Variation in Yield and Physicochemical Quality Traits among Mutants of Japonica Rice Cultivar Wuyujing 3

To select elite germplasms, 112 mutants derived from japonica rice cultivar Wuyujing 3 were evaluated. The yield components such as panicle number per square meter, grain number per panicle, and grain weight were measured. The quality traits such as percentage of chalky grains（PCG）, brown rice yield（BRY）, milled rice yield（MRY）, degree of milling（DM）, amylose content（AC）, protein content（PC）, and relationships among traits were inverstigated. Results showed that grain yield ranged from 2.15 to 12.49 t/hm2 with a mean of 6.4 t/hm2 and number of grains per square meter contributed for 94.64% in grain yield variation. For quality traits, all rice mutants had short size（grain length ≤ 5.5 mm） and bold shape（grain length to width ratio = 1.10-2.00）. Most of rice mutants（87.5%） had PCG values below 20%. All mutants had MRY values above 50%, AC values below 20%, and PC values below 10%. Percentage of chalky grains was significantly negatively correlated with MRY and positively correlated with DM. BRY and MRY were significantly negatively correlated with DM. PC was significantly and positively correlated with MRY and negatively correlated with DM, while AC had no significant correlation with these quality traits. It was concluded that there were 25 rice mutants which fulfilled the major requirements of Jiangsu standard japonica rice such as low percentage of chalky grains, low amylose content, optimal protein content, and which could be used as elite germplasms. Thus the mutants identified may lead to significant progress in improvement of rice quality.

MT 10 Mutant of Rice with Altered Lateral Root Initiation

Mutants with increased resistance to toxic anxin concentrations were first isolated in rice.The present report describes their isolation,genetics and physiological characterization.

Photosynthetic Characteristics of Flag Leaves in Rice White Stripe Mutant 6001 During Senescence Process

Physiological, biochemical and electron microscopy analyses were used to investigate the photosynthetic performance of flag leaves in rice white stripe mutant 6001 during the senescence process. Results showed that the chlorophyll content at the heading and milk-ripe stages in rice mutant 6001 were about 34.78% and 3.00% less than those in wild type 6028, respectively. However, the chlorophyll content at the fully-ripe stage in rice mutant 6001 was higher than that in wild type 6028. At the heading stage, the net photosynthetic rate （Pn） in rice mutant 6001 was lower than that in wild type 6028. Rice mutant 6001 also exhibited a significantly slower decrease rate of Pn than wild type 6028 during the senescence progress, especially at the later stage. Furthermore, Ca2^-ATPase, Mg~^-ATPase and photophosphorylation activities exhibited the similar trends as the Po. During the senescence process, the 68 kDa polypeptide concentrations in the thylakoid membrane proteins exhibited a significant change, which was one of the critical factors that contributed to the observed change in photosynthesis. We also observed that the chloroplasts of rice mutant 6001 exhibited higher integrity than those of wild type 6028, and the chloroplast membrane of rice mutant 6001 disintegrated more slow during the senescence process. In general, rice mutant 6001 had a relatively slower senescence rate than wild type 6028, and exhibited anti-senescence properties.

Study of Genetics and Embryology of Polyembryonic Mutant of Autotetraploid Rice Induced by N^+ Beam Implantation

In the present study autotetraploid rice IR36-4X was treated by an ion implantation technique with nitrogen ion beams. A polyembryonic mutant （named IR36-Shuang） was identified in the M2 generation. The mutant line and its offspring were systematically investigated in regard to their major agronomic properties and the rate of polyembryonic seedling in the M3-M6 generation. The abnormal phenomena in the embryo sac development and the cytological mechanism of the initiation of additional embryo in IR36-Shuang were observed by Laser Scanning Confocal Microscopy. The results were as follows. 1） The plant height, the panicle length and 1000 grain weight of IRB6-Shuang were lower than that of its control by 35.41%, 5.08% and 15.72% respectively, Moreover, the setting percentage decreased 12.39% compared with that in normal IRB6-4X plants. 2） The polyembryonic trait of IRB6-Shuang was genetically stable and the frequency of the polyembryonic seedlings in the IR36-Shuang line was also relatively stable. 3） The rate of abnormal embryo sacs in IR36-Shuang was significantly higher than that in the control IR36-4X. 4） The additional embryo in IR36-Shuang might arise from the double Jet of embryo sacs in a single owry, antipodal cells or endosperm cells. These results suggest that IRB6-Shuang is a polyembryonic mutant and a new apomixis rice line induced by low energy ion implantation. The prospects for the application in production of the IR36-Shuang line are also discussed. The present study may provide a basis for future investigations of apomixis rice breeding via the ion implantation biotechnology.

A dominant semi-dwarf mutant in rice

In the winter of 1997, a semi-dwarf mutant was found inthe F6 population of M9056/ R8018 xuan in HainanProvince. In the spring of 1998, the seeds were sown inHefei, Anhui Province and the plant height of the popula-tion was measured at maturity. Results showed that29. 4% of the plants had the same height as the high par-ent had, and 70. 6% remained semi-dwarf. In the winterof 1998, the reciprocal crosses between the remained se-mi-dwarf line and the two wild-type parental lines were

Construction and modification of chloroplast ultrastructure of a special albino rice mutant W25 during the seedling greenish process

W25 was a gamma-irradiation induced albinorice mutant line, which only expressed in thespecial temperatures (see figure). At 30 Cand 35 C, the seedling leaves of W25 showedgreenish or normal green, but they exhibitedalbino at 25℃, which could be greenish afterthe fourth leaf extension and recovered to be

Changes of carbohydrate and protein metabolism in seedling leaves of a temperature-induced greenable albino mutant line W25 of rice

W25 is a low-temperature-sensitive albino mu-tant line. Temperature not only controls thealbino phenotype expression of W25, but alsodetermines whether it could survive. When thetemperature is lower than 25℃, the leaves ofW25 shows complete albino, but they exhibitsnormal green when temperature is higher than30℃. Meanwhile, at 25℃, it can be greenable

Analysis of variation in temperature-responsive leaf color mutant lines induced from Gamma irradiation in rice(Oryza sativa L.)

Eight lines of temperature-responsive leaf colormutants induced by applying 300 Gy Gamma-ray irradiation to Thermo-sensitive genic malesterile line 2177s,were obtained through con-tinuous selection in seven generations..Theleaves of these lines started to become greenafter the fourth leaf extension,and except

Characterization and cloning of SMALL GRAIN 4, a novel DWARF11 allele that affects brassinosteroid biosynthesis in rice

Brassinosteroids （BRs） are important hormones that regulate plant development and physiology. Substantial progresses have been made in BR-related studies, and especially an increasing number of new genes involved in BR biosynthesis have been identified. Here, we characterize a BR-related rice mutant, small grain 4 （sg4）, obtained from callus culture of japonica cultivar Nipponbare. This mutant showed multiple phenotypes such as dark green, rugose erect leaves and small round grains. It was higher than the wild type, different from the majority of BR- and gibberellin-related mutants. Genetic analysis showed that the mutant phenotypes are controlled by a single recessive locus. The gene was fine-mapped to a 90.7-kb interval with 1,100 F2 recessive individuals by means of map-basedcloning. Totally 11 open reading frames were found in this interval, only one of which was detected with an 8-bp in- sertion in the 5rUTR region by sequencing. Functional complementation test revealed that a DWARFll allele, LOC_OsO4g39430, is answer for the mutant phenotype of sg4. Tissue-specific response to BR and decreased expression levels of BR biosynthetic genes suggest that sg4 is a weak BR-deficient mutant. These results are beneficial to understanding the physiological action of sg4 in a more comprehensive way.

Characterization and Molecular Mapping of a New Virescent Mutant in Rice

Plant leaves play a significant role in photosynthesis. Normal chloroplast development is critical for plant growth and yield performance. Defect of the chlorophyll in chloroplasts may cause abnormal leaf colors, such as yellow, white, or stripe. Chloroplasts have their own genomes encoding for about 100 genes that are essential for plastid protein synthesis and photosynthesis （Kanno and Hirai, 1993; Sato et al., 1999）. Moreover, over 3000 proteins encoded by plant nuclear genomes target to the chloroplasts and participate in the chloroplast development and/or photosynthesis. Hitherto, a number of plant genes, which encode for enzymes involved in chlorophyll biosynthetic pathways,

Characterization and Fine Mapping of a Novel Vegetative Senescence Lethal Mutant Locus in Rice

Mutants showing spontaneous cell death in the absence of pathogen attack are called lesion mimic mutants （lmm） （Lorrain et al., 2003）. These mutants usually exhibit typical hypersensitive responses （HRs） within or around the lesion spots, which are frequently observed in plants challenged with avirulent pathogens （Lorrain et al., 2003）. A number of these mutants have been characterized in rice （Zeng et al., 2004）, Arabidopsis （Guo et al., 2013）, maize （Wang et al., 2013） and barley （Persson et al., 2008）. Most lmm show enhanced resistance to various pathogens （Huang et al., 2011）, because HR is usually accompanied with enhanced defense responses, such as reactive oxygen species （ROS） activation （Qiao et al., 2010） and increased expression of pathogenesis-related genes （Lorrain et al., 2003）. Additionally, most lmm exhibit defects in growth and development due to the disordered physiolog- ical and molecular processes caused by the lesion spots. Thus, lmm are powerful tools for the study of the molecular mech- anisms of cell death, plant development and disease resistance （Lorrain et al., 2003; Babu et al., 2011）.