Mutagenic Improvement of Shattering Characteristic of the Restorer Line of a Hybrid Rice “Xieyou 9308”

The newly developed hybrid rice combination "Xieyou 9308" (Xieqingzao A/T9308) has been regarded as a super-high-yielding rice variety, of which the yield potential reached as high as 12 t/ha. However, its high shattering characteristic (as high as 60%) has limited its wider application. In the current experiment, a non-shattering mutant line, M9308, was developed from T9308 by gamma irradiation. Comparisons were made but no marked differences were found between T9308 and M9308 as well as between their F1 hybrids crossed to Xieqingzao A for major agronomic and grain quality characters as well as resistance to diseases. Genetic analysis indicated that the non-shattering character of M9308 was governed by a single recessive gene.     

Phenotypic Expression of Whitebacked Planthopper Resistance in the Newly Established japonica ／ indica Doubled Haploid Rice Population

A new doubled haploid (DH) rice population was established from a cross between WBPH-resistant japonica Chunjiang 06 (C J-06) and susceptible indica TN1. Sucking inhibitory and ovicidal resistance of the DH rice lines were evaluated on the basis of non-preference response of WBPH immigrants and honeydew excretion by WBPH females, and appearance of watery lesions in the necrotic discoloration of leaf sheaths ovipositied by WBPH,respectively. Both the major gene resistance to WBPH, sucking inhibitory and ovicidal resistance, showed 1 (resistant): 1 (susceptible) segregation ratio in the DH population. Relative density of WBPH populations and damage scores in the DH population indicated combined functions of both the major resistance genes as well as QTLs affecting the host plant response to WBPH infestations. Thus, the newly developed CJ-06/-I-N1 DH population could be a useful material to analyze major genes and QTLs for WBPH resistance in japonica rice.     

Quantitative Trait Locus Analysis for Rice Yield Traits under Two Nitrogen Levels

A recombinant inbred line population derived from a super hybrid rice Xieyou 9308(Xieqingzao B/Zhonghui 9308) and its genetic linkage map were used to detect quantitative trait loci(QTLs) for rice yield traits under the low and normal nitrogen(N) levels. A total of 52 QTLs for yield traits distributed in 27 regions on 9 chromosomes were detected, with each QTL explaining 4.93%–26.73% of the phenotypic variation. Eleven QTLs were simultaneously detected under the two levels, and 30 different QTLs were detected under the two N levels, thereby suggesting that the genetic bases controlling rice growth under the low and normal N levels were different. QTLs for number of panicles per plant, number of spikelets per panicle, number of filled grains per panicle, and grain density per panicle under the two N levels were detected in the RM135–RM168 interval on chromosome 3. QTLs for number of spikelets per panicle and number of filled grains per panicle under the two N levels, as well as number of panicles per plant and grain density per panicle, under the low N level, were detected in the RM5556–RM310 interval on chromosome 8. The above described QTLs shared similar regions with previously reported QTLs for rice N recycling.     

Detection of Sensitivity and Resistance Variation of Magnaporthe grisea to Kitazin P,Carbendazim and Tricyclazole

One hundred and twenty-nine isolates of Magnaporthe grisea from Guangdong, Guangxi, Anhui and Jiangsu provinces of China were tested for resistance frequency to kitazin P and carbendazim, respectively by the distinctive concentration method. The resistance frequency of the isolates to kitazin P which had not been used in practice for about ten years was as high as 79.1%, and only one carbendazim-resistant isolate was detected in Gaoyao, Guangdong Province (with a frequency of 0.78%). Meanwhile, the minimum inhibition concentration (MIC) of hyphal melanization was adopted to detect the sensitivity of M. grisea to tricyclazole. There existed several different degrees of sensitivity to tricyclazole in the melanin biosynthesis of M. grisea, but no relationship was found between these MIC values completely inhibiting melanization in hyphae and the EC50 values of tricyclazole against rice blast tested in vivo. After the isolates were induced by chemical taming or UV irradiation in laboratory, kitazin P-resistant and carbendazim-resistant mutants were recovered by both the methods, but none of tricyclazole-resistant mutant was obtained.     

QTL analysis of leaf photosynthetic rate and related physiological traits in rice(Oryza sativa L.)

Photosynthesis is one of the most important factors that influence the biomass and yield. Recently, more attention has been paid to genetic study on rice photosynthesis and rice breeding for the physiological traits related to high efficient photosynthesis. Chlorophyll content, stomatal resistance, and transpiration rate were very important physiological traits related to photosynthesis. But until now, no genetic study on these traits has been reported. A DH population derived from anther culture of ZYQ8/JX17, a typical indica/japonica hybrid was developed,     

K You 48-2 Developed by Rice and Sorghum Res Inst,Sichuan Acad of Agri Sci

K You 48-2 is a new combination of early hybrid rice with good grain quality and high yield, developed by combining male sterile line K-Qing A having japonica cytoplasm and indica genome and restorer line Ce 48-2. In the regional trial of Hubei Province in 1991, its yield was 4.4% higher than that of the CK Weiyou 48-2, being significant at 0.05 level. In the same year, in another regional trial of Sichuan Province, its yield was 8.9% higher than that of the CK Weiyou 48-2, being significant at 0.01 level. It has the highest yield among all tested varieties in both provincial trials. It has shown good grain quality with 60% head rice recovery and moderate resistance to rice blast.     

lsozyme analysis on progenes of somatic hybrids of Oryza sativa L.and O.officinalis

Some wild species of Oryza possess agronomically useful traits such as disease/insect resis tance and salt tolerance. However, the use of wild Oryza species for rice improvement has been hampered by the sexual incompatibility or sterility of hybrids obtained by conventional methods. We have used protoplast fusion as a method to incorporate useful trait of wild O ryza species into cultivated rice and obtained somatic hybrid plants between O.satlva and O.officinalis and their progenies. Isozyme analysis is a method to confirm somatic hybrids and to determine the nuclear constitution of somatic hybrids. The esterase and peroxidase isozyme analysis in progenies of somatic hybrids were herein reported. Two breeding lines PF52 and PF79 were F_2 lines developed form somatic hybrids of O.sativa L.cv. 02428 and O.officinalis accesion. O.sativa L.cv. 02428 and O.officinalis were used as control. Fresh leaves from plants growing in greenhouse were homogenized with extraction     

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

One of the most effective ways of enhancing rice yield is the utilization of the strong inter-subspecific hybrid heterosis between indica rice and japonica rice in replacement of inter-varietal hybrid heterosis being widely applied. Recently, great progress has been made to increase rice yield in several countries e.g. Japan, Korea, China etc [1]. For example, an indica-japonica hybrid rice combination ‘Xieyou 9308’, which was derived from an indica cytoplasmic male sterile line Xieqingzao…     

Estimating Out-Crossing Rate of Bg 379-2 Using Morphological Markers and Confirmation by Molecular Markers

Rice is largely self-fertilized and accordingly a field population of rice is completely composed of near homozygotes.Due to the emergence of off-types,homozygosity will be affected.With the time,this will cause the reduction of genetic purity in some rice varieties.One of the reasons has been suspected to be the high out-crossing frequencies of such varieties.Studies were conducted at the Rice Research and Development Institute,Batalagoda,Sri Lanka to estimate the out-crossing rate of Bg 379-2,a variety having the problem of maintaining genetic purity.Bg 379-2 was allowed to out-cross with Bg 450 and the number of out-crossed plants were counted using dominant morphological markers such as short-round grain and purple culm of pollen donor.A molecular confirmation of out-crossing was also performed using sequence tagged site(STS) molecular marker pTA248.The variety Bg 379-2 showed a potential out-crossing rate of 3.41% and an average out-crossing rate of 1.29% using dominant morphological markers.Polymorphism was clearly detected between parents and out-crossed plants as well as selfed plants of Bg 379-2 using their banding patterns.A similar study can be performed to determine the out-crossing rates of other varieties which show high percentage of off-types in the population for the better understanding of the breeding behavior of the varieties.     

Multi-Temporal Detection of Rice Phenological Stages Using Canopy Spectrum

Information on rice phenology is essential for yield estimation and crop management. To test the ability of remote sensing in detecting multiple phenological stages, paddy rice canopy spectrum was measured by a hand-held radiometer. Normalized difference vegetation index(NDVI) was calculated from spectrum, and the slope of NDVI was obtained as its difference. We evaluated the response of NDVI and its slope to rice growth with a comparison of two late-season rice cultivars. The results showed that NDVI and its slope curves had distinct variation corresponding to rice development and they could be used as cultivar-independent phenological indicators. The dates of flooding and transplanting, tillering, panicle development, heading and flowering, maturity, harvest stages, and even field management practices, could be deduced from these indicators. ‘NDVI ≤ 0' could be used as a single threshold for the detection of flooding and transplanting. The largest spike in the curve of the NDVI slope indicated the duration of tillering stage. The next spike corresponded to panicle development. The heading and flowering stage was characterized by the maximum NDVI and the change of NDVI slope from positive to negative. At the maturity stage, NDVI decreased continuously, and its slope fluctuated just below zero. When rice grains were completely mature and ready for harvest, NDVI decline was accelerated. At harvest, NDVI slope reached its minimum value. The distinction between heading and maturity stages was obscure, most likely due to NDVI saturation at high biomass. The study might provide references for paddy rice phenology determination through remote sensing images.     

Integrated Approach to Control False Smut in Hybrid Rice in Sichuan Province,China

Severe epidemic of false smut, caused by Ustilaginoidea virens(Cooke) Takahashi(teleomorph Villosiclava virens) has been reported in different parts of Asia and America. Different fungicides or bio-control agents against false smut were applied at different times before heading on a susceptible rice variety Pu-6. A control efficiency as high as 91.92% was resulted from spraying 2.5% Wenquning, a suspension of Bacillus subtilis in solution of validamycin with 4.5 L/hm2 at 6 d before heading. Among the 186 hybrid rice screened in 2010, low significant correlations between the dates of full heading, rates of infected plants and panicles as well as the number of infected florets were found, with the correlation coefficients ranging from 0.2331 to 0.5212. However, significant difference in susceptibility coefficients was also found between the varieties which had the same dates of full heading. In the plot experiments to compare the susceptibility in 2011, the average rates of infected panicles of Yixiangyou 2168, Chuanxiangyou 3, Dexiang 4103, Yixiangyou 2115, Nei5 you 317, Yangxinyou 1 were significantly lower than those of the control varieties Gangyou 725 and Gangyou 188 at the disease nursery located at Qionglai, Sichuan Province, China. When Neixiangyou 8156 and Nei5 you 317 were sprayed with 2.5% Wenquning at 4.5 L/hm2 for two times at 6 d before and 1 d after heading, respectively, the control efficiencies of Nei5 you 317 and Neixiangyou 8156 were respectively 100% and 82.24% compared to that of Gangyou 725. Satisfactory control effects had also obtained by single spray of 2.5% Wenquning at 4.5 L/hm2 at 5–6 d before heading. Therefore, less susceptible hybrid rice in combination with spraying Wenquning at 5–6 d before heading was suggested for the disease control in Sichuan Province, China.     

Development of Hybrid Rice Variety FY7206 with Blast Resistance Gene Pid3 and Cold Tolerance Gene Ctb1

Hybrid rice Fanyou 7206(FY7206), derived from the cross between a sterile line Fanyuan A and a restorer line Fuhui 7206, was bred by the Rice Research Institute, Fujian Academy of Agricultural Sciences, China. FY7206 was characterized by moderate blast resistance, cold tolerance, as well as wide adaptability, and high yields. The blast resistance results indicated that the frequencies of blast races in race B, race C and the total resistance frequency for FY7206 were 95.5%, 100.0% and 97.2%, respectively. The disease resistance results showed that the leaf blast grade for FY7206 was level 1 and panicle blast was level 5. The indoor spray results indicated that FY7206 was resistant to 11 isolates of Magnorpathe oryzae. The blast resistance of FY7206 might be derived from the high expression of blast resistance gene Pid3. The results for simulated cold resistance in an artificial climate chamber indicated that the cold tolerance for FY7206 was moderate at the booting and flowering stages. The cold tolerance results also indicated that FY7206 could be tolerant to temperatures as low as 10 °C at the seedling stage. The q RT-PCR results showed that the expression of cold tolerance gene Ctb1 in FY7206 was relatively high. These results suggested that FY7206 is a hybrid indica rice variety with good comprehensive characteristics, including blast resistance and cold tolerance.     

Identification for Heat Tolerance in Backcross Recombinant Lines and Screening of Backcross Introgression Lines with Heat Tolerance at Milky Stage in Rice

The present study aimed at breeding new rice germplasms with similar genome but significantly differed in heat tolerance during the grain filling stage.A total of 791 BC1F8 backcross recombinant lines,derived from the cross of Xieqingzao B /N22 //Xieqingzao B,were used as materials.Each rice line was separated evenly into two groups,and the heat tolerance of all rice lines were evaluated at natural high temperature in fields.The rice lines with heat tolerant index higher than 90% or lower than 40% were sele...     

Improvement of Resistance to Bacterial Blight by Marker-Assisted Selection in a Wide Compatibility Restorer Line of Hybrid Rice

4183 is a promising wide compatibility restorer line with good grain quality. Its hybrid rice Shuangyou 4183 (Shuangjiu A/ 4183) was registered in Anhui Province in 2003. However, the line and its hybrid rice are susceptible to bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo). R4183 carrying Xa21 was developed to improve bacterial blight resistance of 4183 through introducing the broad-spectrum resistance gene Xa21 by marker-aided selection. R4183 had similar level of bacterial blight resistance to IRBB21, the resistant donor, while maintained the wide compatibility, restoring ability and other good economic traits of the recurrent parent 4183. Critical issues on improvement of bacterial blight resistance of hybrid rice and breeding strategies were also discussed.     

Ⅱ-you 92:a new hybrid rice for late season

Ⅱ-you 92 is an indica hybrid rice that was developed by Jinhua Agri Res Inst, Zhejiang Province. Ⅱ-you 92 has a suitable growth duration of 122—125 d as double—cropping late season rice, 3—4 d shorter than that of Shanyou 64 and 6—7 d shorter than Shanyou 10. It has a compact plant type, high tillering ability and plant height of 85—90 cm. A number of 3.4—3.6 million effective panicles per ha can be reached. Besides, it has 120—125 grains per panicles, about 85% seed-setting rate and 25—26 g 1000-grain weight. The average yield of Ⅱ-you 92 is 7.5—8.0 t/ha, 10% higher than that of the check hybrid Shanyou 64. Ⅱ-you 92 is adaptable to fertile paddy field and resistant to lodging. It is also resistant to rice blast and WBPH. Because Ⅱ-you 92 has a larger stigma and a higher outcrossing rate which derived from its maternal parent Ⅱ-32A, a high yield of F_1 hybrid seed of 3.0-4.5 t/ha can be easily achieved, the cost of hybrid seed production is lower.     

Construction and Testing of a Primary Microsatellite Database of Major Rice Varieties in China

Sixty-three major inbred varieties and parental lines of major F1 hybrids used in the commercial rice production in China were assayed with rice microsatellites screened in a previous study and additional microsatellites on four chromosomes. A set of 24 markers was selected and proposed for its application in the variety identification of rice, which are distributed on all the 12 rice chromosomes with 2 markers on each chromosome. The 63 major varieties and parental lines, as well as 41 major F1 hybrids, were genotyped with the markers. Alleles detected in each line at each marker locus were verified. By matching marker genotypes of corresponding F1, maternal and paternal lines of hybrid rice, high reliability of the maternal lines was verified, data on the paternal lines were modified, and a false hybrid was removed. A database containing genotype data of 103 major rice varieties and parental lines at the 24 marker loci was constructed and analyzed.     

Cadmium Accumulation and Its Toxicity in Brittle Culm 1 （bcl）, a Fragile Rice Mutant

Cadmium （Cd） accumulation and toxicity in rice plants were characterized and identified by using brittle culm 1 （bcl）, a fragile rice mutant and its wild type （Shuangkezao, an indica rice） as materials by hydroponics. The low Cd level didn＇t obviously affect the growth parameters in both rice genotypes, but under high Cd levels （1.0 and 5.0 μmol/L）, the growth of both rice plants were substantially inhibited. Moreover, bcl tended to suffer more seriously from Cd toxicity than Shuangkezao. Cd accumulation in both rice plants increased with the increase of Cd levels. There was a significant difference in Cd accumulation between the two rice genotypes with constantly higher Cd concentration in bcl, which also accumulated more Cd at 0, 0.1, and 1.0 μmol/L Cd levels. The same case was found in the two rice plants grown on Cd-contaminated soil. This suggested that cell wall might play an important role in Cd accumulation in rice plants by the physiological mechanisms. The malondialdehyde （MDA） content, superoxide dismutase （SOD） and peroxidase （POD） activities in rice plants were affected differently under Cd treatments, and which implied that POD might play the main role in detoxifying active oxygen free radical. A significant difference in antioxidative system between the two rice genotypes was found with constantly higher MDA content, SOD and POD activities in bcl. In summary, bcl accumulated more Cd and appeared to be more sensitive to Cd stress compared with its wild type.     

Cadmium Accumulation and Its Toxicity in Brittle Culm 1(bc1),a Fragile Rice Mutant

Cadmium (Cd) accumulation and toxicity in rice plants were characterized and identified by using brittle culm 1 (bc1), a fragile rice mutant and its wild type (Shuangkezao, an indica rice) as materials by hydroponics. The low Cd level didn't obviously affect the growth parameters in both rice genotypes, but under high Cd levels (1.0 and 5.0 μmol/L), the growth of both rice plants were substantially inhibited. Moreover, bc1 tended to suffer more seriously from Cd toxicity than Shuangkezao. Cd accumulation in both rice plants increased with the increase of Cd levels. There was a significant difference in Cd accumulation between the two rice genotypes with constantly higher Cd concentration in bc1, which also accumulated more Cd at 0, 0.1, and 1.0 μmol/L Cd levels. The same case was found in the two rice plants grown on Cd-contaminated soil. This suggested that cell wall might play an important role in Cd accumulation in rice plants by the physiological mechanisms. The malondialdehyde (MDA) content, superoxide dismutase (SOD) and peroxidase (POD) activities in rice plants were affected differently under Cd treatments, and which implied that POD might play the main role in detoxifying active oxygen free radical. A significant difference in antioxidative system between the two rice genotypes was found with constantly higher MDA content, SOD and POD activities in bc1. In summary, bc1 accumulated more Cd and appeared to be more sensitive to Cd stress compared with its wild type.     

Characterization of Myanmar Paw San Hmwe Accessions Using Functional Genetic Markers

Paw San Hmwe(PSM) rice has been cultivated in many areas of Myanmar for a long time. Strong aroma,good taste and its elongation during cooking are the key characteristics of PSM rice. Thirty-one PSM accessions were genotypically characterized,and their physical grain and cooking quality traits were studied. We used specific gene markers associated with aroma,apparent amylose content(AAC) and alkali spreading value to determine the alleles carried by different PSM accessions. The results revealed that six PSM accessions(PSM10,PSM12,PSM13,PSM21,PSM22 and PSM30) had a 3-bp insertion in Os2 AP gene. Gel consistency(GC) allele was predominant among the PSM accessions for gelatinization temperature(GT),however,the phenotype observed was between low and intermediate GT because of the combination of the GC allele with the presence of low GT allele at heterozygous state from the other loci of the SSIIa gene. Intermediate to high AAC was observed among the PSM accessions corresponding to the haplotype identified for the single nucleotide polymorphism G/T and the(CT)n repeat in the Wx gene. The characterization and grouping data of PSM accessions posted benefits to Myanmar seed banks,and our results will help in maintaining the integrity of PSM rice variety.     

Difference of Phytic Acid Content and its Relation to Four Protein Composition Contents in Grains of Twenty-nine japonica Rice Varieties from Jiangsu and Zhejiang Provinces, China

Twenty-nine japonica rice varieties collected from Jiangsu and Zhejiang Provinces, China were planted in Hangzhou, China, to investigate the phytic acid content in brown rice and its frequency distribution as well as the correlation among the contents of phytic acid, total protein and four protein compositions in brown rice. The phytic acid content in brown rice ranged from 0.699% to 1.034%, with a mean of 0.868% for the 29 tested rice varieties. Xiushui series rice varieties generally exhibited lower phytic acid level than Wuyujing and Huai series rice varieties. A rough normal distribution, with a mean of 8.722%, was observed for the total protein contents in the tested varieties. Of the four protein compositions, the glutelin, globulin and albumin contents had larger coefficient of variation than the prolamin content, although the difference in prolamin content was genotype-dependent. No significant correlation was found between the phytic acid and four protein composition contents, whereas the total protein content was significantly and positively related to the glutelin content in brown rice.