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.

Effects of Nitrogen Application Amount during Various Periods on Yield of High Grade Hybrid Rapeseed

[Objective] The paper was to study the nitrogen application amount and nitrogen application model for high grade hybrid rapeseed （Brassica napus L.） to get high yield. [Method] With ＂Youyan 599＂ and ＂Sanbei 98＂ as materials, using quadratic regression orthogonal gyration combination design, the impact of nitrogen application amount during various periods on rapeseed yield was studied. [Result] The combinations of factors to obtain the highest yield index （2 898.211 kg / hm 2 ） of ＂Youyan 599＂ were as follows： living rape fertilizer 89.27 kg / hm 2 , opening fertilizer 120 kg / hm 2 , 12 th lunar month fertilizer 101.12 kg / hm 2 , total nitrogen application amount 310.39 kg / hm 2 . The proportions of living rape fertilizer, opening fertilizer and 12th lunar month fertilizer were 28.76%, 38.66% and 32.58%, respectively. The combinations of factors to obtain the highest yield index （2 870.14 kg/hm 2 ） of ＂Sanbei 98＂ were as follows： living rape fertilizer 120 kg / hm 2 , opening fertilizer 120 kg / hm 2 , 12 th lunar month fertilizer 37.55kg / hm 2 , total nitrogen application amount 277.55 kg / hm 2 . The proportions of living rape fertilizer, opening fertilizer and 12 th lunar month fertilizer were 43.24%, 43.24% and 13.53%, respectively. The combinations of factors to obtain the highest yield index of two combined varieties （2 813.82 kg/hm 2 ）were as follows： living rape fertilizer 120 kg/hm 2 , opening fertilizer 120 kg/hm 2 , 12 th lunar month fertilizer 76.23 kg/hm 2 , total nitrogen application amount 316.23 kg/hm 2 . The proportions of living rape fertilizer, opening fertilizer and 12 th lunar month fertilizer were 37.95% , 37.95% and 24.11% , respectively. [Conclusion] The paper provided theoretical basis for high yield cultivation of high grade hybridized rapeseed.

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.

Comparions of Required Nitrogen Fertilizers by Hybrid Cultivar and Conventional Cultivar of Rapeseed(Brassica napus L.)

[Objective] The aim of this study was to understand the difference of N fertilizer requirement between hybrid rapeseed and conventional rapeseed. [Method] Two hybrid cultivars, ZY5628 and ZY7819, and the conventional cultivar ZS10, were compared through two field experiments. In Experiment 1, seed yield and optimum N application rate were assessed in the field with five N application treatments. In Expedment 2, N was applied uniformly at 180 kg/hm2, and plant biomass and N accumulation were measured at several developmental stages, while N use efficien- cy was calculated for rape at maturity. [Results] The experiment 1 results showed that seed yields of ZY5628 and ZY7819 were both significantly higher than that of ZS10, and compared to ZS10, optimum yield （plateau yield） was higher by 18.7% and 20.2%, while the recommended N application rate was lower by 9.5% and 9.6% for ZY5628 and ZY7819, respectively. The experiment 2 results showed that during vegetative development, all three cultivars exhibited similar accumulations of plant biomass and N, but through flowering and maturity ZY5628 and ZY7819 pro- duced more biomass, acquired more N, and utilized acquired N more efficiently to- wards seed production than ZS10. [Conclusion] With equivalent inputs, the hybrid rapeseed cultivars ZY5628 and ZY7819 tested herein yield more seed with higher N use efficiency than the conventional rapeseed ZS10. This information will be valu- able for growers seeking to improve efficiency while reducing costs of rape production in China.

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.

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.

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.

Ecological Adaptability of New Hybrid Rapeseed Varieties in Sichuan Hilly Areas

[Objective] The aim was to explore rapeseed varieties adapting to local conditions, with optimal yielding capacity and growth period. [Method] The research performed analysis on yield, yielding components, and interaction effects in different groups and test sites based on hybrid rapeseeds in Mianyang during 2012-2015.[Conclusion] Mianyou 33, Mianyou 88 and Mianyou 309 showed insignificant differences in yield. The analysis of variance suggested that yield of Mianyou 309 was the highest and the variety was suitable to be planted in high erucic acid rapeseed bases. Mianyou 88 and Mianyou 33 are double-low varieties, characterized by high and stable yielding. [Conclusion] The research provides references for rapeseed production in hilly areas in Sichuan Province.

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.

Performance and High-Yield Cultural Techniques of Two-Line Hybrid Rice Xinlingyou998 at Direct Seeding Cultivation

Xinliangyou 998 is a new indica two-line hybrid rice variety using Xin＇er Sx H0998 as parent. The variety was introduced and demonstrated in Yingshan County in 2016, and showed intermediate growth duration, strong tillering ability, firm culm, tolerance to high fertility and resistance to lodging, tolerance to high tempera- ture and wide range of adaptation, etc. The high-yield cultural techniques were con- cluded.

Breeding of a Water-saving Drought-resistant Two-line Hybrid Rice Variety Wanliangyou 1008

Drought is one of the important factors limiting rice production,and the application of new water-saving rice varieties is urgently needed in rice production.Wanliangyou 1008 bred by Institute of Rice Research,Anhui Academy of Agricultural Sciences is a new two line hybrid rice variety with some good traits,including high drought resistance,high yield and good disease resistance.Wanlingyou 1008 was obtained by crossing drought-resistant high-quality restorer line DJ1008 and disease-resistant two-line sterile line Wan 25S.In this paper,the breeding process,characteristics and seed production technology of the variety were described in detail.

Construction of Accumulated Temperature Effect Model for Fertility Alteration of Two-line Sterile Line P88S

[Objective]The research aimed at constructing an accumulated temperature effect model for fertility alteration of two-line hybrid rice P88S.[Method]Analyze the experiment datas of fertility alteration of P88S in Hainan from 2005 to 2006.[Result]The fertilities of P88S with temperatures ranging from 26 to 28 ℃ were determined by the absolute values and the accumulation effects of the temperature.An accumulation effect model of temperatures based on the bistable state was obtained.[Conclusion]The temperature asymmetry of fertility alteration for two-line sterility line in spring and autumn can be elucidated effectively using the accumulated temperature effect model,namely,alternating from fertile to sterile requires higher temperatures,and alternating from sterile to fertile requires lower temperatures.

Breeding and Application of Indica PTGMS Line Yan 161S and Its Hybrid Yanliangyou 1618 in Rice

In 2006, the indica photoperiod- and thermo-sensitive genic male sterile （PTGMS） line Yan 161S was successful y bred by crossing the Guangzhan 63S （♀） and the medium indica breeding material Yan 229 （♂）, which was bred by the Institute of Agricultural Sciences in Coastal Region of Jiangsu Province, after years＇ and generations’ selection in different areas. It passed the identification by Jiangsu Provincial Crop Variety Appraisal Committee in 2013. Crossing the Yan 161S with Yanhui 888, a new high-yielding and high-quality two-line hybrid rice combination Yanliangyou 1618 was developed, and it passed the variety identification in 2014. This paper introduced the breeding processes and characteristics of Yan 161S and Yanliangyou 1618 and the cultivation and seed production techniques of Yanliangyou 1618.

High-yielding Seed Production Techniques and Characteristics of Hybrid Rice Yanliangyou 888

According to seed production of Yanliangyou 888, a two-line hybrid rice variety, the research reviewed seed production characters, as follows： to improve outcrossing rate and spike size provided sufficient spikes of female/male parents. The seed production techniques include scientific arrangement of seeding interval, cultivating strong multi-tiller seedlings, scientific arrangement of row ratio of inter- cropping with adequate basic seedlings, scientific water and fertilizer management, improving outcrossing rate by synthesis measures, disease/insect control, and rein- forcing production management.

Effect of Cultivation Conditionss on Quality Parameters of High Grade Hybrid Rape of Brassica napus L.

[Objective] This study aimed to investigate the combined effects of sowing date, plant density, nitrogenous fertilizer, phosphorus fertilizer and potassium fertilizer on quality parameters of high grade hybrid rapeseed. [Method] By using Youyan 599 and Sanbei 98 as experimental materials, quadratic orthogonal rotation combination with five factors was designed for this study. [Result] Erucic acid content was nega- tively correlated with sowing date and nitrogen fertilizer, positively correlated with plant density. Glucosinolate content was negatively correlated with sowing date, positively correlated with potash fertilizer amount. Oil content was negatively correlated with sowing date and nitrogen fertilizer amount, positively correlated with plant density and potash fertilizer amount. Protein content was positively correlated with sowing date and nitrogen fertilizer amount, negatively correlated with plant density and potash fer- tilizer amount. Oleic acid content was negatively correlated with phosphate fertilizer amount, positively correlated with nitrogen fertilizer amount. Palmitic acid was nega- tively correlated with potash fertilizer amount, positively correlated with sowing date, plant density, nitrogen fertilizer amount and phosphate fertilizer amount in Youyan 599, but negatively correlated with sowing date, plant density, nitrogen fertilizer amount and phosphate fertilizer amount in Sanbei 98. Stearic acid content was posi- tively correlated with sowing date, plant density, nitrogen fertilizer amount and phos- phate fertilizer amount. Linoleic acid was positively correlated with density and nitroge- nous fertilizer, but negatively correlated with potash fertilizer amount. Linolenic acid was positively correlated with nitrogen fertilizer amount and potash fertilizer amount. Eicosenoic acid was negatively correlated with sowing date. There were positive cor- relations and negative correlations among cultivation conditions and quality parame- ters, and the positive correlations and negative correlations could counteract each other. Expression of quality parameters for each treatment was the combined effect. Among the 50 pairs of simple correlations of five cultivation factors and ten quality parameters, 26 pairs were consistent between two varieties, 24 pairs of simple corre- lation were not. Sowing date, plant density, nitrogen fertilizer amount and phosphate fertilizer amount showed significant influence on erucic acid of two varieties, but small effect on palmitic acid. [Conclusion] The combined effect of the five cultivation factors could not fundamentally improve the quality traits of high grade hybrid rapeseed.

Effect of Different Fertilization Methods on Grain Yield and Nitrogen Agronomy Efficiency of TwoLine Super Hybrid Rice

ln order to explore the effect of broadcast application of urea （BR-U） and surface concentrated-fertilization on grain yield and nitrogen agronomy efficiency of two-line super hybrid rice, this experiment was conducted with super hybrid rice Y-Liangyou 1 and Liangyou 0293 to determine til ering dynamics, SPAD, LAl and dry matter accumulation. lts total N application was 180 kg/hm2 and different application rate and topdressing methods were set respectively. The results showed that grain yield and nitrogen agronomy efficiency were significantly improved with the T3 and T4 nitrogenous fertilizer application model. The improving of grain yield and nitrogen agronomy efficiency was benefited from rational postponing N application. However, neither single application of base fertilizer （T2） nor single application of topdressing fertilizer （T5 and T6） can coordinate the relationship between source and sink. Both grain yield and nitrogen agronomy efficiency were insignificantly under the broadcast application of urea and surface concentrated fertilization.

Practice and Thought on Developing Hybrid Rice for Super High Yield by Exploiting Inter-subspecific Heterosis

Since the breakthrough of grain yield owing to the development of dwarf rice and three-line system hybrid rice, rice breeding for high yield hardly had showed significant progress in the next successive two decades. It was considered that utilizing heterosis between subspecific varieties (Oryza sativa L.) would be an effective approach to increase yield further. During 1987-1993, an indica-japonica hybrid Yayou 2 yielded as high as 10.5 t/ha; however, it failed to be commercialized because of seed purity problem due to non-uniform emasculation by chemical agent in seed production, and sensitivity of seed setting in Ft plants to environmental conditions. In the past decade, two inter-subspeific hybrids, Liangyoupeijiu (Peiai 64S/9311, javanica/indica) and Liangyou E32 (Peiai 64S/E32, javanica/ laponica); both of them exhibited grain yield higher than 10.5 t/ha, and were widely judged as the pioneers of super hybrid rice. Liangyoupeijiu has been successfully popularized over 4 million hectare in wide climatic areas, while Liangyou E32 made a yield record and offered a model of plant ideotype for super hybrid rice. It was considered that in combination with plant ideotype, active physiological functions, and wide-range adaptability to ecological conditions, exploitation of indica-japonica heterosis would be the key approach for super hybrid rice breeding.

Status and Prospects of Hybrid Rice Breeding in Jiangsu, China

Research on hybrid rice in Jiangsu Province, China began in 1970. Great progress has been made since then, which can be divided into three stages according to the development of hybrid rice breeding and production in Jiangsu Province. The first stage was beginning stage from 1970 to 1980, when progress was mainly made in cytoplasmic male sterile line breeding. The second stage could be described as developing stage, from 1980 to 1995, when indica hybrid rice was rapidly popularized, and japonica hybrid rice became popular later. From 1996, hybrid rice breeding in Jiangsu Province entered the third stage, when both indica and japonica hybrid rice breeding in the three-line system or intersubspecific hybrid rice breeding in the two-line system made a great breakthrough with the successful breeding of the hybrids Feyou 559, 9 You 138 and Liangyoupeijiu. The developing trend of hybrid rice breeding in Jiangsu Province is also discussed.