Aneuploid analysis for protein content and tyrosinase activity in hexaploid wheat (Triticum aestivum L. em. Thell.)

Summary A study was conducted to locate the genes responsible for the determination of kernel protein content and tyrosinase activity in a hexaploid wheat variety UP 301 using Pb. C591 monosomic series. Genes located on chromosomes 4B, 5B, 6B, 7B, 3D and 7D of UP 301 controlled protein content of UP 301. Of these the B genome chromosomes were found to have genes for increased protein content while the D genome chromosomes were found to carry genes for low protein content. A major gene coding for tyrosinase enzyme was detected on chromosome 6B of UP 301 and a modifier on chromosome 5B. This indicated the possibility of improving these quality characters through chromosome manipulation.     

Genetic basis of grain filling rate in wheat (Triticum aestivum L. emend. Thell.)

Summary Grain filling rate in wheat (Triticum aestivum L. emend. Thell.) positively influences grain yield under a wide range of conditions. The effective utilization of this trait in breeding depends on an understanding of its genetic control. A study was, therefore, conducted to determine the genetic basis of grain filling rate in six crosses of wheat. Higher order genic interactions and/or linkage were important in the genetic regulation of grain filling rate (GFR) in the majority of crosses. Additive ([d]) and dominance ([h]) gene effects were important in the control of GFR in main ears (ME) and whole plant ears (WPE). Additive and additive × additive epistatic effects were the most important in the genetic control of GFR in last ears (LE). Location effects on genetic effects for GFR were significant (P < 0.05) in all ear types of some crosses except in ME. Genotype × environment interaction effects were important (P < 0.001) in LE and WPE.It was concluded that the inheritance of GFR is complex and is dependent on ear type. Breeding procedures that facilitate the exploitation of non-additive and additive gene effects were recommended for the genetic improvement of grain filling rate of wheat.     

Growth habit in common wheat (Triticum aestivum L. em. Thell.)

Summary A study of the Vrn genotypes of 642 spring wheats supports the theory that only Vrn1, Vrn2 and Vrn3 exist in Tricticum aestivum. In none of the varieties investigated Vrn4 was present. Seven varieties, which according to literature carry Vrn4, showed to carry Vrn1, Vrn2 and/or Vrn3. Some varieties were mixtures of Vrn-genotypes, which could mislead geneticists in pooled data analysis. Other causes for misinterpretation of the data could be hybrid necrosis, hybrid dwarfness or a wrong determination of plants with a winter habitus. Only Hope was dominant on another Vrn locus. Its haploid Vrn-genotype is Vrn1 vrn2vrn3 Vrn5.     

Major gene control of tolerance of bread wheat (Triticum aestivum L.) to high concentrations of soil boron

Summary The genetic control of tolerance of wheat to high concentrations of soil boron was studied for five genotypes. Each genotype represented one of five categories of response to high levels of boron, ranging from very sensitive to tolerant. Tolerance to boron was expressed as a partially dominant character, although the response of an F₁ hybrid, relative to the parents, varied with the level of boron applied. The F₁ hybrids responded similarly to the more tolerant parent at low B treatments and intermediate to the parents at higher treatments. Ratios consistent with monogenic segregation were observed for the F₂ and F₃ generations for the combinations (WI^*MMC) × Kenya Farmer, Warigal × (WI^*MMC) and Halberd × Warigal. The three genes, Bo1, Bo2 and Bo3, while transgressive segregation between two tolerant genotypes, G61450 and Halberd, suggested a fourth locus controlling tolerance to boron.     

Chromosomal location of powdery mildew resistance genes in common wheat (Triticum aestivum L. em. Thell.) 3. Gene Pm22 in cultivar Virest

Summary Common wheat cultivar Virest possesses mildew resistance which is different from resistances expressed by currently documented mildew resistance genes, detected by response to eleven differential wheat powdery mildew isolates. F₂ populations from hybrids of the 21 Chinese Spring monosomic lines with Virest revealed one major dominant gene, located on wheat chromosome 1D. The new gene is designated Pm22. Italian cultivars Elia, Est Mottin, Ovest and Tudest also showed the disease response pattern corresponding to Virest.     

Genetic control of resistance to soilborne wheat mosaic virus in Brazilian cultivars of Triticum aestivum L. Thell.

In Southern Brazil, under ideal conditions Soilborne Wheat Mosaic Virus (SBWMV) induces yield reductions to the wheat crop of over 50%. The only effective way of controlling the disease is through resistance. However, the inheritance of resistance is not been fully understood. The purpose of this work was to study the genetic control of resistance to SBWMV. Crosses were carried out between the resistant wheat cultivar Embrapa 16 and the susceptible cultivars BR 23 and IAC 5-Maringá, at the National Wheat Research Centre, Passo Fundo, RS, Brazil. The parents, F₁, F₂, and backcrosses were sown in plots in a field where soil was naturally infested with the vector of the virus, the fungus Polymyxa graminis, in order to promote natural infection. All plants were individually evaluated for severity and type of lesions, according to a scale of 0 to 5, where, 0 = absence of symptoms and 5 = plants severely affected by mosaic plus dwarfing and rosetting. The statistical analyses of the data showed broad sense heritability values between 43% and 55%. The data suggested the presence of two genes controlling resistance to SBWMV in the segregating population of both crosses. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic variation for nitrogen use efficiency in winter wheat (Triticum aestivum L.)

Summary The new European Common Agricultural Policy and environmental considerations are certainly to change agricultural practices toward low input cultivation systems. Nitrogen is one of the main inputs of winter wheat in northern France and it contributes highly to phreatic water pollution. A research programme has then been set up in order to study whether it is possible to breed for winter wheat cultivars using more efficiently N fertilisers. Less nitrogen would be applied, decreasing pollution risks and operational costs. It has been shown that a large variation exists for N related traits and for the resistance against N deficiency. On the one hand the cv Arche is very resistant to N deficiency, its yield on low N conditions (with no N fertiliser) is on average 89% of its yield on high N conditions (with a high N application). On the other hand, cv Récital is very susceptible to N deficiency as this same percentage is only 61%. A study on 10 hybrids showed that heterosis for grain yield was higher at low N level than at high N level. This was due to a higher number of grains per m².     

Genetic analysis of hexaploid wheat,Triticum aestivum using intervarietal chromosome substitution lines—protein content and grain weight

Summary The 21 intervarietal chromosome substitution lines of the cultivar Hope in Chinese Spring were used to analyse the genetic differences between the two cultivars Hope and Chinese Spring in grain protein content and grain weight.Only one chromosome of Hope, 5D, significantly influenced grain protein content of Chinese Spring. Its influence was of only minor effect and was to decrease protein content expression of Chinese Spring. It has been postulated that the genetic control of protein content, in this instance, is most likely due to many genes each of small effect.Five chromosomes of Hope influenced the 1000 grain weight value of normal Chinese Spring, all increasing its expression. Chromosomes 1A, 4A and 5B were of major effect and 3A and 6A of comparatively minor effect. A minimal estimate of five genes determines the difference in grain size between these cultivars. The possible evolutionary significance of the contribution of the A genome of bread wheat to grain size determination is discussed. On the basis of certain findings of this study, proposals are made for breeding for increased grain size in hexaploid wheat.     

A reciprocal F1 monosomic analysis of the genetic control of time of ear emergence,number of leaves and number of spikelets in wheat (Triticum aestivum L.)

Summary A reciprocal F₁ monosomic analysis of chromosomal differences between Spica and Bersée was carried out under controlled environment conditions. Chromosomes associated with differences in days to ear emergence, number of leaves and number of spikelets were identified. The results indicated that chromosome 2B of Spica carries a photoperiod insensitivity allele at the Ppd ₂ locus. Both Spica and Bersée appear to have a vernalization insensitity allele at the Vrn ₂ locus on chromosome 5B. On chromosome 3A, 4B, 4D and 6B factors were found with major effects on earliness per se, diffeences in ear emergence and number of spikelets which were independent of photoperiod and vernalization. The possibility that these factors influence growth rate is discussed.     

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em Thell.) 7. Gene Pm29 in line Pova

Chromosomal localization and linkage mapping of a powdery mildewresistance gene were conducted in the resistant wheat line Pova, derivedfrom a Triticum aestivum cv. Poros-Aegilops ovata-alien additionline. Monosomic analysis revealed that a major dominant gene was locatedon chromosome 7D. This gene possessed a distinct disease response patternagainst a differential set of Blumeria graminis tritici isolates andsegregated independently from resistance gene Pm19 also located onwheat chromosome 7D. Molecular genetic analysis showed that theresistance gene in Pova was specifically located on the long arm ofchromosome 7D closely linked to one RFLP and three AFLP markers. It isproposed that the new gene be designated Pm29.     

Genetic control of frost tolerance in wheat (Triticum aestivum L.)

Summary The frost tolerance of winter wheat is one component of winter hardiness. If seedlings are frost resistant, it means that they can survive the frost effect without any considerable damage. To study the genetic control of frost tolerance, an artificial freezing test was used. Frost tolerance is controlled by an additive-dominance system. The results of diallel analyses indicate the importance of both additive and non-additive gene action in the inheritance of this character. The dominant genes act in the direction of lower frost tolerance and the recessive genes in the direction of a higher level of frost tolerance. The results of monosomic and substitution analyses show that at least 10 of the 21 pairs of chromosomes are involved in the control of frost tolerance and winter hardiness. Chromosomes 5A and 5D have been implicated most frequently. The geneFr1 (Frost 1) was located on the long arm of chromosome 5A. Crosses between cultivars, chromosome manipulation and the induction of somaclonal variation may be suitable methods for broadening the gene pool for frost tolerance.     

Physiological studies on grass-dwarf selection lines in wheat (Triticum aestivum L.)

Summary Low power heating wires insulated in a flexible plastic strip were used to heat the shoot meristematic region of grass-dwarf genotypes to a precise temperature. The results indicate that the shoot apical meristem is the region requiring 26°C for the initiation of reproductive development in these genotypes. A secondary effect of the reproductive growth induced by high temperature treatments, was a reduction in the high levels of peroxidase enzymes found in vegetative grass-dwarf plants. The heating wire provides a precise method to identify Type I, II and III grass-dwarf genotypes according to their temperature requirements, of 26°C, 21°C and 16°C respectively, for reproductive growth under the same temperature (16 C) and photoperiod (12 hours).     

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em Thell.). 8. Gene Pm32 in a wheat-Aegilops speltoides translocation line

The wheat-Aegilops speltoides translocation line L501 exhibits a disease response pattern distinctive from that of documented powdery mildew genes after inoculation with differential Blumeria graminis tritici isolates. Results based on cytological C-bandings and monosomic analyses reveal that a dominant resistance gene derived from Ae. speltoides is located on a T1BL·1SS chromosome translocation in this line. The new gene is designated Pm32. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relationship between common wheat (Triticum aestivum L.) gluten proteins and dough rheological properties

This paper reports the correlation between the rheological properties of bread wheat dough and the types and quantities of endosperm proteins in 28 common wheat cultivars. Different methods were used to analyse the allelic composition of these cultivars and the relative quantities of the different proteins contributing to the gluten structure. Neither dough strength (W) nor tenacity/extensibility (P/L) correlated with allelic composition. Different wheats with the same allelic composition (i.e., with respect to glutenins) showed different rheological properties. The glutenins were the most influential components of W and P/L, especially the high molecular weight (HMW) glutenin subunits and in particular the type x form. These proteins seem to increase W and are the main constituents of the gluten network. The gliadins and low molecular weight (LMW) glutenin subunits appear to act as a “solvent”, and thus modify the rheological properties of the dough by either interfering with the polymerisation of the HMW glutenin subunits, or by altering the relative amounts of the different types of glutenin available. Thus, the protein subunits coded for by the alleles Glu-B1x7 and Glu-D1x5 stabilised the gluten network, whereas those coded for by Glu-B1x17 and Glu-D1x2 had the opposite effect. Dough properties therefore appear to depend on the glutenin/gliadins balance, and on the ratio of the type x and type y HMW proteins. The influence of external factors seems to depend on the allelic composition of each cultivar.     

Genetic and cytogenetic studies with a male sterile mutant of common wheat (Triticum aestivum)

Summary Genetic and cytogenetic studies were done on a male sterile mutant of the wheat variety Probus. Association of the 4A chromosome carrying the ms gene was studied in the F₁ of the male sterile Probus with Chinese Spring ditelo 4AS, with Transec and with line T4AS-DRS respectively. The presumption that the genetic male sterility of the mutant was due to a terminal deletion of the short arm of chromosome 4A could be confirmed.Linkage studies showed that the ms gene was at 17 map units from the dwarfing gene (Rht3) of Minister dwarf. This allows selection of short male sterile plants at the seedling stage.     

Stability analysis over seasons and locations of multilines of wheat (Triticum aestivum L.)

Summary Three multilines each of Kalyansona and PV 18 varieties of wheat were compared for their stability of yield and agronomic characters and disease resistance against the respective recurrent parents. The experiments were conducted for four years at nine locations.The multilines had more tillers and bolder seeds than the recurrent parents. There were, however, no differences for plant height, ear length and number of spikelets per spike.The genotypes x years x locations interaction was much more important than genotypes x years or genotypes x locations interaction as well as the main effects for genotypes. It is suggested that the number of test locations should be increased while decreasing the number of years.The stability parameters indicated that the multilines had a higher mean yield in the case of Kalyansona multilines whereas the yield of multilines of PV 18 was not significantly inferior to that of the recurrent parent. The regression coefficients were very close to unity except for KSML 3 (b=1.132). The deviations from regression were much larger for the multilines than for the recurrent parents.For rust resistance the multilines were superior over the varieties Kalyansona and PV 18.This is publication No. 9 of the series Studies on multilines in wheat (Triticum aestivum L.)     

Studies on multilines in wheat (Triticum aestivum L.).12. Breeding of a multiline variety by convergence of breeding lines

Summary The variation among the component lines of the KSML 3 (a multiline based on cultivar Kalyansona, spring bread wheat) was studied for agronomic characteristics. For days to earing and plant height the variation was small. This helped in imparting uniformity to the multiline. The lines had an improved tillering ability and had larger seeds. This partially explained the increased yield potential of the multiline as compared with Kalyansona.All the lines were susceptible only to one or two races of the yellow and brown rust. In no case any race was virulent against all the lines. In the field all the lines were resistant to both rusts.     

Genetic control of esterase-6 isozymes in hexaploid wheat and rye

Summary The EST-6 leaf esterase phenotypes from euploid, nullisomic-tetrasomic and rye chromosome addition and substitution lines of common wheat were determined using polyacrylamide gel electrophoresis. Evidence is presented to demonstrate that Est-6 is a new set of genes, that are expressed in the leaf. The Est-6 gene set were clearly distinguished from the Est-5 genes which are expressed in the grain. The three homoeoallelic loci, Est-A6, Est-B6 and Est-D6, were located on chromosomes 3A, 3B and 3D. An Est-R6 gene was located on chromosome 6R is involved in rye. Some considerations concerning homoeology between homoeologous group 3 of wheat and the rye chromosome 6R are made.     

Partial asynapsis involving specific chromosomes in intervarietal hybrids of Triticum aestivum L.

Summary Metaphase I chromosome association of the monosomic F1 and the backcross progenies made to develop a monosomic line in the Spanish common wheat Pané-247 was analyzed using a Giemsa C-banding technique. This permits the unequivocal identification of nine meiotic chromosomes (4A, 7A and the seven chromosomes of the B genome). The average frequencies of pairing per arm and of univalents for these nine pairs per arm and of univalents for these nine pairs indicate a difference between arms. The F1 showed asynapsis with univalents in 18.5 per cent of PMC's in intervarietal hybrids. This mainly involved chromosomes 4A, 1B and 6B which also have the largest amount of constitutive heterochromatin. The possible causes of reduced metaphase I association and its rapid decrease during backcrossing are discussed in relation to polymorphism between heterozygous homologous chromosomes.     

Inheritance of leaf angle in Triticum aestivum L.

Summary A 6×6 diallel was prepared to study the inheritance of leaf angle in T. aestivum L. Genetic analysis in terms of diallel cross parameters and graphic analysis indicated the control of additive gene effects in the expression of this character. The results of F₁ analysis were supported by the analysis of F₂ data.