Population means and correlation analyses of growth parameters in lisianthus (Eustoma grandiflorum Shinn.)

Summary The variation in growth characteristics among lisianthus (Eustoma grandiflorum Shinn.) genotypes was investigated. The genetic control of several growth parameters was studied by analysing parental, F1, BC1 and F2 populations. The parameters analysed were stem elongation rate (SE), stem diameter (SD), leaf width (LW), number of nodes (NN), node length (NL) and days to flowering (DF). The genotypes tested exhibited great variation for all parameters. A particularly wide variation was noted for SE, ranging from 3 to 56 mm/week. This variation was partially attributed to a differential sensitivity to rosette formation. There was a marked positive heterosis for SE, SD, LW and NN; these parameters proved to be genetically correlated within segregating populations. DF was slightly negatively correlated with SE, NN and NL. It was concluded that SE and DF were independently controlled.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1196-E, 1993 series.     

Interaction between the eui gene and thermo-sensitive genic male sterility in rice

Panicle enclosure is a typical phenotype of almost all male-sterile rice lines. An elongated uppermost internode (eui) mutant exhibited notably rapid elongation of the uppermost internode at the heading stage; this is considered as a potential mechanism to eliminate panicle enclosure. We developed thermo-sensitive genic male-sterile (TGMS) eui mutants that were characterized by notably elongated uppermost internodes. The elongation of the uppermost internode in the TGMS eui mutant Changxuan 3S (CX) is mainly attributed to an increase in cell number and cell elongation, the latter being the more significant process. Temperature treatments revealed that the effects of temperature on panicle exsertion were similar to those on fertility and that the most temperature-sensitive stage coincides with the period from the formation of the pollen mother cell to meiosis during panicle initiation. These results indicate that elongation increases as temperature decreases and that the expression of the eui gene is more efficient at low temperatures than at high temperatures. In hybrid rice seed production using the TGMS eui mutant, the temperature range should be optimized at 24–28°C in order to preserve the development of completely male-sterile pollen and to eliminate panicle enclosure. Consequently, by using TGMS eui rice lines, gibberellin application can be avoided, thereby reducing the cost of hybrid seed production. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genetic studies of speciation in cultivated rice. 5. Inter- and intraspecific differentiation in the waxy gene expression of rice

Summary To get an insight in the gene regulation at the waxy locus of rice, the Wx gene product (Wx protein) controlling the synthesis of amylose was examined by electrophoretic techniques. Among nonwaxy rice strains, two different alleles, Wx ^a and Wx ^b, were found at the waxy locus. Wx ^a drastically enhanced the quantitative level of Wx protein as well as the amylose content in endosperm starch as compared with Wx ^b. The alleles acted additively in triploid endosperms. This implies that regulatory elements responsible for the Wx gene expression are on the same chromosome. The distribution patterns of Wx ^a and Wx ^b in five species of Oryza revealed that the regulatory changes are closely related to racial differentiation within a common rice species (O. sativa), suggesting that Wx ^b might have been selected for through the difference in grain quality during domestication.     

T1 locus in cotton is the candidate gene affecting lint percentage, fiber quality and spiny bollworm (Earias spp.) resistance

A genetic linkage map of chromosome 6 was constructed by using 270 recombinant inbred lines originated from an upland cotton cross (Yumian 1 × T586) F₂ population. The genetic map included one morphological (T₁) and 18 SSR loci, covering 96.2 cM with an average distance of 5.34 cM between two markers. Based on composite interval mapping (CIM), QTL(s) affecting lint percentage, fiber length, fiber length uniformity, fiber strength and spiny bollworm resistance (Earias spp.) were identified in the t₁ locus region on chromosome 6. The allele(s) originating from T586 of QTLs controlling lint percentage increased the trait phenotypic value while the alleles originating from Yumian 1 of QTLs affecting fiber length, fiber length uniformity, fiber strength and spiny bollworm resistance increased the trait phenotypic value.     

Influence of plant age,disease incubation time,and host plant resistance on Verticillium wilt symptom expression in lucerne (Medicago sativa)

Summary The most economical means to control Verticillium wilt in lucerne, caused by Verticillium albo-atrum, is through resistant cultivars. Most Verticillium wilt resistance evaluations use some form of root-cut-soak inoculation procedure. In Trial 1, three lucerne cultivars were inoculated at eight plant ages and plant symptoms were scored at ten successive weekly intervals. Trial 2 consisted of two cultivars inoculated at ten plant ages and symptoms were evaluated at eight weekly intervals. In an experiment to study the genetics of resistance to this pathogen, four plants showing no visual symptoms were selected from each of four germplasms. The selected populations were crossed in diallel fashion. The population crosses plus the parents were evaluated for resistance to V. albo-atrum. Results from Trial 1 and Trial 2 showed disease severity increased with increasing inoculation age and with increasing scoring age. Cultivar symptom expression interacted with inoculation age, but not with scoring age. The diallel analysis supported resistance to Verticillium wilt being conferred by additive gene action, as heterosis was not detected and general combining ability mean square was 3.75 times larger than the specific combining ability mean square.     

The genetic relations between length of time to germination and seed dormancy in lisianthus (Eustoma grandiflorum)

Summary The inheritance of speed of germination and its genetic relations with seed dormancy was investigated in lisianthus (Eustoma grandiflorum). The study was based on data from parental, F1, BC1F1 and F2 generations of a cross between a normally germinating genotype (P1) and a chill-requiring genotype (P2). The mean post-chilling germination speed of P2 was considerably lower than that of P1. Germination speed was found to be under nuclear embryonic control. Analysis of generation means for prechilled seeds revealed an additive gene action with complete dominance of the alleles conferring higher germination speed, since the means of the F1 and the BC1 (P1) were indentical to that of P1. Such dominance was not found for unchilled seeds, in which the mean germination speed of the F1 and the BC1 (P1) was lower than that of P1. It was hypothesized that slow germination speed was induced by pleiotropic effects of seed dormancy alleles. Seed prechilling seemed to eliminate these effects in progeny heterozygous for dormancy alleles, but not in progeny homozygous for dormancy alleles.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, No 1292-E, 1993 series.     

Barley mildew in Europe: population biology and host resistance

Summary Isolates of the barley mildew pathogen from the air spora over a large part of Europe and from fields of variety mixtures, were tested for virulence against 12 host resistance alleles. Subsamples were tested for their response to triadimenol fungicide and analyzed for 10 DNA loci using RAPD markers and PCR. There was a large range of haplotypes spread over Europe; irregularity in the distribution was probably due mainly to non-uniform use of the corresponding host resistances and fungicides. A large range of variation was also detectable within individual fields. Positive gametic disequilibria distorted the distribution of virulence alleles among haplotypes and reduced the number of haplotypes detectable in the sample. Analysis of the spread of the newly selectedVal3 allele into different European sub-populations indicated that gene flow throughout the population may be rapid for alleles that have a selective advantage.Fungicide resistance was widespread in areas known for intensive use of fungicides for mildew control. Four classes of fungicide response were detectable and particular virulence haplotypes were found to be characteristic for each class.Variety mixtures used in the former German Democratic Republic (GDR) reduced mildew infection, and thus fungicide use, during the years 1984–1991 despite the limited variation in host resistance among the mixtures. A tendency for complex pathogen races to increase in mixture crops was reversed by the large-scale re-introduction of fungicides for mildew control in 1991. The mixture strategy appeared to be more successful than using the same resistance alleles in pure monoculture or combining them in a single host genotype.     

Stable gene expression in transgenic apple tree tissues and segregation of transgenes in the progeny — Preliminary evidence

Summary We report here, for the first time, the stable expression and Mendelian segregation of transgenes in a tree species. So far we have evidence for a 1 : 1 segregation of thenos gene in the R1 of transgenic apple progeny. In addition we present evidence for stable gene expression of bothnos and the co-transferred genenptII in the fruit flesh of the apple fruit some 7 years after the initial transformations.     

Transient gene expression in transformed banana (Musa cv. Bluggoe) protoplasts and embryogenic cell suspensions

Summary In order to introduce currently-available genes with agronomical value into banana, two genetic transformation protocols have been optimized.Firstly, regenerable protoplasts isolated from embryogenic cell suspensions of the cultivar Bluggoe have been used for the introduction of several chimaeric uidA gene constructs by electroporation. With the inclusion of polyethylene glycol and heat shock, the frequency of transiently expressing protoplasts reached 1.8% as shown by an in situ -glucuronidase assay. A duplicated 35S promoter with an alfalfa mosaic virus leader sequence (pBI-426) induced the highest expression rate among the constructs tested.Embryogenic cell suspensions of cv. Bluggoe have also been bombarded with accelerated particles coated with a high expression uidA gene construct (pEmuGN) using a biolistic gun. After a partial optimization of the procedure, transient GUS assays reproducibly demonstrated the presence of 400 blue foci in 30 l of settled cell volume (approximately 25 mg cells). Selection and characterization of antibiotic-resistant transformed cultures is in progress.Abbreviations AMV alfalfa mosaic virus - GUS -glucuronidase - TGE transient GUS expression - uidA gene for -glucuronidase     

Relationships between amino acid contents and peroxidase isozymes in leaf blades of mulberry (Morus spp.)

Summary Varietal differences of amino acid contents and total nitrogen content were determined in the leaf blades of mulberry (Morus spp.) which is the food source of the silkworm. Between the peroxidase isozyme genotypes, Px ₁ ¹ Px ₁ ¹ or Px ₁ ¹ Px ₁ ¹ and Px ₁ ² Px ₁ ², there were significant differences at the 1% level in total amino acid content and contents of threonine, aspartic acid and serine, at the 5% levelin contents of isoleucine, glycine and phenylalanine. All of these amino acid contents were higher in Px ₁ ¹ Px ₁ ¹ and Px ₁ ¹ Px ₁ ¹ Px ₁ ¹ than in Px ₁ ² Px ₁ ². But there was no significant difference in contents of the other amino acids and total nitrogen between the genotypes.     

The allelic relationship between A IP(internal pigmentation) and A RC (red cabbage) in Brassica oleracea var. capitata L.

Summary Internal anthocyanin pigmentation (IP), previously reported to be controlled by a single gene dominant to aa of normal green cabbage, was studied further to determine its relationship to A ^RC A ^RC of red cabbage. When IP line R52 was crossed with an early red cabbage line. F₁ heads were pigmented throughout, but pigment intensity was intermediate. Subjective classification of F₂ plants by pigmentation intensity and distribution scores gave a ratio of 1 intense red throughout (red cabbage):2 medium red throughout:1 medium to light red, restricted to the central portion of the head (IP). The genotypes A ^RC A ^RC: A ^RC A ^IP: A ^IP A ^IP. respectively, are proposed to explain these 3 phenotypic classes. F₂ progenies contained no normal green plants, supporting the conclusion that A ^IP and A ^RC are alleles.Technical Paper 7052, Oregon Agricultural Experiment Station.     

The use of general and specific combining abilities in a context of gene expression relevant to plant breeding

Many common traits are believed to be a composite reflection of multiple genetic and environmental factors. Recent advances suggest that subtle variations in the regulation of gene expression may contribute to quantitative traits. The nature of sequence variation affecting the regulation of gene expression either in cis (that is, affecting the expression of only one of the two alleles in a heterozygous diploid) or in trans (that is, affecting the expression of both alleles in a heterozygous diploid) is a key and usually unknown feature for the breeders. If the change in expression acts entirely in cis, then the structural gene can be treated as a candidate gene and a potential target for marker-assisted selection. Therefore, gene surveys for cis-regulatory variation are a first step in identifying potential targets for marker-assisted breeding. Here, we discuss in detail the “genome-wide analysis of allele-specific expression differences” (GASED) approach. The GASED approach was developed to screen for cis-regulatory variation on a genome-wide scale. In GASED, mRNA abundance is treated as if it were a quantitative phenotypic response variable, whose genetic between-F₁ hybrid variance is partitioned into additive and non-additive components. In plant breeding, this partitioning of the genetic variance is well known in the context of estimation of general and specific combining abilities for diallel crossing schemes. We demonstrate the GASED method using Arabidopsis thaliana data. The method can be used to screen for cis-regulatory variation in any crop species for which diallel crossing schemes are appropriate and genomic tools are available.     

Transgenic apples display stable gene expression in the fruit and Mendelian segregation of the transgenes in the R1 progeny

Summary The transfer of genes via Agrobacterium to a perennial tree crop such as apple, requires monitoring of the stability of the genes in the target tissues such as the fruit and leaves. If the same genes are required for introgression into a conventional breeding programme, their expression also needs to be stable and their inheritance should follow a normal Mendelian pattern. In the following report we show, for the first time, the stable expression and Mendelian segregation of transgenes in a tree species. We have evidence for a 1:1 segregation of the nos and nptII genes among R1 progeny from a transgenic apple parent. In addition, we present evidence for stable gene expression of both nos and the co-transferred gene nptII in the flesh of apple fruit 7 years after the initial transformation.Abbreviations nos nopaline synthase - nptII neomycin phosphotransferase - ACC 1-aminocyclopropane carboxylic acid - PVP polyvinylpyrrolidone - PCR polymerase chain reaction - EFE ethylene forming enzyme - B.t. Bacillus thuringiensis     

Hybrid grass-clump dwarfness in wheat: Physiology and genetics

Summary The growth of all grass-clump dwarfs is sensitive to temperature with low temperature giving rise to the grass-clump phenotype and high temperature producing normal phenotype. A continuous temperature of 26°C is required for normal growth of Type 1 dwarfs, a continuous temperature of 21°C is required for normal growth of Ty[e 2 dwarfs and a continuous temperature of 16°C is required for normal growth of Type 3 dwarfs.Genetic studies show that the inheritance of the grass-clump characteristic is due to three complementary dominant genes.The grass-clump growth habit is produced as a result of the temperature sensitivity of the apical meristem. In grass-clump plants low temperature treatment results in the cessation of cell division, DNA synthesis and phospholipid synthesis in the apical meristem. The primary temperature lesion has not been identified. Prolonged low temperature treatment of grass-clump plants results in extensive cell necrosis in a region just below the apical meristem; this cell death results in the permanent inactivation of the apical meristem.Supported in part by the National Research Council of Canada.     

Root pulling resistance in rice: Inheritance and association with drought tolerance

Summary Avoidance of drought stress is commonly associated with root system characteristics and root development. The inheritance of root pulling resistance in rice (Oryza sativa L.) was investigated and its relationship with visual field scores for drought tolerance was studied. Transgressive segregation for high root pulling resistance was observed in 3 crosses (high x high, low x high, and intermediate x intermediate). Both dominant and additive genes control the variation. F₁ superiority for high root pulling resistance was observed and could be exploited in an F₁ hybrid breeding program. F₂ distribution curves indicated that plants highly resistant to root pulling can be obtained not only from low x high and high x high crosses, but also from intermediate x intermediate crosses. Root pulling resistance in rice has a low heritability (39 to 47%). Thus, breeding for a high root pulling resistance may best be accomplished by selection based on line means rather than individual plant selection. Field screening showed significant differences in leaf water potential among random F₃ lines. F₃ lines with higher leaf water potential had better visual scores for drought tolerance. Visual drought tolerance scores were correlated with root pulling resistance. Plants with high root pulling resistance had the ability to maintain higher leaf water potentials under severe drought stress. The usefulness of the root pulling technique in selecting drought tolerant genotypes was confirmed.     

Co-heritability: Its relation to correlated response,linkage, and pleiotropy in cases of polygenic inheritance

Summary The concept of co-heritability is proposed in order to describe the genetic associations within pairs of quantitative traits. The mathematical relations between co-heritability, correlated response, and the coefficient of genetic prediction are shown. From observations in a diallel experiment with 10 year-old slash pine it appeared that the genetic association of a character pair is a phenomenon of low genetic variability and high inheritance. Exploratory indicators are proposed to estimate the nature of the genetic association.     

Linkage studies in rice (Oryza sativa L.): Flowering,growth habit and pigmentation

Summary Genetic analysis of ten characters in a rice cross M 18 × T979 revealed the interaction of duplicate, complimentary, inhibitory and anti-inhibitory genes in conditioning pigment in eight characters and in determining flowering and growth habit. The action of genes and their interactions indicated by complex ratios for all the ten characters are claimed to be the first reports. pleiotropic action of two complementary genes and four duplicate genes has been detected. Two linkage groups, one with three genes (Ai-Plg-Ai-Pau-Pja) and the other with nine genes (Plg_a-Pin_a-Er_a-Ef_a-I-Plg-Pg₁-Pn₁-Pr₁-Pnr₁) have been constituted. The three-gene group is tentatively placed in the IV mp group and the other with nine genes is assigned to the X fh group. As a result of the present investigation Ai-Plg is an addition to the IV mp group and Plg_a, Pin_a, Er_a, I-Plg, Pg₁, Pn₁ Pr₁ and Pnr₁ are contributions to the X fh group.     

Ecological aspects of transgenic sugar beet: transfer and expression of herbicide resistance in hybrids with wild beets

Summary An increasing number of genetically engineered cultivars of several crops is being experimentally released into the environment. In future, crops with new transgenic traits will probably play an important role in agricultural practice. The long-term effect of transgenes on community ecology will depend on the distribution and establishment of transgenic plants in the wild, on the sexual transfer of their new genes to the environment and on the potential ecological impact of the transgenic trait. The starting point was the use of transgenic sugar beet lines, Beta vulgaris subspec. vulgaris var. altissima DÖLL (Helm 1957), with transgenes coding for rhizomania and herbicide (BASTA^®) resistance. The first two questions to answer were: Can the transgenes be transferred via pollen to wild beets, Beta vulgaris subspec. maritima (L.) ARCANG. or cultivated relatives such as red beet or spinach beet and are they expressed in the hybrids? Can transgenes be monitored in young Beta vulgaris-hybrids? The experimental transfer of transgenes was conducted in 1993 at a field location in northern Germany. The beets were hand-pollinated with transgenic pollen. In a non destructive biotest, the hybrid seedlings were tested for herbicide resistance. Transgenic plants showed no noxious phenotypic effects whereas control plants developed leaf necroses. All herbicide resistant hybrids within the biotest were assumed to be transgenic.     

The inheritance of host plant effect on latency period of wheat leaf rust in spring wheat. I: Estimation of gene action and number of effective factors in F1, F2 and backcross generations

Summary Crosses were made between the highly susceptible Little Club and the partially resistant cultivars Westphal 12A, Akabozu and BH 1146 to obtain F1, F2 and backcross generations. Latency period (LP) was determined in plants inoculated at the young flag leaf stage with a monospore culture of race Flamingo of wheat leaf rust. Broad sense heritability of LP in the F2 averaged 0.8. The genes showed partial to almost complete recessive inheritance. Scaling tests indicated that additive gene action was the most important factor in the inheritance of partial resistance. The tests showed that there were no indications for additive x additive, additive x dominance or dominance x dominance interactions. The number of effective factors was estimated as one or two for Akabozu, three or more for Westphal 12A, and two or three for BH 1146. BH 1146 also possessed a (semi-)dominant gene for a lower infection type which was temperature sensitive in its expression. The genes of the various parents had unequal effect on LP.