The production and characterization of recombination between chromosome 3N of Aegilops uniaristata and chromosome 3A of wheat.

Six wheat lines with recombination between Aegilops uniaristata chromosome 3N and wheat chromosome 3A were produced. These were characterized in terms of exchange points by RFLP analysis. Chromosome 3N carries an undesirable brittle rachis gene and three of the recombinant lines had lost this character. The results also support previously published evidence of a pericentric inversion in chromosome 3N relative to the wheat homoeologous group 3 chromosomes.

In vitro propagation of Litsea cubeba (Lours.) Pers., a multipurpose tree.

A rapid clonal propagation system has been developed for Litsea cubeba. Following investigation of a range of cytokinins and a variety of explant sources (shoot tip, node, leaf and petiole) it was established that 6-benzyladenine with shoot tip explants gave optimal multiple-shoot induction. In vitro rooting on growth-regulator-free medium was possible and over 100 plantlets were successfully weaned to the glasshouse.

AFLP variation in wild barley (Hordeum spontaneum C. Koch) with reference to salt tolerance and associated ecogeography.

Thirty-nine genotypes of Hordeum spontaneum were selected from three geographically separated areas (southwestern, northern, and southeastern) of the Fertile Crescent. The lines were subject to AFLP (amplified fragment length polymorphism) analysis from which a similarity matrix was produced. A dendrogram of the data showed, with two exceptions, that the genotypes grouped together according to area of origin. This was confirmed by principal coordinate analysis in which the first principal coordinate separated the genotypes of the southwestern area from the other two areas, which in turn could be separated by the second principal coordinate. While genotypes from the same site of origin can exhibit very similar AFLP profiles, sharp genetic differences were detected between genotypes separated by relatively short distances. Thirty of the 39 genotypes were subjected to hydroculture salt tolerance tests. These were analysed for shoot Na+ content and carbon isotope composition (δ13C) after 4 weeks of treatment (100 mol∙m−3 NaCl). Shoot Na+ content and δ13C were highly correlated. Twelve AFLP markers were found to be associated with both shoot Na+ content and shoot δ13C and were also associated with site of origin ecogeographic data, particularly longitude. The most salt tolerant genotype came from Ilam in the southeastern area and the most salt sensitive genotype originated in the southwestern area. The 12 markers were partitioned into groups that showed significant associations within groups but no significant association between groups. In a multiple regression analysis, three AFLP markers, from separate groups, accounted for more than 60% of the variation for shoot Na+ content and δ13C. The results demonstrate the effectiveness of AFLP fingerprinting in genetic studies of complex traits at the wild species and (or) population level.

Androgenesis of the salt tolerant shrub Atriplex glauca.

Clusters of flowers, 4 to 5 days old, were successfully cultured on Nitsch and Nitsch (1969) medium in the presence of growth regulators. An average of 20 plants per explant were produced after 6 weeks. Organized growth was obtained only from flowers collected during spring or early summer. Microscopic observations during shoot regeneration indicated that shoot organogenesis took place directly from microspores to give rise to shrubby plants. Their subsequent transfer onto fresh medium in the presence of a different set of growth regulators resulted in the production of "haploid" and "diploid" lines in the proportion of 50∶50. The presumed haploid plants were successfully rooted on Woody Plant Medium (Lloyd and McCown 1980) within a week. The significance of androgenic lines for the study of salt tolerance and the genetic improvement of Atriplex forage quality is discussed.

Molecular marker analysis of Helianthus annuus L. 2. Construction of an RFLP linkage map for cultivated sunflower.

A detailed linkage map of Helianthus annuus was constructed based on segregation at 234 RFLP loci, detected by 213 probes, in an F2 population of 289 individuals (derived from a cross between the inbred lines HA89 and ZENB8). The genetic markers covered 1380 centiMorgans (cM) of the sunflower genome and were aranged in 17 linkage groups, corresponding to the haploid number of chromosomes in this species. One locus was found to be unlinked. Although the average interval size was 5.9 cM, there were a number of regions larger than 20 cM that were devoid of markers. Genotypic classes at 23 loci deviated significantly from the expected ratios (1∶2∶1 or 3∶1), all showing a reduction in the ZENB8 homozygous class. The majority of these loci were found to map to four regions on linkage groups G, L and P.

In vitro propagation of Clerodendrum colebrookianum Walp., a potential natural anti-hypertension medicinal plant.

A rapid clonal propagation system for Clerodendrum colebrookianum Walp. (Verbenaceae), a anti-hypertension folk medicinal shrub has been developed. A range of cytokinins has been investigated for multiple shoot induction with shoot apex, axillary shoot, leaf, petiole and root explants. Optimum shoot induction occurred with axillary buds using 6-benzyladenine where an average of 21 shoots were produced per explant in 6 weeks. Subculturing the newly produced shoots, by separating into groups of five shoots, produced an average of 43 new shoots per culture within 4 weeks. In vitro rooting and weaning of over 200 plantlets was completely successful. Cytological studies revealed no visible abnormalities in chromosome number.

Molecular marker analysis of Helianthus annuus L. 1. Restriction fragment length polymorphism between inbred lines of cultivated sunflower.

cDNA and PstI genomic clones have been used to assess levels of restriction fragment length polymorphism (RFLP) in Helianthus annuus and to determine the inter-relationships between a diverse set of 24 inbred lines. Of the cDNA clones screened 45% were useful as RFLP probes, compared to less than 20% from the PstI library, which showed high levels of redundancy for high copy sequences. Fifty-seven low-copy DNA probes (23 PstI and 34 cDNA clones) were used to fingerprint 12 maintainer (B) lines and 12 restorer (R) lines. The average number of RFLP variants per probe was found to be 3.2, with a mean polymorphic index of 0.49, indicating that high levels of nuclear DNA polymorphism are to be found in cultivated sunflower. Cluster and principal coordinate analysis of the fingerprinting data clearly separated the maintainer and restorer lines, but there was a degree of association between 2 unbranched R-lines and the B-line germ plasm pool.

Field performance of derived generations of transgenic tobacco.

Two inbred cultivars of Nicotiana tabacum (tobacco), 'Samsun' and 'Xanthi', were transformed with the plasmid pBI 121 using Bin 19 in Agrobacterium tumefaciens. The plasmid carries the nptII gene conferring kanamycin resistance and the uidA gene encoding ß-glucuronidase (GUS). Progeny carrying the genes in the homozygous condition were identified and selfed over several generations. One line homozygous for the introduced genes and one untransformed control from each cultivar were then selected and crossed reciprocally to give four families per cultivar. Seeds from each family were grown in a replicated field trial and all plants scored for a range of morphological and agronomic characters. In addition, leaf samples were taken and GUS activity measured. In the 'Samsun' material, which contained one copy of the introduced gene at a single locus and showed high levels of GUS expression, the transformed homozygote showed twice the level of GUS activity as the hemizygotes, wheareas in the 'Xanthi' line, which had a lower level of GUS, the hemizygotes showed the same level of GUS activity as the transformed homozygote. The agronomic data showed differences between the families, but the source of such differences could not be ascribed unambiguously. The results are discussed in the light of related information on gene expression and field performance from other transgenic material.

The inheritance of genetic markers in microspore-derived plants of barley Hordeum vulgare L.

Biochemical, molecular and morphological markers have been used to monitor the segregation of alleles at major gene loci in microspore-derived lines of four spring barley crosses and their parents. Significant deviations from the expected Mendelian ratios were observed for four of the ten markers studied in the cross. Distorted ratios were associated with loci located on chromosomes 4H and 6H. The differential transmission of alleles was in favour of the responsive parent (Blenheim) used in the anther culture studies. For the α-Amy-1 locus on chromosome 6H, the preferential transmission of Blenheim alleles was most pronounced in the haploid regenerants that were colchicine treated. These results are discussed in relation to the genetic control of androgenetic response in barley and with respect to the exploitation of another culture in barley improvement.

Cross prediction in a potato breeding programme by evaluation of parental material.

It is shown that it is possible to obtain an indication of the parental value of heterozygous cultivars of potatoes for the characters breeders' preference, total tuber weight, mean tuber weight and number of tubers. Three methods of predicting the characteristics of progeny produced from particular parental cultivars were examined, namely: univariate cross prediction (based on mean and variance), mid-parent values and mid-self values. All provided some indication of which crosses would give superior progeny, but univariate cross prediction gave rankings which correlated most highly with observed performance in the second clonal year for the characters breeders' preference and total tuber weight. Interestingly, mid-self values gave the best predictions in the case of mean tuber weight and number of tubers. It is suggested that such predictions of 'parental value', especially when based on univariate cross prediction at the seedling stage, are worth carrying out in practical breeding programmes.

The use of cross prediction methods in a practical potato breeding programme.

Most previous studies on cross prediction methods have examined relatively few crosses, particularly in relation to the numbers involved in most breeding programmes. In this paper the feasibility of using cross prediction methods was examined in a practical potato (Solanum tuberosum) breeding scheme by the analyses of progeny from 52 crosses. The variate considered was breeder's preference, a visual assessment made of the harvested tubers to estimate their commercial potential. The results showed that it was possible to identify the superior crosses. Cross prediction based simply on the mean preference scores, averaged over scorers and clones within progenies, estimated on seedlings or first clonal year plants, provided the best estimate of a progeny's performance in the third clonal generation. Predictions based on the expected proportion of clones that would transgress a given target value also provided a good indication of a progeny's potential. The poorest prediction was obtained by using the observed frequency of desirable clones in a progeny sample. The implications for potato breeding are discussed.

Selection for yield and yield components in the early generations of a potato breeding programme.

A number of unselected potato (Solanum tuberosum L.) clones were grown at two locations (a seed site and a ware site) in three consecutive years. The repeatability of total yield and yield components in the first two clonal years was compared with the same characters recorded in the third clonal year. Selection for yield in the first clonal year was only marginally more effective than a random reduction in number of genotypes, while selection in the second clonal year appeared to be somewhat more effective as judged by performance in the third clonal year. The inefficiency of selection in the first clonal year was ascribed, at least in part, to the inaccuracy of yield assessment as well as the "carry-over" effect of the mother tubers. Correlations of total yield were higher between different years in the same location than between different locations. Selection under growing conditions suitable for production of seed tubers tended to result in selection of early maturing clones which would not necessarily be optimal for ware growing conditions.

Field performance of lines derived from haploid and diploid tissues of Hordeum vulgare.

Plant tissue culture technology is of increasing interest to plant breeders. As part of a continuing investigation into breeding methods with spring barley two studies were conducted to assess the field performance of the progenies of material regenerated in tissue culture. The first study involved two spring barley cultivars, 'Golden Promise' and 'Mazurka' and compared lines produced from immature embryo (IE) derived callus with those from embryos developed by the Hordeum bulbosum (Hb) technique of chromosome elimination. In general the mean values for the seven characters scored were lower for the IE than the Hb material. In the second study F1 hybrid material ('Golden Promise'x'Mazurka') was used and doubled haploid lines produced by the H. bulbosum and microspore culture (M) techniques were compared with single seed descent (SSD) material. Analysis of these F∝ samples indicated that the mean values for the M lines were significantly lower than those of the Hb and SSD lines. Furthermore, data from the M lines showed significant evidence of variation created during the culture phase. The implications of these findings for barley breeding are discussed.

Competitive effects in monocultures and mixtures of spring barley (Hordeum vulgare).

The presence of significant levels of intergenotypic competition amongst barley (Hordeum vulgare) genotypes has profound consequences for barley breeding programmes. Breeding programmes based on the pedigree system attempt to identify genotypes in genetically heterogeneous populations but the elite genotypes are grown in monoculture. Thus, to attain varietal status genotypes produced by this breeding strategy must perform well in mixtures as well as in pure stands. The effectiveness of early generation selection may be hampered by intergenotypic competition. To examine this problem in spring barley, a modified substitution experiment (Mather and Caligari 1981, 1983) was used and included genotypes sampled from a random set of inbred lines generated without conscious selection. This approach to the investigation of competitive effects in barley indicated the presence of significant levels of intergenotypic competition for a range of agronomic characters. The analyses allowed a distinction to be made between aggression (a) and response (r) with the component r displaying greater variation than a. The lack of correlation in the distribution of a and r suggested that they were under separate genetic control and hence adjustable by selection. The implications of these results for barley improvement, the use of varietal mixtures and mixed cropping are discussed.

Genetical investigations into ß-glucan content in barley.

Random inbred lines produced by doubled haploidy (DH) and single seed descent (SSD) have been used to investigate the genetics of ß-glucan (gum) content in barley (Hordeum vulgare). Genetical analyses indicated that gum content is controlled by a simple additive genetic system. Significant negative genetic correlations were observed between ß-glucan content, thousand grain weight and height in the DH samples. These correlations were much reduced in the SSD samples and would suggest linkage of the genes controlling these characters. The presence of repulsion linkages could be exploited in a barley breeding programme by producing F1 derived DH to generate recombinants with high thousand grain weight and low ß-glucan content. Genetical parameters estimated from DH and F3 samples have successfully been used to predict the number of inbred lines transgressing the parental range for ß-glucan content and bivariate combinations involving ß-glucan.

The use of pollen irradiation in barley breeding.

Second generation progenies (M2) derived from crosses using barley pollen irradiated at 500, 1,000 1,500 and 2,000 rads increasingly resembled the maternal parent. 'Golden Promise', but contained some characteristics derived from the paternal parent, 'Magnum'.

Competitive interactions in Drosophila melanogaster.

A competition experiment with Drosophila melanogaster is reported which comprised a replacement series with two genotypes, together with pure cultures of both genotypes at the same densities as they appeared in the mixtures. The results for total numbers and weights make clear the need to separate the intergenotypic from the intragenotypic interactions if an unambiguous interpretation of the outcome of such mixtures is to be obtained. Further experiments were carried out to investigate the behaviour of pure cultures in order to gain insight into the relative simplicity or complexity of the intragenotypic interactions that needed to be taken into account when investigating mixtures. It was found that transformation of the measurements into percent survival and average weight per fly led to relations with density which were more nearly linear than the originals and, hence, were more readily amenable to analysis. Two main points emerged from the experiments. First, the relationship between the two transformed characters did not appear straightforward. Secondly, the intragenotypic interactions, particularly for percent survival, were complex and thus provided not support for assuming them to be simple when present in mixtures of genotypes.

Genetical analysis of components of overall plant shape.

The genetical control of six characters, which were taken as jointly reflecting the overall shape of the plant, was analysed using four true-breeding lines of Nicotiana rustica. F1 F2 and first backcross generations were raised from all of the possible pairwise combinations between the lines. The particular relationships between the lines provided a basis for the analysis which was an extension of the normal model fitting procedures described by Mather and Jinks (1971).The first step in the analysis was to test whether the allelic differences present between the inbred lines p1 and P5 had been maintained in the two lines B2 and B35, derived from an earlier cross between the former. If the allelic differences between p1 and P5 were present between B2 and B35, it was possible to proceed straight-forwardly by fitting a model consisting of m, two symmetrical [d]'s and the relevant non-additive parameters. If B2 and B35 were homozygous for the same alleles at loci by which p1 and P5 differed, in other words if significant asymmetry in the gene distributions was present, the model had to be extended to cover the effects of such genes.All six characters investigated were shown to be subject to genetical variation. From the composition of the genetical models that were necessary to account for the observations from each of the characters, it was inferred that they should be amenable to at least partially independent adjustment by selection.

Genotype x environment interactions. IV. The effect of the background genotype.

Experimental evidence from sternopleural chaeta number and yield of offspring in Drosophila melanogaster bears out the expectation (Mather, 1975) that the value of the regression of g, measuring genotype X environment interaction, on e, measuring the overall effect of environmental change , depends on genes in which the contrasting genotypes are alike as well as on the genes in which they differ. With yield of offspring there is evidence of some genotypes reacting to the environmental changes in the opposite direction to others.