Higher leaf area through leaf width and lower leaf angle were the primary morphological traits for yield advantage of japonica/indica hybrids

The yield potential of japonica/indica hybrids(JIH)has been achieved over 13.5 t ha–1 in large-scale rice fields,and some physiological traits for yield advantage of JIH over japonica inbred rice(JI)and indica hybrid rice(IH)were also identified.To date,little attention has been paid to morphological traits for yield advantage of JIH over JI and IH.For this reason,three JIH,three JI,and three IH were field-grown at East China(Ningbo,Zhejiang Province)in 2015 and 2016.Compared with JI and IH,JIH had 14.3 and 20.8%higher grain yield,respectively,attributed to its more spikelets per panicle and relatively high percentage of filled grains.The advantage in spikelets per panicle of JIH over JI and IH was shown in number of grains on the upper,middle,and lower branches.Compared with JI and IH,JIH had higher leaf area through leaf width and lower leaf angle of upper three leaves,higher leaf area index and leaf area per tiller at heading and maturity stages,higher stem weight per tiller and K and Si concentrations of stem at maturity,higher dry matter weight in leaf,stem,and panicle at heading and maturity stages,and higher biomass accumulation after heading and lower biomass translocation from stem during ripening.Leaf width of upper three leaves were correlated positively,while leaf angle of upper three leaves were correlated negatively with biomass accumulation after heading,stem weight per tiller,and per unit length.Our results indicated that the grain yield advantage of JIH was ascribed mainly to the more spikelets per panicle and relatively high percentage of filled grains.Higher leaf area through leaf width and more erect leaves were associated with improved biomass accumulation and stem weighing during ripening,and were the primary morphological traits underlying higher grain yield of JIH.

Morpho-physiological traits contributing to better yield performance of japonica/indica hybrids over indica hybrids under input-reduced practices

It is widely reported that japonica/indica hybrids(JIH)have superior grain yield over other main varietal groups such as indica hybrids(IH)under sufficient resource inputs.To date,little attention has been paid to yield performance of JIH under input-reduced practices,and whether JIH could have better grain yield performance over IH under input-reduced practices.In this study,three JIH varieties and three IH varieties were compared in grain yield and their related morpho-physiological traits under two cultivation modes,i.e.,conventional high-yielding method(CHYM)and double reductions in nitrogen rate and planting density(DRNP).Our results showed that JIH had 8.3 and 13.3%higher grain yield over IH under CHYM and DRNP,respectively.The superior grain yield of JIH over IH under DRNP was mainly attributed to larger sink size and improved sink filling efficiency.Three main morpho-physiological traits were concluded for better yield performance of JIH over IH under DRNP.Firstly,JIH had the reduced unproductive tillers growth,indicated by a higher percentage of productive tillers and the percentage of effective leaf area index(LAI)to total LAI at heading stage.Secondly,a synergistic increase in biomass accumulation and harvest index were achieved of JIH,supported by higher biomass accumulation and leaf area duration during the main growth periods,and improved non-structural carbohydrate(NSC)remobilization after heading.Thirdly,JIH had an improved canopy structure,showing as higher leaf area of upper three leaves and lower light extinction coefficient.Our results suggested that improved morpho-physiological traits of JIH could lead to better grain yield performance over IH under input-reduced practices.

Yield characteristics of japonicalindica hybrids rice in the middle and lower reaches of the Yangtze River in China

Although a lot of researches have been done on yield characteristics of japonica/indica hybrid rice,there is itte information on differences of yield characteristics between different types of hybrid.To determine common characteristics of japonical indica hybrid rice(JIHR)and identify the differences between different types of JIHR,the present study assessed yield characteristics,such as panicle trait,leaf area index(LAI),above-ground biomass accumulation,and nitrogen absorption and uilization,among three types of cultivar of JIHR.In our field experiments,three types of JIHR,e.g.,Yongyou,Chunyou and Jiayouzhongke,were divided,and each of them has two cultivars,which were used as materials,meanwhile,using conventional japonica rice(CJR)Wuyingjing 31 and Sujing 9 were as controls.The results showed that the mean yield of those JIHR was above 12 t ha^-1 in 2017 and 2018,and was 31.9 and 32.2%,respectively higher than that of CJR in the two years.Spikelet number per panicle of JIHR resulted in high yield.Higher yield of JIHR was likely contributed to greater panicle number and more spikelets per panicle.Higher yielding JIHR showed stronger tllering capacity,larger LAI and above-ground biomass accumulation from jointing to heading stages,which likely contributed to the higher number of spikelets per panicle.The long duration from heading to maturity stages allowed more nitrogen accumulation of higher yielding JIHR.

Developmental Analysis of Genetic Behavior of Brown Rice Width in indica-japonica Hybrids

The developmental genetic behaviors of brown rice width （BRW） have been studied in indica-japonica hybrid rice （Oryza sativa L.）, in which seven indica male sterile lines and five japonica restorer lines were applied, by using the developmental genetic models and corresponding statistical approaches for quantitative traits of triploid in cereal crops. The BRW of indica-japonica hybrid rice was co-determined by gene expression of tdploid endosperm, cytoplasm, diploid maternal plant and their genotype × environmental interaction effects. Unconditional analysis showed that the endosperm additive and matemal additive effects were predominant for the development of BRW from early- to late-stage of the grain development, but the endosperm dominant effect together with matemal effect and cytoplasmic effect became the major factor determing the BRW at the ripening stage. Moreover, conditional analysis found that there were new onset and offset of gene expression at different developmental stages of BRW in indica-japonica hybrid rice. Maternal and cytoplasm general heritabilities and their interaction heritabilities were more important compared to other components of heritability for BRW at all the five developmental stages.

Suitable growing zone and yield potential for late-maturity type of Yongyou japonica/indica hybrid rice in the lower reaches of Yangtze River, China

Late-maturity type of Yongyou japonica/indica hybrids series （LMYS） have shown great yield potential, and are being widely planted in the lower reaches of Yangtze River, China. Knowledge about suitable growing zone and evaluation of yield advantage is of practicall importance for LMYS in this region. Fifteen LMYS, two high-yielding inbred japonica check varieties （CK-J） and two high-yielding hybrid indica check varieties （CK-I） were grown at Xinghua （119.57°E, 33.05°N） of Lixiahe region, Yangzhou （119.25°E, 32.30°N）of Yanjiang region, Changshu （120.46°E, 31.41°N）of Taihu Lake region, and Ningbo （121.31°E, 29.45°N） of Ningshao Plain in 2013 and 2014. The results showed that maturity dates of the 15 were later than the secure maturity date at Xinghua and 6, 14 and 15 LMYS were mature before the secure maturity date at Yangzhou, Changshu and Ningbo, respectively. One variety was identified as high-yielding variety among LMYS （HYYS） at Yangzhou, 8 HYYS in 201：3 and 9 HYYS in 2014 at Changshu, 9 HYYS at Ningbo. HYYS here referred to the variety among LMYS that was mature before the secure maturity date and had at least 8% higher grain yield than both CK-J and CK-I at each experimental site. Grain yield of HYYS at each experimental site was about 12.0 t ha-1 or higher, and was significantly higher than CK varieties. High yield of HYYS was mainly attributed to larger sink size due to more spikelets per panicle. Plant height of HYYS was about 140 cm, and was significantly higher than check varieties. Significant positive correlations were recorded between duration from heading to maturity stage and grain yield, and also between whole growth periods and grain yield. HYYS had obvious advantage over check varieties in biomass accumulation and leaf area duration from heading to maturity stage. Comprehensive consideration about safe matudty and yield performance of LMYS at each experimental site, Taihu Lake region （representative site Changshu） and Ningshao Plain （representative site Ningbo） were thought suitable growing zones for LMYS in the lower reaches of Yangtze River. The main factors underlying high yield ofHYYS were larger sink size, higher plant height, longer duration from heading to maturity stage and whole growth periods, and higher biomass accumulation and leaf area duration during grain filling stage.

Solar radiation-use characteristics of indica/japonica hybrid rice (Oryza sativa L.) in the late season in southeast China

New indica and japonica hybrid rice cultivars,such as the Yongyou series,provide farmers with very high yield potential.However,information on their canopy light capture and solar radiation use efficiency in the late season is limited.Field experiments were performed to compare the radiation-use parameters of four rice types:indica rice(IR),inbred japonica rice(IJR),hybrid japonica rice(HJR),and hybrid indica/japonica rice(HIJR),from 2016 to 2018 during the late season in Hangzhou,China.The grain yield,aboveground biomass,intercepted solar radiation(SI),and radiation-use efficiency(RUE)of the HIJR were on average respectively 13.4%–53.4%,14.3%–30.6%,7.6%–21.4%,and 8.2%–14.9%higher than those of the HJR,IJR,and IR.The leaf area index(LAI)of the HIJR was 18.2%–57.0%greater than that of the IJR and HJR at four growth stages,resulting in respectively 17.8%–38.5%and 10.7%–42.8%greater canopy light interception rates(LIR)and amount of intercepted solar radiation during the vegetative stage.The prolonged grain-filling stage also led to respectively 33.9%–52.6%and 30.5%–51.4%increases in amounts of incident and intercepted radiation for the HIJR relative to the IR during grain filling.These results indicate that the SI superiority of the HIJR was caused by canopy closure as rapid as that of the IR during the vegetative stage(greater LAI and canopy LIR during the growing season)and a grain-filling stage as long as that of the HJR.For grain-filling stage,differences in leaf Pn between HIJR,IR,and IJR were not significant,suggesting that the greater RUE of the HIJR(12.7%–52.8%higher)than that of the other rice types resulted from improved canopy architecture after flowering(FL).Principal components analysis(PCA)revealed that the superiority of the HIJR in terms of solar radiation use resulted from the greater canopy light capture capability of IR and the prolonged growth period(especially during grain filling)of japonica rice in the late growing season.

Grain yield,nitrogen use efficiency and physiological performance of indica/japonica hybrid rice in response to various nitrogen rates

Utilizing the heterosis of indica/japonica hybrid rice(IJHR)is an effective way to further increase rice grain yield.Rational application of nitrogen(N)fertilizer plays a very important role in using the heterosis of IJHR to achieve its great yield potential.However,the responses of the grain yield and N utilization of IJHR to N application rates and the underlying physiological mechanism remain elusive.The purpose of this study was to clarify these issues.Three rice cultivars currently used in rice production,an IJHR cultivar Yongyou 2640(YY2640),a japonica cultivar Lianjing 7(LJ-7)and an indica cultivar Yangdao 6(YD-6),were grown in the field with six N rates(0,100,200,300,400,and 500 kg ha^(-1))in 2018 and 2019.The results showed that with the increase in N application rates,the grain yield of each test cultivar increased at first and then decreased,and the highest grain yield was at the N rate of 400 kg ha^(-1)for YY2640,with a grain yield of 13.4 t ha^(-1),and at 300 kg ha^(-1)for LJ-7 and YD-6,with grain yields of 9.4–10.6 t ha^(-1).The grain yield and N use efficiency(NUE)of YY2640 were higher than those of LJ-7 or YD-6 at the same N rate,especially at the higher N rates.When compared with LJ-7 or YD-6,YY2640 exhibited better physiological traits,including greater root oxidation activity and leaf photosynthetic rate,higher cytokinin content in the roots and leaves,and more remobilization of assimilates from the stem to the grain during grain filling.The results suggest that IJHR could attain both higher grain yield and higher NUE than inbred rice at either low or high N application rates.Improved shoot and root traits of the IJHR contribute to its higher grain yield and NUE,and a higher content of cytokinins in the IJHR plants plays a vital role in their responses to N application rates and also benefits other physiological processes.

Relationship of Parental Indica-Japonica Indexes with Yield and Grain Quality Traits of Japonica Hybrid Rice in Northern China

Taking the main parents （10 male sterile lines and 10 restorer lines） and their 100 combinations of japonica hybrid rice in northern China as materials, the relationships of parental indica-japonica indexes determined by the methods of the Cheng’s index as well as simple sequence repeat （SSR） markers with yield and grain quality traits of hybrid rice were studied. For the parents, the Cheng’s index （Chi） ranged from 13.5 to 19.3 and the indica index in SSR markers （ADi） were from 0.12 to 0.38. The classification of parents by Chi was not completely consistent with that by ADi. The Chi of male parent was more closely related to hybrid traits than that of female parent, as contrasted to ADi. At the same time, the difference between parents （PD） in Chi was more closely related to hybrid traits than that in ADi. The indica-japonica indexes of parents and their difference between parents appeared quadratic relationship to hybrid traits with the critical extremum. The directions of the correlation of indica-japonica indexes of parents and their differences with hybrid yield traits were on the opposition to those with hybrid grain quality traits. Therefore, the female parent should match the male parent moderately in indica-japonica index to obtain the optimum of hybrid traits, high yield as well as good quality.

Development and Characterization of Elite Doubled Haploid Lines from Two Indica Rice Hybrids

Despite significant yield advantage over inbred rice, the adoption rate of hybrid rice in India is very low due to the high seed cost and poor quality of the produce. To alleviate the problem, we initiated a doubled haploid （DH） breeding approach to develop new lines from two elite indica rice hybrids （CRHR5 and CRHR7） through rapid fixation of homozygosity in the recombinants. In vitro culture of the rice anthers resulted in 243 and 186 fertile DH lines of CRHR5 and CRHR7, respectively. Flow cytometric and pollen fertility analyses confirmed the DH ploidy status of the regenerations. Morpho-agronomic evaluation revealed 100% uniformity and stability for all the characters in the DH lines of both hybrids. Nineteen promising DH lines of each hybrid were advanced to A2 generation for yield evaluation. The yield levels of the DH lines ranged from 5 097-6 965 kg/hm^2 for CRHR5 and 5 141-7 235 kg/hm^2 for CRHR7, which were at par or higher than the parental hybrids. Physico-chemical characterization and cooking quality analyses revealed significant and acceptable values for grain length and width, alkali spreading value, amylose content and water uptake ratio of the selected DH lines. Three DH lines, CR5-10, CR5-49, CR5-61 from CRHR5, and four DH lines, CR7-5, CR7-7, CR7-12 and CR7-52 from CRHR7, showed significant grain yield and quality characteristics and have been recommended for multi-location trials for subsequent release as new indica doubled haploid rice varieties.

A Preliminary Study on the Relationship Between the Indica-Japonica RAPD Differentiation of Parents and Heterosisin Dian Type Hybrid Rice

The relationship between the indica-japonica differentiation of parents and heterosis of hybrid in rice was studied with 10 sterile lines, 10 maintainer lines of the sterile lines, 38 restorer lines of Dian type hybrid rice and 40 hybrids derived from the sterile lines and restorer lines. The results indicated that there was a parabolic correlation between the indica-japonica differentiation of parents detected by RAPD markers and heterosis of hybrid rice. When certain indica-japonica differentiation of parents exists, the percentage of combinations with positve heterosis and the mean heterosis of hybrids were high. But that didn't mean too much difference of parents could lead to stronger hetesosis, that meant overdiffernt parents seldom bring positve het-erotic hybrids. Suitable difference of percent of indica alleles of parents of stronger heterotic hybrid was 12 -16%.

Different Aluminum Tolerance among Indica, Japonica and Hybrid Rice Varieties

Hydroponic cultures were conducted to compare the aluminum（Al） tolerance among different rice（Oryza sativa L.） varieties, including indica, japonica and their hybrids. The results showed that the root growth of rice plant was inhibited in different degrees among Al treated varieties. The Al tolerance observed through relative root elongation indicated that five japonica varieties including Longjing 9, Dharial, LGC 1, Ribenyou and Koshihikari were relatively more tolerant than indica varieties. Most indica varieties in this study, such as Aus 373 and 9311（awnless）, were sensitive to Al toxicity. The Al tolerance of most progenies from japonica × indica or indica × japonica crosses was constantly consistent with indica parents. The differences of Al tolerance among Longjing 9（japonica）, Yangdao 6（indica） and Wuyunjing 7（japonica） were studied. Biomass and the malondial-dehyde content of Yangdao 6 under Al exposure decreased and increased, respectively, while there was no significant effect on those of Longjing 9 and Wuyunjing 7. Remarkable reduction of root activities was observed in all these three rice varieties. Significantly higher Al content in roots was found in Yangdao 6 compared to Longjing 9 or Wuyunjing 7.

Effects of chilling tolerance induced by spermidine pretreatment on antioxidative activity,endogenous hormones and ultrastructure of indica-japonica hybrid rice seedlings

Spermidine（Spd） is known to be involved in the regulation of plant responses to chilling stress and counteract the adverse effect of stress conditions.Antioxidant activities,endogenous hormones and ultrastructure change under chilling stress were investigated in indica-japonica hybrid rice seedlings.12-d-old seedlings were subjected to exogenous Spd（1 mmol L^（-1）） and then a chilling stress（6℃,4 d） was induced,followed by a subsequent recovery（25℃,4 d）.Results showed that malondialdehyde（MDA） and proline content were enhanced significantly,whereas shoot fresh and dry weights decreased during chilling stress and after recovery;chlorophyll content of chilling-stressed seedlings increased slightly but declined after recovery;additionally,total soluble sugar,sucrose,fructose and starch contents increased significantly during chilling stress,and only soluble sugar and fructose contents were observed in increase after recovery;chilling stress-induced increases in superoxide dismutase（SOD）,peroxidase（POD） and catalase（CAT） activities,but declined after recovery,and the level of ascorbate peroxidase was lower during chilling stress and after recovery;however,endogenous indole-3-acetic acid（IAA）,zeatin riboside（ZR）,gibberellic acid（GA_3）,and abscisic acid（ABA） levels were induced decreased compared with Spd pretreatment.The microscopic analysis revealed that chilling stress-induced destruction of the chloroplast envelope during chilling stress and increased the number of plastoglobuli along with aberrations in thylakoid membranes after recovery.In contrast,exogenous Spd protected rice seedlings from chilling-induced injuries in terms of lower malondialdehyde,proline and carbohydrates accumulation coupled with increased endogenous hormones metabolism.After recovery,Spd pretreatment chilling-exposed seedlings showed higher activities of antioxidant enzymes and normal physiological function of chloroplasts.These results suggest that Spd could promote effectively chilling tolerance which might be largely attributable to the integrity of cell structure and normal metabolism of endogenous hormones in indica-japonica hybrid rice seedlings.

Resistance Evaluation of Some Hybrid Rice, Conventional Early Indica and Late Japonica Rice to Magnaporthe grisea

Thirty isolates of Magnaporthe grisea collected from 18 provinces/cities representing 21 pathotypes and 9 different lineages were inoculated to rice varieties with known resistance genes and some hybrid rices, conventional early indica and late japonica varieties cultivated recently in China. Virulence spectrum of the 30 isolates was very different, showing that they recognize numerous different resistance genes. Varieties also revealed very different resistance patterns showing that they carry different resistance genes or combinations of resistance genes. On the basis of comparisons with international differential varieties with known resistance genes, resistance genes in certain Chinese varieties could be speculated. The results indicated that some of them were resistant to most of the isolates tested and that they could be of interest as resistance sources for hybrid parents or to be planted in the field directly.

Megasporogenesis and Megagametogenesis in Autotetraploid Indica/Japonica Rice Hybrid

Autotetraploid indic, a/japonica rice hybrid combines both the advantages of polyploidy and the heterosis between indica and japonica rice. Embryo sac abortion is an important factor influencing spikelet fertility in autotetraploid dce hybrid. To clarify the cytological mechanism of embryo sac abortion, the megasporogenesis and megagametogenesis in an autotetraploid japonicaAndica hybrid were examined by the whole-mount eosin B-staining confocal laser scanning microscopy （WE-CLSM） technique. Abnormalities were observed from the megasporocyte stage to the mature embryo sac stage. The degeneration of the tetrad cells and the functional megaspore was the characteristic of abnormalities during megasporogenesis. Abnormal small embryo sacs and disordered number of nuclei were frequently observed during embryo sac development. Some interesting phenomena, such as two functional megaspores, the diplospory-like megasporocyte, and five-nucleate embryo sac were found. The abnormalities that occurred during female gametophyte development resulted in more than five types of abnormal embryo sacs （i.e. embryo sac degeneration, embryo sac without female germ unit, embryo sac without egg apparatus, embryo sac with abnormal polar nuclei and abnormal small embryo sac） in autotetraploid japonica/ndica hybdd. Embryo sac fertility was lower in diploid japonica/ndica hybdd than in autotetraploid japonicaAndica hybrid although many abnormal phenomena were observed in autotetraploid hybrid.

Studies on the Growth Habits and Characteristics of Two Polyploid Indica-Japonica Hybrid Rice with Powerful Heterosis

Based on a series of polyploid indica-japonica hybrid plant lines obtained from a new breeding strategy of using double predominance of wide cross and polyploidization to breed super flee, two polyploid indica-japonica hybrids, PSR073 and PSR120 were studied in their growth periods to show the powerful heterosis in a larger scale and to study the characteristics of polyploid indica-japonica hybrids more elaborately. The leaf age, tiller growth, flowering habits, and agronomic traits of them were observed to analyze their growth habits and characteristics. The results showed that the.agronomic traits of PSR073 and PSR120, such as the plant height, panicle length, grain length, grain width, and 1000-grain weight, all acquired obvious predominance of polyploidy, and that the seed setting rate was more than 83%. No significant difference was observed between the two tetraploids and common diploids in the leaf age, tiller growth, and flowering habits. It was concluded that the characteristics of the two powerful heterosis polyploid hybrids were different from those of the polyploid rice reported earlier. Wide cross and polyploidization had no negative effects on their growth habits and characteristics; on the contrary these had powerful heterosis. This had provided theoretic and practical evidences for their application to agricultural production.

Effect of Environment and Genetic Recombination on Subspecies and Economic Trait Differentiation in the F_2 and F_3 Generations from indicajaponica Hybridization

indica and japonica are the two most important subspecies of Asian cultivated rice. Identifying mechanisms responsible for population differentiation in these subspecies is important for indica-japonica hybridization breeding. In this study, subspecies and economic trait differentiation patterns were analyzed using morphological and molecular （InDel and Intron Length Polymorphism） data in F2 and F3 populations derived from indica-japonica hybridization. Populations were grown in Liaoning and Guangdong provinces, China, with F3 populations generated from F2 populations using bulk harvesting （BM） and single-seed descent methods （SSD）. Segregation distortion was detected in F3-BM populations, but not in F3- SSD or in F2 populations. Superior performance was observed with respect to economic traits in Liaoning compared with that in Guangdong and 1 000-grain weight （KW）, seed setting rate （SSR） and grain yield per plant （GYP） were significantly correlated with indica and japonica subspecies types. Analysis of molecular and morphological data demonstrated that the environment is the main factor giving rise to population differentiation in indica-japonica hybridization. In addition, we also found that KW, SSR and GYP are related to subspecies characteristics and kinship, which is possibly a significant factor resulting in economic trait differentiation and determining environmental adaptability. Our study has provided new insights into the process of population differentiation in these subspecies to inform indica-japonica hybridization breeding.

Breeding of New Japonica-indica Hybrid Rice Combination Chunyou 284

Chunyou 284 is a medium- japonica hybrid combination,as well as an indica-japonica subspecific hyrbid with super-high yield,which was developed from Chunjiang 23A,a thermo-sensitive CMS line with very early anthesis time,and C84,an indica-japonica intermediate type restorer line with wide compatibility.This combination has the advantages of high yield potential,early maturity,excellent comprehensive agronomic traits and wide adaptability.It was approved by Jiangsu Provincial Crop Variety Approval Committee in June,2018.The breeding process,main characteristics,cultivation techniques and seed production points of the combination were introduced.

Genetic Analysis of Leucine Content in Indica-Japonica Hybrid Rice (Oryza sativa L.)

Genetic control of leucine content in indica-japonica hybrid rice (Oryza sativa L.) was studied in 35 crosses of F1 and F2 generations, which were derived from crossing 7 male sterile indica rice lines with 5 restorer japonica rice lines along with their parents. Two genetic models and their corresponding statistical methods for quantitative traits of triploid seeds in cereal crops were used for the analysis. The first was the unconditional genetic model, which refers to the analysis of cumulative measurements (from flowering to a specific time) along the developmental stages, while the second was the conditional genetic model, which relates to analysis from one developmental stage to another stage (t - 1→t). The results showed that leucine content of indica-japonica hybrid rice was controlled by the expression of triploid endosperm effect (endosperm additive effect and endosperm dominant effect), cytoplasm effect, diploid maternal plant effect (maternal additive effect and maternal dominant effect) and their environmental interaction effects. Of these effects, endosperm dominant effect and maternal dominant effect were more important at the earlier stages, while endosperm additive effect and maternal additive effect were more important at the later stages of rice grain development under both unconditional and conditional genetic analyses. Due to the high heritabilities, which came from endosperm, maternal and cytoplasm effects for leucine content at different developmental stages, selection for leucine content of indica-japonica hybrid rice would be more efficient at early generations in breeding programs.

Gametic selection in a doubled haploid population derived from anther culture of indica/japonica hybrid of Oryza Sativa L.

It is one of the key problems for application ofanther culture in hybrid breeding, geneticanalysis, and molecular mapping whether thedoubled haploid (DH) population derived fromanther culture of rice crosses represents a ran-dom array of the microspore population, i.e.whether gametic selection occurs in androgene-sis. A DH population including 132 lines de-