Effect of a novel dwarfing mutant site on chromosome 4B on agronomic traits in common wheat.

The introduction of dwarfing genes triggered a wave of "green revolution". A number of wheats dwarfing genes have been reported in previous studies, and only a small fraction of these have been applied to production practices. Therefore, the development of novel dwarfing genes for wheat is of great value. In this study, a novel dwarfing site, Rht-yz, identified in the Yanzhan mutation, is located on chromosome 4B (30-33MB) and its mechanism of action is different from that of Rht-B1b (C-T mutation), but whether it affects the Rht-B1a (TraesCS4B02G043100) or other genes is unclear. Exogenously applied GA3 experiments showed that Rht-yz is one of the gibberellin-insensitive dwarf genes. The effects of the dwarf gene Rht-yz on agronomic traits in wheat were evaluated in the field using Yanzhan, Yanzhan mutations, F2:3 and F3:4 lines. The results showed that Rht-yz improved lodging resistance by reducing plant height, increasing diameter, wall thickness and mechanical strength of the basal stem. In terms of yield traits, Rht-yz had negative effects on tiller number plant-1, biomass plant-1 and yield plant-1, but had no significant effect on harvest index, 1000-kernel weight and spike traits. In addition, Rht-yz significantly increased crude protein, wet gluten and starch content. Therefore, the rational use of the new dwarfing site Rht-yz has potential and value in dwarf wheat breeding.

Post-anthesis supplementary irrigation improves grain yield and nutritional quality of drip-irrigated rice (Oryza sativa L.).

Introduction: Approximately 50% of irrigation water is saved during drip-irrigation of rice, which has tremendous potential for water-saving agriculture, particularly in areas where water resources are scarce. However, the grain yield and quality of drip-irrigated rice are adversely affected. Methods: In this study, we investigated the effects of different irrigation strategies on the grain yield and quality of drip-irrigated rice using field experiments. Four irrigation treatments were studied: whole growing season flooding (FI), whole growing season normal drip irrigation (DI, soil relative moisture (RSM) was maintained in the range of 90-100%), pre-anthesis drip irrigation and post-anthesis water stress (SAF, the RSM was maintained in the range of 80-90% after anthesis), pre-anthesis drip irrigation, and post-anthesis flooding (FAF). Results: The results showed that grain yield, harvest index, seed setting rate and 1000 grain weight in DI and SAF were significantly lower than in FI and FAF. These parameters were not significantly different between FI and FAF but were significantly greater in DI than in SAF. Compared with FI and FAF, the source capacity, source activity time, and sink activity of DI and SAF decreased, and the sink-source difference increased. The sink-source difference had a significant negative correlation with rice yield and 1000 grain weight. The activities of ADP-glucose pyrophosphorylase, starch branching enzyme, and amylopectin content in grains in the middle panicles of FAF were significantly higher than those of DI and SAF. SAF resulted in increased amylose/amylopectin ratio and total protein content in grains but decreased proportion of glutenin in total protein. Irrigation after anthesis of drip-irrigated rice narrowed the difference between sink sources in rice plants, increased the grain yield and harvest index by 29.2% and 11%, respectively, compared to DI, increased water productivity by 19% compared to FI, and improved the grain quality of drip-irrigated rice. Discussion: This study highlights that post-anthesis sufficient irrigation of drip-irrigated rice plays a positive role in maintaining the source-sink balance. This study serves as a foundation for the development of more effective rice farming methods that conserve water, while increasing the grain yield and quality of drip-irrigated rice.

Increasing the yield of drip-irrigated rice by improving photosynthetic performance and enhancing nitrogen metabolism through optimizing water and nitrogen management.

Drip irrigation under plastic film mulching is an important technique to achieve water-conserving and high-efficiency rice (Oryza sativa L.) production in arid areas, but the grain yield of drip-irrigated rice is much lower than the expected yield (10.9-12.05 t·hm-2) in practical production applications. Therefore, we hope to further understand the photosynthetic physiological mechanism of drip-irrigated rice yield formation by optimizing water and nitrogen management during the growth period and provide a scientific reference for improving yield and nitrogen use efficiency (NUE) of drip-irrigated rice in arid areas. In 2020 and 2021, T-43 (a drought-resistant; V1) and Liangxiang-3 (a drought-sensitive cultivar; V2) were cultivated under two water treatments (W1: limited drip irrigation, 10200 m3·hm-2; W2: deficit drip irrigation, 8670 m3·hm-2) and three nitrogen fertilization modes with different ratios of seedling fertilizer:tillering fertilizer:panicle fertilizer:grain fertilizer (N1, 30%:50%:13%:7%; N2, 20%:40%:30%:10%; and N3, 10%:30%:40%:20%). The photosynthetic characteristics, nitrogen metabolism, yield, and NUE were analysed. The results showed that compared with other treatments, the W1N2 resulted in 153.4-930.3% higher glutamate dehydrogenase (GDH) contents and 19.2-49.7% higher net photosynthetic rates (P n) in the leaves of the two cultivars at 20 days after heading, as well as higher yields and NUE. The two cultivars showed no significant difference in the physiological changes at the panicle initiation stage, but the P n, abscisic acid (ABA), indole acetic acid (IAA), gibberellic acid (GA3), and zeatin riboside (ZR) levels of V1 were higher than those of V2 by 53.1, 25.1, 21.1, 46.3 and 36.8%, respectively, at 20 days after heading. Hence, V1 had a higher yield and NUE than V2. Principal component analysis revealed that P n and GDH were the most important physiological factors affecting rice yield performance. In summary, the W1N2 treatment simultaneously improved the yield and NUE of the drought-resistant rice cultivar (T-43) by enhancing the photosynthetic characteristics and nitrogen transport capacity and coordinating the balance of endogenous hormones (ABA, IAA, GA3, and ZR) in the leaves.

iTRAQ proteomics reveals the regulatory response to Magnaporthe oryzae in durable resistant vs. susceptible rice genotypes.

Rice blast disease caused by Magnaporthe oryzae (M. oryzae) is one of the most serious diseases. Although previous research using two-dimensional gel-based proteomics to assess the proteins related to the rice blast resistance had been done, few proteins were identified. Here, we used the iTRAQ method to detect the differentially expressed proteins (DEPs) in the durable resistant rice variety Gangyuan8 (GY8) and the susceptible rice variety Lijiangxintuanheigu (LTH) in response to M. oryzae invasion, and then transcriptome sequencing was used to assist analysis A total of 193 and 672 DEPs were specifically identified in GY8 and LTH, respectively, with only 46 similarly expressed DEPs being shared by GY8 and LTH.39 DEPs involved in plant-pathogen interaction, plant hormone signal transduction, fatty acid metabolism and peroxisome biosynthesis were significantly different between compatible interaction (LTH) and incompatible interaction (GY8). Some proteins participated in peroxide signal transduction and biosynthesis was down-regulated in GY8 but up-regulated in LTH. A lot of genes encoding pathogenesis-related gene (PR), such as chitinase and glucanase, were significantly up-regulated at both the transcriptome and proteome levels at 24 hours post-inoculation in GY8, but up-regulated at the transcriptome level and down-regulated at the proteome level in LTH. Our study reveals that the pathogen-associated molecular pattern (PAMP)-triggered immunity defense system may be activated at the transcriptome level but was inhibited at the protein level in susceptible rice varieties after inoculation. The results may facilitate future studies of the molecular mechanisms of rice blast resistance.

Starch accumulation, activities of key enzyme and gene expression in starch synthesis of wheat endosperm with different starch contents.

In order to investigate starch accumulation, and the enzymes activity changes and the expression levels of genes and their relationships among them at different developmental stages of wheat grain. We choose Annong9912 and E28 were used in the study. During starch accumulating rate and grain filling rate, and there were obvious genotype difference between Annong9912 and E28. Whether low or high starch content of starch content, the accumulation courses of amylopectin, amylose and total starch were well fitted to the logistic equation by relating starch contents against DAP. The simulation parameters revealed that the higher contents of amylopectin and amylose resulted from earlier initiating accumulation time and greater accumulation rate. And amylose, amylopectin and total starch accumulation rate of two wheat cultures were significantly and positively correlated with activities of SBE, SSS and GBSS, but amylose accumulation rate of E28 had no correlation with the activities of SBE. In addition, there were significant correlations among activities of SBE, SSS and GBSS in two wheat cultivars. We speculated that these enzymes proteins may have a coordinating action in starch biosynthesis within the amyloplast, operating as functional multiprotein complexes. And expression levels of enzyme genes demonstrated a single-peak curve, and 12-18 DAP reached their peaks and then began to drop, and all had high expression level in earlier stage of endosperm development, but in E28 were higher than in Annong9912. The GBSS-I transcripts on average were expressed over 60 times more than GBSS-II transcript in E28. SBE, SSS, DBE may control starch synthesis at the transcriptional level, and GBSS-I may control starch synthesis at the post transcriptional level. The expression level of DBE on average was lower than SS-1 and SBE-IIa genes, and similar to SS-III and SBE-IIb genes, but higher than GBSS-I and GBSS-II genes.

[Inheritance analysis of resistant starch content in kernels of wheat].

In this study, three wheat (Triticum aestivum L.) cultivars with high and low levels of resistant starch contents each were selected to obtain 15 F1 combinations from a diallel cross without reciprocals to be used to study the inheritance of resistant starch content. The results of this study are useful to select new wheat cultivar with high level of resistant starch content. Annong 90202 and D68-20 were the best among the wheat cultivars tested for general combining ability of resistant starch content, which significantly increased the resistant starch content in its progenies. The specific combining ability of Annong 90202 x 04 Dan 28 and 06-5 x D68-20 were the best among the F1 combinations, and the values of specific combining ability effects were significantly higher than other combinations. The inheritance of resistant starch content fitted the additive-dominance model, and the degree of dominance was super dominance. The alleles for increasing resistant starch content were recessive. The distribution of alleles for increasing and reducing resistant starch contents in the parental lines was not even. The number of recessive alleles for resistant starch content was greater than the dominant alleles. Annong 90202 and 04 Dan 28 had more recessive genes controlling resistant starch content, while Ningchun 18 and Xinchun 5 had more dominant genes. The narrow sense heritability of resistant starch content was 36.49%.