Transcriptomic and metabolomic analysis provides insights into lignin biosynthesis and accumulation and differences in lodging resistance in hybrid wheat

The use of hybrid wheat is one way to improve the yield in the future.However,greater plant heights increase lodging risk to some extent.In this study,two hybrid combinations with differences in lodging resistance were used to analyze the stem-related traits during the filling stage,and to investigate the mechanism of the difference in lodging resistance by analyzing lignin synthesis of the basal second internode(BSI).The stem-related traits such as the breaking strength,stem pole substantial degree(SPSD),and rind penetration strength(RPS),as well as the lignin content of the lodging-resistant combination(LRC),were significantly higher than those of the lodgingsensitive combination(LSC).The phenylpropanoid biosynthesis pathway was significantly and simultaneously enriched according to the transcriptomics and metabolomics analysis at the later filling stage.A total of 35 critical regulatory genes involved in the phenylpropanoid pathway were identified.Moreover,42%of the identified genes were significantly and differentially expressed at the later grain-filling stage between the two combinations,among which more than 80%were strongly up-regulated at that stage in the LRC compared with LSC.On the contrary,the LRC displayed lower contents of lignin intermediate metabolites than the LSC.These results suggested that the key to the lodging resistance formation of LRC is largely the higher lignin synthesis at the later grain-filling stage.Finally,breeding strategies for synergistically improving plant height and lodging resistance of hybrid wheat were put forward by comparing the LRC with the conventional wheat applied in large areas.

Research and Breeding Application Progress of the Technique of Producing Double Haploid of Wheat by Wide Hybridization between Wheat and Maize

The technique of producing doublehaploid of wheat by distant hybridization between wheat and maize has characterized with better inducing effect, shorter in- ducing period, easy operation, and so on. At present, it is the most efficient and has great potential of application in breeding of wheat. This article reviewed princi- ple and production process of the technique, research situation of the three key in- dicators of the technology（embryo rate, seedling rate and success rate of doubling）in recent years, and application of the technology in breeding, genetics, germplasm improvement of wheat. At last, both the achievements and the direction of further improvement and development of the technology in our program were discussed.

Solutions to Insecurity Problems in Seed Production of Two-line Hybrid Rice

The insecure problems of seed production have seriously hampered the healthy and sustainable development of two-line hybrid rice.The safety issues on seed production of two-line hybrid rice and current research situation were pointed out in this paper.The three main reasons for unsafety in seed production of twoline hybrid rice were unsuitable site selection,high critical sterility-inducing temperature and the drift of critical temperature.In this paper,strategies and measures were put forward based on many years of practice.It could minimize the risk in seed production of two-line hybrid rice by selecting dual-purpose genic male sterile line with lower critical sterility-inducing temperature and long lower temperature resistant time.Based on the climate data and climatic demands of the ＂three safe-periods＂ in seed production,a new idea for determining appropriate bases and periods for seed production was proposed by using computer technology,which solved the aimless selection of sites and periods for the seed production of two-line hybrid rice.Besides,we established a system of single plant selection and identification method and original seed propagation with cyclic cold water,which could reduce the generation number of original seed propagation in seed production and avoid the drift of critical sterility-inducing temperature.This paper improved the seed production safety in the three aspects of seed nature,seed source and seed production site.

Effects of Nitrogen Quantity on Grain-filling Characters of Two-line Hybrid Rice with Large Ear

[Objective] The aim was to research effects of N quantity on grain-filling characters of two-line hybrid rice cultivars with large ears. [Method] Peiza 67 and 88, two-line hybridized rice with large ears, were made use of to study on effects of N fertilizer in different quantities （LN： 90 kg/hm2;MN： 180 kg/hm2;HN： 270 kg/hm2） on plumpness and grain-filling characters. [Result] When N fertilizers were excessive, for inferior grains, grain-filling rate decreased and grain-filling time extended, resulting in plumpness decline after degradation of leaves＇ function. When N fertilizers were inadequate, maximal and average grain-filling rates decreased and the differences between superior and inferior grains in grain-filling rate increased, leading to decline of grain＇s weight and plumpness degree. On the other hand, quantity of N fertilizers had little effect on superior grains in plumpness. [Conclusion] The research provided references for reasonable use of N fertilizer and improvement of rice yield and N use.

Cytogenetical Analysis of Hybrid F1 from Common Wheat and Aegilops ventricosa × Aegilops cylindrica Amphidiploid

[Objective] The aim of this study is to investigate the chromosome pairing of F1 from Aegilops Ventricosa-Aegilops Cylindrica amphiploid × common wheat.[Method] Microsporogenesis and pollen development of Yannong15,SDAU18 and their hybrid F1 were observed cytologically by squash method.[Result] The results showed that microsporogenesis and pollen development of two parents including Yannong15 and SDAU18 were basically normal,and their seed setting was also basically normal.However,the microsporogenesis of their hybrid F1 was chaotic.Univalent and bivalent with high frequency of 10.11 and 18.29 per cell respectively occurred in meiotic MI（metphaseI） of PMC（pollen mother cell）.Nevertheless,only quite low frequency of multivalents occurred in meiotic PMC MI.The laggards at meiotic AI（anaphaseI） were 5 per cell on average.The number of micronucleoli in tetrad was 4.43 per cell averagely.The aborted pollen with different frequency occurred at every stage of hybrid F1 pollen development but mainly after single nucleus pollen stage.The fertile pollen rate of hybrid F1 was only 31% at 3-nucleated stage.[Conclusion] This study provides cytogenetics basis for further analysis and utilization of the amphiploid.

Breeding of National Authorized Two-line Hybrid Rice Yanliangyou 2208

The breeding processes, characteristics and comprehensive characters of two-line hybrid rice Yanliangyou 2208 and its parents （Yan 220S and Yanhui 888） taking part in the national rice regional test of southern rice regions were introduced. Yanliangyou 2208 was approved by the National Crop Variety Appraisal Committee in 2013. The achievement has been transformed successfully and has been applied in production. It has good development and promotion prospects.

Breeding and Cultivation Technique of Recessive Genic Male Sterility Hybrid Wheat New Variety Xinan 112

Xinan 112 is the hybrid combination（11S12） by wheat recessive genic male sterility line 2011Z1 （08L5070） and restoring line K152-2, particpating in the regional test of 2011-2012, 2012-2013 and production test of 2013-2014 in Chongqing. The results showed that 3 years average yield was 4 167.5 kg/hm2, which was increased 10.5% compared with CK Yumai 7, 1 000-grain weight was 45.8 g, which was 1.7 g heavier than the control; grain number per ear was 39.3, more than 1.6 grains compared with CK. The results of 2 years quality determination were： bulk density of 811 g/L, falling number of 353 s, crude protein of 15.15%, wet gluten of 31.2%, water adsorption of 62.9 ml/100 g, formation time of 5.5 min, stable time of 6.5 min, softening degree of 90 F.U., and powder quality coefficient of 96 mm. Therefore, Xinan 112 is a high yield and high protein gluten wheat variety and is suitable for cultivated in Chongqing and climate contion similar areas.

The contribution of distant hybridization with decaploid Agropyron elongatum to wheat improvement in China

Wheat is a staple food crop in the world as well as in China. Because of the progress of wheat breeding and other agricultural ＂sci-technologies, the wheat grain yield per unit area has increased more than five folds from 1952 to 2006 in China. The first part of this article briefly reviews the history of wheat breeding in China. Second, the establishment of ＂Triticum aestivum-Agropyron＂ distant hybridization system and its contribution to wheat production and breeding in China are summarized. Finally, the future challenges of wheat breeding are discussed, which include how to increase the utilization efficiencies of water, soil nutrient and light energy through breeding. As an example, our research progress on how to increase light use efficiency in wheat through breeding is introduced and discussed.

Programmed cell death, antioxidant response and oxidative stress in wheat f lag leaves induced by chemical hybridization agent SQ-1

Male sterility induced by a chemical hybridization agent （CHA） is an important tool for utilizing crop heterosis. Leaves, especially the flag leaves, as CHA initial recipients play a decisive role in inducing male sterility. To investigate effects of different treatment times of CHA-SQ-1 used, morphological, biochemical and physiological responses of wheat flag leaves were detected in thistudy. CHA induced programmed cell death （PCD） as shown in terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling （TUNEL） and DNA laddering analysis. In the early phase, CHA-SQ-1 trig- gered organelle changes arid PCD in wheat leaves accompanied by excess production of reactive oxygen species （O2- and H202） and down-regulation of the activities of superoxide dismutase （SOD）, catalase （CAT） and guaiacol peroxidase （POD）. Meanwhile, leaf cell DNAs showed ladder-like patterns on agarose gel, indicating that CHA-SQ-1 led to the activation of the responsible endonuclease. The oxidative stress assays showed that lipid peroxidation was strongly activated and photosynthesis was obviously inhibited in SQ-l-induced leaves. However, CHA contents in wheat leaves gradually reduced along with the time CHA-SQ-1 applied. Young flags returned to an oxidative/antioxidative balance and ultimately developed into mature green leaves. These results provide explanation of the relations between PCD and anther abortion and practical application of CHA for hybrid breeding.

Thoughts and Practice on Some Problems about Research and Application of Two-Line Hybrid Rice

The main problems about research and application of two-line hybrid rice were reviewed, including the confusing nomenclature and male sterile lines classification, the unclear characteristics of photoperiod and temperature responses and the unsuitable site selection for male sterile line and hybrid dce seed production. In order to efficiently and accurately use dual-purpose genic male sterile lines, four types, including PTGMS （photo-thermo-sensitive genic male sterile rice）, TGMS （thermo-sensitive genic male sterile rice）, reverse PTGMS and reverse TGMS, were proposed. A new idea for explaining the mechanism of sterility in dual-purpose hybrid rice was proposed. The transition from sterile to fertile was involved in the cooperative regulation of major-effect sterile genes and photoperiod and/or temperature sensitive ones. The minor-effect genes with accumulative effect on sterility were important factors that affected the critical temperature of sterility transfer. In order to make better use of dual-purpose lines, the characterization of responses to photoperiod and temperature of PTGMS should be made and the identification method for the characterization of photoperiod and temperature responses of PTGMS should also be put forward. The optimal ecological site for seed production could be determined according to the historical climate data and the requirements for the meteorological conditions during the different periods of seed production.

The Growth Analysis in the Kernel Filling Process of K-Type Hybrid 901 and Its Parent Wheat

Using Matlab software, the grain filling process of hybrid wheat 901 and its parents was fitted by Richards equation W = A/（1 ＋ Be^-kt in order to study the characteristics of grain filling of the hybrid. The active grain growth period of the hybrid was 6 d longer than that of Shaan 229, and its final grain weight （43.7 g/1 000 grains） was higher than that of Shaan229 （36.3 g/1 000 grains）. N values of 901 and R205 were both less than 1, and their grain growth was faster in the early filling stage, while slower in the middle-late stage. N value of Shaan 229 was 〉1~ and its growth was slower in the early stage and faster in the middle stage. The period of early stage of 901 was shorter and of middle-late stage was longer. The situation of Shaan 229 was totally reversed. For parents, the father plant R205 was similar to hybrid wheat 901, whereas its mother plant K3314A similar to Shaan 229. It has been found that Richards equation was more suitable for fitting the grain filling process of wheat than Logistic equation.

Grain Sink Strength Related to Carbon Staying in the Leaves of Hybrid Wheat XN901

XN901 is a K-type three-line hybrid wheat with a high yield potential, and its leaves and stem remaining green during grain maturation, suggesting much assimilate stay in leaves and stem. The grain water content, grain volume, carbohydrate content, and enzyme activity of sucose metabolism in the grain, as well as source-sink relationship were studied in order to investigate the physiological reason of the assimilate remaining in leaves and stem at the late stage. The results showed that the hybrid grains had more water and soluble sugar, higher activities of acid invertase and sucrose synthase at the early stage that led to a faster expansion growth, greater grain volume and faster starch synthesis at the early to mid stage of grain development. Also it had a longer period for actively filling. As a result, the grain weight and yield of the hybrid were increased by 14 and 15% respectively compared to that of Shaan 229. Additionally, the biomass of XN901 was 41.7% more than that of control, but its harvest index was 9% lower than Shaan 229. However, its lower activity of sucrose synthase indicated a lower sink activity at the late stage, resulting in a slow rate of filling and starch synthesis. Also, the hybrid wheat XN901 had a large source-sink ratio. It is the main reason for much assimilate remaining in the straw at the late stage and lower harvest index. Strengthening the sink activity and raising the harvest index should be the key means of improving the yield of hybrid wheat.

Research on Theories and Techniques of Irrigation for Safeguarding Seed Production of Two-Line Hybrid Rice

By inducing frequency, intensity and duration of lower temperature in the middle and last ten-day periods in August in the rice-growing areas of southern China, increasing temperature for safe seed production was defined as 2℃. During the sensitive period of fertility, characters of panicle height and canopy structure of TGMS rice, Pei＇ai64S, were measured. Results showed that temperature changes caused by irrigation in fields were below 40 cm of rice plant, and heating effect was significant at 20 cm when the temperature was increased by 3.1 ℃. For the present study, the following irrigation techniques were put forth： the water depth of 15-20 cm, current water used, irrigating after 17：00 and bailing at 10：00 in sunny or cloudy weather, irrigating on whole day, in shady or rainy weather, increasing inflows and outflows in large fields. In the present experiment, pollen fertility and self-fertilized seed setting rate accepted that the techniques were feasible and effective for against lower temperature and safeguarding seed production of two-line hybrid rice.

Causes of Poor Grain Plumpness of Two-Line Hybrids and Their Relationships to the Contents of Hormones in the Rice Grain

This study was designed to elucidate the grain filling characteristics and the causes of poor grain plumpness of some two-line hybrid rice combinations and their hormonal mechanism. Six varieties, including three two-line hybrid rice combinations, that show differences in seed-setting and grain filling, were used. And the contents of starch, sucrose, zeatin （Z） ＋ zeatin riboside （ZR）, indole-3-acetic acid （IAA）, and abscisic acid （ABA）, the ethylene evolution rate, activities of sucrose synthase （SuSase） and starch synthase （StSase） in grains, the seed-setting and grain filling rate were investigated. The correlations amongst these were analyzed. The results showed that the poor grain filling of two-line hybrids was mainly attributed to the higher unfilled grain rate and the lower filling degree of inferior grains. During the early and mid grain filling periods, the sucrose content in inferior grains was greater than that in superior grains for the combinations with poor grain filling, indicating that the substrate concentration was not the principal factor for their slow grain filling and poor grain plumpness of the inferior grains of two-line hybrids. Z ＋ ZR, IAA, and ABA in superior grains were obviously greater than those in inferior grains at early grain filling stage. The maximum and mean contents of Z ＋ ZR, IAA, and ABA were positively very significantly correlated with the maximum and mean grain-filling rate, filling degree, and grain weight. The evolution rate of ethylene was greater in inferior grains than in superior grains and greater for the combinations with poor grain plumpness than those with good grain plumpness at the early or mid filling stages. The evolution rate of ethylene was negatively and significantly correlated with the grain filling rate, the grain filling degree, and the grain weight. Spraying ethephon （ethylene-releasing agent） at the early grain filling stage increased the evolution rate of ethylene, reduced the ABA content and activities of SuSase and StSase, and decreased the grain filling degree and the grain weight. The results were reversed when cobatous nitrate （an inhibitor of ethylene synthesis） was applied. The results suggested that the hormones and their balance play a role in the regulation of grain filling and enzymatic activities, and the poor grain filling is attributed to the low contents of Z ＋ ZR, IAA, and ABA, and the high evolution rate of ethylene in the inferior grains of some two-line hybrid rice combinations. The results suggested that hormones play important roles in the grain filling of some two-line hybrid rice combinations, and their filling degree can be improved by regulating the hormonal contents.

Research and application of hybrid wheat in China

Hybrid wheat is recognized as a preferred approach to improve wheat yield,and it will be a competition focus in high-tech seed industry in the future. We have made a breakthrough for the first time in creation of two-line hybrid wheat system,which reaches the world leading level in wheat research and has laid an important foundation for the future direction of the world wheat research. Similar to hybrid rice,the innovation of two-line hybrid wheat system is another achievement in science and technology. The application of hybrid wheat in China will greatly increase the food production,and make a great significance to food production and food security. This paper introduces the development process and major breakthrough of hybrid wheat in China,and the main bottleneck and countermeasures in the application of hybrid wheat.

Inheritance Pattern of Two-line Hybrid Rice Resistance to False Smut

[Objective] The aim of this study was to explore the inheritance pattern of the resistance of two-line hybrid rice to false smut. [Method] A moderate susceptible TGMS line 33S as the female parent, was crossed with 30 susceptible restorer lines and 23 resistant restorer lines. Then false smut resistance of the hybrid F1 and parents were identified. [Result] All F1 of 33S crossed with 30 susceptible re- storer lines were susceptible to rice false smut. The F1 of 33S crossed with 23 re- sistant restorer lines showed dominant, incompletely dominant or recessive inheri- tance. Dominant and incompletely dominant inheritance accounted for 87.0%. The diseased panicle rate, disease index, average diseased grains per panicle, and the highest diseased grains per panicle of F1 shared highly significant positive correla- tions with corresponding indicators of restorer lines. [Conclusion] This study provides references for genetic improvement of two-line hybrid rice.

Yield-related agronomic traits evaluation for hybrid wheat and relations of ethylene and polyamines biosynthesis to filling at the mid-grain filling stage

Because of the yield increase of 3.5-15%compared to conventional wheat,hybrid wheat is considered to be one of the main ways to greatly improve the wheat yield in the future.In this study,we performed a principal component analysis(PCA)on two-line hybrids wheat and their parents using the grain weight(GW),the length of spike(LS),the kernel number of spike(KSN),and spike number(SPN)as variables.The results showed that the variables could be classifed into three main factors,the weight factor(factor 1),the quantity factor 1(factor 2)and the quantity factor 2(factor 3),which accounted for 37.1,22.6 and 18.5%,respectively of the total variance in different agronomic variables,suggesting that the GW is an important indicator for evaluating hybrid combinations,and the grain weight of restorer line(RGW)could be used as a reference for parents selection.The hybrid combination with a higher score in factor 1 direction and larger mid-parent heterosis(MPH)of the GW and its parents were used to carry out the analysis of grain fling,1-aminocylopropane-1-carboxylicacid(ACC)and polyamine synthesis related genes.The results suggested that the GW of superior grain was significantly higher than that of inferior grains in BS1453xJS1(H)and its parents.Both grain types showed a weight of H between BS 1453(M)and JS1(R),and a larger MPH,which may be caused by their differences in the active fling stage and the grain fling rate.The ADP-glucose pyrophosphorylase(AGPase),granule bound starch synthase I(GBSS/),starch synthaseⅡ(SSS),and starch branching enzyme-Ⅰ(SBE-1)expression levels of H were intermediated between M and R,which might be closely related to MPH formation of the GW.Compared with R and H,the GW of M at maturity was the lowest.The expression levels of spermidine synthase 2(Spd2),ornithine decarboxylase(ODC)and S adenosylmethionine decarboxylase(SAMDC)had significantly positive correlations with the grain flig rate(1=0.77,0.51,0.59"),suggesting their major roles in the grain flling and heterosis formation.These provide a theoretical basis for improving the GW of photo-thermo-sensitive male sterile lines(PTSMSL)by changing the endogenous polyamine synthesis in commercial applications.

Analysis on Genetic Differences between Parents of Two-line Medium Indica Hybrid Rice by SSR Markers

The genetic diversity of 50 parents or improved lines of two-line medium Indica hybrid rice were analyzed based on 48 pairs of SSR markers. The results showed that the clustering results were highly accordant with the parental pedigree information of the tested materials. The male sterile lines and the restoring lines were clustered into 2 distinct groups （Ⅰ and Ⅱ）, respectively. There were no significant difference in intra-group average genetic distances （GD） between the 2 groups. Most of the male sterile lines from Hunan Longping High-tech Seed Science Research Institute Co., Ltd. were grouped into a single subgroup （Ⅰ-4） under the male sterile group with the largest average GD compared with the rest male sterile subgroups. Huazhan derived lines and Guangzhou inbred lines were founded to be independent of 9311 and its derivatives or closely-related lines. Meanwhile, they have obviously been differentiated into 2 subgroups （Ⅱ-2 and Ⅱ-3）. The lines derived from Huazhan （or genetic closely related lines） showed a genetic homogenization phenomenon. Therefore, the Huazhan-derived lines should be further improved by the utilization of germplasms with good quality, high resistance and wide adaptability from Southern China to widen the GD between Huazhan derived lines and the male sterile subgroup developed by Hunan Longping High-tech Seed Science Research Institute Co., Ltd., so as to further promote the heterosis level between the groups.

Effects of Different Row Ratios of Male and Female Parents and Application Amount of Nitrogen Fertilizer on Hybrid Wheat Seed Production and Its Component Factors

In order to screen suitable high hybrid wheat seed production technology,the split-plot experiment design was adopted and study was carried out about the effects of the different row ratios of male and female parents and application amount of nitrogen fertilizer on hybrid wheat seed production and its component factors. The results showed that the seed production increased with the increase in the number of female parent row. When the row ratio of male and female parents was 2 ∶ 6,the seed production was 3 683. 8 kg/ha; when the application amount of nitrogen fertilization was 50 kg/ha,the seed production was 3 649. 4 kg/ha; the interaction between the row ratio of male and female parents and the application amount of nitrogen fertilizer indicated that when the row ratio of male and female parents was 2∶ 6 and the application amount of nitrogen fertilizer was 300 kg/ha,the seed production reached the highest( 4160. 6 kg/ha). The row ratio of male and female parents and application amount of nitrogen fertilizer had significant effect on the component factors of seed production,including the number of grains per spike,spike weight and setting percentage. When the row ratio of male and female parents was 2∶ 5,the number of grains per spike,spike weight and setting percentage were the highest at 26. 7 grains,1. 12 g,and 62. 6% respectively; when application amount of nitrogen fertilizer was 450 kg/ha,the number of grains per spike,spike weight and setting percentage were the highest at 26. 0 grains,1. 08 g,and59. 2% respectively; the interaction of row ratio of male and female parents and application amount of nitrogen fertilizer had significant effect on the number of grains per spike,spike weight and setting percentage; when the row ratio of male and female parents was 2∶ 5 and the application amount of nitrogen fertilizer was 300 kg/ha,the number of grains per spike,spike weight and setting percentage were the highest at 29. 6grains,1. 24 g,and 71. 6% respectively. The number of grains per spike is the largest component factor for seed production. Increasing the number of grains per spike can increase the seed production. According to the effects of row ratio of male and female parents and application amount of nitrogen fertilizer on the component factors of seed production,the optimal condition was 2∶ 5-2∶ 6 for row ratio of male and female parents and 300-450 kg/ha for application amount of nitrogen fertilizer.

Comparative Proteomic Analysis of Wheat (Triticum aestivum L.) Hybrid Necrosis

Hybrid necrosis is the gradual premature death of leaves or plants in certain Fj hybrids of wheat （Triticum aestivum L.）. Comparison of protein expression in necrotic and normal wheat leaves showed that the abundance of 33 proteins was changed significantly, and 24 of these proteins were identified. These proteins were involved in plant growth and development, antioxidation, photosynthesis and carbon assimilation, amino acid and protein biosynthesis, cytological signal transduction, DNA and RNA modification, protein transport, folding and assembly according to their functions. The down-regulation of uroporphyrinogen decarboxylase and the up-regulation of lipoxygenases in necrotic leaves may be related to the oxidative stress in the necrotic cells. The heat shock proteins may play the cytoprotective role. The differential expression of photosynthesis and carbon assimilation related proteins indicated chlorophyll biosynthesis and chloroplast development were inhibited and might finally cause the gradual chlorosis and cell death in necrotic leaves. The results of this study give a comprehensive picture of the post-transcriptional response to necrosis in hybrid wheat leaves and serve as a platform for further characterization of gene function and regulation in wheat hybrid necrosis.