Natural variation in the cytochrome c oxidase subunit 5B OsCOX5B regulates seed vigor by altering energy production in rice

Seed vigor is a crucial trait for the direct seeding of rice.Here we examined the genetic regulation of seed vigor traits in rice,including germination index(GI)and germination potential(GP),using a genome-wide association study approach.One major quantitative trait locus,qGI6/qGP6,was identified simultaneously for both GI and GP.The candidate gene encoding the cytochrome c oxidase subunit 5B(OsCOX5B)was validated for qGI6/qGP6.The disruption of OsCOX5B caused the vigor traits to be significantly lower in Oscox5b mutants than in the japonica Nipponbare wild type(WT).Gene co-expression analysis revealed that OsCOX5B influences seed vigor mainly by modulating the tricarboxylic acid cycle process.The glucose levels were significantly higher while the pyruvic acid and adenosine triphosphate levels were significantly lower in Oscox5b mutants than in WT during seed germination.The elite haplotype of OsCOX5B facilitates seed vigor by increasing its expression during seed germination.Thus,we propose that OsCOX5B is a potential target for the breeding of rice varieties with enhanced seed vigor for direct seeding.

Effects of Sunflower Artificial Aging on Seed Vigor and Physiological Characteristics

[Objective]The aim was to study the effects of sunflower artificial aging on seed vigor and physiological characteristics.[Method] The varieties of seed germination capacity,vigor of germination,germination index,vigor index,peroxidase（POD） activity,superoxide dismutase（SOD） activity and malondialdehyde（MDA） content for four sunflower germplasms such as＇SunM20＇,＇Deep Purple Minle＇,＇Da San Kui Hua 4＇and＇Ji Kui 24＇were studied under high temperature and high humidity conditions（100% RH,45 ℃） for different days（0 d,2 d,4 d,6 d,8 d,10 d）.[Result]The result showed that the germination capacity,vigor of germination,germination index,vigor index,POD activity,SOD activity declined gradually with the increase of seed aging days,whereas MDA content enhanced by degrees;The diggerences of resistance to artifical aging existed among the four accessions,＇SunM20＇was the most resistant one,and exhibited the strongest seed vigor,highest activities of two protective enzyme（POD,SOD） and lowest content of MDA at the uniform condition,moreover,the seed vigor and protective enzyme activities of＇SunM20＇changed slowest among the four materials during the aging process.[Conclusion]The distinct reduction of POD,SOD activities maybe the main reasons for the decrease of sunflower seed vigor at the artificial aging,and the gradual accumulation of a few MDA accelerated seeds aging.

Study on Seed Vigor of Rice Photo-ThermoSensitive Genic Male Sterile(PTGMS) Line with Low Temperature Storage

To explore the change rule of seed vigor and seed application technology of rice PTGMS lines with low temperature storage,Zhun S,Y58S,Feng S and Guangzhan 63-4S stored in the seed bank with the temperature of 8-10 ℃ and with the relative humidity of 55% for different years were used as the materials to study the properties of seed vigor,growth and development in the field, etc. The re- sults showed that the germination potential, germination rate, germination index and vigor index of rice PTGMS lines seeds showed downward trends as the time of low temperature storage prolonged,and all of the germination rates of the seeds within five years were over 60%. The conductivity in the soaked solution of seeds was significantly increased with the prolonged low temperature storage time. Seedling rate,root length,white root number,base stem width and seedling dry weight of seeds showed downward trends as the time of low temperature storage prolonged. There was no significant difference between two integral seedling qualities of seeds within 4-6 years in low temperature storage. Compared with the germination rate of low temperature storage seeds soaking for 6,12 and 24 h,the appropriate soak time of long time low temperature storage or low vigor seeds was 12 h. A serious natural aging phenomenon occurred in low temperature storage seeds after out of the storage. The germination rate of seeds placed under natural condition for 50 d decreased obviously. The duration from seeding to heading of Zhun S,Y58S and Feng S shortened as the time of low temperature storage prolonged, while the vari- ation of panicle duration of all PTGMS lines was not obvious. In conclusion, rice PTGMS line seeds with low temperature storage in 5 years could still be used nor- mally. However.seeds after low temperature storage should be sowed as soon as possible, and the soaking time of low vigor seeds should be shortened,and the possibility that the decreased duration from seeding to heading should also be con- sidered.

Advances on Seed Vigor Physiological and Genetic Mechanisms

Seed vigor is a more promising seed quality character reflecting potential seed germination, field emergence and seed storage ability under different conditions than standard germination. Standard germination is influenced by genetic background and environmental effects during seed development and storage conditions. The latest research on physiological mechanism in seed vigor showed that at the late stage of seed development, the development of seed vigor involves some stress-resistant substances including late embryogenesis abundant （LEA） protein, oligosaccharides and abscisic acid （ABA）. Whereas the loss of seed vigor, or seed aging and deterioration, could be attributed to lipid peroxidation, chromosome deformation and genes aberrance, and embryo protein degradation, etc. Seed vigor is a quantitative character controlled by multi-genes. Genetic and quantitative trait locus （QTL） analyses on seed-vigor trait in model plants, such as Arabidopsis and rice, are mostly concentrated on related morphology traits, whereas few physiological traits have been researched. It was concluded that, all of the QTL genetic characteristics of seed vigorincluding QTL quantities, its locus on chromosome, genetic effects, and interaction effects between genetic and environment, differed with plant species and used seed-vigor traits.

Improving the assessment method of seed vigor in Cunninghamia lanceolata and Pinus massoniana based on oxygen sensing technology

Oxygen sensing technology was employed to study the rapid methods for seed vigor assessment of Chinese fir （Cunninghamia lanceolata） and Masson pine （Pinus massoniana）. Firstly, seeds of five lots were performed using accelerated aging （AA） into three vigor levels. Then, four oxygen sensing indices, including increased metabolism time （IMT）, oxygen metabolism rate （OMR）, critical oxygen pressure （COP）, relative germination time （RGT） and the control indiees such as labora- tory germination indices, dehydrogenase activity （DA）, and electrical conductivity （EC） were analyzed by the tests of 15 samples. The results of correlation analysis between these indices and field emergence per- formances based on two-year and two-spot data showed that RGT and OMR should be indicated as the optimal oxygen sensing indices to rap- idly and automatically evaluate seed vigor of Chinese fir and Masson pine, respectively. On the basis, one-variable linear regression equations were built to forecast their field emergence performances by the two oxygen sensing indices.

Hyperspectral imaging technology to detect the vigor of thermal-damaged Quercus variabilis seeds

This study investigated the feasibility of hyperspectral imaging techniques to estimate the vigor of heatdamaged Quercus variabilis seeds.Four thermal damage grades were classified according to heat treatment duration(0,2,5,and 10 h).After obtaining hyperspectral images with a 370–1042 nm hyperspectral imager that included visible and near infrared light,germination was tested to confirm estimates.The Savitzky–Golay(SG)second derivative was used to preprocess the spectrum to reduce any noise impact.The successive projections algorithm(SPA),principal component analysis,and local linear embedding algorithm were used to extract the characteristic spectral bands related to seed vigor.Finally,a model for seed vigor classifi-cation of Q.variabili s based on partial least squares support vector machine(LS-SVM)with different spectral data sets was developed.The results show that the spectrum after SG second derivative preprocessing was better for developing the model,and SPA performed the best among the three feature band selection methods.The combination SG second derivative-LS-SVM provided the best classification model for Q.variabilis seed vigor,with the prediction set reaching 98.81%.This study provides an important basis for rapid and nondestructive assessment of the vigor of heat-damaged seeds using hyperspectral imaging techniques.

Effects of Pb Pollution on Seed Vigor of Three Rice Cultivars

An experiment was conducted to study the effects of different Pb concentrations on rice seed germination and seedling growth in three cultivars （Jiayu 293, Jiayu 948 and Xieyou 963）. The method of qualitative traits combining with quantitative traits by orthogonal polynomials was applied to analyze rice seed vigor by regression model. The seeds from different rice cultivars had different sensitivity to Pb poison. In the Pb concentration of 100-700 mg/L, Pb significantly decreased root length and shoot height, and the degree of the restraint would aggravate with the increasing of Pb concentration. However, Pb did not reduce root dry weight and shoot dry weight, which indicated that different physiological characteristics had different sensitive reactions to Pb. The predicting equations of regression were developed, which could be used to predict the effects of different Pb concentrations on rice seed vigor.

Effects of Seed Maturity of Turf-Type Tall Fescue on the Seed Vigor and the Optimal Harvesting Time

By assay of accelerated aging germination, germination index, vigor index, seedling length, seedling weight, electric conductivity, dehydrogenase activity, ATP content and acid phosphoesterase activity during seed development of turf-type tall fescue, the seed vigor of tall fescue were studied. Combining with seed moisture content and yield, the optimal harvesting time of tall fescue was determined. The results indicated that the seed vigor increased continuously along with seed maturity, and the higher seed vigor was achieved at 19th day after perk anthesis and maintained continuously until 31st day after peak anthesis. At 25th day after peak anthesis, the highest yield of 3 533 kg ha-1 and the good quality of seeds of tall fescue were harvested with 32.19% moisture content. From 22nd to 31st day after peak anthesis, the seed yield of 3 300 kg ha-1 and the good quality seeds of tall fescue were harvested with 40 - 12. 43% moisture content, and the span was the optimal harvesting time.

Effects of Artificial Aging on Physiological Characteristics and Seed Vigor of Medicago ruthenica Seeds

As shown by the changes in physiological characteristics and seed vigor of three Medicago ruthenica samples during artificial aging process, the germination potential, germination rate, germination index, vigor index and simple vigor index declined with the extension of aging time on the whole. After artificial aging for 6 min, the vigor was higher than that of the control. The conductivity, malondialdehyde content and soluble polysaccharide content of seed leachate increased with the aging time and negatively correlated （ P 〈 0.05） with the seed vigor indicators. The physiological indicators were very significantly correlated （P 〈 0.01 ） with the vigor indicators in the Medicago ruthenica sample from Dorbod Qi, UIanqab City（China）.

Effects of Artificial Aging on Seed Vigor and Ultraweak Luminescence of Wheat Seeds

In order to ascertain the effect of artificial aging on ultraweak lumines- cence （UWL） and the correlation between UWL and seed vigor, and explore a new way of seed vigor non-destructive testing, seeds of wheat variety ‘Jimai 22＇ were used to study the change of UWL intensity and its relationship to seed vigor and ATP content during artificial aging. The results showed that with the extension of artificial aging time, the germination percentage, germination potential, germination index, UWL intensity and ATP content decreased gradually; after artificial aging for 48 h, they were reduced by 19.19%, 34.34%, 38.78%, 27.77% and 13.84%, re- spectively, compared with CK. Correlation analysis indicated that the UWL intensity was significantly positive correlated with germination percentage, germination poten- tial, germination index and ATP content. It was concluded that UWL as a fast, non- destructive and sensitive detection method could be applied in the study of seed vigor non-destructive testing.

Effect of Corona Treatment and Dielectric Separation on Seed Vigor of Hybrid Rice

[Objectives] The aim was to investigate the effects of corona field and dielectric separation on the seed vigor of hybrid rice.[Methods] The seeds of 6 hybrid rice varieties were processed with corona field, dielectric separation and corona field ＋ dielectric separation.[Results] When the field intensity was 200 km/m and the processing time was 4 min, the seed vigor was significantly increased. The seed vigor of Y Liangyou 9918 （2014） increased the most, and the germination potential and the germination rate increased by 17 and 12 percentage points respectively compared to the control. Corona field reduced seed conductivity, and for seedlings, it decreased their MDA content, increased proline content, improved peroxidase activity, and enhanced root activity. When the rotating speed of the drum was 30 r/min, the dielectric separation voltage of 4 500 V could achieve good separation effect, and the vitality of seeds at different grades was significantly different. Under the optimized corona field combined with optimized voltage processing of dielectric separation, the seed vigor at all grades from the separation was significantly higher than that of the dielectric separation processing alone. The combined separation processing separated no seeds with germination rate of higher than 80% from the hybrid rice seeds with germination rate of lower than 60%, yet it could effectively separate the seeds with germination rate of higher than 80% from the hybrid rice seeds with germination rate of 65%-70%. After the combined processing, the germination rates of separated Grade I seeds of Wangliangyou 6 （2015）, N Liangyouhuazhan （2015）, Wangliangyou 6 （2016） increased by 20, 15, 20 percentage points from the germination rates of the control, while the germination rates of N Liangyouhuazhan （2016） and Y Liangyou 9918 （2016）, which had the germination rates of higher than 80%, increased by 3 and 9 percentage points from the control, suggesting insignificant separation effect.[Conclusions] This study provided a new technical approach for the processing of hybrid rice seeds.

Evaluation of seed vigor in soybean germplasms from different eco-regions

Seed vigor plays an essential role in soybean production.Soybean seed is sensitive to environment and easy to get seed deterioration.Generally soybean seed vigor can be maintained for less than one year and have to be multiplied every year.Varieties with good seed vigor are essential for maintaining planting population and stable yield.In this research,419 germplasms from three eco-regions,South China,Huanghuai region and Northeast China,were evaluated for seed vigor by assessing germination ratio,germination potential and germination index.About 34.8%of tested germplasm had germination ratio equal or more than 85%,suggested by the national soybean seed quality standard of China.Only 9 from 82 tested cultivars met the seed standard.Seed germination ratio distribution had obvious regional feature.Landraces performed better seed vigor than cultivars.Germplasms from South China had stronger seed vigor compared to those from Huanghuai and Northeast regions.Seed vigor has no significant relationship with maturity and 100-seed weight.Totally 21 germplasms with strong seed vigor,favor maturation and seed size were identified and can be used in future breeding program.

Investigation of GhFAT Genes Related to Seed Oil Content and Fatty Acid Composition in Gossypium hirsutum L.

Fatty Acyl-ACP thioesterase(FAT)is a key enzyme controlling oil biosynthesis in plant seeds.FATs can be divided into two subfamilies,FATA and FATB according to their amino acid sequences and substrate specificity.The Upland cotton genome contains 20 GhFAT genes,amongst which 6 genes were of the GhFATA subfamily and 14 of the GhFATB subfamily.The 20 GhFAT genes are unevenly distributed on 14 chromosomes.The GhFATA genes have 5 or 7 exons and the GhFATB genes have 6 or 7 exons.All GhFAT proteins have the conserved Acyl-ACP_TE domain and PLN02370 super family,the typical characteristics of plant thioesterases.Analyses of the expression level of GhFATs and the compositions of fatty acid in 5-60 days-post-anthesis seeds showed that the ratio of saturated fatty acids to unsaturated fatty acids was consistent with the expression profile of GhFATB12,GhFATB3,and GhFATB10;the ratio of monounsaturated fatty acid to polyunsaturated fatty acids was consistent with the expression profile of GhFATA3.The oil contents of mature cottonseeds were positively correlated with the contents of palmitic acid and linolenic acid as well as seed vigor.These results provide essential information for further exploring the role(s)of the specific GhFATs in determining oil biosynthesis and cottonseed compositions.

Effects of Different Seed Coating Agents on the Quality of"Grey-matter"Hybrid Rice Seeds

[Objectives]This study was conducted to select suitable mixed seed coating agents for improving the quality of"grey-matter"hybrid rice seeds.[Methods]Three different mixed seed coating agents(A,B,C)were used to coat the seeds of two varieties(Taiyou 390 and Zhenliangyou 8612)of hybrid rice with different"grey-matter"content(5%,15%,25%),and the results were investigated and compared.[Results]The combinations of treatment B(seed coating agent A+Linong)and treatment C(Manshijin+seed coating agent A)could significantly improve indexes including seed germination potential,germination rate,seed vigor,seedling height,fibrous roots and fresh weight of the two varieties with a"grey-matter"content greater than 15%,but had no significant effects on main root length,dry weight,leaf number and tiller number,and the effects of treatment B was better than those of treatment C.That is to say,mixed seed coating agent B(seed coating agent A+Linong)was suitable for use as a seed coating agent to improve the quality of"grey-matter"seeds.[Conclusions]This study provides a reference plan for the safe use of mixed seed batches with"grey-matter"deterioration.

Structure and Expression Analyses of a Gene Encoding Fructose-6-Phosphate, 2-Kinase/Fructose-2,6-Bisphosphatase from Maize

A full-length cDNA encoding fructose-6-phosphate, 2-kinase/fructose-2,6-bisphosphatase from maize (Zea mays L.) was cloned by the methods of reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE), and designated as mF2KP. The encoded protein is composed of two regions. Its COOH-terminal region is catalytic region and homologous to the enzymes from other eukaryotes; and its NH 2-terminal region is common and special region only in plant. A truncated fragment of mF2KP covering integrated catalytic region was expressed in Escherichia coli. The fusion protein had the activities of fructose-6-phosphate, 2-kinase as well as fructose-2,6-bisphosphatase. Northern blot showed that the transcript level of mF2KP in seedlings initiated from strong-vigor seeds is lower than that from weak-vigor seeds.

Effects of Specific Gravity-based Seed Grading on Seed Germination, Seedling Emergence and Grain Yield of Hybrid Rice

Using the commercial seeds of two hybrid rice varieties including Lu- liangyou 996 and Liangyoupeijiu as the materials, four specific gravity-based seed grading treatments, Le., the specific gravity of 〈1.0 （T1）, 1.0-1.09 （T2）, 1.1-1.19（T3） and ≥1.2 （T4）, by selection with different saline solutions, and the control without seed grading （CK） were designed to study the effects of seed grading on seed germination, seedling emergence, seedling quality and grain yield. The results showed that the treatments of T2, T3 and T4 had higher or significantly higher seed germination rate, germination index and vigor index, seedling emergence rate and adult seedling rate than the CK, while T1 had significantly lower values of these traits than the CK. Compared with the CK, the number of spikelets per pani- cle was found to be the main reason for the yield increase of these treatments with high seed viability.

The Optimal Time for Harvesting the Seeds of Gui 39722, the Female Parent of a Maize Hybrid Guidan 0810

To determine the optimal time for harvesting the seeds of Gui 39722, which is the female parent of a newly-developed maize hybrid Guidan 0810, the cobs of Gui 39722 were harvested 31 （the first stage）, 34 （the second stage）, 37 （the third stage）, 40 （the fourth stage）, 43 （the fifth stage） and 46 （the sixth stage） d after pollination and oven dried at 38 ~C to constant weight. Then, the 1 000-ker- nel weight, germination rate and the agronomic traits of three-leaf seedlings were measured and compared. The results showed that the seeds of Gui 39722 harvest- ed 43 d after pollination （the fifth stage） had the greatest germination rate, seedling height, vigor index, root dry weight, shoot dry weight and germination potential, and high 1 000-kernel weight （very close to the highest level）, root length, number of roots per seedling and root-shoot ratio. Therefore, 43 d after pollination was the op- timal time for harvesting the seeds of Gui 39722, when the effective accumulated temperature after pollination reached 780.7 ℃ and the ear leaf dried. The seeds harvested at this stage had the highest yield and the best quality. Field sampling revealed that 89.00% to 95.00% （with an average of 91.15%） of the seedlings of six stages of seeds grew well.

Selection for high quality pepper seeds by machine vision and classifiers

This research aimed to improve selection of pepper seeds for separating high-quality seeds from low-quality seeds. Past research has shown that seed vigor is significantly related to the seed color and size, thus several physical features were identified as candidate predictors of high seed quality. Image recognition software was used to automate recognition of seed feature quality using 400 kernels of pepper cultivar 101. In addition, binary logistic regression and a neural network were applied to determine models with high predictive value of seed germination. Single-kernel germination tests were conducted to validate the predictive value of the identified features. The best predictors of seed vigor were determined by the highest correlation observed between the physical features and the subsequent fresh weight of seedlings that germinated from the 400 seeds. Correlation analysis showed that fresh weight was significantly positively correlated with eight physical features： three color features （R, a＊, brightness）, width, length, projected area, and single-kernel density, and weight. In contrast, fresh weight significantly negatively correlated with the feature of hue. In analyses of two of the highest correlating single features,＇ germination percentage increased from 59.3 to 71.8% when a＊〉3, and selection rate peaked at 57.8%. Germination percentage increased from 59.3 to 79.4%, and the selection rate reached 76.8%, when single-kernel weight 〉0.0064 g. The most effective model was based on a multilayer perceptron （MLP） neural network, consisting of 15 physical traits as variables, and a stability calculated as 99.4%. Germination percentage in a calibration set of seeds was 79.1% and the selection rate was 90.0%. These results indicated that the model was effective in predicting seed germination based on physical features and could be used as a guide for quality control in seed selection. Automated systems based on machine vision and model classifiers can contribute to reducing the costs and labor required in the selection of pepper seeds.

Effects of Ultra-drying Treatment on Large Amounts of Four Kinds of Crop Seeds

This study was to understand the physiological changes of four kinds of crop seeds including baby corn, cowpea, radish and rape- seed, under the treatment of ultra-drying. Large amounts of seeds as experimental materials （ 10 kg for each material） were respectively dried to the suitable water content consistent with the ultra-dried seed criterion via heating at 50 ~C; then the physiological indices of these ultra-dried seeds such as water content, seed germination, dehydrogenase activity and SOD activity were measured. The results showed that except cowpea seeds, whose ultra-drying treatment should be controlled between two and four days, other three kinds of seeds were tolerant to high tem- perature and low water content. The ultra-dried seeds assumed similar or even higher activities than CKs, but showed no damage symptom. Our result proves that ultra-drying treatment via heating at 50 ℃ is safe and efficient to experimental seeds.

Relationship of Ultraweak Luminescence Intensity with Physiological Metabolism of Maize Seeds during Artificial Aging

The seeds of maize （Zea mays L.） variety Zhengdan 958 were used to study the change of ultraweak luminescence （UWL） intensity and its relationship with seed vigor, relative electric conductivity and ATP content during artificial aging. The results indicated that the germination percentage, germination potential, germination index, UWL intensity and ATP content decreased gradually, while the relative electric conductivity increased with the prolongation of artificial aging. The correlation analysis showed that UWL intensity was significantly positively correlated with ger- mination percentage, germination potential, germination index and ATP content, while significantly negatively correlated with relative electric conductivity. It was concluded that UWL was closely related to the energy level symbolized by ATP content, and as a fast nondestructive physical indicator with better sensitivity, it could be applied into the study of seed vigor nondestructive testing.