The comprehensive analyses of the cytogenetical and comparative genomic studies related to the genome structure and evolution of Brassica diploids were made in this review. From the comparisons of DNA sequences from the species sequenced, evolutionary process of the ancestral paleohexaploid genome specific for the Brassiceae tribe was at first the derivation of the x=7 karyotype from the ancestral Brassicaceae karyotype with x=8 by the chromosome reduction, and then the formation of the hexaploid genome by the whole genome triplication event, and finally the speciation of the 3 diploids. On the basis of genomic sequences of 3 diploids, their ancestral genome including 9 chromosomes were constructed and the chromosomal components of each diploid were given. Traditional and molecular cytogenetical studies provided direct evidences for the polyploidy nature of these diploid genomes and their homoeologous relationships. In particular, the degrees of homoeology at chromosomal levels were revealed by the meiotic pairing of the monosomic additional lines involving 2 of 3 diploids. Finally, the research strategy for germplasm enrichment and genetic improvement of Brassica crops was suggested with the consideration of the genome structure of the relatives.
Application of industrial nitrogen fertilizer to a certain extent satisfied the high-yield demand of crops, but its excessive application might bring serious environmental and ecological problems. How to use the green and high efficiency nitrogen provided by biological nitrogen fixation to replace industrial synthetic nitrogen is a hot topic. Although the efficiency of symbiotic nitrogen fixation system is high, fertilizer nitrogen and rhizosphere microorganisms might have negative effects on the utilization of nodulation nitrogen fixation system. Therefore, starting with the key factors restricting the development of symbiotic nitrogen fixation, namely, the content of soil available nitrogen and rhizosphere microbial community, the establishment of symbiosis system of legume plant - Rhizobium was summarized, as well as the response of external nitrogen, the relationship between rhizobia community and rhizobia symbiosis efficiency were summarized and analyzed. The physiological and molecular mechanism of nitrogen efficient utilization was also analyzed. The optimal control technology was proposed to improve the nitrogen utilization rate and provide theoretical support for the efficient utilization of nitrogen in legume crops.
Oil crops are one of the essential sources of edible oil and nutrition in daily life. With the improvement of quality demand for edible oil, quality traits have become more important for breeding objectives. Traditional breeding efficiency was low and time consuming, thus genome-wide association analysis (GWAS) became more attractive. GWAS based on the principle of linkage imbalance, which provides a new way to mine candidate genes for quantitative traits controlled by multiple genes. It has been used in many crops because of its advantages of high positioning accuracy, wide range and short cycle. In this paper, GWAS was reviewed on oil crops, as soybean, rapeseed, peanut, sesame, flax, sunflower and other several important oil-bearing crops. The quality researches related properties of oil content, fatty acid, and protein content were summarized. Shortcomings of the present research, and future development were also discussed and prospected. The aim is to provide references for analyzing the genetic basis of quality related traits of oil crops and breeding high quality oil crop materials by GWAS.
In recent years, with the rapid development of genetically modified technology and industrialization in China, the safety supervision of agricultural genetically modified organisms has faced higher requirements and challenges. The research and application of genetically modified rapid detection technology is particularly important to our supervision work. In this article, we divide genetically modified rapid detection technologies into 3 categories: rapid detection technologies based on nucleic acid levels and protein levels respectively, and other rapid detection technologies. The principles, research progress, advantages and disadvantages and applications of important technologies were introduced, such as nucleic acid rapid extraction, nucleic acid isothermal amplification, nucleic acid test strip, immunochromatographic test strip and biosensors. The development trend, application prospects and bottleneck problems of rapid detection technology for genetically modified products were also summarized and discussed, to promote the development of rapid detection technologies and to provide effective support for the safety supervision of agricultural genetically modified organisms in China.
Virus induced gene silencing (VIGS) is a reverse genetics method based on post-transcriptional gene silencing. It can be used to identify gene function quickly. This technique has the advantages of short period of testing, simple operation, low cost, high efficiency, fastly obtaining phenotype, and high throughput. It has been widely used in gene function studying in plants. Legumes are of great economic significance as sources of starch, protein, oil and vegetables in human food. In the study, the application of virus-induced gene silencing technology in legumes was reviewed from technical principle, development and improvement vectors, and influencing factors of VIGS. The reviews will provide reference for conducting related studies by means of VIGS in legumeinous plants.
Sclerotinia stem rot caused by Sclerotiniasclerotiorum is an important fungi disease in oil crops especially in Brassica napus. For plant breeding, screening of Sclerotinia resistance genes is important. Most F-box genes participated in plant defense response, and LRR regarded as the important domain of resistant genes. Thereby, F-box genes were investigated in this study. Genome-wide identification of F-box-LRR gene in B. napus was conducted by bioinformatics method. Based on published data of tissue expression in Zhongshuang 11 and transcriptome data of inoculation fungi on leaves of susceptible Westar and resistant Zhongyou 821, corresponding Bn-F-box-LRR genes were identified and then verified by qRT-PCR. 161 BnF-box-LRR genes were found and classified into 4 subgroups （FBXLRR1 to FBXLRR4）. The fourth subgroup, FBXLRR4, was significantly different from the other three in the conserved protein distribution and gene structure. It was clustered into the same clade with the homologous genes which involved in plant stress resistance in Arabidopsis thaliana. Therefore, it is speculated that this subgroup might be mainly involved in plant stress response. Based on transcriptome data, it was found that most FBXLRR4 genes were highly expressed in root and leaves, and showed significant expression alternation after S.sclerotiorum induction, indicating these genes potentially in Sclerotinia disease resistant.
Diploid wild species Arachis duranensis (AA) and A. ipaensis (BB) are the most possible ancestors of cultivated peanut. Peanuts synthesized by ancestral species are important materials for studying the origin and evolution. In this study, a new interspecific hybrid W1824 of A. duranensis (PI 497262) and A. ipaensis (PI 468322) was created and identified by hybridization, tissue culture, oligonucleotide probe staining FISH (OS FISH) and genomic in situ hybridization (GISH). Analysis of pollen fertility, meiosis behavior and phenotypic traits showed that W1824 had high sterility, its average chromosome configuration was 0.5 III + 3.5 II + 11.5 I, and its height of main stem, length of first primary branch and leaf area showed super-parent advantage. This indicated that the two accessions PI 497262 and PI 468322 had high cross-compatibility and suggested that the tetraploid peanut synthesized using the two accessions might have significantly higher biological yield than their parents and unstable inheritance in chromosomal level.
Purple acid phosphatases (PAPs) are the members of metallo-phosphoesterase family genes, which involve in multiple physiological functions, such as phosphorus utilization, carbon metabolism, and cell wall synthesis, especially adapt to phosphorus deficiency. In this study, we used bioinformatics method to identify the PAP gene family in peanut plant (Arachis hypogaea L.) at genome-wide level, analyzed their phylogenetic relationship, conserved domain, gene structure, and expression pattern in 22 tissues. Results showed that a total of 39 AhPAP genes were characterized in peanut genome, their amino acid sequence length ranged from 205 to 905, the isoelectric points of majority PAP proteins were less than 7, as well the metallophosphatase domain existed in the C-terminal of PAP protein sequences. Phylogenetic tree was constructed with 74 PAPs that obtained from peanut, Arabidopsis, rice and medicago genome, and the entire PAPs could be divided into 4 subgroups. Each subgroup contained PAPs from different plant species, and they were not clustered into one category due to the species difference. Furthermore, the expression of several AhPAPs presented tissue-specific, arahy.P03NME and arahy.DAPS6C exhibited the highest expression levels in nodule, but lower or not detected in other tissues. Totally, our results laid a foundation for next revealing the biological function of AhPAPs in peanut.
In order to explore the feasibility of data fusion technology in the origin identification of neighboring soybean producing area, 216 soybean samples were collected from Heilongjiang Agricultural Reclamation Jiusan Administration and Suihua area, and the contents of 13 mineral elements such as magnesium (Mg), aluminum (Al) and phosphorus (P) and 5 fatty acids such as palmitic acid, stearic acid and oleic acid were determined. Support vector machine (SVM) with 4 kernel functions were established by mineral elements, fatty acids, data-level fusion and feature-level fusion data. After parameter optimization by grid search algorithm combined with 50% cross-validation, the recognition accuracy of the model increased to 90.77%, 92.31%, 89.23% and 95.38% respectively. The results showed that the feature-level data fusion technology had a significant effect on the origin identification of neighboring soybean producing area, which was superior to the other three data identification technologies. It could accurately and effectively distinguish soybean origin in neighboring areas by feature-level data fusion technology to establish support vector machine origin identification model, which provided a new research direction for geographical indication product protection technology.
Distinguishing elite germplasm with high nitrogen-use-efficiency is critical to high-yield breeding in soybean. In this study, we employed hydroponic assay and evaluated biomass and tolerance index of low nitrogen stress of 78 accessions at two nitrogen levels, i.e. normal (7.5mmol/L) and low (0.75mmol/L). Based on performance of aboveground dry weight, whole-plant dry weight and low nitrogen tolerance index, 8 elite accessions, including 3 low-nitrogen-tolerant genotypes (2011-X-559, 2011-X-618, 2011-X-639), 3 low-nitrogen-sensitive genotypes (2011-X-472, 2011-X-531, 2011-X-547) and 2 intermediate genotypes (Jiyu 86, Dongnong 53), were distinguished. Furthermore, we focused on the 8 accessions and examined 17 traits, covering chlorophyll content, biomass, nitrogen percentage and root morphology. By means of variation coefficient, Pearson correlation and principal component analysis, 6 traits （composing of dry biomass, total nitrogen percentage, total nitrogen accumulation, total root length, root volume and root surface area） could be considered as the main indicators for screening low nitrogen tolerant soybean germplasm at seedling stage. Consequently, a low nitrogen tolerant accessions 2011-X-618 and a low nitrogen sensitive accessions 2011-X-531 were further validated. We hoped to shed light on deciphering the mechanism of nitrogen use efficiency and provide excellent germplasm for high yield breeding in soybean.
Soybean is sensitive to photoperiod, and the cultivation area of each soybean variety is restricted to a very narrow latitudinal range. The adaptability of soybean between different latitudes is closely related to flowering time. In order to excavate the genes controlling flowering time of soybean, we performed QTL mapping for flowering time by using recombinant inbred line (RIL) population derived from Huapidou × Qihuang 26 cross and high-density linkage map constructed based on specific length amplified fragment sequencing (SLAF-seq). In total, 11 QTLs were identified on 7 chromosomes. Of them, 4 QTLs (qFT8, qFT20-2, qFT14 and qFT16) were newly identified in this study. Furthermore, 6 QTLs (qFT6-1, qFT8, qFT11-1, qFT19, qFT20-1 and qFT20-2) exist stably in 2 environments. By performing the sequences and bioinformatics analysis of genes between 6 stable QTL intervals, 4 candidate genes related to flowering time regulation had been identified. The results of this research were expected to provide a foundation for understanding the molecular mechanism of soybean adaptability and cultivating the varieties with wide adaptability.
Maturity group （MG） is a widely-used system for soybean classification in the world. In order to clarify the MG types of national soybean materials, varieties （lines） from 4 trails （Yangtze River Valley Summer-Planting Late-maturing Soybean Reginal and Joint Qualification Trials, Summer-Planting Vegetable-soybean Reginal and Joint Qualification Trials） of the year were summer-planted in Nanchong （Sichuan Province） from 2019 to 2020. By comparing with 24 MG standard varieties from the North America, regression analysis method was established with growth duration and relative maturity group values. Results showed that growth duration of the standard varieties presented constant increase from MGⅠ to MGⅦ, but the boundaries between MGⅡ and MGⅢ, MGIV and MGV, were not obvious. Of the 47 tested varieties in 2 years, totally 4, 4, 11, and 5 varieties belonged to MGII, MGⅢ, MGIV, MGV, respectively, accounting for 8.5%, 8.5%, 23.4%, 10.6% of the total number. 22 varieties belonged to MGⅥ-MGⅦ, accounting for 46.8%. It indicated that most varieties in Yangtze River Valley summer-planting and late-maturing soybean group and summer planting vegetable soybean group belong to MGIV-MGⅦ. These results were expected to provide references for breeding and promotion of soybean bteeding in Sichuan, and also for introduction in other regions in China.
Camellia oleifera is the largest edible oil tree species in China. In order to select C. oleifera varieties for popularization and application in northern producing areas, 8 Changlin series (Changlin 3, 4, 18, 23, 27, 40, 53, and 55) from Henan Province (as in Guangshan County, and Xin County) and Anhui Province (as Jinzhai County) were used as materials. Fruit traits were determined and varieties with better comprehensive quality were screened by principal component analysis. Results showed that: different sites had significantly effects on fruit diameter and seed yield of fresh fruits, and had very significantly effects on fresh fruit weight, fruit height and fresh seed weight. However, different sites had no significant effect on contents of fatty acid in camellia oil. There were significant differences in fresh fruit weight, fruit height, fruit diameter, fresh seed weight, fresh fruit seed yield rate, dry kernel oil content among varieties. There was no significant difference in the contents of fatty acids in camellia oil among different varieties, and the average content of unsaturated fatty acids in Changlin 53 was the largest. Only from the perspective of unsaturated fatty acids, Changlin 53 in Jinzhai County showed better performance. According to the principal component analysis, only considering the first principal component, Changlin 55 has the highest evaluation value (0.935). The ranking of the experimental sites was as follows: Jinzhai County (1.103) > Guangshan County (0.032) > Xin County (-1.153). The comprehensive evaluation showed that Changlin 53, Changlin 4, Changlin 18 and Changlin 55 had better fruit traits than the other 4 varieties in the northern C. oleifera production area, and could be used as the superior varieties for priority popularization and application in this area.
To better understand the effect of potassium deficiency on rapeseed (Brassica napus L.), hydroponic experiment was carried out using 2 cultivars Chuanyou 36 (sensitive) and Youyan 57 (tolerant) exposed to 7% PEG6000 simulated drought stress. Two potassium (K) levels were set as 0.01 and 1.0 mmol/L K2SO4, referred to LK and NK respectively. Drought stress hindered rapeseed growth seriously, and K levels affected the growth and endogenous hormone levels significantly. Compared to NK, LK caused a more dramatic decrease in biomass and content of indole acetic acid (IAA), cytokinin (CTK) and brassinolide (BR) in leaf, while abscisic acid (ABA) increased significantly. LK decreased photosynthesis significantly under drought, including net photosynthetic rate, stomatal conductance, enzyme activity of ribulose 1,5-bisphosphate carboxylase (RuBP carboxylase) and phosphoenolpyruvate carboxylase (PEPC). The maximum change of photosystem I (PSI) P700 (Pm) and P700 under light (Pm') decreased significantly under drought. Under LK, Pm' was significantly lower, while nonphotochemical quantum yield by acceptor side limitation of PSI [Y(NA)] was significantly higher. The maximum photochemical quantum yield (Fv/Fm) of photosystem II (PSII) decreased significantly under drought. Fv/Fm and quantum yield of regulated energy dissipation [Y(NPQ)] decreased significantly under LK treatment, while non-regulatory energy dissipation [Y(NO)] increased significantly. Drought tolerant cultivar Youyan 57 kept higher level of IAA, CTK, chlorophyll, net photosynthetic rate, and Fv/Fm than those of Chuanyou 36 under LK, with larger biomass. In summary, K deficiency could induce accumulation of ABA and inhibit synthesis of IAA, CTK and BR, then inhibited rapeseed growth under drought. It decreased growth and of photosynthesis under drought by decreasing activities of RuBP carboxylase and PEPC, over reducing acceptor side limitation of PSI and quantum yield of regulated energy dissipation of PSII, increasing quantum yield of nonregulated energy dissipation, resulted in decrease of PSI and PSII activities.
In order to explore the net carbon exchange characteristics and carbon sequestration capacity of winter rapeseed, vorticity correlation method was used to continuously observe the carbon flux of rapeseed ecosystem in central Hunan Province from October 2019 to May 2020. Variation characteristics of carbon flux during the whole growth period of rapeseed were also analyzed. Results showed that the carbon flux had obvious diurnal and seasonal variations during rapeseed growth. The monthly average diurnal variation of carbon flux and the diurnal variation of different growth stages showed a "U" shaped unimodal curve, which was high at night, low in the day and reached the lowest point at noon. The difference between different months and different growth stages was mainly reflected in the range of curve change. The carbon sequestration capacity of rapeseed was different in different growth stages, and the order of carbon sequestration was in: flowering stage, pod stage, bolting stage, and seedling stage. The carbon sequestration capacity generally increased with the growth process. The total net ecosystem exchange, gross primary productivity and ecosystem respiration were -101.62 gC·m-2, 461.67 gC·m-2 and 360.05 gC·m-2 respectively. Net CO2 uptake was 1.02 t·hm-2. These results indicated that the rapeseed ecosystem showed a certain carbon sink function.
To better understand the mechanism underlying nitrogen efficiency of rapeseed （Brassica napus L.） at seedling stage, two accessions with contrasting N efficiency （A294 with high efficiency, and A364 with low efficiency） were applied on investigating their C and N metabolism. The differences in root morphology, N absorption, transport and assimilation, and physiological indices related to photosynthetic C metabolism and gene expressions involved were compared between the two accessions through hydroponics, under normal N （CK, 9.5 mmol/L） and low N （LN, 0.475 mmol/L） nutrient solutions respectively. Results showed that, N-efficient accession A294 had stronger root system, with significantly higher plant biomass and N accumulation amount than those of A364 under low N condition. The ability for N absorption and transportation of A294 were also greater. However, activities of nitrate reductase and glutamine synthetase had no significant differences in two accessions. SPAD value, photosynthetic pigment content, net photosynthetic rate, and sucrose phosphate synthase gene （BnaSPS）
This study was carried out to explore signaling effects of H2O2 homeostasis on soybean （Glycine max） drought resistance and provide theoretical basis for soybean drought resistance cultivation. ‘Kefeng 1’ was used as material and treated in 0.5% and 5% PEG-6000 solution to simulate different drought levels. The relative water content, degree of membrane lipid peroxidation, level of reactive oxygen species, activity of antioxidant enzymes, content of antioxidants and activity of related enzymes in ascorbic ascorbate-glutathione （ASA-GSH） cycle of soybean leaves were determined under different stress conditions. The results showed that drought increased the content of active oxygen, promoted the membrane lipid peroxidation and decreased the relative water content of soybean leaves. Under mild drought stress, H2O2 accumulated in leaves and formed a continuous homeostasis by the regulation of antioxidant enzymes and antioxidants, which produced signal effect to induce the further increase of antioxidant enzyme activity and AsA content in plants under stronger drought stress, significantly reduction in MDA and H2O2 content, improved drought resistance, and maintained stability of relative water content in leaves. The effect of the signal is time-dependent and would be weakened with the lasting of mild drought stress.
In order to clarify the effects of different compounding of sodium nitrophenolate and nitrogen levels on soybean growth, and promote the practical application of new regulators to determine the cultivation and management measures. Five south main soybean varieties were used as experimental materials to study the effects of different concentration gradient of compounding of sodium nitrophenolate and nitrogen levels spraying on soybean photosynthetic physiological characteristics, yield and quality by field experiments. The effects of compounding of sodium nitrophenolate and nitrogen on photosynthetic characteristics yield and quality of soybean were analyzed by measuring leaf chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration in the early flowering stage (R1) and granulation stage (R5). The experiment was carried out in a field-split plot design with three replicates, five nitrogen treatments and three experiment areas. The results showed that SPAD value, net photosynthetic rate, effective pod number per plant, grain weight per plant, other yield components, and the yield of South China soybean varieties were increased under the application of nitrogen. In addition, the yield of You 6019, Zhongdou 44, Zhongdou 41 and Zhongdou 63 were increased under the combination of nitrogenous fertilizer and sodium nitrophenolate, but fat and protein levels did not change much. The yield of Wandou 28 was not increased, but the fat and protein content were increased. After nitrogen treatment, there was a positive correlation between yield and quality of You 6019. In conclusion, the combined spraying of nitrogen fertilizer and sodium nitrophenol has the potential to further synergically improve the yield and quality of soybean varieties in southern China. However, due to the different effects on different varieties, the best treatment plan should be developed for different soybean varieties with different genotypes.
In this paper, Kenfeng 16 (drought-sensitive) and Hefeng 50 (drought-tolerant) were used as test materials, the potted method was used to study the effects of indole butyrate potassium (IBA-K) seed dressing on root morphogenesis and physiological metabolism of the two varieties of soybean under normal water supply, drought and rewatering conditions. The result showed that compared with normal water supply, drought stress inhibited the growth and development of soybean roots. Dry matter accumulation, morphogenesis, antioxidant enzyme activity and osmotic adjustment substance content of two varieties under IBA-K treatment were higher than their drought control under different soil moisture conditions, reducing the degree of membrane damage. SOD activity, POD activity, soluble sugar and proline content of the two varieties under IBA-K treatment were significantly higher than the drought control under drought conditions, MDA content and relative conductivity were significantly lower than the drought control. Root surface area, average root diameter, root volume, POD activity and CAT activity of the two varieties under IBA-K treatment were higher than their drought control under rewatering conditions, and no significant difference was reached. After rewatering, the dry weight and total root length of Kenfeng 16 roots under IBA-K treatment were significantly increased by 3.13% and 24.51% compared with the drought control, respectively. Dry weight and total root length of Hefeng 50 did not reach significant differences compared with its drought control. The MDA content and relative conductivity of Hefeng 50 under the IBA-K treatment were significantly lower than the drought control by 11.80% and 15.09%, and the SOD activity and soluble sugar content were significantly increased by 14.90% and 3.94% compared with the drought control. The relative conductivity, MDA content, SOD activity and soluble sugar content of Kenfeng 16 did not reach significant differences compared with its drought control. The proline content in the roots of two soybean varieties under IBA-K treatment was significantly increased by 10.62% and 10.70% respectively compared with the drought control. IBA-K treatments and different soil moisture treatments had significant or extremely significant effects on the morphology and physiological indexes of the roots of both varieties, and the interaction between the two had no significant regulatory effect. In summary, IBA-K can reduce the MDA content and relative conductivity by increasing root dry matter accumulation, antioxidant enzyme activity and osmotic adjustment substance content, reducing drought stress on soybean roots at the seedling stage.
The objective of this study was to explore the photosynthetic physiological responses of Cyperus esculentus seedlings under different concentrations of saline-alkali stress, and to reveal the salt tolerance mechanism and salt-alkali resistance ability, it was expected to provide a theoretical basis for large-scale cultivation and reasonable planting areas division of C. esculentus in Xinjiang. Two kinds of neutral salts (NaCl and Na2SO4) and two alkaline salts (NaHCO3 and Na2CO3) were used to prepare the corresponding solution at the ratio of 2:1 for stress treatment. The low, medium and high concentrations were 80, 160, 320 mmol·L-1 and 40, 80, 120 mmol·L-1, respectively for salt and alkaline stress treatments. The chlorophyll content, photosynthetic parameters and fluorescence parameters were measured after 15 days of seedling emergence. The results showed that the contents of chlorophyll a (Chl a), chlorophyll b (Chl b), total chlorophyll (Chl T), carotenoid content (Car), net photosynthesis (Pn), stomatal conductance (Gs) and transpiration rate (Tr) were decreased, while the maximum fluorescence (Fm), actual photochemical efficiency (ΦPSⅡ) , maximal photochemical efficiency (Fv/Fm) and photochemical quenching coefficient (qP) were inhibited, and non regulatory energy dissipation (Y(NO)) was increased with the stress degree increasing. We observed that Pn positively correlated with Gs, Tr, Chl a (P<0.01), and with Car， Chl T， Fm， ΦPSⅡ， qP at 0.05 level， but negatively correlated with Y(NO). These results suggested that the main reason of the decrease of photosynthetic rate under saline-alkali stress is related to the decrease of Gs, Tr and Chl a. Moreover, the dynamic balance of water supply and photosynthetic system could be maintained by reducing Gs, Tr, leaf water content (WC), increasing water use efficiency (WUE) and initiating heat. There was higher inhibition degree of alkaline stress than that of salt stress at the same concentration.
Clubroot, one of the major diseases of crucifer crops, is caused by the obligate biotrophic protist Plasmodiophora brassicae. The disease seriously affects the yield and quality of crucifer crops (canola, cabbage, radish, etc.). To better understand the disease and for early diagnosis and prediction, 2 radish varieties were used in this study to explore the disease resistance mechanism of clubroot disease in host. The differences of infection process between resistant and susceptible radish were observed. qPCR was performed to detect the content of P. brassicae, and ultraviolet spectrophotometry were used to detect the activities of defensive enzymes and soluble sugar. Results showed that root hair (primary) infection occurred both in resistant and susceptible radish, while the cortical infection (secondary) only occurred in susceptible radish. It suggested that secondary zoospores fail to develop into resting sporangial plasmodium might be the reason of clubroot resistance in radish. During 25-45 d post inoculation (dpi), the pathogen content increased in the susceptible radish but decreased in the resistant radish significantly, suggesting that 25-45 dpi is an important period for rapid propagation in susceptible radish. Meanwhile, the activity of SOD, POD and soluble sugar content in the roots of resistant radish were higher than those of susceptible radish, but the activity of CAT in the roots of resistant radish was lower than the susceptible. It was indicated that the feature of higher of SOD, POD activity and soluble sugar content, and the lower CAT activity, might play a certain role for clubroot resistance in radish.
Soybean root rot was a worldwide soil-borne disease that reduced soybean production. Pathogen identification is the premise and foundation for soybean root rot control. A total of 432 soybean rotten root samples were collected from main producing areas of Shandong Province in 2019-2020. Strains of 279 fungi were isolated and purified from watery soybean roots by tissue separation method, according to morphological identification and ITS， CoxII， β-tubulin sequence analyze， 52 strains were identified as Pythium aphanidermatum, Pythium ultimum and Pythium sylvaticum. The isolation frequencies of P. aphanidermatum, P. ultimum, and P. sylvaticum were 50%, 34.62% and 15.38%, respectively, and P. aphanidermatum was the dominant pathogen. The pathogenicity test of the above 3 Pythium species was carried out and the symptoms of soybean root rot could be repeated in all the 3 Pythium species. This is the first report of adult stage soybean root rot caused by P. sylvaticum in China. The results could not only increase the pathogen understanding of soybean root rot, but also provide scientific basis for the disease control and resistance breeding.
Brassica napus, B. rapa and B. juncea rapeseeds were used as raw materials, the changes of quality and volatile flavor components of rapeseed oil after popping pretreatment were investigated. The results showed that the acid values and peroxide values of the three types of rapeseed oil were significantly increased （P<0.05） by 0.25, 0.49, 0.39 mg KOH/g and 0.20, 0.18, 0.18 mmol/kg, respectively, within the limits of Codex standard. The oxidation induction time of three types of rapeseed oil were significantly increased （P<0.05） by 17.32, 10.06 and 13.99 h, respectively. Popping pretreatment had no significant effect on fatty acid composition of the three types of rapeseed oil. After popping pretreatment, the contents of sulfur compound such as phenylacetonitrile, 3-methylcradonitrile and 5-hexenitrile, the kinds and contents of heterocyclic substances and oxidative volatiles in the three types of rapeseed oils were significantly increased （P<0.05）. Pyrazines and aldehydes were the main components in heterocyclic substances and oxidative volatiles, respectively.
The double-low rapeseed oil-based organogels were prepared by 12-hydroxystearic acid, beeswax, sunflower wax, sodium stearoyl lactylate, monoglyceride, stigmasterol, diosgenin, and cinnamic acid under the condition of concentration (2%, 4% and 6%, m/m), and the physical properties and crystallization properties were studied by measuring oil binding capacity (OBC), rheological properties, microstructure, X-ray diffraction (XRD) and Fourier infrared spectroscopy (FTIR). The appearance and oil retention results showed that except for beeswax and cinnamic acid, other gelator could form organogel at a low concentration (2%). When the concentration was 6%, except for organogel prepared by diosgenin and cinnamic acid, the OBC value of the organogel could reach more than 94%. The rheological analysis found that G' value of 12-hydroxystearic acid organogel was relatively large, and its structure was not easily changed by external forces. The organogel formed by stigmasterol had the best thermal stability (phase transition temperature 93.4℃). Crystal microstructure analysis showed that 12-hydroxystearic acid formed dense fibrous network structure in rapeseed oil, and stigmasterol and diosgenin formed needle-like crystals in the oil. Cinnamic acid formed sparse flaky crystals, and other organogel were small particles crystals. The crystal form and interaction force between the crystal and the crystal mainly depended on the molecular structure of the gelators.
To further enhance mechanized harvesting level on oil flax, a self-propelled flax combine harvester was developed and tested. It was expected to complete integrated working procedure of flax cutting, threshing and cleaning. On the premise setting of transmission system by flax combine harvester, design and debugging of its key working parts were carried out. Structures and motion parameters were determined on anti-wind header, combined threshing- separating device of flax shear flow-transverse axial flow, flax threshing material cleaning device. And performances of their prototypes were tested. Under field experiments, results showed that when the advance speed of the self-propelled flax combine harvester was in 2.92-6.00 km/h, the total grain loss rate was 2.26%, grain impurity rate was 1.82%, grain breakage rate was 0.98%, and qualified rate of anti-wind was 100%. In the innovated process of mechanized harvesting, no flax stem hanging nor entwining was found on the cutting header, the drift loss of flax stem became lower, and the stubble distribution turned uniform. It showed that the prototype working performance met the requirements of flax mechanized harvesting, and the test results met both design and practice.
