Genotypic diversity and environmental stability of starch physicochemical properties in the USDA rice mini-core collection

"Structure-function" analysis using starches isolated from Lycoris chinensis bulbs of different developmental stages

In this study, Lycoris chinensis bulbs of four developmental stages were compared for starch characteristics. Based on correlation analysis and hierarchical cluster analysis, the relationships among 36 traits were discussed. Compared to commonly consumed starches, L. chinensis starch had higher amylose content (33.4-43.2 %) and weight-average molar mass (36410-82,781 kDa), lower gelatinization temperature (61.8-68.1 °C), gel hardness (19.0-39.5 g) and viscosities. Among developmental stages, starches varied significantly in characteristics. As compared to juvenile stage (S1), mature bulbs (S4) had higher amylose content, lower gelatinization temperature, weight-average molar mass and degree of polymorphism. Correlation analysis revealed that the molecular weight-related traits had significantly positive correlations to gelatinization temperature (Tp, p < 0.05), positive but weak correlations to traits of particle size distribution, significantly negative correlations to AAC and many parameters of viscosity properties (p < 0.05). Based on the results of correlation analysis and hierarchical cluster analysis, the 36 traits of starch characteristics were proposed to be divided into three groups: particle size-related traits, molecular weight-related traits and AAC-related traits. The information presented in the current study are useful for future studies on starches of Lycoris and other bulb species, and instructive for future studies in investigating the "Structure-Function" relationship in starch.

Structural and physicochemical properties of bracken fern (Pteridium aquilinum) starch

Introduction

Bracken fern (Pteridium aquilinum) starch is a non-mainstream, litter-researched starch, thus the starch characteristics remain largely unknown.

Methods

The structural and physicochemical properties of two bracken starches were systematically investigated, by use of various techniques that routinely applied in starch analysis.

Results and Discussion

The starches had amylose contents of 22.6 and 24.7%, respectively. The starch granules possessed C-type polymorph with D (4,3) ranging from 18.6 to 24.5 μm. During gelatinization event, the bracken starches showed lower viscosity than typical for rice starch, and lower gelatinization temperature than typical for cereal starches. After gelatinization event, bracken starches formed much softer and sticky gel than rice and potato starch. The molecular weight and branching degree (indexed by Mw, Mn and Rz values) of bracken starches were much higher than starches of many other sources. The branch chain length distributions showed that the bracken starches were structurally similar to some rice varieties (e. g. BP033, Beihan 1#), as reflected by proportions of A, B1, B2, and B3 chains. Notable differences in some starch traits between the two bracken starches were recorded, e. g. amylose content, gel hardness, gelatinization temperature and traits of structural properties. This study provides useful information on the utilization of bracken starch in both food and non-food industries.

Characterization of starch extracted from seeds of Cycas revoluta

Introduction

Starch is major component in the big seeds of Cycas revoluta, however the characteristics of Cycas revoluta remain unknown.

Methods

In this study, the physicochemical and structural properties of two starch samples extracted from Cycad revoluta seeds were systematically investigated, using various techniques.

Results

The amylose contents of the two samples were 34.3 % and 35.5%, respectively. The spherical-truncated shaped starch granules possessed A-type crystallinity, and had an average diameter less than 15 μm. Compared to most commonly consumed cereal and potato starch, Cycad revoluta starch showed distinctive characteristics. For physicochemical properties, in the process of gelatinization, the Cycad revoluta starch showed similar viscosity profile to starches of some potato varieties, but Cycad revoluta starch had higher gelatinization temperature. Upon cooling, Cycad revoluta starch formed harder gels than rice starch. For structure, the molecular weight (indexed by Mw, Mn and Rz values), branching degree and the branch chain length distribution were determined.

Discussion

The results suggested that Cycad revoluta starch were different in structure from the main-stream starches. Notable differences in some starch traits between the two samples were recorded, which could be attributed to environmental factors. In general, this study provides useful information on the utilization of Cycad revoluta starch in both food and non-food industries.

Diversity analysis of starch physicochemical properties in 95 proso millet (Panicum miliaceum L.) accessions

In this study, 95 accessions of proso millet (Panicum miliaceum L.) were characterized for starch physicochemical properties, including apparent amylose content (AAC), gel textural properties, Rapid Visco Analyzer (RVA) pasting viscosity properties, thermal and retrogradation properties. Based on genotypic data, the genetic diversity and inter-relationship of these starch traits were analyzed. Diverse starch quality was found, for example, AAC ranged from 0 to 32.3%, gelatinization temperature (GT) varied from 71.5 to 79.0 ℃, and RVA profile showed distinct patterns among proso millet of different AAC types. Interestingly, high AAC proso millet usually had GT lower than that of low AAC proso millet, which is different from the findings in rice starch. Many starch traits were significantly correlated and most of the 18 tested traits could be classified as either AAC-related traits or GT-related traits. In summary, the information presented here will be useful for further development of proso millet products.

Association Analysis of Markers Derived from Starch Biosynthesis Related Genes with Starch Physicochemical Properties in the USDA Rice Mini-Core Collection

Rice eating and cooking quality is largely determined by starch physicochemical properties. The diverse accessions in the USDA rice mini-core collection (URMC) facilitate extensive association analysis of starch physicochemical properties with molecular markers specific to starch biosynthesis related genes. To identify significant trait-marker associations that can be utilized in rice breeding programs for improved starch quality, we conducted two association analyses between 26 molecular markers derived from starch biosynthesis related genes and 18 parameters measured of starch physicochemical properties in two sets of the mini-core accessions successfully grown in two environments in China. Many significant trait-marker associations (P < 0.001) were detected in both association analyses. Five markers of Waxy gene, including the (CT)n repeats, the G/T SNP of intron 1, the 23 bp sequence duplication (InDel) of exon 2, the A/C SNP of exon 6, and the C/T SNP of exon 10, were found to be primarily associated with starch traits related to apparent amylose content (AAC), and two markers targeting the 4,329-4,330 bp GC/TT SNPs and 4,198 bp G/A SNP of SSIIa gene were mainly associated with traits related to gelatinization temperature (GT). Two new haplotypes were found in the mini-core collection based on the combinations of the 23 bp InDel and three SNPs (G/T of intron 1, A/C of exon 6, and C/T of exon 10) of Waxy gene. Furthermore, our analyses indicated that the (CT)n polymorphisms of Waxy gene had a non-negligible effect on AAC related traits, as evidenced by significant variation in AAC related traits among rice accessions with the same Waxy SNPs but different (CT) n repeats. As the five Waxy markers and the two SSIIa markers showed consistent major effects on starch quality traits across studies, these markers should have priority for utilization in marker-assisted breeding.