Genetic Polymorphism of Wx Gene and Its Correlation with Main Grain Quality Characteristics in Rice

The allelic variation of the Wx gene in 50 non-glutinous rice varieties （lines） was analyzed by using the microsatellite marker RM190 [for （CT）n simple sequence repeat （SSR）] and cleaved amplified polymorphic sequence（CAPS） marker 484/W2R-ACCⅠ[for G/T single nucleotide polymorphism （SNP）]. Six homozygous （CT）n types, namely （CT）20, （CT）19, （CT）18, （CT）17, （CT）16, （CT）14, （CT）11 and （CT）10, and a heterozygous genotype （CT）11/（CT）18 were detected for RM190, of which （CT）11 and （CT）18 were predominant. Two homozygous Wx genotypes （G/G and T/T） and one heterozygous （G/T） were detected using 484/W2R-ACC Ⅰ. Most of the materials with a RM190 of （CT）11 were G/G for SNP of 484/W2R-ACC Ⅰ, while T/T for SNP was predominantly appeared in materials with （CT）18. The materials tested could be grouped into 10 categories using the two markers together. Results indicated that 59.3% variance of amylose content was attributed to the polymorphism of Wx gene revealed by RM190, while 56.1% and 24.6% of the variances in amylose content and gel consistency were respectively to the polymorphism of Wx gene revealed by 484/W2R-ACC Ⅰ. Furthermore, with both SSR and CAPS markers, 72.4% of the variance in amylose content could be explained. In addition, the application prospects of the two markers in breeding were also discussed.

Genetic Analysis and Gene Mapping of Multi-tiller and Dwarf Mutant d63 in Rice

A spontaneous mutation, tentatively named d63, was derived from the twin-seedling progenies of rice crossed by diploid SARIII and Minghui 63. Compared with wild-type plants, the d63 mutant showed multiple abnormal phenotypes, such as dwarfism, more tillers, smaller flag leaf and reduced seed-setting rate and 1000-grain weight. In this study, two F2 populations were developed by crossing between d63 and Nipponbare, d63 and 93-11. Genetic analysis indicated that d63 was controlled by a single recessive gene, which was located on the short arm of chromosome 8, within the genetic distance of 0.40 cM from RM22195. Hence, D63 might be a new gene as there are no dwarf genes reported on the short arm of chromosome 8.

Characterization and Genetic Analysis of a Novel Mutant mst of Rice Defective in Flower Development

A spontaneous mutant with multiple stigmas （msf） was found in an indica rice line 466. The mst mutant exhibits normal at the vegetative development stage and produces normal inflorescence structures. The difference between the mutant and the wild type was observed when the stamen primordium began to develop. In the mst florets, palea and lemma opened, Iodicules were homeotically transformed into palea/lemma-like structures, and stamens were homeotically transformed into carpel-like structures. It looked like multiple stigmas being full of the whole floret. The phenotypic changes of rest were very similar to that of B-like mutant spwl. Compared with other mutants with pistillate morphologies, the severe mstflorets showed that the inner three floral organs were completely changed into palea/lemma-like structures. Moreover, the mutant was female sterile. Occasionally, with the changing environment, one or two stamens were fertile. Genetic analysis indicated that the mutant traits were controlled by a single recessive gene.

Special DNA Methylated Sites Between Haploid of Twin-Seedling and Its Hybrids in Rice(Oryza sativa)

DNA methylation is one of the epigenetic phenomena which can be transferred to the offspring by cell division in the evolution of organisms. The epigenetic regulation accompanied by gene expression can be found directly in the phenotype of haploidy plants. DNA cytosine methylation at the 5＇-CpCpGpG sites of haploid, Shuhui 527, Shuhui 363 and their hybrids was analyzed by methylation sensitive amplification polymorphism （MSAP） method. There were 765 DNA methylated sites detected and the methylation level was lower in hybrids than parents. Meanwhile, the different bands between hybrids and parents were analyzed and two types of methylated sites were detected, of which one inherited from haploid, and the other did not. The biological functions of genes related to methylated sites involved in cell structure, metabolize and response factor. Therefore, DNA methylated modifications can activate and silence the genes and play an important role in plant growth, development and evolution.

Analysis of Chloroplast Ultrastructure,Photosystem Ⅱ Light Harvesting Complexes and Chlorophyll Synthesis in a Chlorophyll-Less Rice Mutant W2555

A comparative study on chloroplast ultrastructure and light harvesting complex of photosystem Ⅱ （LHC Ⅱ） was conducted between a new rice mutant （W2555） and its wild type （WT）. The chloroplasts of W2555 had less thylakoids and grana stacks compared with the wild type. There was no significant change in the composition of LHC Ⅱ polypeptide in W2555, while a decline had been noted in LHC Ⅱ content. Northern blot analysis with a specific cab gene probe showed no appreciable difference in the LHC Ⅱ mRNA level between the W2555and its wild type. The precursors of chlorophyll synthesis, 6-aminolevulinic acid （ALA） and porphobilinogen （PBG） were over accumulated in W2555, but the other precursors were all decreased. These results indicated that the decreased level of LHC Ⅱ in the mutant W2555 was attributed to the change of cab gene transcription, but a blockage in chlorophyll biosynthesis due to the formation of uroporphyrinogen Ⅲ （Urogen Ⅲ）.

Yield Stability of Maize Hybrids Evaluated in Maize Regional Trials in Southwestern China Using Nonparametric Methods

Analysis of multi-environment trials （METs） of crops for the evaluation and recommendation of varieties is an important issue in plant breeding research. Evaluating on the both stability of performance and high yield is essential in MET analyses. The objective of the present investigation was to compare 11 nonparametric stability statistics and apply nonparametric tests for genotype-by-environment interaction （GEI） to 14 maize （Zea mays L.） genotypes grown at 25 locations in southwestern China during 2005. Results of nonparametric tests of GEl and a combined ANOVA across locations showed that both crossover and noncrossover GEI, and genotypes varied highly significantly for yield. The results of principal component analysis, correlation analysis of nonparametric statistics, and yield indicated the nonparametric statistics grouped as four distinct classes that corresponded to different agronomic and biological concepts of stability. Furthermore, high values of TOP and low values of rank-sum were associated with high mean yield, but the other nonparametric statistics were not positively correlated with mean yield. Therefore, only rank-sum and TOP methods would be useful for simultaneously selection for high yield and stability. These two statistics recommended JY686 and HX168 as desirable and ND108, CM12, CN36, and NK6661 as undesirable genotypes.

waxy Locus and Its Mutant Types in Maize Zea mays L.

The waxy （wx） locus of Zea mays L. encodes a granule-bound starch synthase （GBSS I = waxy protein） required for the synthesis of amylose in endosperm and pollen grain. This review covers recent advances in understanding the waxy locus in maize, focusing particularly on the new information on mutant type and mutation mechanisms. The results showed that the insertion and deletion played an important role in the generation of spontaneous wx-mutations. The current status of utilizing waxy locus has been summarized and the perspectives of the further studies on this locus have also been proposed.

Identification of a Herbicide Safener AD-67 Inducible cDNA in Rice

A herbicide safener AD-67 inducible cDNA was identified in an indica rice variety 9311 by mRNA differential display. The transcript was increased 6 h after sprayed with the safener solution, and 4 days later, the expression still could be detected. The fragment was recycled from the polygel and sequenced, and homologous analysis revealed the cDNA was 100% identical to some ESTs and cDNAs in rice database, and the amino acid sequence was 60-84% homologous to those of the Yippee genes in several eukaryotes. The fragment was extended to the whole long cDNA, and thus a primer pair was designed. RT-PCR analysis for the designed primer supported the induction result.

Photosynthetic Characteristics and Heterosis in Transgenic Hybrid Rice with Maize Phosphoenolpyruvate Carboxylase (pepc) Gene

Three F3 hybrids derived from the sterile rice lines Gang 46A, 776A and 2480A and the improved restorer line Shuhui 881 containing maize phosphoenolpyruvate carboxylase （pepc） gene were used to analyze the effect of pepc gene on the heterosis and photosynthetic characteristics, while the F3 obtained by crossing Shuhui 881 with the above three sterile lines served as controls. The dynamics of photosynthetic characteristics in leaves of three F1 with pepc gene and their controls were determined at the initial-tillering, maxium-tillering, elongation, initial-heading, heading, maturity stages, and other different times after flag leaf fully expanded. The PEPCase activities of the three F1 with pepc gene increased significantly as compared with control plants during the whole developmental stages. Moreover, the net photosynthesis rate （Pn） also increased to certain extent. The data showed that PEPCase activity was significantly correlated to Pn with a correlation coefficient of 0.6081. The photosynthetic indexes of the three F1 with pepc gene were obviously superior to respective controls in apparent quantum efficiency, light compensation point and carboxylation efficiency, while the CO2 compensation point was lower than that of corresponding control. The Pn of the three F1 with pepc gene at light saturation point and CO2 saturation point was also higher than that of control plants. in addition, the three F1 with pepc gene had an average increase of 37.10% in grain yields per plant in comparison with control plants. The results indicated that the photosynthetic characteristics of hybrid rice containing pepc gene had been improved to some extent due to the introduction of pepc gene.

Characteristics of Rice Plant with Heavy Panicle

Using 15 indica rice varieties with different panicle weight, some ideal plant type characteristics in heavy panicle type of hybrid rice （HPT） and their relation to yield and its components were studied. Results showed that the leaf area index （LAI） of the HPT varieties was lower than that of medium panicle type （MPT） and light panicle type （LPT） varieties, but its decreasing rate of LAI and efficient LAI after heading was slower and had much higher percentage of efficient LAI, specific leaf weight, and ratio of grain to leaf area （cm^2） in comparison with the MPT and the LPT varieties. The length, width, thickness, and area of top three leaves of the HPT varieties were significantly larger than those of the MPT and the LPT varieties, and these components of top three leaves were significantly and positively correlated with the number of spikelets and filled grains, grain weight per panicle, and grain yield. The flag leaf in HPT varieties was erect with sorrow leaf angle, and their leaf angle of 2nd and 3rd leaf from top increased in sequence. The plant height of the HPT varieties was higher than that of the MPT and the LPT varieties, and their leaf site of top three leaves also increased in sequence. Therefore, HPT varieties as an ideal plant type could increase the utilization efficiency of sunlight energy. The ideal plant type characteristics and their adjuncts for the HPT varieties are proposed in this article.

Patterns of DNA cytosine methylation between haploids and corresponding diploids in rice

Eighteen pairs of diploid-haploid twin-seedlings were identified and screened out fromspecial rice SARII-628 population. Five pairs of themwere selected and randomly designated as A, B, C, Dand E. Simple sequence repeats (SSR) analysisshowed that there was no difference among 310 siteswhich indicated that there was no base mutation onDNA primary structure. DNA methylation plays animportant role in gene expression regulation duringgrowth and development stages in eukaryotes. Amodified AFLP technique (methylation-sensitiveAFLP, MSAP) was employed to detect the DNA me-thylation patterns in the 5′-CCGG sites of the fivepairs of twin-seedlings. Although no methylationmutation was detected among the five diploids,forty-three methylation mutation sites were foundfrom the corresponding haploids. The MSAP ratios,which were the ratios of MSAP sites to the total am-plified sites, in five haploids were 18.79%, 19.35%,18.49%, 18.45% and 18.75%, respectively. And cor-responding full methylation levels (5′-CmCGG indouble strands) of those haploids were 10.58%,11.3%, 10.11%, 10.09% and 10.34%, respectively.Both MSAP and full methylation levels in the fivehaploids were higher than that of their correspondingdiploids, which suggested that hypermethylation oc-curred in some 5′-CCGG sites. Five types of MASPpatterns among the five pairs of twin-seedlings weredetected as follows: (1) no changes, methylation lev-els were the same in both haploids and diploids; (2) demethylation, diploid was methylated but no me-thylation in the same site in haploid; (3) hypermethy-lation, the methylation level in haploid was higher than those in diploid; (4) hypomethylation, methyla-tion in haploid was lower than those in diploid; (5) undecided pattern, change trend of methylation lev-els in haploids was not decided. The bands of 18 sites were reclaimed, then sequenced and searched on website to determine the sites of those sequences on rice chromosomes. The result showed that the methylation mutation involved the whole rice genome and 12 pairs of chromosomes. The mutation was site-related and there were different mutation sites for different haploids. Compared to diploids, the higher methylation level in haploids might be a readjusting reaction to the decrease in ploidy for the sake of sur-vival.

Source-Sink Relationship in Intersubspecific Hybrid Rice

Three indica restorer lines （Mianhui 725, Shuhui 527, Shuhui 881）, an American rice variety Lemont and a javanica rice variety Xiangdali were crossed with japonica Kitaake, and five F1 hybrids were obtained to study the photosynthetic and agronomic traits. The data on photosynthetic characteristics indicated that the net photosynthetic rate （Pn） of the five F1 hybrids was significantly higher than that of their parents （or one of them） under high photosynthetic flux density （PFD）; while the overall performance of hybrids was better than their respective parents in apparent quantum yield （AQY）, carboxylation efficiency （CE） and CO2 compensation point （CCP）. Moreover, the photosynthetic performance of the five F1 were different due to the variation in heredity and the typical indica-japonica hybrids, Mianhui 725/Kitaake and Shuhui 527/Kitaake, were better than the others on this aspect. The agronomic traits revealed that the five F1 exhibited different heterosis, with Shuhui 881/Kitaake the largest sink followed by Mianhui 725/Kitaake, Shuhui 527/Kitaake, Lemont/Kitaake and Xiangdali/Kitaake. The production potential of indica-japonica hybrids was higher than that of the other two hybrids, which was consistent with the performance of Pn. However, the superior trait of indica-japonica hybrids on sink size has not been fully turned into high yield because of abnormal seed setting. Therefore, attention should be paid to the proper genome coordination and appropriate genetic distance so as to achieve super high yielding.

The microarray analysis for gene expression in haploids and diploids derived from twin-seedling rice

In this study, microarray technique was employed to analyze the gene expression at the RNA level between haploids and corresponding diploids derived from a rice twin-seedling line SARII-628. Differ- ent degrees of expression variations were observed in the plant after haploidization. The main results are as follows: (1) after haploidization, the ratio of the sensitive loci was 2.47% of the total loci designed on chip. Those loci were randomly distributed on the 12 pairs of rice chromosomes and the activated loci were more than the silenced ones. (2) Gene clusters on chromosome were observed for 33 se- quences. (3) GoPipe function classification for 575 sensitive loci revealed an involvement in the bio- logical process, cell component and molecular function. (4) RT-PCR generally validated the result from microarray with a coincidence rate of 83.78%. And for the randomly-selected activated or silenced loci in chip analysis, the coincidence rate was up to 91.86%.