Construction of Mutant Population and Analysis of Dwarf Mutants in "6421"(Capsicum annuum L.)through EMS Mutagenesis

[Objective] The aim was to improve the genetic property of peppers, the mutant population of Capsicum annuum L cultivar ＂6421＂ was constructed. [Method] The seeds of ＂6421＂ were treated with 0.2% to 1.2% ethyl methane sulfonate to identified LD50, and then 10 000 LD^o of treated seeds were sowed to construct mutant population. The agronomic characters and genetic regularity of dwarf mutants in M4 generation were analyzed. [Result] Our results showed that GR and SSR were 45.2% and 40.2% respectively at 1.0% EMS, close to LD50, with GI （17.6） and seed Ⅵ （19.7） being half of that of control; 562 M4 mutants were identified in 2015, and the mutation could be characterized according 11 major categories and 32 subcategories; Simultaneously, we found that plant height, plant width, diameter of mainstem, length of main-stem, the number of main-stem nodes and branch of lines E29, E58, E142 and E312 were all significantly different from that of the control. The mutation of lines E29, E58 and E312 was all controlled by a single recessive gene. [Conclusionl The study first created a pepper mutant population, which provides not only the germplasm resources for further breeding but also direct and effective materials for genomic study of the pepper.

Characterization of dwarf mutants and molecular mapping of a dwarf locus in soybean

Plant height is one of the most important traits in soybean. The semi-dwarf soybean cultivars could improve the ability of lodging resistance to obtain higher yield. To broaden the dwarfism germplasm resources in soybean, 44 dwarf mutants were identified from a gamma rays mutagenized M-2 population. Two of these mutants, Gmdwf1（Glycine max dwarf 1） and Gmdwf2（Glycine max dwarf 2）, were investigated in this study. Genetic analysis showed that both mutants were inherited in a recessive manner and their mutated regions were delimited to a 2.610-Mb region on chromosome 1 by preliminary mapping. Further fine mapping study proved that the two mutants had a common deletion region of 1.552 Mb in the target region, which was located in a novel locus site without being reported previously. The dwarfism of Gmdwf1 could not be rescued by gibberellin（GA） and brassinolide（BR） treatments, which indicated that the biosynthesis of these hormones was not deficient in Gmdwf1.

Isolation and Characterization of Storage Protein Subunit-null-dwarf Mutants in Soybean(Glycine max(L.) Merr.)

Dwarfing is useful to reduce plant height,when breeding high-yielding and non-lodging crops.In this study,a set of natural storage protein subunit-null dwarf mutants of soybean was reported that showed strongly reduced plant stature and deficiency in various 7S and 11S subunits,designated as snd1 mutants.Under normal growth conditions,the snd1 mutants showed a severe dwarf phenotype,with plant height of about 25 cm.Compared with wild-type DN47,the mutant snd1 exhibited no obvious morphological differences at the early stage of development.All the snd1 mutants examined had fewer nodes and shorter than normal internodes;the leaves were similar in shape to normal parents,but were dark-green at the mature stage.The flower size was similar to DN47;however,the flowering period was shorter than in the wild-type.Significant variation was noted for protein content,oil content of the seeds and size of seeds(weight of 100 seeds)among 17 snd1 dwarf lines.Genetic analysis indicated that the dwarfism of snd1 was controlled by a single recessive gene.The snd1 dwarf mutant had markedly different dynamic levels of the endogenous hormones gibberellin(GA),brassinosteroid,indole-3-acetic acid and abscisic acid,at the seedling stage.Exogenous GA3 treatment led to recovery of the plant height phenotype of the snd1 mutant;GA3 at 0.1 mm had the largest effect on enhancing plant height.Using molecular markers,snd1 gene was approximately mapped in an interval of 603 kb between markers Satt166 and Satt561 on chromosome 19.Snd1 mutant provided valuable material for hypoallergenic soybean breeding and the snd1 gene might be a novel gene related to plant height in soybean.

Cloning and Expression of Gene Responsible for High-Tillering Dwarf Phenotype in Indica Rice Mutant gsor23

High-tillering dwarf mutant gsor23 was generated from an indica rice variety Indica9 radiatied by y-ray. Genetic analysis showed that this phenotype was controlled by one single recessive gene, which was mapped within a physical distance of 386 kb between two insertion-deletion （InDel） markers CI-WT2 and C1-WT4 on the long arm of chromosome 1. There is a known gene DIO within this region, the mutation of which causes high-tillering in rice. Sequence analysis of the DIO allele in gsor23 revealed that the base cytosine （C） at the 404th position in the coding region was deleted, which would cause frameshift mutation after the 134th amino acids. The mutation site and indica background of gsor23 were different from the previously reported japonica mutants d10-1 and d10-2. Therefore, gsor23 is a novel allelic mutant of D10 which encodes the carotenoid-cleaving dioxygenase 8 （CCD8）, a key enzyme involved in the biosynthesis of the new plant hormone strigolactones （SLs）. After treatment with GR24, a synthetic analogue of SLs, the high-tillering phenotype of gsor23 was restored to normal. Real-time RT-PCR analysis showed that D10 expression was high in roots, but low in leaves. Compared with the wild type Indica9, the expression of the SL biosynthesis gene DIO was upregulated, while genes likely involved in the SL signal transduction pathway such as D3 and D14 were down-regulated in the gsor23 mutant.

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 Expression Profiling of Genes Encoding the Gibberellin 3-oxidase in Dasypyrum villosum Dwarf Mutant

Gibberellin 3-oxidase catalyzes the conversion of inactive gibberellin(GA) species into GAs with biological activity and it is subjected to strict developmental controls in the life cycle of a plant. In this study, 33 gene sequences, encoding the gibberellin 3-oxidase(GA3ox) from Dasypyrum villosum and its dwarf mutant, were obtained. Each contained a 1 107 bp coding sequence(CDS) that encoded a putative protein containing 369 amino acids. The GA3ox protein showed 77% to 97% homology and shared the major conserved structural domains of GA3ox proteins with rice, sorghum bicolor, oat, barley, and wheat. Sequence alignment showed that there were 20 single nucleotide polymorphisms(SNPs) and 22 Insertion/deletions(In Dels) among these sequences, which could be divided into 2 haplotypes, haplotypes Ⅰ and Ⅱ. Haplotype Ⅰ was found in the wild type and was1 495 bp in length, and haplotype Ⅱ was found in the dwarf mutant and was 1 485 bp in length. The Q-PCR results showed that GA3ox was expressed in the leaves, roots, internodes, and stem nodes, and that there was a significant difference in the transcript level of the GA3ox between the wild type and dwarf mutant. The transcript levels of GA3ox in the leaves at the seedling stage, stem elongation stage and the heading stage, in the root and stem nodes at the stem elongation stage and in the internodes at the heading stage of the wild type, were significantly higher than those in the dwarf mutant. However, GA3ox expression in the rest of the wild type tissues at the 3 stages was slightly higher than or not different from the dwarf mutant.The results suggested that the wild type and mutant allele sequences of GA3ox in D. villosum showed 2 amino acid changes in exons and variations in the lengths of introns or the SNPs in introns, which most probably impaired the function of the enzyme,affected the GA3ox expression level, and eventually gave rise to dwarfing.

Investigation on Agronomic Characters of Dwarf Mutant 778 in Broomcorn Millet(Panicum miliaceum L.)and Analysis of Its Sensitivity to GA

In order to investigate the differences between agronomic traits of dwarf mutant and original material 260 and whether the cause of dwarf is related to GA synthesis or signaling pathway,this experiment used dwarf mutant 778 and its original material 260 as experimental materials.Morphological observation and determination were performed for agronomic traits on plant height,ear length,internode length,internode number,seed length,seed width and number of seeds in different growth periods and different concentrations.The plants were treated by GA spraying,and the changes of plant height,root length,stem width,leaf length and leaf width were measured.The results are as follows:①The plant height of the dwarf mutant material was significantly different from that of the original high material,which was mainly caused by the difference between above-ground basal part and the length of the first and second elongation joints.②Comparing and analyzing the differences of traits between dwarf mutant material 778 and original high material 260,it was found that the plant height,ear length,internode number,grain number per ear and internode length of dwarf mutant 778 were significantly lower than that of high stalk 260(P<0.01),and the seed length of dwarf mutant 778 was significantly higher than that of high stalk 260(P<0.05).③Different concentrations of gibberellin(0,50,100,200 mg/L)had no significant effect on plant height and root length of dwarf mutant 778(P>0.05).Different concentrations of gibberellin had significant effects on plant height,root length and sensitivity coefficient of high stalk 260(P<0.05).And compared with the control group,all high materials 260 treated with different concentrations of gibberellin performed differently in plant morphology and growth potential.④Under the conditions of 100 and 200 mg/L GA,the difference of plant height between the dwarf mutant and the high stalk control decreased with time,and there was no difference at the end.There were no differences in sensitivity coefficient GRI between different concentrations of gibberellin treatment groups,indicating that the external gibberellin could restore the scorpion dwarf mutant to the original high stalk,and the gene that causes the mutation might be related with the gibberellin synthesis pathway.

Genetic Analysis of a Novel Dwarf Mutant,AISHENG98,from Upland Cotton

Cotton(Gossypium hirsutum L.) is the most important textile fiber and the second most important oil seed source in the world.To control excessive growth of cotton plant height,which may result in shading and lodging,farmers and researchers have used plant growth regulators that