Pair Of Dominant Genes Research Articles

The AP2 Transcription Factor BrSHINE3 Regulates Wax Accumulation in Nonheading Chinese Cabbage.

Wax is an acellular structural substance attached to the surface of plant tissues. It forms a protective barrier on the epidermis of plants and plays an important role in resisting abiotic and biotic stresses. In this paper, nonheading Chinese cabbage varieties with and without wax powder were observed using scanning electron microscopy, and the surface of waxy plants was covered with a layer of densely arranged waxy crystals, thus differentiating them from the surface of waxless plants. A genetic analysis showed that wax powder formation in nonheading Chinese cabbage was controlled by a pair of dominant genes. A preliminary bulked segregant analysis sequencing (BSA-seq) assay showed that one gene was located at the end of chromosome A09. Within this interval, we identified BraA09000626, encoding an AP2 transcription factor homologous to Arabidopsis AtSHINE3, and we named it BrSHINE3. By comparing the CDS of the gene in the two parental plants, a 35 bp deletion in the BrSHINE3 gene of waxless plants resulted in a frameshift mutation. Tissue analysis showed that BrSHINE3 was expressed at significantly higher levels in waxy plant rosette stage petioles and bolting stage stems than in the tissues of waxless plants. We speculate that this deletion in BrSHINE3 bases in the waxless material may inhibit wax synthesis. The overexpression of BrSHINE3 in Arabidopsis induced the accumulation of wax on the stem surface, indicating that BrSHINE3 is a key gene that regulates the formation of wax powder in nonheading Chinese cabbage. The analysis of the subcellular localization showed that BrSHINE3 is mainly located in the nucleus and chloroplast of tobacco leaves, suggesting that the gene may function as a transcription factor. Subsequent transcriptome analysis of the homology of BrSHINE3 downstream genes in nonheading Chinese cabbage showed that these genes were downregulated in waxless materials. These findings provide a basis for a better understanding of the nonheading Chinese cabbage epidermal wax synthesis pathway and provide important information for the molecular-assisted breeding of nonheading Chinese cabbage.

Identification and Fine Mapping of the Candidate Gene Controlling Multi-Inflorescence in Brassica napus.

As a desirable agricultural trait, multi-inflorescence (MI) fulfills the requirement of mechanized harvesting and yield increase in rapeseed (Brassica napus L.). However, the genetic mechanism underlying the multi-inflorescence trait remain poorly understood. We previously identified a difference of one pair of dominant genes between the two mapping parental materials. In this study, phenotype and expression analysis indicated that the imbalance of the CLAVATA (CLV)-WUSCHEL (WUS) feedback loop may contribute to the abnormal development of the shoot apical meristem (SAM). BnaMI was fine-mapped to a 55 kb genomic region combining with genotype and phenotype of 5768 BCF1 individuals using a traditional mapping approach. Through comparative and expression analyses, combined with the annotation in Arabidopsis, five genes in this interval were identified as candidate genes. The present findings may provide assistance in functional analysis of the mechanism associated with multi-inflorescence and yield increase in rapeseed.

OsGL6, a conserved AP2 domain protein, promotes leaf trichome initiation in rice

Trichomes are specialized epidermal cells that play crucial roles in resisting environmental stress and enhancing plant development. In Arabidopsis thaliana, the main genes controlling trichome formation have been consecutively identified. However, few genes like this were reported in rice. In this study, we identified the hairy phenotype of indica variety 75-1-127. This was used to construct a segregation population with a cross of hairless variety Minghui63 (MH63) to fine map the trichome formation genes. Genetic analysis indicated that hairy phenotype was controlled by a pair of dominant genes on chromosome 6, which was designated as GLABRA6 (OsGL6). OsGL6 was an allele of HL6 gene whose sequences containing rich variations in genomes. Compared to wild type, the overexpressing transgenic lines revealed that OsGL6 promoted trichome initiation. We found that OsGL6 interacted with serine/threonine protein kinase OSK3 (OSK3) or COP9 signalosome complex subunit 5a (CSN5) in yeast. These results provide potential information for understanding the molecular mechanism of trichome formation in rice.

Inheritance of Transgenes in Transgenic Bt Lines Resistance to Helicoverpa armigera in Upland Cotton.

Six transgenic Bt cotton cultivars (lines) including GKsu12, GK19, MR1, GK5, 109B, and SGK1 are highly resistant to bollworm from the seedling to boll-setting stages in bioassays with detached cotton leaves, though there are differences in resistant level and Bt toxin content in these transgenic cottons. Genetics analysis reveals that the resistance to Helicoverpa armigera in these six transgenic Bt cotton cultivars (lines) are controlled by one pair of dominant genes. Allelic tests further demonstrate some populations are in Mendel segregation for two nonallelic genes, i.e., the inserted Bt gene in GKsu12 is nonallelic to that of SGK1, GK5, 109B, and GK19, and Bt genes in GK19 and SGK1 are likely inserted in the same or in close proximity (genetically closely linked), while some F2 produce abnormal segregation patterns, with a segregation of resistance to Helicoverpa armigera which vary between 15:1 and 3:1, though their Bt segregation fit into 15:1 by PCR analysis, suggesting Bt gene silence in these populations. Two genes silence may occur in these populations due to the homologous sequence by crossing since the silenced individuals accounted for 1/16 of the F2 populations for allelic test. To those silenced populations, one of their parents all showed high resistance to bollworm.

Transfer of Downy Mildew Resistance from Wild Basil (Ocimum americanum) to Sweet Basil (O. basilicum).

Sweet basil (Ocimum basilicum) is susceptible to downy mildew caused by the oomycete foliar pathogen Peronospora belbahrii. No resistant varieties of sweet basil are commercially available. Here, we report on the transfer of resistance gene Pb1 from the highly resistant tetraploid wild basil O. americanum var. americanum (PI 500945, 2n = 4x = 48) to the tetraploid susceptible O. basilicum 'Sweet basil' (2n = 4x = 48). F1 progeny plants derived from the interspecific hybridization PI 500945 × Sweet basil were resistant, indicating that the gene controlling resistance (Pb1) is dominant, but sterile due to the genetic distance between the parents. Despite their sterility, F1 plants were pollinated with the susceptible parent and 115 first backcross generation to the susceptible parent (BCs1) embryos were rescued in vitro. The emerging BCs1 plants segregated, upon inoculation, 5:1 resistant/susceptible, suggesting that resistance in F1 was controlled by a pair of dominant genes (Pb1A and Pb1A'). Thirty-one partially fertile BCs1 plants were self-pollinated to obtain BCs1-F2 or were backcrossed to Sweet basil to obtain the second backcross generation to the susceptible parent (BCs2). In total, 1 BCs1-F2 and 22 BCs2 progenies were obtained. The BCs1-F2 progeny segregated 35:1 resistant/susceptible, as expected from a tetraploid parent with two dominant resistant genes. The 22 BCs2 progenies segregated 1:1 resistant/susceptible (for a BCs1 parent that carried one dominant gene for resistance) or 5:1 (for a BCs1 parent that carried two dominant genes for resistance) at a ratio of 4:1. The data suggest that a pair of dominant genes (Pb1A and Pb1A') residing on a two homeologous chromosomes is responsible for resistance of PI 500945 against P. belbahrii.

Gen dan QTL Pengendali Toleransi Tanaman terhadap Keracunan Aluminium dan Aplikasinya untuk Pemuliaan Tanaman di Indonesia

<p>Genetic knowledge of loci controlling Al toxicity tolerance is the key for a successful breeding program in developing Al<br />tolerant cultivars. Tolerance level of crop plants to Al toxicity is genetically controlled. The gene inheritance pattern is mainly<br />resulted from intensive studies of cereal crops, such as wheat, sorghum, maize, and rice. The trait can be controlled by a<br />single dominant gene, a single dominant gene with many alleles, a pair of dominant genes, or by many genes (QTL). The<br />majority of the Al tolerance genes identified so far belongs to two independent groups of gene families, i.e. aluminumactivated<br />malate transporter (ALMT) and multidrug and toxic compound extrusion (MATE), both encoding transport proteins<br />involved in Al-activated organic acid release, mainly citrate and malate. The variations in Al toxicity tolerance phenotypes are<br />strongly correlated with the expressions of such genes in the root apical cells. Many Al tolerance QTLs have been mapped in<br />the genomes of various crop species and were found to be colocated with the ALMT and MATE genes. The genetic maps of<br />the Al tolerance genes and QTLs facilitate breeding programs for developing Al-tolerant cultivars through marker-assisted<br />breeding methods. Al tolerance genes that have been isolated from genetically unrelated species can be used in genetic<br />transformation studies of crop genotypes sexually incompatible to the gene source genotypes. The application of these<br />molecular breeding methods expedites breeding programs to develop crop cultivars tolerance to Al toxicity and acid soils.<br />Genomic technologies by using next-generation sequencing and high-throughput genotyping system accelerate Al toxicity<br />tolerance gene and QTL discoveries of various crop species. The modern genomic technologies also facilitate more<br />comprehensive PGR characterization and utilization to accelerate identification and isolation of the Al tolerance genes and<br />QTLs to be used in a more comprehensive breeding program to support national food self sufficiency and food security<br />programs.</p>

Progress in understanding resistance of <italic>Bombyx mori</italic> to nucleopolyhedrovirus

Bombyx mori nucleopolyhedrovirus (BmNPV) causes an important viral infectious disease in sericulture, and is responsible for 60% of the total cocoon production loss caused by various silkworm diseases. Horizontal resistance of silkworms to BmNPV is well known but we have identified a local line, named NB, whose LD50 is more than 1000 times higher than that of susceptible strains, and that has the highest resistance to BmNPV out of 344 silkworm lines. Through 10 years of crossbreeding and systematic selective breeding using line NB, we have constructed a commercial variety of Bombyx mori that is highly resistant to BmNPV. These genetic studies indicate the existence of BmNPV resistance genes in silkworm, and a pair of dominant genes has been implicated. Recently, we constructed a BmNPV-resistant near-isogenic line (NIL) via interspecific hybridization and backcrossing. Using this model and molecular techniques, such as fluorescent differential display-PCR, suppression subtractive hybridization, DNA microarray and proteomic analyses, we have identified molecules involved in BmNPV resistance. This review summarizes the current research status of BmNPV resistance in silkworms and discusses molecules involved in anti-BmNPV processes.

English

Inheritance and fruit production studies were carried out with an Abelmoschus esculentus cultivar, Okpa mkpe (P1), which expresses a mutant trait that produces multiple small fruits per node (msfpn) and two elite A. esculentus cultivars, Awgu early (P2) and Mpi ele (P3), as well as a high yielding A. callei cultivar, Ogolo (P4); all of which produce the conventional solitary fruit per node (sofpn). The aim was to meet consumer’s need for small sized fresh marketable okra fruits in the region. The inheritance studies showed that the mutant trait was controlled by a pair of dominant genes. The fruit morphometric studies showed that the A. esculentus cultivars and their hybrids differed significantly in length of fruit (LOF), diameter of fruit (DOF), circumference of fruit (COF), area of fruit (AOF) and volume of fruit (VOF). The direct cross of the mutant parent to the two elite A. esculentus cultivars showed that all the F1 hybrids produced small sized fruits. On the average, multiple small sized marketable fruits were produced on 61% of fruit-bearing nodes of P1, 58% of P1 x P2 hybrid and 52% of P1 x P3 hybrid fruit-bearing nodes, respectively. The percentage reduction in fruit parameters of the msfpn fruits in comparison with the sofpn fruits ranged from 14.28 to 23% for LOF, 10.47 to 15.12% for DOF and 11.18 to 18.89% for COF fruit parameters. Attempts to cross the msfpn parent (P1) with an A. callei (late okra) elite cultivar, P4, proved inconclusive. The discovery of the msfpn trait on an A. callei cultivar, Ojo ogwu, creates a possible opportunity for transferring the trait among A. callei cultivars. It is concluded that exploitation of the msfpn mutant trait could result to meeting okra consumers’ need for small sized fruits in the region and pave the way for exporting small sized fruits; which are in great demand by okra canning industries overseas. Key words: Abelmoschus species, mutant trait inheritance, multiple fruits per node, smallsized fruits.

Development of the molecular markers for identifying red pericarp trait in rice

Red rice attracts people's attention greatly for its special nutritional value. Red pericarp phenotype of rice is controlled by two pairs of dominant genes,Rc and Rd,on non-homologous chromosomes,and rice pericarp will be red only while Rc and Rd genes are both present. In this study we developed two molecular markers,namely Rc( + 5150) and Rd( + 276),directly on key loci of Rc / rc allele and Rd / rd allele affecting the rice pericarp color. The results show that the two molecular markers could discriminate the different genotypes of Rc / rc and Rd / rd. This study provides an important help for breeding red rice new varieties quickly and efficiently by using molecular marker-assisted selection.

Comparative analysis of fertility restoration genes for WA, Y, and DA cytoplasmic male sterility in rice

Rice chromosome single segment substitution line (SSSL) W23-19-06-06-11 with the genotype Rf3Rf3/Rf4Rf4, a strong restorer line for wild-abortive (WA) cytoplasmic male sterility (CMS), was recently identified from the SSSL library. To investigate the genetic mode of Rf genes and the genetic relationship among WA, yegong (Y), and dwarf-wildabortive (DA) CMS systems, the plants derived from three BC3F2 populations involving W23-19-06-06-11 and the three CMS lines, that carried the Rf3Rf3/Rf4Rf4, Rf3Rf3/rf4rf4, and rf3rf3/Rf4Rf4 genotypes and WA-, Y-, and DA-CMS cytoplasm, were selected and their pollen and spikelet fertility were evaluated. The results show that the genetic effect displayed a trend of Y-CMS > WA-CMS > DA-CMS in the genetic background of W23-19-06-06-11, the effect of Rf4 appeared to be slightly larger than that of Rf3, and their effects were additive for the three CMS systems. Two pairs of dominant genes governed the fertility restoration in pollen and spikelet in the W23-19-06-06-11 which indicates that the genetic mode of the Rf genes was a qualitative character for the three CMS systems.

Evaluation of Restorability of Two Fertility Restorer Genes in the Rice Chromosome Single Segment Substitution Lines (SSSLs)

Rice chromosome single segment substitution line (SSSL) S15, a strong restorer line for WA-, and DA-CMS, was recently isolated at Guangdong Provincial Key Laboratory of Plant Molecular Breeding, South China Agricultural University. The present study was carried out with the objective to investigate the genetic mode of fertility restorer (Rf) genes and the genetic relationship between WA- and DA-CMS systems. The SSSL S15 was used to pollinate WA-CMS line of Bobai A and DA-CMS line of Xieqingzao A for generation of two BC3F2 populations by using marker-assisted selection (MAS) and traditional backcrossing. The results were as follows: (1) The genetic effect showed a trend of WA-CMS DA-CMS in the genetic background of SSSL S15, and the effect of Rf4 was slightly larger than that of Rf3 for the two CMS systems. (2) Two pairs of dominant genes governed restoration of pollen fertility restoration, and some modifying or minor genes were involved in the inheritance of restorer ability besides Rf3 or Rf4 in SSSL S15, indicating that the genetic mode of Rf genes showed a qualitative-quantitative characteristic for WA-, and DA-CMS system. (3) When 202 SSR markers were used to analyze the genetic background and average length of substituted chromosome segments of the two BC3F2 individuals, carrying the genotypes Rf3Rf3/rf4rf4 or rf3rf3/Rf4Rf4, the mean of segments of inherited background of them was 1.0, while the average lengths of the substituted chromosome segments, corresponding to Rf3 and Rf4 loci, of them were 12.9 cM and 18.4 cM, respectively.

Interaction of Restorer Genes in ‘WA’-type Cytoplasmic Male Sterility System in Rice (Oryza sativa L.)

The inheritance of fertility restoration of ‘WA’ type of cytoplasmic male sterility system in rice was studied using three cytoplasmic male sterile (A) lines and their respective maintainer (B) lines and four restorer lines which were used in crossing to produce three generations (A × R) F1, (A × F1) BC1 and (A × R) F2. Segregation pattern in F2 generation for pollen fertility indicated that the fertility restoration ability was governed by two pairs of dominant genes (Rf 3 Rf 3 Rf 4 Rf 4 ), one of which was stronger in action than the other. The cross combinations, Pusa 6A × Basmati 564, Pusa 3A × HUR-FG-79 and Pusa 6A × HUR-FG-78 exhibited epistasis with incomplete dominance (F2 ratio 9:6:1 and BC1 ratio 1:2:1). In cross combinations, Pusa 3A × Basmati 564, Pusa 3A × HUR-FG-78 and Pusa 5A × Basmati 564, the fertility restoration was governed by dominant genes with recessive epistatic interaction (F2 ratio, 9:3:4 and BC1 ratio 1:1:2). Pusa 5A × HUR-FG-81 the only cross combination which exhibited dominant gene interaction (F2 ratio 12:3:1 and BC1 ratio 2:1:1). An allelism test involving four restorer lines revealed that Basmati 564, HUR-FG-81, HUR-FG-78 and HUR-FG-79 possessed different pairs of fertility restorer genes.

Diaporthe/Phomopsis species on soybean in Serbia

A complex of soybean diseases is caused by species from the genus Diaporthe /Phomopsis. Diaporthe phaseolorum (anamorph Phomopsis phaseoli) and Phomopsis longicolla (teleomorph unknown) are described as soybean pathogens. The first species includes three varieties: D. phaseolorum var. sojae, anamorph Phomopsis sojae, the causal agent of pod and stem blight, and D. phaseolorum var. caulivora and D. phaseolorum var. meridionalis, agents of northern and southern stem canker. The species P. longicolla is the most common and most damaging agent of soybean seed decay. The diseases caused by parasites from this genus were first observed and described on soybean in the USA. Presently they are widespread in most soybean-growing regions around the world. Soybean in Serbia is attacked by all pathogens mentioned above, except for D. phaseolorum var. meridionalis, the causal agent of the southern stem canker. D. phaseolorum var. caulivora (northern stem canker) has the greatest economic importance because it causes wilt and drying of plants during pod development and grain filling. Most intensive outbreaks of the disease occurred in the 1980s in southern and southeastern Banat, southern Backa and Srem. Prematurely wilted plants yielded 50% to 62% (depending on variety) less than healthy plants. Such heavy losses raised the question of the profitability of soybean growing. P. sojae and P. longicolla are less important in Serbia at the moment. Intensive infections of soybean seed break out occasionally. It was found that P. longicolla is the primary agent of seed decay and latent infections of seed in our country, although the other members of this genus may cause identical symptoms. Sexual cycle of development (teleomorph stage) of the fungi of the genus Diaporthe /Phomopsis form perithecia with asci and ascospores, while in the asexual cycle (anamorph stage) various types of conidia (? and ?) are formed in pycnidia. The species P. longicolla has no teleomorph stage. Infected harvest residues and soybean seeds are main sources of the inoculum. D. phaseolorum var. caulivora forms perithecia with ascospores on overwintered harvest residues. During growing season, ascospores infect leaf laminas, petioles, or injured plant parts. P. sojae and P. longicolla form pycnidia (P. sojae sometimes forms perithecia), and they infect plants by means of conidia. Seed infection by conidia or ascospores unfolds via pods. Infected crop residues are the main source of the inoculum, while infected seeds help the parasites spread over large distances. Humidity and temperature (soil and air) are the mains factors that affect the dynamics of fruiting body formation, spore release, establishment of infection and the development of disease symptoms on soybean plants. Considerable attention is devoted to finding effective sources of resistance to the disease complex caused by species from the genus Diaporthe/Phomopsis. Resistance to the agents of seed decay was found in several introduced (PI) genotypes. This resistance is controlled by one or two pairs of dominant genes. Some cultivars are resistant to D. phaseolorum var. meridionalis (southern stem canker). Their resistance is controlled by two or four pairs of genes (Rdc). There is no physiological resistance to D. phaseolorum var. caulivora, the agent of northern stem canker, but significant differences in susceptibility level exist among soybean genotypes. Molecular techniques (RAPD, PCR-RFLP) showed that significant variability was present within the population of D. phaseolorum var. sojae. Other species of fungi were suspected to exist within that population, which could not be distinguished on the basis of their morphological characteristics. This was subsequently confirmed by the sequencing of different regions of ribosomal DNA.

Genetic Analysis and Mapping of Resistance Gene to Seed Coat Mottle in Soybean

Soybean mosaic virus(SMV) causes a worldwide disease in soybean,reducing yield and making mottling of soybean seeds,and so largely losing soybean economy value. Resistant variety breeding is the most effective way to protect against the seed coat mottle. In this study,an F2:3 population,derived from Dongnong 3C624(susceptible) × Dongnong 8143(resistant) ,was used to study the genetic mechanism of the resistance,and map the resistant gene of seed coat mottle by simple sequence repeat(SSR) markers with bulked segregation analysis(BSA) method. Two parents and their F2,F3 population were inoculated with SMV strain No.1 in 2006 and 2007. Identification results in two years showed that resistance to SMV strain No.1 of Dongnong 8143 was controlled by one pair of dominant genes. Six hundred pairs of SSR primers were screened,and five SSR markers,Sat_297,Sat_229,Sat_317,Satt335,and Sct_188,were mapped near the resistance gene. Linkage analysis indicated that the re-sistance gene locus was located on the linkage group F. The order and genetic distance among the resistance gene and markers were Sat_297–12.4 cM–Sat_229–3.6 cM–SRSMV1–1.7 cM–Sat_317–2.4 cM–Satt335–13.8 cM–Sct_188. Sat_229,Sat_317,and Satt335 can be used for molecular assisted breeding.

Inheritance and gene tagging of male fertility restoration of cytoplasmic‐nuclear male‐sterile line NJCMS1A in soybean

AbstractThe F1, F2 and F2:3 of the NJCMS1A × ‘Zhongdou 5’ cross were used to analyse the inheritance of the male fertility restoration of the cytoplasmic‐nuclear male‐sterile line NJCMS1A in soybean. The results of genetic analysis showed two pairs of dominant genes conferring the male fertility restoration of NJCMS1A, which further confirmed previous results. The F2 population from the NJCMS1A × ‘Zhongdou 5’ cross was used for tagging the restorer genes for NJCMS1A with 664 pairs of simple sequence repeat primers selected randomly from the genetic linkage map of soybean published by Cregan et al. (1999). Satt626 on linkage group M and Satt300 on linkage group A1 of the integrated linkage map by Song et al. (2004) were found to link to the two restorer genes of NJCMS1A. The maximum‐likelihood estimates of the genetic distance between the two markers, Satt626 and Satt300, and the two restorer genes of ‘Zhongdou 5’ were 9.75 and 11.18 cM, respectively.

Inheritance of male fertility restoration of the cytoplasmic-nuclear male-sterile line NJCMS1A of soybean [Glycine max (L) Merr.

At present, no report on inheritance of male fertility restoration has been released, yet more than 10 cytoplasmic-nuclear male-sterile soybean lines as well as their maintainers and restorers have been developed. Based on our previous work, 25 restorers for the male-sterile line NJCMS1A were identified and the inheritance of male fertility restoration for these restorers was studied. The results showed that F1s between NJCMS1A and its restorers were completely male-fertile. The numbers of fertile and sterile plants in the F2 population of Cross I (NJCMS1A × N23601) and Cross II (NJCMS1A × N23683) corresponded to a segregation ratio of 15:1, and the numbers of non-segregation lines, 3:1 segregation lines and 15:1 segregation lines in F2:3 of the same two crosses fitted a 7:4:4 genotypic segregation ratio. The testcross BC1F1s between the F1s of the above two crosses and NJCMS1A, NJCMS1B showed a 3:1 segregation ratio. Accordingly, it was inferred that two pairs of duplicate dominant genes controlled the male fertility restoration of NJCMS1A in both crosses. Meanwhile, F2 of other 23 crosses between NJCMS1A and its 23 restorers showed a fertility segregation ratio of 3:1 or 15:1. The F1s of the five testcrosses between NJCMS1A and the F1s of five crosses selected from the above 23 crosses showed that fertility segregation was 3:1 in BC1F1s between NJCMS1A and F1s of the crosses of which fertility segregation fitted 15:1 in F2 population, while fertility segregation in BC1F1s was 1:1 for those fertility segregation fitted 3:1 in F2 population. Allelism tests showed that restore genes of all restorers in the experiment were allelic to two pairs of dominant genes. All results showed that some restorers bore one pair of dominant restore gene and the others bore two pairs of duplicate dominant gene. The mechanism of F1 male sterility of the cross N8855 × N2899 was discussed.

Inheritance of agronomic traits from the Chinese barley dwarfing gene donors 'Xiaoshan Lixiahuang' and 'Cangzhou Luodama'

The inheritance of agronomic traits from the barley dwarfing gene donors ‘Xiaoshan Lixiahuang’ and ‘Cangzhou Luodamai’ was studied. The results indicated that dwarf plants, six-row and short spikes, dense spikelets and naked kernels, respectively, were controlled by one pair of recessive genes, but a toothed awn was determined by one pair of dominant genes in both barley cultivars. The genes for the six characters in ‘Xiaoshan Lixiahuang’ were allelic to those in ‘Cangzhou Luodamai’. Genetic linkage was found among the genes for plant height, spike length and spikelet density. They were located on the long arm of chromosome 3 (3HL) in the order: plant height, spikelet density, spike length. The genes for naked kernels, six-row spikes and tooth awns were independent of each other, and carried on the long arms of chromosomes 1(7H), 2(H) and 7(5H), respectively. The dwarfing genes were the same as the gene uz in Japanese and Korean barley cultivars.

HERANÇA DA TOLERÂNCIA AO ALUMÍNIO EM TRIGO

Cruzamentos e retrocruzamentos foram efetuados entre os cultivares de porte semi-anão IAC-24 e Anahuac, tolerante e sensível à toxicidade de alumínio, respectivamente. Plântulas dos parentais e da geração F1 do cruzamento entre eles bem como dos retrocruzamentos para ambos os parentais foram avaliadas em soluções nutritivas de tratamento contendo 2 mg/litro de Al3+. Progênies de gerações F2 e F3 do cruzamento e progênies F2 dos retrocruzamentos foram também avaliadas . A tolerância à toxicidade de alumínio foi medida pela capacidade de crescimento da raiz primária central em solução nutritiva completa, após um tratamento de 48 horas em solução contendo 2 mg/litro de Al3+. O cultivar IAC-24 diferiu do Anahuac por um par de genes dominantes para tolerância à presença dessa concentração de alumínio nas soluções nutritivas.

CONTROLE GENÉTICO DA TOLERÂNCIA DO TRIGO À TOXICIDADE DE ALUMÍNIO EM SOLUÇÕES NUTRITIVAS

O cultivar IAC-227 (P1), de porte alto e tolerante à toxicidade de alumínio, foi cruzado com os genótipos mexicanos de porte semi-anão: CMH 79.481/CMH 77A.917 (P2), sensível à toxicidade de alumínio, e CMH 80A.747 (P3), tolerante. Plântulas dos parentais e da geração F1, bem como das gerações F2 e F3 dos cruzamentos P1 x P2 e P1 x P3 , e da geração F2 dos retrocruzamentos (P1 x P2) x P1, (P1 x P2) x P2, (P1 x P3) x P1 e (P1 x P3) x P3, foram avaliadas em soluções nutritivas de tratamento contendo 3 mg.L-1 de Al3+. A tolerância à toxicidade de alumínio foi medida pela capacidade de crescimento da raiz primária central em solução nutritiva completa, após um tratamento de 48 horas em solução contendo 3 mg.L-1 de Al3+. O cultivar IAC-227 diferiu do genótipo CMH 79.481/CMH 77A.917 por um par de alelos dominantes para tolerância à presença dessa concentração de alumínio nas soluções nutritivas. Os genótipos IAC-227 e CMH 80A.747 não diferiram quanto ao número de pares de alelos para tolerância. O CMH 80A.747 pode ser utilizado como fonte genética dessa tolerância, além de outras características agronômicas em programas de melhoramento.

CDNA Cloning, Characterization, and Functional Expression of 4S-(−)-Limonene Synthase fromPerilla frutescens

A molecular biological study on limonene synthase that catalyzes the cyclization of geranyldiphosphate to yield the olefin 4(S)-limonene, an intermediate in the biosynthesis of a monoterpenoid, perillaldehyde, inPerilla frutescensBritton has been carried out. We isolated and characterized 10 cDNAs homologous to spearmint limonene synthase cDNA from an expression library constructed from cotyledons of aPerillastrain homozygous for two pairs of dominant genes,GandH,which are responsible for the formation of 4(S)-limonene. Two of these cDNA clones were functionally expressed inEscherichia coli,yielding enzymes which were catalytically active in generating 4(S)-limonene from geranyldiphosphate. The longest open reading frame in the representative cDNA clone PFLC1 consisted of 1812 nucleotides corresponding to 603 amino acids. Its identity to the ORFs of spearmint limonene synthase, tobacco 5-epi-aristolochene synthase, and castor bean casbene synthase were 65, 35, and 30%, respectively. Genomic Southern blot analyses of various genotypes (GGHH, GGhh, ggHH,andgghh) ofP. frutescenssuggested that more than one copy of the PFLC1 DNA exists in strains having theHHgenotype. In contrast, no PFLC1 DNA sequences were found in the genomes of strains with thehhgenotype that are incapable of producing cyclohexanoid monoterpenes for lack of limonene synthase activity. Northern blot analyses, using a PFLC1 3′-flanking region as a hybridization probe, showed that PFLC1 mRNA accumulated in all the aerial parts of theGGHHplants, particularly in the leaves. In theggHHplants, on the other hand, PFLC1 mRNA was detected only in minute amounts in the stem and calyx.