Maternal inheritance of plant variegation in cowpea, Vigna unguiculata (L.) Walp.

A chimeric plant was observed in the F₂ generation of a cross between a mutant cultivar, Ife BPC, and a germplasm line, TVu 2, in cowpea, Vigna unguiculata (L.) Walp. The chimeric plant had four lateral branches, one of which was intensely variegated, while the others were mostly green with few white sectors. F₃ progeny from the intensely variegated branch of this plant were all variegated, while seed derived from the mostly green branches produced only green progeny. In subsequent generations, the descendants of the variegated branch bred true for the variegated trait, while those of the mostly green branches were also true-breeding for green colour. No pure-green or pure-white shoots were observed in any of the variegated plants examined in this study. Consequently, no pure-green or pure-white seedlings were produced from seeds harvested from the variegated plants. The results of reciprocal crosses between variegated and normal green plants indicate that variegation is inherited in a strictly uniparental maternal fashion. This is the first report of a cytoplasmically inherited mutation affecting foliage colour in cowpea. Received: 10 March 2000 / Accepted: 16 May 2000     

Gene mapping related to yellow green leaf in a mutant line in rice (Oryza sativa L.)

A mutant, which derived from the restorer line Jinhui10 treated with EMS, showed completely yellow green leaves, and it had low chlorophyll content and poor agronomic characteristics during the growing stage. The F1 plants from the cross between normal × the mutant showed normal green leaves, and the segregation ratio of normal to yellow green leaves was 3 : 1 in F₂ population. It indicated that the trait was controlled by a single recessive nuclear gene, temporarily designated asygl3. The geneygl3 was mapped between RM468 and RM3684 with genetic distances 8.4 cM and 1.8 cM on chromosome 3. This result would be used as genetic information for fine mapping and map-based cloning ofygl3 gene.     

Evaluation of early generations for iron chlorosis in relation to productivity in groundnut (Arachis hypogaea L.)

Five popular but iron-inefficient cultivars were crossed with three efficient genotypes and both parents and F₁s were evaluated for iron-efficiency in potted calcareous and noncalcareous soil. The iron-efficient genotypes were dark green or green in both noncalcareous and calcareous soils whereas inefficient types were light green to yellow in calcareous soil. The chlorophyll and active iron (Fe²⁺) concentration of leaves was less in iron-efficient genotypes compared to efficient types in calcareous soil and reduction of both the parameters from noncalcareous to calcareous soil was considerably high in iron-inefficient lines. There was significant correlation between visual scores, chlorophyll and active iron content. There were no differences among F₁s for iron chlorosis and they were all iron-inefficient. The frequency of iron-inefficient plants was higher than the efficient plants in all F₂ populations. But most of the productive plants came from iron-efficient segregants indicating strong association between iron-efficiency and productivity. Based on the results selection for iron-efficiency in early generations and extensive evaluation for productivity in advanced generations is suggested for developing varieties for cultivation in calcareous soils.     

Inheritance of fenoxaprop-P-ethyl resistance in a blackgrass (Alopecurus myosuroides Huds.) population

A blackgrass population has developed resistance to fenoxaprop-P-ethyl following field selection with the herbicide for 6 consecutive years. Within this population, 95% of the individuals are also resistant to flupyrsulfuron. Both the inheritance(s) and the mechanism(s) of resistances were investigated by making crosses between the resistant and a susceptible biotype. The inheritance was followed through the F₁ and F₂ generations either by spraying the herbicide on seedlings at the three-leaf stage or using a seedling bioassay, based on coleoptile length. No maternal effects were evident in the fenoxaprop-P-ethyl responses of the F₁ plants, suggesting that the inheritance was nuclear. Some F₁ families treated with fenoxaprop-P-ethyl segregated in a 3:1 (resistant:susceptible) ratio, indicating that the resistance was conferred by two dominant and independent nuclear genes. This was confirmed by the 15:1 (R:S) ratio observed in the F₂ generation treated with fenoxaprop- P-ethyl. The use of selective inhibitors of herbicide de-toxifying enzymes (aminobenzotriazole, pyperonylbutoxide, malathion and tridiphane) with the F₂ plants suggested that each of the two genes may govern two different mechanisms of fenoxaprop-P-ethyl resistance: the ACCase mutation previously postulated and an enhanced herbicide metabolism, mediated by cytochrome P 450 mono-oxygenases (P 450) susceptible to malathion. The P 450 activity may also confer resistance to flupyrsulfuron. This study clearly indicates that two distinct mechanisms of resistance may co-exist in the same plant. Received: 18 August 2000 / Accepted: 6 December 2000     

Inheritance of spontaneous male sterility in peas

A plant with a mutant phenotype was observed in a Longittee cultivar. The plant was late in maturity, had white-translucent anthers, and was male sterile. The inheritance of this mutant was studied in a cross involving the mutant and the mother parent and their F₁, F₂, F₃ and BC₁F₁ generations. The results suggested that the sterile character was genetic and due to a recessive gene.     

Assisted-selection of naturally caffeine-free coffee cultivars—characterization of SNPs from a methyltransferase gene

Breeding of caffeine-free coffee cultivars require tools for an early selection of progenies bearing this later trait. Genes from caffeine synthesis and degradation represent major targets for the development of molecular markers for assisted selection. In this study, we characterized SNPs identified on the caffeine synthase gene from AC1 mutant, a naturally caffeine-free arabica coffee plant. Molecular analysis of normal and mutant sequences indicates the occurrence of SNPs in protein domains, potentially associated with caffeine synthesis in coffee. Progenies F₂, F₁BC₁ and BC from crosses of AC mutants and elite cultivars were evaluated regarding caffeine content in grains and genomic segregation profile of selected SNPs. Genotyping analysis allowed the discrimination between homozygous and heterozygous plants. Quantification of caffeine content indicated a significant variability among progenies and a low frequency of caffeine-free plants. Statistical analyses of genotyping and phenotyping results showed significant association between presence of selected SNPs and reduced caffeine content. Moreover, this association occurs through all evaluated genetic backgrounds and generations, indicating an inheritance stability of both trait and markers. The molecular markers described here represent a successful case of assisted-selection in coffee, indicating their potential use for breeding of caffeine-free cultivars.     

Cytoplasmic male sterility and nuclear restorer genes in a natural population of Beta maritima: genetical and molecular aspects

Summary One natural population (F₀ generation) of Beta maritima situated on the French Atlantic coast has been analysed. It was composed of 62% female, 30% hermaphrodite and 8% intermediate plants. The analysis of half-sib progeny (F₁ generation) obtained from in situ open pollination demonstrates the cytoplasmic determination of male sterility in Beta maritima and the restoration of fertility by nuclear genes. The mitochondrial DNA (mtDNA) and the chloroplast DNA (ctDNA) of sixteen F₁ plants, extracted from offspring of the three sexual phenotypes, were analysed using the restriction enzymes Sal I and Bam HI, respectively. Two cytoplasmic lines with their own peculiar genetic characteristics were distinguished using the restriction enzyme patterns of mtDNA: (i) the S cytoplasmic line was found in segregating progeny of two F₀ plants; all three phenotypes were produced (that is, progeny including hermaphrodite, female and intermediate plants); (ii) the N cytoplasmic line was found in the progeny of one F₀ hermaphrodite plant; this produced only hermaphrodites. Thus, segregating and non-segregating hermaphrodite F₀ plants can be distinguished. The nuclear genes maintaining sterility or restoring fertility are expressed in line S. At the same time the analysis of Beta vulgaris material has been carried out at the molecular level: N cytoplasmic lines of B. vulgaris and B. maritima differed only by 3 fragments of mtDNA; but the S cytoplasmic line of B. maritima was very different from Owen's cytoplasmic male sterile line of B. vulgaris. No variation in the ctDNA pattern was detected within and between the two taxa.     

The origin and fate of morphological intermediates between wild and cultivated soybeans in their natural habitats in Japan

The spread of transgenes into the genome of wild soybean is a concern when transgenic and wild soybeans are planted sympatrically. The objectives of this study were to investigate the origin and fate of morphological intermediates between wild and cultivated soybeans in their natural habitats in Japan. Twenty nuclear microsatellite and two chloroplast dCAPS markers were used to evaluate genetic variation of 468 wild, 17 intermediate, and 12 cultivated soybean samples collected from six sites between 2003 and 2006. Allelic differentiation of microsatellite markers between wild and cultivated soybeans was sufficient to detect their hybrids. Based on levels of observed heterozygosity, intermediate soybean plants were from two generations: either F₁ or an early segregating generation. Genetic admixture analysis and parentage assignment analysis revealed that the parents of all intermediate soybean plants could be assigned to a particular wild soybean plant and late‐maturing cultivar. The chloroplast DNA haplotypes revealed that all intermediate soybean plants originated from gene flow from cultivated to wild soybeans at all sites. Based on monitoring at both the phenotypic and molecular levels, hybrids quickly disappeared from natural habitats, and secondary gene flow from these plants to wild soybean was not detected. Thus, while gene flow from transgenic soybean into wild soybean can occur, gene introgression appears to be rare in natural habitats in Japan. This is the first report on the detection of gene flow from cultivated to wild soybean at the molecular level.     

Sid: a Mendelian locus controlling thylakoid membrane disassembly in senescing leaves of Festuca pratensis

Summary A spontaneous mutation arising in Festuca pratensis has the effect of stabilizing the pigmentproteolipid complexes of thylakoid membranes so that leaf tissue does not turn yellow during senescence. Inheritance of the non-yellowing character was analysed in crosses between the wild-type cultivar Rossa and a mutant line Bf 993. Electrophoretic variants of cytoplasmic phosphoglucoisomerase coded by alleles of the nuclear gene Pgi-2 were used to identify hybrids during intercrossing. About 96% of the F₁ progeny were heterozygous and all were phenotypically yellowing. In the F₂ generation yellow green segregated in a ratio of 2.141, not significantly different from 31. In the backcross between F₁ and Bf 993 the ratio was 11 yellow green. There was no indication of linkage to Pgi-2. Senescence of detached Bf 993 and Rossa leaves was compared with that of the F₁ hybrid. The hybrid behaved in an essentially identical fashion to the wildtype parent, and in marked contrast to the mutant, in all aspects of the senescence syndrome investigated, including loss of chlorophyll, carotenoids and the light-harvesting chlorophyll-protein of thylakoid membranes, and elevation of the particulate protein chlorophyll ratio in the terminal stages. It is concluded that there exists in Festuca pratensis a nuclear gene, designated Sid (senescence-induced degradation) which regulates turnover of hydrophobic components of photosynthetic membranes in ageing leaf tissue and which occurs in at least two allelic forms, y (yellow) dominant over g (green).Abbreviations PGI phosphoglucoisomerase - Pgi nuclear gene coding for PGI - TSH tris buffer containing 2-mercaptoethanol - SDS sodium dodecyl sulphate - Chl chlorophyll - LHCP light-harvesting chlorophyll a/b binding protein - ELISA enzyme-linked immunosorbent assay     

Inheritance of spontaneous male sterility in pigeonpea

 A male-sterile plant was observed in the UPAS-120 cultivar of pigeonpea (Cajanus cajan). The plant was about 5–7 days late-flowering and had white translucent anthers with complete pollen sterility. The inheritance of this spontaneous male sterility was studied in a cross involving the mutant and fertile UPAS-120, including their F₁, F₂, BC₁F₁ and BC₂F₁ generations. The results suggested that the male sterility was genetic and due to a recessive gene. Received: 12 November 1996/Accepted: 17 January 1997     

GENETIC HISTORY AND GENERAL COMPARISONS OF TWO ALBINO MUTATIONS OF HELIANTHUS ANNUUS

Wallace , Raymond H. (U. Connecticut, Storrs.), and Helen M. Habermann . Genetic history and general comparisons of two albino mutations of Helianthus annuus. Amer. Jour. Bot. 46(3) : 157-162. Illus. 1959.—The genetic history of the progeny of a single ultrasonically-treated seedling of Helianthus annuus L. has been summarized for the 6 generations for which quantitative data are available. A yellow mutation was found in the F₂ generation and later in the F₅, a second, white mutation occurred. Both mutants have been grown to maturity by grafting them onto normal green host plants and they have set viable seeds. Both pigment-deficient conditions are inherited as single recessive factors. These albino strains form chlorophyll during their seedling stages if they are grown at low light intensities. Chlorophyll is destroyed, however, under bright illumination and, once bleached, the capacity for chlorophyll formation appears to be lost. The yellow mutant contains xanthophyll but no traces of carotene have been found. In the white mutant, neither carotene nor xanthophyll have been detected. Flower color in the yellow mutant is normal while the flowers of the white mutant have no apparent pigmentation. The growth pattern of grafted yellow mutants is normal, save for a stiffer and woodier condition and a greater resistance to wilting. These characteristics have also been observed in grafted white mutants. In addition, there is a pronounced reduction in leaf size in the white mutant.     

Location of the recessive gene ym (yellow margin) on chromosome 12 of diploid Solatium tuberosum by means of trisomic analysis

Summary Ten out of twelve primary trisomics of dip-loid S. tuberosum were crossed as females with a recessive mutant for yellow margin (ym ym) obtained from S. phureja. All primary trisomics used proved to be homozygous dominant. Trisomic plants from all ten F₁'s were backcrossed with the mutant and trisomics from eight F₁'s were crossed also with a disomic heterozygous f₁ plant from triple 10 X mutant.In both BC₁ and half sib progeny of each trisomic type the mutant plants were easily identified because of their typical small roundish leaflets with yellow or reddish margins. The observed segregation ratios for normal to mutant were tested against the expected non-critical ratios and against various expected critical ratios.From the results of these tests it is concluded that the gene ym is located on chromosome 12 of the potato. A hypothesis of linkage between ym and a gene l _x for lethality is put forward. It is concluded that l _x is not identical with a previously detected recessive gene l ₂ which is responsible for yellow cotyledons and lethality.     

Stability and inheritance of endosperm-specific expression of two transgenes in progeny from crossing independently transformed barley plants

To study stability and inheritance of two different transgenes in barley, we crossed a homozygous T₈ plant, having uidA (or gus) driven by the barley endosperm-specific B₁-hordein promoter (localized in the near centromeric region of chromosome 7H) with a second homozygous T₄ plant, having sgfp(S65T) driven by the barley endosperm-specific D-hordein promoter (localized on the subtelomeric region of chromosome 2H). Both lines stably expressed the two transgenes in the generations prior to the cross. Three independently crossed F₁ progeny were analyzed by PCR for both uidA and sgfp(S65T) in each plant and functional expression of GUS and GFP in F₂ seeds followed a 3:1 Mendelian segregation ratio and transgenes were localized by FISH to the same location as in the parental plants. FISH was used to screen F₂ plants for homozygosity of both transgenes; four homozygous plants were identified from the two crossed lines tested. FISH results showing presence of transgenes were consistent with segregation ratios of expression of both transgenes, indicating that the two transgenes were expressed without transgene silencing in homozygous progeny advanced to the F₃ and F₄ generations. Thus, even after crossing independently transformed, homozygous parental plants containing a single, stably expressed transgene, progeny were obtained that continued to express multiple transgenes through generation advance. Such stability of transgenes, following outcrossing, is an important attribute for trait modification and for gene flow studies.     

Analysis of transgene(s) (psy+crtI) inheritance and its stability over generations in the genetic background of indica rice cultivar Swarna

Rice the major staple food crop which feeds more than half of the world’s population but, lacks pathway to synthesize and accumulate provitamin A in endosperm therefore rice eaters particularly children, and pregnant women suffer due to vitamin A deficiency. The pathway for provitamin A synthesis in rice endosperm has been engineered and transgenic rice lines have yellow endosperm, called ‘Golden Rice’. The present study aimed at studying the inheritance of transgene(s) in six transgenic events of ‘Golden Rice’ and transfer of provitamin A trait from transgenic lines to a widely grown mega rice variety Swarna. The events E1, R1 and W1 showed normal Mendelian inheritance in F₂, BC₁F₁ and BC₁F₂ generations. The event W1 was studied in BC₁F₃ as well and showed normal Mendelian inheritance of 3:1. The inheritance pattern in L1 event in BC₁F₁ and BC₁F₂ showed normal Mendelian inheritance following expected ratio 1:1 and 3:1 respectively. The two events G1 and T1 showed distorted segregation in BC₁F₂ and BC₂F₂ respectively in Swarna genetic background. In G1 event, transgene inheritance showed segregation distortion in BC₁F₂ in favour of transgene negative plants. In T1 event, inheritance followed expected Mendelian segregation in BC₁F₁, BC₂F₁ and BC₂F₂, generations. However, when tested against co-dominant inheritance 1:2:1 pattern in BC₂F₂, segregation distortion was observed with less than the expected transgene homozygotes. While against 3:1 ratio, it showed the expected segregation pattern in BC₂F₂ generation. Segregation distortion probably due to differential transmission of transgene positive/negative gametes through either/both parents which needs further study.     

Orange, yellow and white-cream: inheritance of carotenoid-based colour in sunflower pollen

Inheritance of pollen colour was studied in sunflower (Helianthus annuus L.) using three distinct pollen colour morphs: orange, yellow and white‐cream. Orange is the most common colour of sunflower pollen, while the yellow morph is less frequent. These two types were observed in the inbred lines F11 and EF2L, respectively. White‐cream pollen is a rare phenotype in nature, and was identified in a mutant, named white‐cream pollen, recovered in the R₂ generation of an in vitro regenerated plant. The F11 inbred line was used as starting material for in vitro regeneration. The carotenoid content of these three pollen morphs differed, and was extremely reduced in white‐cream pollen. The phenotype of F₁ populations obtained by reciprocal crosses revealed that the orange trait was dominant over both white‐cream and yellow. Segregation of F₂ populations of both crosses, orange × yellow and orange × white‐cream, approached a 3:1 ratio, indicating the possibility of simple genetic control. By contrast, a complementation cross between the two lines with white‐cream and yellow pollen produced F₁ plants with orange pollen. The F₂ populations of this cross‐segregated as nine orange: four white‐cream: four yellow. A model conforming to the involvement of two unlinked genes, here designated Y and O, can explain these results. Accessions with yellow pollen would have the genotype YYoo, the white‐cream pollen mutant would have yyOO and the accession with orange pollen would have YYOO. Within F₂ populations of the cross white‐cream × yellow a new genotype, yyoo, with white‐cream pollen was scored. The results of the cross yyoo × YYoo produced only F₁ plants with yellow pollen, supporting a recessive epistatic model of inheritance between two loci. In this model, yy is epistatic on O and o. In F₂ populations, the distributions of phenotypic classes suggested that the genetic control of carotenoid content is governed by major genes, with large effects segregating in a background of polygenic variation. These three pollen morphs can provide insight into the sequence in which genes act, as well into the biochemical pathway controlling carotenoid biosynthesis in anthers and the transfer of these different pigments into pollenkitt.     

SIMILAR UNSTABLE MUTATIONS IN THREE SPECIES OF GRACILARIA (RHODOPHYTA)1

Unstable mutants with similar variegated pigmentation were genetically characterized in the red algae. Gracilaria tikvahiae (McLachlan), G. foliifera (Forsk.) Børg. and. G. sjoestedtii (Kylin). All three mutants were green plants with flecks of red tissue where cells had reverted to wild type. The mutant green phenotypes were all recessive, and their genetic behavior in crosses indicated that each was the result of a single, unstable, nuclear gene. Wild-type revertant tissue was stable one it arose. Revertant plants obtained from spores and revertant fronds taken from variegated plants could not be distinguished from the normal wild type, either phenotypically or genetically. Reversion to wild type occurred during all phases of the life cycle. In crosses between the mutants and wild type, most of the F₁ tetrasporophytes were heterozygous wild-type plants, an observation consistent with the recessive nature of the mutations; however, a low frequency of homozygous unstable-green F₁ tetrasporophytes was also obttained from these crosses. The molecular basis of neither the mutant instability, i.e. the reversion to wild type, nor of the process producing the unstable green F₁ tetrasporophytes can yet be deduced, but the phenotype of the plants and genetic results suggest the involvement of transposable genetic elements.     

Inheritance of resistance to wheat yellow rust at adult plant stage

In order to investigate on inheritance and gene action for resistance to yellow rust, the resistant line C.B227 was crossed with the susceptible variety Avocet. Parents (P1 and P2) and the resulting F1, F2 and F3 generations were planted in a randomised complete block design with two replications in the field. The plants were inoculated with 70E0A⁺ pathotype of yellow rust in the research station of Gharakhil, Iran, and evaluated for resistance at adult plant stage. Disease severity and infection type of flag leaf were recorded for each single plant and final coefficient of infection was calculated. The results of weighted ANOVA indicated that the difference among the generations was significant (p?<?0.01) for the trait final infection type. Generation mean analysis showed that dominant effect was more important than additive one. The degree of dominance indicated the presence of complete dominance. Additive, dominance and epistasic additive?×?additive [i] effects were important in genetic control of resistance. The results of generation variance analysis were consistent with generation mean analysis.     

太空诱变玉米核不育突变体矮化的遗传及外施赤霉素分析

为了解太空诱变玉米核不育突变体矮化的遗传规律和原因,该研究以不育突变体为母本,自交系178、478为父本,对测交 F1、F2群体进行育性鉴定和株高分析,对 F2可育株进行基因型和株高分析,对姊妹交后代分离群体进行育性鉴定和株高、雄穗长度、节间数、节间长度分析,同时,还对姊妹交后代分离群体进行施赤霉素处理,调查育性和株高的变化。结果表明：178和478背景下的 F1表现出与测交母本一样的极显著差异;在178和478核背景下的 F2中,不育株株高极显著矮于可育株,两核背景下的不育株间株高差异不显著,而可育株间株高差异极显著;F2中纯合和杂合可育株的株高差异不显著;姊妹交后代分离群体中不育株株高、雄穗长度、节间数和节间长度极显著小于可育株;外施赤霉素的不育株在苗期表现出对赤霉素一定的敏感性,但株高最终未恢复正常高度。因此,得出该突变体矮化表现稳定,与不育性状并存,且不受细胞核背景的影响;核不育基因对植株株高的矮化无剂量效应;突变体的矮化与雄穗长度、节间数和节间长度有关;突变体不完全属于赤霉素不敏感型,其矮化并不是单一缺乏赤霉素而引起。该研究结果为认识太空诱变玉米核不育突变体矮化的遗传和生理机制提供了参考。     

Dominant pleiotropy controls enzymes co-segregating with paraquat resistance in Conyza bonariensis

Summary The genetics of paraquat-resistance in Conyza bonariensis was studied. Reciprocal crosses were prepared between resistant and sensitive individuals. The enzymes of the pathway that detoxifies superoxide to innocuous oxygen species involved in resistance were evaluated in the F₁ and F₂ generations. All F₁ plants were as resistant as the resistant parent, irrespective of parental sex, demonstrating dominance and excluding maternal inheritance. The activities of superoxide-dismutase, ascorbate-peroxidase and glutathione-reductase in the F₁ were constitutively as high as in the resistant parent. Resistance in the F₂ generation was distributed in a 31 ratio (resistant to sensitive). Leaves from F₂ plants were removed for a resistance assay and enzyme immuno-assays of single plants were performed. The high levels of superoxide-dismutase and glutathione-reductase, the two enzymes for which antibodies were available, were similar in resistant individuals to the levels in the resistant parent; the levels were low in the susceptible individuals. These results indicate either a very tight linkage, or more probably, that one dominant nuclear gene controls resistance by pleiotropically controlling the levels of enzymes of the activeoxygen detoxification pathway.     

Inheritance of chloroplast and mitochondrial DNA in alloplasmic forms of the genus Daucus

The inheritance of mitochondrial (mt) and chloroplast (ct) DNA in the progeny from interspecific crosses between the cultivated carrot (Daucus carota sativus) and wild forms of the genus Daucus was investigated by analysis of mt and ct RFLPs in single plants of the parental and filial generations. We observed a strict maternal inheritance of the organellar DNAs in all interspecific crosses examined. Previous studies on putative F₂ plants from a cross between Daucus muricatus x D. carota sativus suggested paternal inheritance of ctDNA. Our reinvestigation of this material revealed that the mtDNA of the putative F₂ plants differed from the mtDNA of both putative parents. Therefore, our data suggest that the investigated material originated from other, not yet identified, parents. Consequently, the analysis of this material cannot provide evidence for a paternal inheritance of ctDNA.