Liqin Hu

Background and Objectives: Amylose and protein are key factors influencing starch digestibility in rice. This study aimed to characterize the starch digestibility of “double‐high” rice varieties—defined by concurrently high amylose and protein contents—and to identify the pasting and textural properties underlying their digestibility patterns. To achieve this, three “double‐high” rice varieties were compared with three rice varieties containing relatively lower contents of both amylose and protein. Findings: The three “double‐high” varieties had average amylose and protein contents of 27.3% and 9.7%, respectively—approximately 120% and 38% higher than those of the other three varieties—and exhibited a 65% longer active digestibility duration along with a 44% lower glucose production rate. While correlation analysis showed that these digestibility indicators were significantly related to both amylose and protein contents, partial correlation analysis demonstrated that the effects were mainly driven by higher amylose content rather than protein content. Compared with the other three varieties, the three “double‐high” varieties had 16%–62% lower peak and breakdown viscosities, alongside 34%–194% higher trough, final, and setback viscosities. They also showed 33%–212% increases in hardness, cohesiveness, resilience, and chewiness. Conclusions: The “double‐high” varieties exhibited slower starch digestibility, which was mainly attributed to their higher amylose content rather than higher protein content. This slower digestibility pattern was closely linked to distinctive flour viscosity properties and a more compact cooked rice texture. Significance and Novelty: These findings provide insight into the physiochemical characteristics of “double‐high” rice and inform the development of varieties with slower starch digestibility.

Plant growth and development require water, but excessive water hinders growth. Sesame (Sesamum indicum L.) is an important oil crop; it is drought-tolerant but sensitive to waterlogging, and its drought tolerance has been extensively studied. However, the waterlogging tolerance of sesame still has relatively few studies. In this study, two kinds of sesame, R (waterlogging-tolerant) and S (waterlogging-intolerant), were used as materials, and they were treated with waterlogging stress for 0, 24, 72, and 120 h. Physiological analysis showed that after waterlogging, sesame plants responded to stress by increasing the contents of ascorbate peroxidase (APX), glutathione (GSH), and some other antioxidants. The results of the multi-omics analysis of sesame under waterlogging stress revealed 15,652 (R) and 12,156 (S) differentially expressed genes (DEGs), 41 (R) and 47 (S) differentially expressed miRNAs (DEMis), and 896 (R) and 1036 (S) differentially accumulated metabolites (DAMs). The combined DEMi-DEG analysis that 24 DEMis regulated 114 DEGs in response to waterlogging stress. In addition, 13 hub genes and three key pathways of plant hormone signal transduction, glutathione metabolism, and glyoxylate and dicarboxylate metabolism were identified by multi-omics analysis under waterlogging stress. The results showed that sesame regulated the content of hormones and antioxidants and promoted energy conversion in the plant through the above pathways to adapt to waterlogging stress. In summary, this study further analyzed the response mechanism of sesame to waterlogging stress and provides helpful information for the breeding of plants for waterlogging tolerance and genetic improvement.

Background and Objectives: Increasing the water‐to‐rice (W/R) ratio can alleviate the hardness of cooked rice with high amylose content. However, whether it affects starch digestibility remains unknown. To determine the effect of the W/R ratio during cooking on starch digestion and texture properties, three W/R ratios, that is, 1.2, 1.6, and 2.0, two cultivars with different amylose contents: Zhenguiai (ZGA, 26.8 g/100 g) and Yuzhenxiang (YZX, 17.2 g/100 g) were evaluated.Findings: Our results showed that the different W/R ratios had no significant effect on the glucose production rate (GPR) of the ZGA and YZX cultivars. However, when the W/R ratio increased from 1.2 to 2.0, the hardness and chewiness of ZGA decreased by 33.5% and 42.0%, respectively. The hardness and chewiness of ZGA were quite close to YZX under the 2.0 W/R ratio. In addition, the GPR of ZGA was 48% lower than that of YZX under the same cooking condition.Conclusions: The hard texture of the high amylose content cultivar can be maximally adjusted without affecting digestion properties by increasing the W/R ratio in the range of 1.2–2.0.Significance and Novelty: Diabetic patients will not have to endure the hard texture of high‐amylose rice. Rice producers can recommend more than one W/R ratio for consumers.

Consuming rice with low starch digestibility is beneficial for reducing the risk of diabetes. Several factors have been shown to influence starch digestibility, but the combined effects of these factors on starch digestibility have not been studied. We assessed multidimensional relationships between the glucose production rate (GPR) of cooked rice with 16 indexes, including physicochemical, pasting and textural properties in 30 rice varieties. The stepwise multiple regression analysis showed that amylose content (AC), gel consistency (GC) and pasting temperature (PT) were closely related to GPR. This relationship could be described by the equation: GPR = −0.080 AC + 0.008 GC + 0.034 PT + 0.720, with a determination coefficient of 0.84. The variation partitioning analysis further indicated that AC, GC and PT independently explained 36%, 5% and 4% of the GPR variation, respectively. The interaction of AC and GC explained 46% of the variation in GPR. This study identifies the key indexes (AC, GC and PT) affecting starch digestibility and quantifies contributions of these indexes to the variation in GPR. The finding of our study provides useful information for breeding and selecting rice varieties with low GPR.

Late‐season rice, a major contributor to the production of high‐quality rice in China, often experiences low temperatures during the flowering period. The objective of this study was to determine the effect of low temperature stress on grain quality and to identify related physiological factors in late‐season rice. Sink and source characteristics and grain quality traits of two high‐quality late‐season rice cultivars were compared between a year in which low temperatures occurred during the flowering period (2020) and a normal year (2019) under field conditions. Low temperatures during the flowering period in 2020 resulted in a reduction in spikelet filling and consequent increases in source–sink ratios and grain weight and N content compared to 2019. The head rice rate and protein content of the milled rice were increased in 2020 compared to 2019. Starch gel consistency and peak, trough, breakdown, final, and consistency viscosities were reduced while setback viscosity, paste temperature, and texture properties (hardness, springiness, cohesiveness, resilience, and chewiness) were increased for milled rice (or milled rice flour or cooked milled rice) in 2020 compared to 2019. The glucose production rate and total glucose production from in vitro digestion of cooked milled rice was reduced in 2020 compared to 2019. The results of this study suggest that low temperature stress during the flowering period can improve milling, nutritional, and health qualities but reduce the cooking and eating quality in late‐season rice by altering the source–sink relationship.