【Objective】Rice grain size is a quantitative trait controlled by multiple genes. They can be dissected into a single segment substitution line (SSSL), which is of great significance for their genetic mechanism study and breeding by design. 【Method】Z492, a chromosome segment substitution line in the genetic background of Nipponbare, was used as material to dissect QTL for rice grain size by mixed linear model (MLM) method. 【Result】The F2 population was constructed from Nipponbare/Z492 to identify four QTL for grain size, including qGL6 and qGL7 for grain length and qRLW7 and qRLW12 for rate of grain length to width. Then three single-segment substitution lines (SSSL, S1-S3) and 3 dual-segment substitution lines (DSSL, D1-D3) carrying these QTL were further constructed. And the SSSL were then used to detect eight QTL for grain size, including qGL6, qGL7 and six newly identified QTL (qGW6, qRLW6, qGW7, qGWT7, qGL12, qGW12). Simultaneously, the genetic model of different QTL in 3 DSSL were analyzed. The results showed that interaction of qGL6 (a=0.26 mm) and qGL7 (a=0.21 mm) produced -0.21 mm of grain length epistatic effect, which resulted in the genetic effect (0.26 mm) of D1 equal to the additive effect of each QTL. Thus, the grain length (7.98 mm) of D1 displayed no difference from those (7.89 and 7.98 mm) of S2 with qGL7 and S1 containing qGL6, while significantly longer than that (7.47 mm) of Nipponbare. The result indicated that it is not necessary to pyramid qGL6 and qGL7 in breeding by design for increasing grain length. qGW6 (a=0.07 mm) and qGW12 (a=0.06 mm) belonged to independent inheritance in D2, thus, the genetic effect (0.13 mm) after pyramiding of qGW6 and qGW12 caused the grain width (3.65 mm) of D2 broader significantly than any of the SSSL with the single QTL. So, qGW6 and qGW12 can be selected to increase grain width in breeding by design. Interaction of qGW7 (a=0.11 mm) and qGW12 (a=0.06 mm) yielded -0.10 mm of epistatic effect, causing the grain width genetic effect (0.07 mm) of D3 parallel to the additive effect of qGW12. Thus, the grain width (3.59 mm) of D3 exhibited no difference with that (3.56 mm) of S3 carrying qGW12, while wider significantly than that (3.44 mm) of Nipponbare and narrower significantly than that (3.66 mm) of S2. 【Conclusion】It is very necessary for breeding by design to identify QTL for different important traits using SSSL and DSSL. Pyramiding different QTL produce various genetic models. Some display independent inheritance, and others exhibit various epistatic effects. In addition, to cross with S1 and S3 can realize the goal of longer, wider and heavier rice grain, and to cross with S1 and S2 can reach the target of heavier grain weight, while to cross with S2 and S3 have no any effects in grain size.
【Objective】 The study aims to measure the iron (Fe) concentration in the grain, flour, and bran of newly developed high-yielding wheat varieties (lines) in major wheat production regions of China. It investigates the impact of yield, yield components, and soil factors on Fe absorption and distribution within the wheat, and determine the effects of these variables on Fe concentrations in its different parts. The objective is to provide a basis for grain Fe nutritional fortification in wheat. 【Method】A study was conducted on 104 newly developed wheat varieties (lines) through multi-point trials across 17 provinces in major wheat production regions of China. The research analyzed Fe concentration in wheat grain, flour and bran, along with yield, yield components, Fe absorption and distribution, soil physicochemical properties, and fertilizer application rates during the 2021-2022 and 2022-2023 growing seasons, to study the Fe concentration in different parts of the grain of newly developed wheat varieties (lines) in China, as well as the absorption and distribution of Fe and environmental influencing factors. 【Result】Significant variations for Fe concentrations were observed in the wheat grain, flour and bran among new varieties (lines) in the major wheat production regions of China,with the range of 20.2-57.1, 2.1-37.5, and 31.2-144.5 mg·kg-1, and the average of 34.6, 10.8, and 72.8 mg·kg-1, respectively. Wheat varieties (lines) in the southern wheat regions exhibited higher Fe concentrations in grains and its different parts compared to that in the northern regions, and the Fe concentration in flour and bran showed a positive correlation with its in grain. For every 1.0 mg·kg-1 increase in grain Fe, flour saw a 0.2 to 0.3 mg·kg-1 rise, and bran experienced a 1.9 to 2.3 mg·kg-1 increase. The Fe concentration in grains was negatively correlated with yield, biomass, and spike number. With each 1.0 t·hm-2 increase in yield, there was a decrease of 1.2 mg·kg-1 in grain Fe concentration. For every 100×104/hm2 increase in spike number, the grain Fe concentration decreased by 0.3 mg·kg-1. The flour Fe concentration showed negative relationship with Fe absorption in grain, straw, glume and bran. The grain Fe concentration was negatively correlated with calcium, and positively with manganese, copper, and zinc. The grain Fe concentrations varied over locations, and different locations contributing 39% to 70% to the variation in grain Fe concentration. Soil pH, available phosphorus, Fe and manganese as major environmental factors affecting Fe nutrition in wheat grains. Grain Fe concentrations were negatively correlated with soil available phosphorus. Meanwhile, flour Fe concentrations were negatively correlated with soil pH, and positively correlated with soil available iron and manganese. 【Conclusion】High-Fe varieties (lines) were found among the newly developed high-yielding wheat varieties (lines) in China. Maintaining stable spike number, regulating soil pH, increasing grain Fe harvest index, soil available phosphorus, iron, manganese and appropriately applying N, P to enhance soil fertility were conducive to achieving a synergistic enhancement of both yield and Fe concentrations in wheat grain and flour.
【Objective】Husk is an important trait that affects the mechanical harvesting of maize grain, and identification of the genetic loci and candidate genes can provide theoretical basis for genetic improvement of maize husk traits. 【Method】To identify significantly associated single nucleotide polymorphisms (SNPs) and predict candidate genes for three husk traits, 251 maize inbred lines were used as plant materials and evaluated for husk number (HN), length (HL), and coverage (HC) in two environments. The genome-wide association study (GWAS) was conducted by multi-locus random-SNP-effect mixed linear model (mrMLM) with 32 853 SNPs across entire genome. 【Result】The three husk traits exhibited abundant variation among 251 maize inbred lines with 10.65%-40.60% of phenotypic variation coefficients. The variances of genotype, environment, and the genotype×environment interactions were significant at P<0.01 for each trait, and the broad-sense heritability for each trait was more than 80%. A total 92 SNPs significantly associated with three husk traits were identified in two environmental and best linear unbiased predictors (BLUP) across two environments values by GWAS. Among these SNPs, 35 SNPs were significantly associated with HN, and the phenotypic variance explained by single SNP ranged from 1.48% to 10.53%. 33 SNPs were significantly associated with HL, and the phenotypic variance explained by single SNP ranged from 1.61% to 21.69%. 24 SNPs were significantly associated with HC, and the phenotypic variance explained by single SNP ranged from 2.17% to 20.86%. However, none of SNP could be significantly associated with two husk traits. Five of 92 SNPs were stable, as they were repeatedly detected in two environments and BLUP, also they were novel loci for first reported in this study. Based on the five stable SNPs and qRT-PCR analysis for husk tissue of 17 maize inbred lines, three candidate genes (Zm00001d003850, Zm00001d033706 and Zm00001d025612) related to maize husk were screeded out, which encoded BOI-related E3 ubiquitin-protein ligase, GeBP transcription factor, and protein of unknown function, respectively. 【Conclusion】A total of 92 SNPs significantly associated with three husk traits were identified, including five stable SNPs. Three candidate genes were predicted that might be involved in maize husk growth and development.
【Objective】Aiming at the problems of large amount of nitrogen fertilizer input, low utilization rate and single fertilizer source in traditional spring wheat planting in the oasis irrigation area of Northwest China, the effects of multiple cropping green manure after spring wheat on photosynthetic source, growth characteristics and yield of spring wheat under the condition of reduced nitrogen application were studied, with a view to provide the technical support for the construction of a nitrogen-saving and high-yield green planting model of spring wheat in the experimental area. 【Method】The split plot experiment was carried out in the oasis irrigation area of Hexi Corridor from 2021 to 2023. The main area was set up with two planting modes: post-wheat fallow (W) and post-wheat multiple cropping of hairy leaf (W-G), and the split plot was the traditional full nitrogen application of 100% (N1, 180 kg·hm-2), reduced nitrogen application of 15% (N2, 153 kg·hm-2) and reduced nitrogen application of 30% (N3, 126 kg·hm-2). The photosynthetic source, stay-green of leaves, growth characteristics and yield performance related indicators of spring wheat under different treatments were measured and calculated. The Logistic equation of dry matter accumulation, the correlation between different indicators and the compensation index were constructed. The objective was to explore the compensation effect of multiple cropping green manure on the growth and yield of nitrogen-reduced spring wheat. 【Result】Post-wheat multiple cropping of green manure could compensate for the loss of photosynthetic source, growth characteristics and yield caused by nitrogen reduction to a certain extent. Among them, the compensation effect was the best under the condition of multiple cropping green manure after spring wheat combined with 15% nitrogen reduction (W-GN2), which showed super compensation and equal compensation effect. Multiple cropping of green manure significantly increased leaf area index, leaf area duration and stay-green of leaves in spring wheat at the late reproductive stage. Compared with the traditional post-wheat fallow total nitrogen fertilization (WN1), W-GN2 increased the average leaf area index, leaf area duration and stay-green of leaves by 17.7%, 17.5% and 7.6% on the 75-90 days after seedling, respectively. W-GN2 optimized the growth characteristics of spring wheat. Compared with WN1, the average dry matter accumulation, the maximum growth rate of dry matter and crop growth rate under W-GN2 increased by 6.2%, 6.9% and 5.1%, respectively, and the net assimilation rate decreased by 6.2%. Due to the compensation of multiple cropping green manure for photosynthetic source and growth characteristics, the photosynthesis, population growth and material accumulation rate of spring wheat remained high in the late growth stage, which was conducive to the improvement of grain yield. The grain yield under W-GN2 was 14.7% higher than that under WN1, which was mainly attributed to the compensation of the spike number, 1000-grain weight and harvest index by multiple cropping green manure, and W-GN2 was 6.5%, 6.9% and 13.2% higher than that under WN1, respectively. According to the correlation analysis, it was found that W-GN2 treatment had better performance in photosynthetic source, growth characteristics and grain yield formation, and mainly promoted the formation of yield by compensating the photosynthetic source of spring wheat. 【Conclusion】Multiple cropping of hairy vetch after spring wheat with 15% reduction of nitrogen application could be used as a perfect production technology to regulate the photosynthetic source and growth characteristics of spring wheat in the northwest oasis irrigation area to achieve nitrogen saving and yield increase.
【Objective】This study explored the effects of different mulching methods on the production of photosynthetic substances and water use of maize under the intercropping mode of maize and soybean, aiming to determine the suitable mulching method for maize and soybean plantation in dryland agriculture in northern Shaanxi, so as to provide a basis for high-yield and efficient production of maize and soybean and ecological environment protection. 【Method】This study was conducted in irrigated land and nonirrigated land in 2022, using 'Zhonghuang 30' soybean and 'Xianyu 335' maize as materials. The two-factor complete randomized design was carried out, and the control group combined single crop (maize “M”, soybean “S”) and film mulching (bare land, interbrane “J”), and the test group combined intercropping crop (maize “M”, soybean “S”) and film mulching (bare land, interbrane “J” and whole film “Q”), with a total of 13 treatment groups. The characteristics changes of growth, photosynthesis, and water use efficiency of intercropped maize under different mulching methods were studied. 【Result】 (1) From jointing to silking stage, the growth space of intercropped maize was limited, resulting in a disadvantage in aboveground biomass of intercropped maize compared with monoculture. The biomass during the jointing stage of S/MQ, SQ/MJ, and SQ/MQ was 5.1%, 6.3%, and 1.7% higher than that of monoculture M, respectively; under intercropping, SJ/MJ maize plants had the fastest growth rate and a sharp increase in growth. SQ/MQ S/M, S/MJ, SQ/MJ, and SJ/M in dry land had a better promoting effect on the photosynthetic products of maize during the silking stage, and the aboveground biomass was 0.6%-105.9% higher than that of monoculture M. (2) To some extent, intercropping and mulching treatments improved the photosynthetic characteristics of maize, and the net photosynthetic rate (Pn) content of paddy maize. There was a certain degree of positive relationship between stomatal conductance (Gs), cellular CO2 concentration (Ci) and transpiration rate (Tr). The photosynthetic parameters of SQ/MJ and SJ/MQ were relatively high, while SJ/M and SQ/MQ were lower than non film coated S/M; there was a weak negative correlation between Pn and Ci in dryland maize, and the effect of maize mulching was not significant among different treatments. The Gs of intercropping treatment was 5.7% -38.1% lower than that of monoculture M, and Tr was also reduced by 5.6% -25.6%. Only the Pn of SJ/M and SQ/M, as well as the Ci of SQ/MJ and S/M, were higher than monoculture M. (3) The intercropping film mulching had a significant impact on water use efficiency (WUE). The WUE of the intercropping treatment was 41.1% -74.0% higher than that of monoculture M, among which SJ/M, S/M and S/MJ were relatively high; among all treatments in arid land, SQ/MJ had the highest WUE (19.04 kg∙mm-1∙hm-2), followed by SJ/MJ (17.07 kg∙mm-1∙hm-2), and the WUE of SJ/M and SQ/M was significantly lower than that of monoculture M by 26.7% and 20.6%, respectively. (4) Compared with monoculture M, intercropping S/MJ between irrigated land and dry land SJ/M and SJ/MJ maize increased yields by 76.8%, 73.0%, and 72.3%, respectively, while soybean yield reduction was relatively less among all intercropping treatments, demonstrating higher economic benefits; dry land intercropping SJ/MJ and SJ/MQ maize increased production by 17.1% and 23.5%, respectively, while economic benefits decreased by 17.5% and 22.8%, respectively. 【Conclusion】Compared with single cropping M, SJ/MJ model improved the photosynthetic performance, biomass, and yield of maize in irrigated land, and improved system economic benefit and promoted water use efficiency. In dry land, through the complementary effect and resource allocation in the intercropping system, it maintained maize yield and improved water use efficiency, but the increase of total input in agricultural materials reduced the economic feasibility. Therefore, in the dryland agriculture of Northern Shaanxi, the intercropping planting pattern of maize with degradable film and soybeans with degradable film was recommended for both irrigated land and moderately irrigated dry farm, aiming to enhance water use efficiency, increase production and profitability, and promote sustainable ecological agriculture development.
【Objective】Apple ring rot is one of the serious fungal diseases in apple production caused by Botryosphaeria dothidea. The aim of this study is to obtain strains of B. dothidea with weak pathogenicity carrying dsRNA viruses, identify the types of viruses, and clarify the distribution of these viruses in China, so as to provide new biological control resources for the prevention and control of apple ring rot and new insights into the diversity and systematic evolution of fungal viruses. 【Method】Samples of branches with typical symptoms of apple ring rot were collected from across China, and pure cultures were obtained through tissue isolation and single-spore isolation. Virus-carrying strains were identified through dsRNA band analysis, and the types of dsRNA viruses carried by the virus-carrying strain WH-2L were identified using high-throughput sequencing and molecular cloning techniques. The presence of two types of dsRNA viruses in B. dothidea from six provinces (autonomous region) in China was determined by RT-PCR. Pathogenicity differences among representative strains carrying different viruses were clarified through pathogenicity tests. Finally, the transmission characteristics of the two viruses were revealed through analysis of vertical and horizontal transmission properties. 【Result】For the first time in apple-producing regions of China, strains of B. dothidea causing apple ring rot were found to be co-infected with two viruses: Botryosphaeria dothidea chrysovirus 1 (BdCV1), belonging to the family Chrysoviridae and genus Chrysovirus, and Botryosphaeria dothidea victorivirus 2 (BdVV2), belonging to the family Totiviridae and genus Victorivirus. It was clarified that BdCV1 and BdVV2 are widely distributed in B. dothidea causing apple ring rot in China. BdCV1 was detected in strains from Liaoning, Shandong, Henan, Hebei, Shaanxi, and Xinjiang, except for Yan’an in Shaanxi and Shijiazhuang in Hebei, with an average detection rate of 53.6%. BdVV2 occurred in Liaoning, Shandong, Henan, Hebei, and Shaanxi, but was not detected in Yan’an in Shaanxi, Shijiazhuang and Handan in Hebei, Aksu in Xinjiang, Taian and Qingdao in Shandong, with an average detection rate of 28.6%. It was clarified that the pathogenicity of strains with co-infection of the two viruses and single infection of BdCV1 on branches, apple fruits, and pear fruits was significantly reduced. The vertical transmission efficiency of BdCV1 and BdVV2 was 100%, and the horizontal transmission efficiency was 9% and 3%, respectively. 【Conclusion】The strain WH-2L of B. dothidea with weak pathogenicity carries two viruses, BdCV1 and BdVV2. The detection rates of BdCV1 and BdVV2 in B. dothidea causing apple ring rot in six apple-producing regions in China were 53.6% and 28.6%, respectively. Both viruses can cause reduced pathogenicity in their hosts, with high vertical transmission efficiency and certain horizontal transmission efficiency, and have potential for development as biological control resources for apple ring rot.
【Background】Hulless barley ear (or spike) rot epidemically occurs only in the Qinghai-Xizang Plateau, which has been getting heavier and spreading more widely in recent years. It has become one of the major diseases in the staple food crop, hulless or naked barley (Hordeum vulgare var. nudum), referred to as Qingke in local areas. It seriously threatens the guarantee of high yield and stable production of hulless barley crops. Grass mite (Siteroptes spp.) plays the role of inoculum transmission vector of the pathogen Dactylobotrys graminicola. The disease cycle is still unclear, and a control method is not available at present. 【Objective】In this study, the migration and clustering of grass mites were investigated in order to disclose the processes of pathogen inoculum transmission and the infection of inflorescence of hulless barley. The results obtained here will serve as a scientific basis for developing technologies for ear rot control. 【Method】Variations in the number of mites in samples of surface soil and on hulless barley plants, as well as their distributions, were detected. The fungi carried by grass mites were microscopically observed and isolated for species identification, and the infection processes of hulless barley inflorescences were also detected under a microscope. The fungal spores stored in the sporothecae of grass mite vectors near the lesions of inflorescences and those collected from the soil were tested using the lactophenol cotton blue dyeing method. The initial invasion time of grass mites into hulless barley seedlings and their distribution within the plants were verified in the greenhouse. The pathogen D. graminicola was inoculated onto hulless barley tissues for testing its pathogenicity. 【Result】The overwintering mites initially moved in from the horn-shaped opening of the first leaf after the blade unfolded and gathered at the adaxial side of its basal part. About 87.63%-99.34% of the grass mites found in hulless barley plants were distributed in their main stems, with only 0.66%-12.37% in tillers. The majority of mites in the main stems (95.48%-99.74%) were gathered around the basal parts of young leaves, over 30% of which moved onto inflorescences at the early booting stage. The incidence of ear rot in the main stem was 6.37 times that of the tiller. Greenish yellow, water-soaked lesions appeared on the glumes and awns of young spikelets, and adult mites were usually found near them at the early booting stage; 28.57% of these mites contained fungal spores in their sporothecae, significantly lower than the 46.70% ratio of spore-carrying mites in the soil. After seedling emergence, the mite density in the soil remained at a relatively low level for a long time until hulless barley was harvested, and it abruptly increased by 2.85 times compared to before sowing. About 88.66% of the fungal isolates from grass mites and 76.47% of those from lesion tissues of inflorescences were identified as D. graminicola, and the pathogen was only strongly pathogenic to the inflorescences. 【Conclusion】The overwintering mites mainly migrated from the soil and flocked to hulless barley seedlings during the early stage after plant emergence, first entering the basal part of the first leaf through the horn-shaped opening formed after leaf blade unfolded. Over 30% of mites clustering around the newly born leaves of a main stem subsequently moved onto the inflorescence at the early booting stage and then released D. graminicola spores to cause infection. The disease cycle of D. graminicola was completed with the essential aid of grass mite mediator. Ear rot mainly infected the main stems of hulless barley plants. It was not until at the repining stage that there were plenty of adult mites produced on the diseased ears, resulting in a significant increase in the mite density in surface soil after harvesting. Therefore, ear rot of hulless barley is a monocyclic disease mediated by vector grass mite.