Carbon usage in yellow-fleshed Manihot esculenta storage roots shifts from starch biosynthesis to cell wall and raffinose biosynthesis via the myo-inositol pathway.

Cassava is a crucial staple crop for smallholder farmers in tropical Asia and Sub-Saharan Africa. Although high yield remains the top priority for farmers, the significance of nutritional values has increased in cassava breeding programs. A notable negative correlation between provitamin A and starch accumulation poses a significant challenge for breeding efforts. The negative correlation between starch and carotenoid levels in conventional and genetically modified cassava plants implies the absence of a direct genomic connection between the two traits. The competition among various carbon pathways seems to account for this relationship. In this study, we conducted a thorough analysis of 49 African cassava genotypes with varying levels of starch and provitamin A. Our goal was to identify factors contributing to differential starch accumulation. Considering carotenoid levels as a confounding factor in starch production, we found that yellow- and white-fleshed storage roots did not differ significantly in most measured components of starch or de novo fatty acid biosynthesis. However, genes and metabolites associated with myo-inositol synthesis and cell wall polymer production were substantially enriched in high provitamin A genotypes. These results indicate that yellow-fleshed cultivars, in comparison to their white-fleshed counterparts, direct more carbon toward the synthesis of raffinose and cell wall components. This finding is underlined by a significant rise in cell wall components measured within the 20 most contrasting genotypes for carotenoid levels. Our findings enhance the comprehension of the biosynthesis of starch and carotenoids in the storage roots of cassava.

Identification of novel loci associated with starch content in maize kernels by a genome-wide association study using an enlarged SNP panel.

Starch is a major component of cereals, comprising over 70% of dry weight. It serves as a primary carbon source for humans and animals. In addition, starch is an indispensable industrial raw material. While maize (Zea mays) is a key crop and the primary source of starch, the genetic basis for starch content in maize kernels remains poorly understood. In this study, using an enlarged panel, we conducted a genome-wide association study (GWAS) based on best linear unbiased prediction (BLUP) value for starch content of 261 inbred lines across three environments. Compared with previous study, we identified 14 additional significant quantitative trait loci (QTL), encompassed a total of 42 genes, and indicated that increased marker density contributes to improved statistical power. By integrating gene expression profiling, Gene Ontology (GO) enrichment and haplotype analysis, several potential target genes that may play a role in regulating starch content in maize kernels have been identified. Notably, we found that ZmAPC4, associated with the significant SNP chr4.S_175584318, which encodes a WD40 repeat-like superfamily protein and is highly expressed in maize endosperm, might be a crucial regulator of maize kernel starch synthesis. Out of the 261 inbred lines analyzed, they were categorized into four haplotypes. Remarkably, it was observed that the inbred lines harboring hap4 demonstrated the highest starch content compared to the other haplotypes. Additionally, as a significant achievement, we have developed molecular markers that effectively differentiate maize inbred lines based on their starch content. Overall, our study provides valuable insights into the genetic basis of starch content and the molecular markers can be useful in breeding programs aimed at developing maize varieties with high starch content, thereby improving breeding efficiency. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-023-01437-6.

Effects of starch content of calf starter on rumen properties and blood concentrations of metabolites and hormones in dairy calves under a high plane of milk feeding.

The objective of this study was to investigate the effects of calf starters with different starch content on rumen and blood properties in calves fed under a high plane of nutrition program. Twenty-seven Holstein calves (14 female, 13 male) were assigned to one of three starter treatment groups in a randomized block design: high-starch (41.8%) (n = 9), H; medium-starch (31.9%) (n = 9), M; low-starch (22.0%) (n = 9), L. Milk replacer on powder basis was fed up to 1.2 kg/day as fed, gradually reduced from 6 weeks of age; calves were weaned at 8 weeks of age. Each starter (up to 3.5 kg/day as fed) and chopped hay were provided ad libitum from 5 days of age. Blood was collected from 4 to 13 weeks of age. Rumen fluid was collected at 6, 8, 10, and 13 weeks of age. Serum urea nitrogen concentration after weaning was the lowest in H. Plasma IGF-1 concentrations were higher in H than in L. Ruminal pH was not different, but the molar proportion of ruminal propionate was higher in H than in L throughout the study period. In summary, a high-starch starter may increase propionate production and microbial protein synthesis in the rumen, inducing higher plasma IGF-1 concentrations.

Effect of harvest-to-cooling delay and precooling on Kufri Jyoti (Solanum tuberosum) potato quality.

Precooling is the rapid removal of field heat in harvested crops to preserve their quality and increase their shelf life. The following study was conducted to understand the importance of precooling and to optimize the precooling condition to extend the storage life of potatoes. Therefore, the study was divided into two components. In the first part, the Kufri Jyoti potatoes were subjected to field heat for 0-64 h, then were precooled for 48 h before sending to cold storage for 60 days. The results demonstrated that when the time delay was doubled, starch content (SC) decreased by 15.86%, reducing sugar content (RSC) increased by 32.71%, ascorbic acid content (AAC) decreased by 5.94% and total plate count (TPC) increased by 20.06%. Microstructural changes in potatoes due to the exposure to field heat were visible in SEM images. These results suggested a decrease in the quality of potatoes with an increase in time delay between harvest and cooling. In the second part of the study, the potatoes were precooled for 48 h at different temperatures (T) (6 °C, 8 °C, and 10 °C) and relative humidity (RH) (87%, 91%, and 95%), and their effect was studied on the same quality parameters after storage. Regression models were developed for each response, and models with non-significant lack of fit were selected for optimization. The analysis of the observations has shown that precooling aided in better quality retention of potatoes during cold storage.

Combined effects of nitrogen limitation and overexpression of malic enzyme gene on lipid accumulation in Dunaliella parva.

Overexpression of Dunaliella parva (D. parva) malic enzyme (ME) gene (DpME) significantly increased DpME expression and ME enzyme activity in transgenic D. parva. Nitrogen limitation had an inhibitory effect on protein content, and DpME overexpression could improve protein content. Nitrogen limitation increased carbohydrate content, and Dunaliella parva overexpressing malic enzyme gene under nitrogen limitation (DpME-N-) group showed the lowest starch content among all groups. Dunaliella parva overexpressing malic enzyme gene under nitrogen sufficient condition (DpME) and DpME-N- groups showed considerably high mRNA levels of DpME. ME activity was significantly enhanced by DpME overexpression, and nitrogen limitation caused a smaller increase. DpME overexpression and nitrogen limitation obviously enhanced lipid accumulation, and DpME overexpression had more obvious effect. Compared with control (wild type), lipid content (68.97%) obviously increased in DpME-N- group. This study indicated that the combination of DpME overexpression and nitrogen limitation was favorable to the production of microalgae biodiesel.

Differences and Mechanism of Waxy Corn Starch and Normal Corn Starch in the Preparation of Recrystallized Resistant Starch (RS3).

This study prepared resistant starch (RS) from waxy corn starch and normal corn starch and analyzed the effects of its molecular and microstructural characteristics on RS content. The RS content of waxy corn resistant starch (RS-WCS) was highest at 57.8%, whereas that of normal corn resistant starch (RS-NCS) was 41.46%. The short-chain amylose contents of RS-WCS and RS-NCS were 47.08% and 37.24%, respectively, proportional to their RS content. Additionally, RS content positively correlated with crystallinity, short-range order degree, and degree of polymerization (DP), exceeding 25. Electron microscopic images, before and after enzymolysis, revealed that RS-WCS was hydrolyzed from the surface to the center by pancreatic α-amylase, while RS-NCS underwent simultaneous hydrolysis at the surface and center. These results indicate that the higher RS content in RS-WCS, compared to RS-NCS, is attributable to the synergistic effects of molecular structure and microstructure.

Effects of starch content of calf starter on feed intake, growth performance, and fecal properties in dairy calves under a high plane of milk replacer feeding.

The objective of this study was to investigate the effects of different starch contents in calf starter on the growth, feed intake, and fecal characteristics in dairy calves fed under a high plane of nutrition. Twenty-seven Holstein calves were assigned equally to one of three calf starter treatment groups in a randomized block design: high (H) starch (41.8%); medium (M) starch (31.9%); and low (L) starch (22.0%). Milk replacer was fed up to 1.2 kg/day as fed, gradually reduced from 6 weeks of age; calves were weaned at 8 weeks of age. Each starter (up to 3.5 kg/day as fed) and chopped hay were provided ad libitum from 5 days of age. Fecal samples, along with body measurements, were collected from 4 to 13 weeks of age. The average daily gain after weaning was greater in the H group than in the L group. The average starter intake for 3 days before weaning was not different among treatments but was greater after weaning in the H group than in the L group. Starter starch content did not affect the number of days with diarrhea or fecal starch concentration. The high-starch starter had no adverse effects during the weaning transition.