuberous root growth of sweet potato; notably, T3 treatment significantly increased the number of sweet potato branches. Under Cd stress, the synthesis of chlorophyll in sweet potato was significantly suppressed, and the Rubisco activity experienced significant reductions. With the increasing Cd concentration, the function of PS II was also affected. The soluble sugar content underwent no significant change in low Cd concentration treatments. In contrast, it decreased significantly under high Cd concentrations. Additionally, the tuberous root starch content decreased significantly with the increase in Cd concentration. Throughout the plant growth, the activity levels of catalase, peroxidase, and superoxide dismutase increased significantly in T2 and T3 treatments. By comparison, the superoxide dismutase activity in T1 treatment was significantly lower than that of CK. With the increasing application of Cd, its accumulation accordingly increased in various sweet potato organs. The the highest bioconcentration factor was detected in absorbing roots, while the tuberous roots had a lower bioconcentration factor and Cd accumulation. Moreover, the transfer factor from stem to petiole was the highest of the potato organs. These results demonstrated that sweet potatoes had a high Cd tolerance and a restoration potential for Cd-contaminated farmland.

A glutathione S-transferase IbGSTL2 interacts with IbcPGM to increase starch content and improve starch quality in sweetpotato

A glutathione S-transferase (GST) gene IbGSTL2 was cloned and characterized from sweetpotato. It harbored a variation associated with starch content in storage roots. Overexpression of IbGSTL2 increased starch content and amylopectin proportion, decreased gelatinization temperature, and improved degree of crystallinity in sweetpotato storage roots, while its RNA interference resulted in the opposite trends. IbGSTL2 physically interacted with IbcPGM, an enzyme of sucrose metabolism, and improve starch content and quality by regulating genes involved in starch biosynthesis.

Protein kinase MeSnRK2.3 positively regulates starch biosynthesis by interacting with the transcription factor MebHLH68 in cassava.

Starch biosynthesis involves numerous enzymes and is a crucial metabolic activity in plant storage organs. Sucrose non-fermenting related protein kinase 2 (SnRK2) is an abscisic acid (ABA)-dependent kinase and a significant regulatory enzyme in the ABA signaling pathway. However, whether SnRK2 kinases regulate starch biosynthesis is unclear. In this study, we identified that MeSnRK2.3, an ABA-dependent kinase, was highly expressed in the storage roots of cassava and was induced by ABA. Overexpression of MeSnRK2.3 in cassava significantly increased the starch content in the storage roots and promoted plant growth. MeSnRK2.3 was further found to interact with the cassava basic helix-loop-helix 68 (MebHLH68) transcription factor in vivo and in vitro. MebHLH68 directly bound to the promoters of sucrose synthase 1 (MeSUS1), granule-bound starch synthase I a (MeGBSSIa), and starch-branching enzyme 2.4 (MeSBE2.4), thereby upregulating their transcriptional activities. Additionally, MebHLH68 negatively regulated the transcriptional activity of sucrose phosphate synthase B (MeSPSB). Moreover, phosphorylated MebHLH68 by MeSnRK2.3 up-regulated the transcription activity of MeSBE2.4. These findings demonstrated that the MeSnRK2.3-MebHLH68 module connects the ABA signaling pathway and starch biosynthesis in cassava, thereby providing direct evidence of ABA-mediated participation in the sucrose metabolism and starch biosynthesis pathway.

Optimizing starch content prediction in kudzu: Integrating hyperspectral imaging and deep learning with WGAN-GP

Rapid and non-destructive prediction of starch content in kudzu is essential for the food industry. In this work, we present an approach combining hyperspectral imaging (HSI) and deep learning (DL) techniques for predicting kudzu root starch content. Practical constraints such as equipment and experimental conditions limit the quantity of spectral data and labels obtained, which leads to diminish model performance. To address this restriction, we employ Wasserstein generative adversarial networks with gradient penalty (WGAN-GP) to augment spectral and starch content data simultaneously. Through numerous iterations, synthetic data that closely resemble real data is generated, which is validated through comprehensive evaluations using various qualitative and quantitative analysis. Additionally, we establish and compare partial least squares regression (PLSR), support vector regression (SVR) and one-dimensional convolutional neural network (1DCNN) model before and after data augmentation. Experimental results demonstrate that the introduction of synthetic data could improve model performance significantly. Particularly, 1DCNN model exhibits the best performance, achieving correlation coefficients (R2) of 92.97% and 93.43% for starch content in the two types of kudzu roots. Overall, this study not only provides an effective method for rapidly, non-destructively, and accurately determining starch content in kudzu roots, but also addresses the challenge of requiring a large amount of data.

The Effect of Lotus Root Starch Content on the Water Barrier Properties and Biodegradability of Cassava Bioplastic Films

Biodegradable films demand increases due to the awareness of the environmental effects of synthetic plastics. However, biodegradable films based on starch have high water sensibility and poor mechanical properties. This led to an interest among the scientist in improving the properties of biodegradable films. The objectives of this study were to investigate the effect of lotus root starch content on the water solubility, water absorption, water vapor permeability and biodegradability of cassava bioplastic films. The lotus root starch was added at 10%, 20%, 30%, 40% and 50% of cassava starch. The results showed that the water absorption properties decreased by 122% to 21% and the water vapor permeability showed a decreasing trend as the lotus starch content increased. The water solubility increased from 4% to 36% with the increase of lotus starch content and biodegradability increased by 87.5% at 50% of lotus starch content. The results exposed the potential of cassava/ lotus starch bioplastic films for food packaging applications.

Relationship of potassium doses with bioethanol yield in sweet potato in Cerrado soil

Sweet potato-bioethanol yield was evaluated in response to potassium fertilizer application. Experiments were performed using a 5 × 2 factorial design in which factors included the amount of K2O applied to the soil, with five levels (0, 30, 60, 120, and 240 kg ha-1) and genotype, with two levels (industrial genotype BDGPI #25 and table genotype BDGPM #04). Root yield, root starch and soluble solid contents, bioethanol yield, and economic viability of potassium application for bioethanol production were evaluated. Potassium affected root yield of both genotypes, with the highest yield observed at 140 kg K2O ha-1. Root starch concentration at harvest depended on genotype potential rather than potassium dose. Soluble solid content in fresh roots was lower than that in cooked roots, in which case, maximum conversion efficiency was observed at 109,69 and at 123.75 kg K2O ha-1 for BDGPM#04 and BDGPI#25, respectively. Bioethanol yield reached 10,484 and 9,839 L ha-1 at 151.87 and 136 kg K2O ha-1 for BDGPI#25 and BDGPM#04, respectively. Genotype BDGPI#25 was more efficient than sugarcane in converting potassium to bioethanol at 151.87 kg K2O ha-1, producing 10,484.29 L of bioethanol. In turn, BGDPM#04 showed maximum conversion efficiency relative to sugarcane at 122 kg K2O ha-1.

Growth and non-structural carbohydrates response patterns of Eucommia ulmoides under salt and drought stress.

Salinity and droughts are severe abiotic stress factors that limit plant growth and development. However, the differences and similarities of non-structural carbohydrates (NSCs) responses patterns of trees under the two stress conditions remain unclear. We determined and compared the growth, physiology, and NSCs response patterns and tested the relationships between growth and NSCs concentrations (or pool size) of Eucommia ulmoides seedlings planted in field under drought and salt stress with different intensities and durations. We found that drought and salt stress can inhibit the growth of E. ulmoides, and E. ulmoides tended to enhance its stress resistance by increasing proline concentration and leaf thickness or density but decreasing investment in belowground biomass in short-term stress. During short-term drought and salt stress, the aboveground organs showed different NSCs response characteristics, while belowground organs showed similar change characteristics: the starch (ST) and NSCs concentrations in the coarse roots decreased, while the ST and soluble sugar (SS) concentrations in the fine roots increased to enhance stress resistance and maintain water absorption function. As salt and drought stress prolonged, the belowground organs represented different NSCs response patterns: the concentrations of ST and SS in fine roots decreased as salt stress prolonged; while ST in fine roots could still be converted into SS to maintain water absorption as drought prolonged, resulting in an increase of SS and a decrease of ST. Significant positive relationships were found between growth and the SS and total NSCs concentrations in leaves and branches, however, no significant correlations were found between growth and below-ground organs. Moreover, relationships between growth and NSCs pool size across organs could be contrast. Our results provide important insights into the mechanisms of carbon balance and carbon starvation and the relationship between tree growth and carbon storage under stress, which were of great significance in guiding for the management of artificial forest ecosystem under the context of global change.

Coordination between non-structure carbohydrates and hydraulic function under different drought duration, intensity, and post-drought recovery

The maintenance of non-structural carbohydrates (NSCs) and hydraulic function during drought and post-drought recovery is crucial for tree survival, but previous studies lack systematic investigation of their relationship under different drought conditions. We exposed seedlings to varying degrees of drought intensity for three years, followed by short-term, high-intensity drought and re-irrigation, to explore the coordination between NSCs and hydraulic function. We found that long-duration drought reduced native embolism in all organs, and NSCs were consumed in trunks and branches in response to drought. In contrast, total soluble sugar and starch concentrations in roots under severe drought stress increased by 33.90 % and 24.97 %, respectively, in order to survive and adapt to the drought environment. When short-term and high-intensity drought caused hydraulic dysfunction, plants accumulated soluble sugars, including glucose, sucrose, and maltose, mainly driven by starch depletion. Meanwhile, drought-adapted plants had higher embolism resistance at the cost of consuming NSCs. After re-irrigation, drought-adapted plants maintain lower carbon consumption and improve carbon reserves in their roots to cope with future drought conditions. In summary, long-term drought treatment improves plant survival under extreme drought stress. This study systematically illustrates the long-term drought legacy effects on short-term drought and re-irrigation responses.

Can boron application increase the starch content in cassava roots?

Boron is one of the essential micronutrients that is important for cassava growth, one of which is in the formation of starch, but research on the effect of boron on cassava plants is still rarely reported. Therefore, the aim of this study was to know the effect of boron application on cassava starch content. The experiment was conducted in Tanjung Bintang District, South Lampung Regency, Lampung Province from February to December 2020. Waxy clone cassava was used as planting material and 45% boric acid fertilizer as treatment material. There were five boron treatments (B0 (0 kg boron ha-1), B1 (0.31 kg boron ha−1), B2 (0.63 kg boron ha−1), B3 (0.94 kg boron ha−1), and B4 (1.26 kg boron ha−1)) applied to waxy clone cassava. The experiment was arranged in a Completely Randomized Block Design (CRBD) with 3 replicates. The results showed that treatment B2 showed the average weight of cassava roots is 2.15 kg/plant and starch content is 23.83%. Treatment B2 also showed the highest mean of those two variables compared to other treatments.

The influence of chilling hours on root starch content, growth and yield of strawberry tray plants

The chilling requirements of two strawberry cultivars (‘Sonata’, ‘Albion’) were assessed by evaluating the starch accumulation levels in the tray plants’ root system and their subsequent growth and yielding. The research was conducted in an experimental orchard and a greenhouse of the National Institute of Horticultural Research in Skierniewice, Poland, in 2017–2019 (2 cycles of obtaining planting material and growing plants). The tray plants (rooted tips) were grown in the natural field conditions until they were transferred in batches to a cold store (–2°C) on five different dates: 12 Oct., 30 Oct., 20 Nov., 11 Dec., and 3 Jan. (of the following year). The number of accumulated chilling hours less than 7°C was recorded for each transfer date, and the roots were analysed for starch content at the time of transfer. After the end of cold storage (3 months, standardised for all treatments), the plants were planted in pots and transferred to a greenhouse to assess growth and plant yielding. The obtained results indicate that chilling induces changes in the extent of starch accumulation. The highest starch accumulation in ‘Sonata’ roots was recorded when the plants received about 500 h of chilling (under Polish conditions accumulated in November/December). In the ‘Albion’ strawberry case, the maximum was found at the lower chilling level – about 300 h (middle of November). The highest fruit yields were produced by ‘Sonata’ plants, for which the number of chilling hours (0–7°C) was 500–800 h. In the case of ‘Albion’, the values were 2–3 times lower. A more extended period of keeping tray plants in field conditions (over 1000 h of chilling) resulted in a deterioration in fruit yield.

Polyploid GWAS reveals the basis of molecular marker development for complex breeding traits including starch content in the storage roots of sweet potato.

Given the importance of prioritizing genome-based breeding of sweet potato to enable the promotion of food and nutritional security for future human societies, here, we aimed to dissect the genetic basis of storage root starch content (SC) when associated with a complex set of breeding traits including dry matter (DM) rate, storage root fresh weight (SRFW), and anthocyanin (AN) content in a mapping population containing purple-fleshed sweet potato. A polyploid genome-wide association study (GWAS) was extensively exploited using 90,222 single-nucleotide polymorphisms (SNPs) obtained from a bi-parental 204 F1 population between 'Konaishin' (having high SC but no AN) and 'Akemurasaki' (having high AN content but moderate SC). Through the comparison of polyploid GWAS on the whole set of the 204 F1, 93 high-AN-containing F1, and 111 low-AN-containing F1 populations, a total of two (consists of six SNPs), two (14 SNPs), four (eight SNPs), and nine (214 SNPs) significantly associated signals were identified for the variations of SC, DM, SRFW, and the relative AN content, respectively. Of them, a novel signal associated with SC, which was most consistent in 2019 and 2020 in both the 204 F1 and 111 low-AN-containing F1 populations, was identified in homologous group 15. The five SNP markers associated with homologous group 15 could affect SC improvement with a degree of positive effect (~4.33) and screen high-starch-containing lines with higher efficiency (~68%). In a database search of 62 genes involved in starch metabolism, five genes including enzyme genes granule-bound starch synthase I (IbGBSSI), α-amylase 1D, α-amylase 1E, and α-amylase 3, and one transporter gene ATP/ADP-transporter were located on homologous group 15. In an extensive qRT-PCR of these genes using the storage roots harvested at 2, 3, and 4 months after field transplantation in 2022, IbGBSSI, which encodes the starch synthase isozyme that catalyzes the biosynthesis of amylose molecule, was most consistently elevated during starch accumulation in sweet potato. These results would enhance our understanding of the underlying genetic basis of a complex set of breeding traits in the starchy roots of sweet potato, and the molecular information, particularly for SC, would be a potential platform for molecular marker development for this trait.

Produtividade e qualidade da batata-doce em função da adubação fosfatada em diferentes solos

ABSTRACT Phosphorus (P) is an essential nutrient for growth and yield of sweet potatoes; in sandy soils, sweet potato yield and quality may be limited by application of low P doses, mainly in degraded areas. The objective of this work was to evaluate the effect of P doses on yield and quality of sweet potato root tubers grown in tropical sandy soils with different initial P availabilities: 23.2 mg dm-3 (high P - crop rotation) and 3.7 mg dm-3 (low P - post degraded pasture). Two experiments were carried out in a randomized block design, with four replicates. The treatments consisted of P doses (0, 22, 44, 88, and 176 kg ha-1) applied to the planting bed. Tuber yield, number and mean weight of tubers, P concentration in leaves and tubers, exported P, as well as the percentage of starch, reducing sugars, total sugars, and sucrose in the tubers were evaluated. P concentration in the soil was evaluated at the end of the experiment. In the area with high P availability (> 20 mg dm-3 - resin), increasing P doses did not increase root tuber yield and decreased root starch concentrations. In the area with low P availability (< 3.7 mg dm-3 - resin), root tuber yield and starch concentration peaked when applying 68 and 33 kg ha-1 of P, respectively. In areas after degraded pasture, with low initial soil P concentration, P fertilization for sweet potato crops should be carried out with a P dose of 68 kg ha-1. In areas with crop rotation and adequate soil P concentration, P fertilization should be carried out to replace the amount of P exported by the harvested root tubers to avoid decreases in soil fertility.

Magnesium chelatase subunit D is not only required for chlorophyll biosynthesis and photosynthesis, but also affecting starch accumulation in Manihot esculenta Crantz

BackgroundMagnesium chelatase plays an important role in photosynthesis, but only a few subunits have been functionally characterized in cassava.ResultsHerein, MeChlD was successfully cloned and characterized. MeChlD encodes a magnesium chelatase subunit D, which has ATPase and vWA conservative domains. MeChlD was highly expressed in the leaves. Subcellular localization suggested that MeChlD:GFP was a chloroplast-localized protein. Furthermore, the yeast two-hybrid system and BiFC analysis indicated that MeChlD interacts with MeChlM and MePrxQ, respectively. VIGS-induce silencing of MeChlD resulted in significantly decreased chlorophyll content and reduction the expression of photosynthesis-related nuclear genes. Furthermore, the storage root numbers, fresh weight and the total starch content in cassava storage roots of VIGS-MeChlD plants was significantly reduced.ConclusionTaken together, MeChlD located at the chloroplast is not only required for chlorophyll biosynthesis and photosynthesis, but also affecting the starch accumulation in cassava. This study expands our understanding of the biological functions of ChlD proteins.

Belowground carbon allocation, root trait plasticity, and productivity during drought and warming in a pasture grass.

Sustaining grassland production in a changing climate requires an understanding of plant adaptation strategies, including trait plasticity under warmer and drier conditions. However, our knowledge to date disproportionately relies on aboveground responses, despite the importance of belowground traits in maintaining aboveground growth, especially in grazed systems. We subjected a perennial pasture grass, Festuca arundinacea, to year-round warming (+3 °C) and cool-season drought (60% rainfall reduction) in a factorial field experiment to test the hypotheses that: (i) drought and warming increase carbon allocation belowground and shift root traits towards greater resource acquisition and (ii) increased belowground carbon reserves support post-drought aboveground recovery. Drought and warming reduced plant production and biomass allocation belowground. Drought increased specific root length and reduced root diameter in warmed plots but increased root starch concentrations under ambient temperature. Higher diameter and soluble sugar concentrations of roots and starch storage in crowns explained aboveground production under climate extremes. However, the lack of association between post-drought aboveground biomass and belowground carbon and nitrogen reserves contrasted with our predictions. These findings demonstrate that root trait plasticity and belowground carbon reserves play a key role in aboveground production during climate stress, helping predict pasture responses and inform management decisions under future climates.

A 6-yr evaluation of prescribed-fire timing on yearling cattle growth performance and plant community dynamics on native tallgrass prairie in the Kansas Flint Hills

Abstract A 6-yr experiment was conducted to determine the effects of prescribed-fire season on stocker cattle growth performance and rangeland plant community characteristics in the Kansas Flint Hills. Eighteen pastures were grouped by watershed and each watershed was randomly assigned to 1 of 3 prescribed-fire treatments: spring (11 April ± 5.7 d), summer (25 August ± 6.2 d), or autumn (2 October ± 9.0 d). All burns were applied prior to grazing in years 1, 2, 3, and 5; however, no burns were applied in year 4 because of unfavorable burn conditions. Over 5 consecutive grazing seasons, 1,939 yearling stocker calves (initial BW = 281 ± 58.9 kg) were grazed from May to August at a targeted stocking density of 280 kg live-weight + ha−1. Beginning in June of 2018 (pretreatment), a permanent 100-m transect was established in each pasture and was used to determine plant-species composition using a modified step-point method. Forage biomass accumulation and root carbohydrate concentrations of 4 native tallgrass plant species were also measured. All data were analyzed as a completely randomized design using a mixed model. Average daily gain (ADG) was 0.05 to 0.07 kg greater (P = 0.02) for calves grazing spring-burned pastures compared with calves grazing summer- or autumn-burned pastures; however, ADG did not differ (P ≥ 0.55) between calves assigned to the summer or autumn prescribed-fire treatments. Basal cover of all graminoids and all forbs did not differ (P ≥ 0.30) among prescribed-fire treatments; however, basal cover of C3 grasses tended (P = 0.06) to be greater while basal cover of C4 grasses tended (P = 0.08) to be less in autumn-burned pastures compared with spring-burned pastures. Forage biomass accumulation did not differ (P = 0.58) among treatments. In addition, root starch or root water-soluble carbohydrate concentrations in big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), or purple prairieclover (Dalea purpurea) did not differ (P ≥ 0.26) among prescribed-fire treatments. Overall, we interpreted these data to suggest that prescribed-fire timing had small influences on yearling stocker cattle growth performance and rangeland plant composition but did not influence forage biomass accumulation or root carbohydrate concentrations of key native tallgrass plant species in the Kansas Flint Hills.

Respostas morfológicas e produtivas de videiras 'BRS Vitória' submetidas à nutribioirrigação com água residuária da piscicultura

Abstract The objective of this work was to evaluate the agronomic responses of 'BRS Vitória' grapevines under bio-fertigation with and without conventional soil fertilizer. A completely randomized design was used, with three treatments and 18 replicates. The treatments were: CFI, conventional soil fertilizer and irrigation; BF+CF, bio-fertigation and conventional fertilizer; and BF, only bio-fertigation. The following variables were evaluated: graft and rootstock diameters; plant growth; number of lateral buds; root, leaf, petiole, and gem starch contents; bunch number per plant, length, circumference, and fresh weight; berry number per bunch, length, diameter, fresh weight, soluble solid contents, titratable acidity, and pH; yield; and leaf macro- and micronutrient contents. From 100 to 150 days after transplanting (DAT), rootstock and graft diameters were similar, increasing from 250 to 300 DAT in the CFI treatment. The highest root starch content was 7.19% in BF at 150 DAT and 37.35% in BF+CF at 300 DAT. The plants in BF+CF showed the best results for bunch number per plant and fresh weight, resulting in a fruit yield 22% higher than that obtained in the other treatments. 'BRS-Vitória' grapevines show a satisfactory agronomic performance when bio-fertigated.

Changes in sucrose metabolism patterns affect the early maturation of Cassava sexual tetraploid roots

Cassava (Manihot esculenta Crantz) is an important multiuse crop grown for economic and energy purposes. Its vegetative organs are storage roots, in which the main storage material is starch. The accumulation characteristics of starch in cassava roots can directly affect the yield, starch content and maturation of cassava storage roots. In this study, we used a cassava sexual tetraploid (ST), which showed early maturation heterosis in previous work, as the main test material. We analyzed the sucrose metabolism and starch accumulation characteristics of the ST and its parents from the leaf "source" to the storage root "sink" during different developmental stages and explored the regulatory mechanisms of ST storage root early maturation by combining the transcriptome data of the storage roots during the expansion period. The results showed that the trends in sucrose, glucose and fructose contents in the ST leaves were similar to those of the two parents during different stages of development, but the trends in the ST storage roots were significantly different from those of their parents, which showed high sucrose utilization rates during the early stage of development and decreased utilization capacity in the late developmental stage. Transcriptome data showed that the genes that were expressed differentially between ST and its parents were mainly involved in the degradation and utilization of sucrose in the storage roots, and four key enzyme genes were significantly upregulated (Invertase MeNINV8/MeVINV3, Sucrose synthase MeSuSy2, Hexokinase MeHXK2), while the expressions of key enzyme genes involved in starch synthesis were not significantly different. The results revealed that the pattern of sucrose degradation and utilization in the cassava ST was different from that of its parents and promoted early maturation in its tuberous roots. Starch accumulation in the ST from sucrose mainly occurred during the early expansion stage of the storage roots, and the starch content during this period was higher than that of both parents, mainly due to the regulation of invertase and hexokinase activities during sucrose metabolism. This study provides a basis for further genetic improvements to cassava traits and for breeding varieties that mature early and are adapted well to provide starch supply requirements.

Plastidial Phosphoglucomutase (pPGM) Overexpression Increases the Starch Content of Transgenic Sweet Potato Storage Roots.

Sweet potato (Ipomoea batatas), an important root crop, has storage roots rich in starch that are edible and serve as a raw material in bioenergy production. Increasing the storage-root starch contents is a key sweet potato breeding goal. Phosphoglucomutase (PGM) is the catalytic enzyme for the interconversion of glucose-6-phosphate and glucose-1-phosphate, precursors in the plant starch synthetic pathway. Plant PGMs have plastidial and cytosolic isoforms, based on their subcellular localization. Here, IbpPGM, containing 22 exons and 21 introns, was cloned from the sweet potato line Xu 781. This gene was highly expressed in the storage roots and leaves, and its expression was induced by exogenous sucrose treatments. The mature IbpPGM protein was successfully expressed in Escherichia coli when a 73-aa chloroplastic transit peptide detected in the N-terminus was excised. The subcellular localization confirmed that IbpPGM was localized to the chloroplasts. The low-starch sweet potato cultivar Lizixiang IbpPGM-overexpression lines showed significantly increased starch, glucose, and fructose levels but a decreased sucrose level. Additionally, the expression levels of the starch synthetic pathway genes in the storage roots were up-regulated to different extents. Thus, IbpPGM significantly increased the starch content of the sweet potato storage roots, which makes it a candidate gene for the genetic engineering of the sweet potato.

Predicting starch content in cassava fresh roots using near-infrared spectroscopy.

The cassava starch market is promising in sub-Saharan Africa and increasing rapidly due to the numerous uses of starch in food industries. More accurate, high-throughput, and cost-effective phenotyping approaches could hasten the development of cassava varieties with high starch content to meet the growing market demand. This study investigated the effectiveness of a pocket-sized SCiO™ molecular sensor (SCiO) (740-1070 nm) to predict starch content in freshly ground cassava roots. A set of 344 unique genotypes from 11 field trials were evaluated. The predictive ability of individual trials was compared using partial least squares regression (PLSR). The 11 trials were aggregated to capture more variability, and the performance of the combined data was evaluated using two additional algorithms, random forest (RF) and support vector machine (SVM). The effect of pretreatment on model performance was examined. The predictive ability of SCiO was compared to that of two commercially available near-infrared (NIR) spectrometers, the portable ASD QualitySpec® Trek (QST) (350-2500 nm) and the benchtop FOSS XDS Rapid Content™ Analyzer (BT) (400-2490 nm). The heritability of NIR spectra was investigated, and important spectral wavelengths were identified. Model performance varied across trials and was related to the amount of genetic diversity captured in the trial. Regardless of the chemometric approach, a satisfactory and consistent estimate of starch content was obtained across pretreatments with the SCiO (correlation between the predicted and the observed test set, (R2 P): 0.84-0.90; ratio of performance deviation (RPD): 2.49-3.11, ratio of performance to interquartile distance (RPIQ): 3.24-4.08, concordance correlation coefficient (CCC): 0.91-0.94). While PLSR and SVM showed comparable prediction abilities, the RF model yielded the lowest performance. The heritability of the 331 NIRS spectra varied across trials and spectral regions but was highest (H2 > 0.5) between 871-1070 nm in most trials. Important wavelengths corresponding to absorption bands associated with starch and water were identified from 815 to 980 nm. Despite its limited spectral range, SCiO provided satisfactory prediction, as did BT, whereas QST showed less optimal calibration models. The SCiO spectrometer may be a cost-effective solution for phenotyping the starch content of fresh roots in resource-limited cassava breeding programs.