M1 Plants Research Articles

A Series of Novel rps2 Alleles Disrupt the RPS2-avrRpt2 Gene-for-gene Interaction

The Arabidopsis resistance (R) RPS2 gene confers resistance to Pseudomonas syringae (P. syringae) strains that express the avirulence (avr) avrRpt2 gene [Kunkel et al., 1993]. When Arabidopsis plants containing RPS2 are challenged with P. syringae bacteria carrying avrRpt2, the plants activate disease resistance responses, including a specialized type of programmed cell death known as the hypersensitive response (HR) [Kunkel et al., 1993; Hammond-Kosack and Jones, 1997]. The interaction between RPS2 and avrRpt2 products leads to an excellent model for pathogen-induced resistance responses and signal transduction events. As a typical resistance protein of the nucleotide-binding site-leucine-rich repeat (NBS-LRR) class, the RPS2 protein, consisting of 909 amino acids, contains several possible functional peptide motifs, including an Nterminal hydrophobic region, a putative leucine zipper (LZ), a NBS and a LRR (Fig. 1A) [Hammond-Kosack and Jones, 1997]. Additional motifs found in NBS-LRR resistance genes, such as GLPL and KMH motifs, are present in the RPS2 sequence [Traut, 1994]. The LZ and LRR domains have been implicated in regards to proteinprotein interactions (Alber, 1992; Kobe and Deisenhofer, 1994). The conserved central NBS domain is hypothesized to bind either to ATP or GTP involving kinase activities, containing 3 motifs: the P loop (or kninase-1a), kinase-2 and less conserved kinase-3a [Traut, 1994]. These structural features regarding the RPS2 protein suggest that it is involved in signal transduction processes for disease resistance responses. For studies of the molecular function of RPS2 and signaling by RPS2-avrRpt2 interaction, about 20 mutants including rps2-101C have so far been isolated [Kunkel et al., 1993; Mindrinos et al., 1994; Axtell et al., 2001]. In order to study on the spatial structure and function of RPS2, we tried to isolate numerous additional mutants, defective in RPS2-avrRpt2 dependent cell death, by using Axtell et al. [2001]’s method with minor modifications. Transgenic Col-0 Arabidopsis seeds, possessing a dexamethasone-inducible avrRpt2 transgene (pTA7001avrRpt2) [McNellis et al., 1998], were obtained from Dr. Brian J. Staskawicz (University of California, Berkeley, CA), and then mutagenized with 0.1% ethyl methane sulfonate (Sigma, St. Louis, MO). M2 plants based on the self-fertilization of M1 seeds were grown on soil. When dexamethasone (30 μM) was sprayed onto 2-week-old M2 plants, almost were yellowish in color, had aborted growth rates and eventually died a few days later (Fig. 1B). To identify the presence of the avrRpt2 transgene in the surviving plants, genomic DNAs were isolated from leaves, then the polymerase chain reaction (PCR) was performed by using two specific primers (data not shown). The upstream and downstream sequences were 5'-ATGAAAATTGCTCCAGTTGCCAT-3' and 5'-TTAG CGGTAGAGCATTGCGTGT-3', respectively. Twenty-six mutants out of the surviving plants were screened by PCR. Some mutations were expected to eliminate expression of the avrRpt2 transgene due to mutations in the dexamethasone-inducible expression system (pTA7001 expression cassette). To test this possibility, we performed a Northern blot analysis (Fig. 1C). Total RNA was isolated from leaves taken 1 day after application of dexamethasone. The accumulation of avrRpt2 transcripts was detected in 7 out of 26 mutants as well as rps2-101C as a positive control line. To examine whether 7 mutants showed the ability to mount an HR in response to avrRpt2, we performed a secondary screening procedure by inoculating mutant leaves with the P. syringae pv. maculicola strain DG6 (carrying avrRpt2) at OD600=0.1 [Guttman and Greenberg, 2001]. The typical resistance response to this interaction *Corresponding author Phone: +82-53-950-7753; Fax: +82-53-958-6880 E-mail: jtsong68@knu.ac.kr

Production of a fully waxy line and analysis ofwaxygenes in the allohexaploid crop, Japanese barnyard millet

With 4 figures and 2 tables Abstract Foxtail millet, common millet and Japanese barnyard millet have traditionally been important food sources in East Asian countries. Although waxy types of foxtail and common millet have been identified, a waxy mutant of the allohexaploid crop Japanese barnyard millet has not yet been reported. However, several Japanese landraces have been identified that have approximately half the level of amylose found in other varieties. We employed one of the low amylose landraces, `Noge-Hie', to produce waxy Japanese barnyard millet using a γ-radiation treatment. The seeds from a single M2 plant stained red-brown with iodine solution, indicating the starch in the seeds lacked amylose. Colorimetric tests indicated that amylose was not present in endosperm tissue of the mutant, and analysis of starch granule bound proteins showed that waxy (Wx) protein was absent from the starch granules. The waxy trait was stably inherited in subsequent generations. Additionally, a PCR-based analysis demonstrated the presence of three separate waxy genes in the millet, and indicated that the low amylose landraces carry a deletion in one of these three genes.

Genetic analysis of a novel aurea mutant in wheat

A novel spontaneous chlorina mutation of wheat (Triticum aestivum L.) was found in 2000. Three types of phenotypes, i.e., green plant, intermediate yellow-green plants (or chlorina), and yellow plant (aurea), were observed in the selfed progenies of the mutant. The aurea plants usually died before heading stage, and the intermediate plants were viable but less vigorous and developed later than the green plant. The mutant wheat was analyzed genetically after self-pollination and crossing with normal green plants. Selfing the M1 plant (chlorina) results in 1:2:1 segregation ratio of aurea:chlorina:green plants. The progenies of M1 green plants were all green. The test cross between a chlorina plant and a normal plant (as male or female) gave a 1 normal green: l yellow-green segregation ratio. The result can be explained on the assumption that the aurea is homozygous for au and the chlorina heterozygous for Au. Based on these findings, this mutant is controlled by a partial dominant nucleus gene. The genotypes of aurea, chlorina, and normal plants are au/au, Au/au, and Au/Au, respectively.

INDUCED MUTAGENESIS AND NATURAL GENETIC VARIATION IN TOMATO 'MICRO-TOM'

INDUCED MUTAGENESIS AND NATURAL GENETIC VARIATION IN TOMATO 'MICRO-TOM'

A Modified TILLING Method for Wheat Breeding

The large genome and polyploidy of wheat (Triticum aestivum L.) makes it difficult to identify desirable genetic changes based on phenotypic screening due to gene redundancy. Forward genetics is, therefore, more difficult in wheat than in diploid plants. A modified TILLING (Targeting Induced Local Lesions IN Genomes) method including the harvest of five heads per M1 plant, storage of M2 seeds, using unlabeled primers and agarose gels for mutation detection, and crossing of useful mutants for desired grain quality was explored in this report. A soft wheat cultivar, QAL2000, and a hard wheat cultivar, Ventura, were mutagenized with ethyl methanesulfonate (EMS). Screening of the waxy genes Wx‐A1 and Wx‐D1 in 2348 EMS‐treated M2 plants allowed identification of 121 mutants, including silent, missense, and knockout (truncation) mutations. A complete waxy wheat was successfully bred in 18 mo by crossing two truncation mutants (Wx‐A1‐truncation and Wx‐D1‐truncation; Wx‐B1 is naturally null in both mutants). Screening of two puroindoline genes (Pina and Pinb) in QAL2000 identified 19 mutants. A hard grain variant of a soft cultivar was identified due to a mutation in Pinb caused by a premature stop codon. Background mutations were observed and further self‐fertilization or crossing with a wild type was performed to eliminate deleterious mutations. With the rapid accumulation of wheat genomics information, many potential target genes of interest can be screened for mutations in these TILLING populations.

Development of ‘naked-tufted’ seed coat mutants for potential use in cotton production

Use of chemical mutagenesis has been highly successful in most major crops. The objective of this research was to develop ‘naked-tufted’ seed mutants and to incorporate this genetic trait into cotton to enhance crop quality and reduce processing costs. In 1997, six commercial cultivars were treated with 2.45% v/v ethyl methane sulfonate. In 1999, three M3 plants were identified that had partially naked seed coats. The trait was stabilized through individual plant selections from 2000 to 2004. During 2005 and 2006, the homozygous naked-tufted M8 mutant lines were evaluated for lint yield, lint percent, fibers/seed, fibers/mm2, fiber quality, seed oil content, ginning efficiency and yarn spinning performance. Overall, the naked-tufted seed mutants had lower lint yield, lower fibers/seed, lower lint/seed, and lower fibers/mm2 when compared with their original fuzzy parents. The lint turnout from the mutants was similar to the fuzzy parents and the commercial cultivars. The naked-tufted seed mutants had higher seed oil percent, 6–17% lower short fiber contents, significantly reduced seed coat neps (37–42%), higher elongation and yarn tenacity than their fuzzy counterparts. Preliminary data also showed that the naked-tufted mutants required less energy to gin.

Selection and molecular characterization of imidazolinone resistant mutation-derived lines of Tritordeum HT621

Imidazolinone herbicides resistant varieties, induced by mutations at the AHAS gene (acetohydroxyacid synthase), have been developed in many crops. Hexaploid tritordeum (Tritordeum Asch. & Graebn.) is the amphiploid derived from the cross between Hordeum chilense (HchHch) and durum wheat Triticum turgidum L. (Thell) (AABB). Tritordeums have the potential to become a new crop with high added-value for food or feed. Mutagenesis with EMS was conducted to obtain imidazolinone resistant lines derived of the tritordeum HT621. Eleven M3 plants were selected after imidazolinone treatment and five descendants of two of these lines (HT621-M3R1-3 and HT621-M3R10-1) were analyzed at the molecular level. Partial sequences of the three homologous AHAS loci in genomes A, B, and Hch were obtained as well as those of HT621. A partial sequence of the AHAS gene in Hordeum chilense is first described in this work, and the designation ahasL-Hch1 is proposed. A single Ser-Asn627 substitution at the AHAS locus in the B genome is responsible of resistance in both lines. We propose the name AhasL-B2 for this resistance allele. This is the first report of the selection of imidazolinone resistant lines of tritordeum and the molecular characterization of the mutation conferring this resistance.

Low-oxalate Spinach Mutant Induced by Chemical Mutagenesis

Spinach (Spinacia oleracea L.) accumulates large amounts of oxalate, which reacts with calcium, inhibiting its absorption and forming urinary stones in humans. In this study, low-oxalate spinach mutant was induced through chemical mutation. Seeds of the gynomonoecious line of ‘Shin-Nippon’ were treated with 50 mM ethyl methane sulphonate (EMS) for 6 h. Self-fertilized M2 seeds were harvested from M1 plants individually. Total oxalate (water soluble and insoluble) concentrations of M2 plants were measured, and four low-oxalate plants were selected. Self-fertilized M3 seeds were harvested from these M2 plants individually. In the progenies of three M2 plants, oxalate concentration ranged from 9 to 19 mg·g−1FW; there were no low-oxalate plants; however, in the progeny of one M2 plant, five of eight plants had low oxalate; their concentration were lower than 2 mg·g−1FW. Self-fertilized M4 seeds were harvested from low-oxalate M3 plants individually. The progenies of low-oxalate M3 plants, named low-oxalate lines, were grown and compared with the original ‘Shin-Nippon’ and gynomonoecius line (wild types). Leaves of low-oxalate lines were slightly smaller and thinner than wild types, whereas the leaf number and color were similar. Oxalate concentrations of leaves in low-oxalate lines strongly decreased; one third to one sixth of those in wild types. Nitrate concentrations did not decrease in low-oxalate lines.

INDUCED MALE-STERILITY ALTERS DRY MATTER DISTRIBUTION IN SOLANUM VILLOSUM MILL.

INDUCED MALE-STERILITY ALTERS DRY MATTER DISTRIBUTION IN SOLANUM VILLOSUM MILL.

Red-purple flower due to delphinidin 3,5-diglucoside, a novel pigment for Cyclamen spp., generated by ion-beam irradiation

We previously bred fragrant cyclamen cultivars by interspecific hybridization between cultivars of Cyclamen persicum and the wild species Cyclamen purpurascens. One of these fragrant cultivars, Kaori-no-mai, blooms purple flowers containing malvidin 3,5-diglucoside as the major anthocyanin. Here, we irradiated etiolated petioles of Kaori-no-mai with a 320-MeV carbon-ion beam at 0–16 Gy to increase flower color variation by mutation. Some of the M2 plants derived from self-pollination of M1 plants irradiated at 2 Gy were flower-color mutants that retained desirable flower shape, flower size, and leaf color. One of the mutants bloomed novel red-purple flowers, the major anthocyanin of which was delphinidin 3,5-diglucoside. Loss of methylation activity at the anthocyanin 3′- and 5′-hydroxyl groups with little influence on anthocyanin concentration was attributed to the mutation. Because the major anthocyanins in flowers of Cyclamen spp. were previously restricted to malvidin, peonidin, and cyanidin types, the generation of a cyclamen containing mostly the delphinidin-type anthocyanin is an important breakthrough in cyclamen breeding. We expect this mutant to become not only a commercial cultivar itself, but also a valuable genetic resource for cyclamen breeding.

Rapid characterization of plant mutants with an altered ion‐profile: a case study using Lotus japonicus

Legumes are second only to cereals in their importance to humans, and study of their functional genomics of nutrition and other trace elements is crucial for agricultural production and food fortification. We describe here an ionomic screening experiment carried out to investigate the accumulation of 15 elements in shoots of mutants of Lotus japonicus, a good genetic tool for legume study.Approximately 2000 mutagenized M2 plants were cultivated in a novel low-cost high-throughput system and their elemental profiles were determined by inductively coupled plasma mass spectroscopy (ICP-MS).After triple-checking the element concentrations in M2 or M3 plant shoots, 31 mutants with altered elemental profiles were identified. Surprisingly, the number of genes regulating essential elements was similar to the number regulating nonessential elements. Magnesium (Mg) and nickel (Ni) were correlated in a number of mutants.Further investigation suggested that phosphorus (P) and cobalt (Co) might be involved in the ion homeostasis network of Mg and Ni.The results suggested that the pathways for element uptake or translocation were highly linked through the ion transport-related genes. Ionomics proved to be a powerful functional genomics tool for determining genes related to ion homeostasisin this study.

Study of Radio sensitivity in Tomato by Gamma Radiation

The study was conducted in the field of Hort. Dept. College of Agriculture University of Baghdad during the two seasons 1993 and 1994 as a part of tomato breeding and improvement program by inducing mutation by experimental mutagenesis. In first program was study the radio sensitivity in tomato to determine the lethal doses and useful mutagenesis. Two tomato varieties of super marimand which were local and Gluss grow and five Radio doses were chosen. (0, 15, 30, 45 and 60 Krad of gamma Co60). The result showed that lethal dose to tomato crop was between 45 and 60 krd gamma radiation. To determine doses of useful mutagenesis, six radio doses were chosen (0, 20, 25, 30, 35 and 40 krd) by using two tomato strains. The experiment was conducted by using a randomize complete block design. The strains were differ from each other in radio sensitivity and the radio sensitivity was increased as radio doses were increased. For induction of initial genetic material of mutagenesis breeding of plants wee done for two generation. In M1 the above two strains in addition to strains of Enka company were used. The experiment was conducted by using of split – plot design with three replications. The evaluation of radiation effects were done on M1 plants according to radio morphosims. The higher of plants were selected from local strains (526 selections) followed by strains of Gluss company (290 selections) and (40) selection from strain of Enka company. The radio doses were differ from each other in number of selected plants. Doses of 20, 25, 30 krd of the three strains had more number of selections. In M2 radio generation work was reduced and continued by using strains of Gluss grow company only. The number of variations selected in this generation was 109 variated. Dose of 25 krd was produced a higher number of variated followed by 20, 30, 35 and 40 krd doses, respectively.

A functional genomics resource for Brassica napus: development of an EMS mutagenized population and discovery of FAE1 point mutations by TILLING

Two ethylmethanesulfonate (EMS) mutant populations of the semi-winter rapeseed cv. Ningyou7 were constructed with high mutant load, to provide a TILLING platform for functional genomics in Brassica napus, and for introduction of novel allelic variation in rapeseed breeding. Forward genetic screening of mutants from the M2 populations resulted in identification of a large number of novel phenotypes. Reverse genetic screening focused on the potentially multi-paralogous gene FAE1 (fatty acid elongase1), which controls seed erucic acid synthesis in rapeseed. A B. napus BAC library was screened, and loci in a reference mapping population (TNDH) were mapped to conclude that there are two paralogous copies of FAE1, one on each of the B. napus A and C genomes. A new procedure is demonstrated to identify novel mutations in situations where two or more very similar paralogous gene copies exist in a genome. The procedure involves TILLING of single plants, using existing SNPs as a positive control, and is able to distinguish novel mutations based on primer pairs designed to amplify both FAE1 paralogues simultaneously. The procedure was applied to 1344 M2 plants, with 19 mutations identified, of which three were functionally compromised with reduced seed erucic acid content.

CdCl2-induced morphogenetic variation of Triticum aestivum cultivars

The effect cadmium chloride on released local cultivars of soft spring wheat (Triticum aestivum) has been studied under laboratory and field conditions in order to widen the variation spectrum of this plant. It has been found that treatment of grains with a 0.01% aqueous solution of CdCl2 induces the appearance of tall, strong plants with productive bushiness in the M1 generation that are characterized by various morphological changes: elongated ears, scales, and grains; increased number of grains per ear and mass of 1000 grains; anthocyan pigmentation of the stem and leaf axil; etc. Study of meiosis showed chromosome aggregation, displacement of the mitotic spindle of the metaphase plate, and empty (sterile) cells in anaphases (AI and AII). The altered characters of M1 plants are preserved in the M2-M4 generations.

Induction and Identification of a Small-Granule, High-Amylose Mutant in Cassava (Manihot esculenta Crantz)

Only two mutations have been described in the literature, so far, regarding starch and root quality traits in cassava. This article reports on an induced mutation in this crop, first identified in 2006. Botanical seed from five different cassava families were irradiated with gamma rays. Seed was germinated, transplanted to the field (M1 plants), and self-pollinated to produce the M2 generation. Abnormal types regarding starch granule morphology were identified during the single plant evaluation of M2 genotypes. To confirm these characteristics, selected genotypes were cloned and a second evaluation, based on cloned plants obtained from vegetative multiplication, was completed in September 2007. Two M2 genotypes presented small starch granules, but only one could be fully characterized, presenting a granule size of 5.80 +/- 0.33 microm compared with three commercial clones with granule sizes ranging from 13.97 +/- 0.12 to 18.73 +/- 0.10 microm and higher-than-normal amylose content (up to 30.1% in cloned plants harvested in 2007, as compared with the typical values for "normal" cassava starch of around 19.8%). The gels produced by the starch of these plants did not show any viscosity when analyzed with the rapid viscoanalyzers (5% suspension), and the gels had low clarity. Low viscosity could be observed at higher concentrations (8 or 10% suspensions). Preliminary results suggest that the mutation may be due to a lesion in a gene encoding one of the isoforms of isoamylase (probably isa1 or isa2).

Genetic and embryological evidences of apomixis at the diploid level in Paspalum rufum support recurrent auto-polyploidization in the species

Gametophytic apomixis is an asexual mode of reproduction by seeds. This trait is present in several plant families and is strongly associated with polyploidy. Paspalum rufum is a forage grass with sexual self-incompatible diploids (2n = 2x = 20) and aposporous-apomictic pseudogamous tetraploids (2n = 4x = 40). In previous work embryological observations of the diploid genotype Q3754 showed 8.8–26.8% of the ovaries having one meiotic plus an aposporous-like embryo sac, suggesting some capability for apomictic reproduction. The objective of this work was to characterize progenies derived from Q3754 to determine if aposporous sacs were functional and generated progenies via apomixis at the diploid level. Re-examination of Q3754 ovaries showed that 12.5% of them contained one sexual plus an aposporous sac confirming previous results. Progeny tests were carried out on two experimental families (H1 and S1) employing heterozygous RAPD marker loci. Family H1 was obtained crossing Q3754 with a natural diploid genotype (Q3861) and S1 derived from the induced self-pollination of Q3754. Genetic analysis of H1 showed that all individuals derived from sexual reproduction. However, 5 out of 95 plants from S1 showed the same heterozygous state as the mother plant for 14 RAPD loci suggesting a clonal origin. Further experiments, designed to test the functionality of aposporous sacs by flow cytometric analyses, were carried out on a third family (M1) obtained by crossing Q3754 with the tetraploid plant Q3785. Histograms of 20 M1 plants showed 15 diploids (75%), 4 triploids (20%) and 1 tetraploid (5%). Triploids and the tetraploid may have originated from functional aposporous embryo sacs. Likewise, the reconstruction of the developmental route of 40 individual seeds demonstrated that 11 of them (27.5%) derived from fertilized aposporic sacs. The results presented in this work indicate that gametophytic apomixis is effectively expressed at the diploid level in Paspalum rufum and could be the foundation of a recurrent auto-polyploidization process in the species.

Effect of Ar+ Implantation and Maize Genome DNA on Autotetraploid Rice

The effect of Ar+ beam implantation and maize genome DNA on autotetraploid rice is studied. Better mutation types and higher mutation rates were discovered in M2 of T3 with ion implantation and immersion in maize genome DNA. In the five agronomic categories investigated, the mutation rate of the seed setting rate was 9.1%, and the total mutation rate was 14.8% in the T3. However, the total mutation rate was 2.1% with the treatment of only ion implantation and 1.3% with the treatment of only immersion in maize genome DNA. Mutant FA36(4) was discovered in M1 with ion beam implantation and immersion in maize genome DNA. Its RuBPCase activity, PEPCase activity and seed setting rate were 32%, 153%, and 36.79%, respectively, higher than its parent IR36(4). Rapid analysis of polymorphicDNA (RAPD) analysis of three M2 plants of FA36(4) (FM1, FM2, FM3) and two controls (purple maize and IR36(4)) were also conducted with 40 random primers. S5-3 was RAPD fragment amplified with a template of purple maize, FM2 and FM3 genome DNA using primer S5. There was no S5-3 in the RAPD pattern of IR36(4) or FM1.

Inducement of chromosome translocation with small alien segments by irradiating mature female gametes of the whole arm translocation line

Haynaldia villosa Schur. (syn. Dasypyrum villosum Candargy, 2n=14, VV) has been proved to be an important genetic resource for wheat improvement. The development of translocation with small alien chromosome segments, especially interstitial translocation, will be helpful for better utilization of its useful genes. Up to now, most of the reported Triticum aestivum-H. villosa translocation lines are involved in a whole arm or large alien fragments. In this paper, we report a highly efficient approach for the creation of small chromosome segment translocation lines. Before flowering, the female gametes of wheat-H. villosa 6VS/6AL translocation line were irradiated by 60CO-gamma ray at 160 Rad/M dosage rate and three dosages (1600, 1920, 2240 Rad). Anthers were removed from the irradiated florets on the same day and the florets were pollinated with normal fresh pollens of T. aestivum cv. Chinese Spring after 2 - 3 days. Genomic in situ hybridization (GISH) at mitosis metaphase of root-tip cell of M1 plants was used to detect the chromosome structural changes involving 6VS of H. villosa. Among the 534 M1 plants screened, 97 plants contained small segment chromosome structural changes of 6VS, including 80 interstitial translocation chromosomes, 57 terminal translocation chromosomes and 55 deletion chromosomes. For the 2240 Rad dosage treatment, the inducement frequencies of interstitial translocation, terminal translocation and deletion were 21.02%, 14.01%, and 14.65%, respectively, which were much higher than those previously reported. The M2 seeds were obtained by backcrossing of 74 M1 plants involving 146 chromosomes structural changes of 6VS, and it was found that the structural aberrations in the M1 plants could be transmitted to their progenies. Irradiating mature female gametes of whole arm translocation is a new and highly efficient approach for creation of small segment chromosome structural changes, especially for interstitial translocations.

Identification of low lectin mutants in soybean

AbstractLectin is one of the known antinutritional factors that deteriorate the soybean protein quality and development of cultivars with low lectin content will help to improve nutritional quality of soybean [Glycine max (L.) Merrill]. Therefore, attempts were made to induce mutations for low lectin content in the cultivar ‘MACS 450’. Soybean cultivar ‘MACS 450’ was subjected to combination treatments of γ‐rays and ethyl methane sulphonate (EMS) with an objective to induce variability for low lectin content. The treatments of different combinations of γ‐rays and EMS were 50 Gy + 0.2% EMS, 50 Gy + 0.4% EMS, 100 Gy + 0.2% EMS and 100 Gy + 0.4% EMS. Of the 3200 treated M1 seeds sown, 16 400 M2 plants were raised. In M2, 72 plants were identified for low lectin content [<40 × 105 haemagglutination unit (HAU)/mg] and were carried up to M5 generation. In M5 generation, lectin content in ‘MACS 450’ was 39.23 to 50.0 × 105 HAU/mg, and was compared with the nine true breeding lines identified having low lectin content, ranging from 2.3 × 105 to 27.46 × 105 HAU/mg. Three mutants were found to possess very low lectin content (ranging from 2.0 × 105 to 3.0 × 105 HAU/mg). Thus, the identified mutant lines with low lectin content will greatly improve soybean protein quality, thereby reducing financial burden on the soybean industry for processing soybean meal and also making it suitable for human consumption. All the mutants showed normal seed development, having soluble protein content similar or higher than that in the parent (32.0 mg/ml). This indicates that the change in lectin content does not have any negative impact on the plant growth and protein content.

A revisit of mutation induction by gamma rays in rice (Oryza sativa L.): implications of microsatellite markers for quality control

Mutation techniques have been used for generating genetic variation and breeding new varieties during the past decades. However, the skepticism has also persisted during the course on the sole mutational origin of genetic variation in mutated populations. We addressed this issue using three unique rice genetic lines in this study. First, we confirmed that gamma rays had significant effect on the growth of M1 plants, leading to significant reduction of fertility, seed set and plant height at doses 200 Gy and above. Second, we proved that out-crossing derived genetic variants existed in M2 population (0.8%) and among selected putative mutants (0–33.3%), in addition to induced mutants. Third, we demonstrated that true induced mutant lines had identical microsatellite haplotypes to their parents. We proposed microsatellite assay as a method to exclude any genetic contaminants from induced mutants, with appropriate numbers for different levels of power based on reported microsatellite mutation rate and microsatellite polymorphic index.