The International Board for Plant Genetic Resources has recently coordinated efforts to augment the world soybean collection. A key step to exploiting the genetic resources of the subgenus Glycine in soybean improvement is obtaining viable hybrids between these species and soybean. Several specific attributes present among the perennial Glycine, and of potential use in soybean improvement can be listed. In broad outline the perennial Glycine exhibits a striking diversity of geno-types and ecological adaptation. Typically, the perennial Glycine species are minor, inconspicuous components of semi-open Eucalyptus woodland. The most promising results of more recent hybridizations are with a newly described species, G. argyrea Tind. The development represents a significant new contribution from wild perennial germplasm. These developments are the assembly of a large and diverse collection, the achievement of hybrids between the perennials and soybean, and the uncovering of diverse sources of resistance to soybean leaf rust.

Near-isogenic resistant and susceptible lines of barley (Hordeum vulgareL.) were inoculated with a virulent race of the causal agent of leaf scald,Rhynchosporium secalis, and the expression patterns of specific barley (1→3)-β-glucan endohydrolase (EC 3.2.1.39) isoenzymes monitored. Induction of (1→3)-β-glucanase activity occurred 1 day earlier and to higher levels in the resistant backcross line BC-200 than in the susceptible parent line. Thus, the resistant plants of this backcross line responded more rapidly to pathogen invasion than susceptible lines. The increased (1→3)-β-glucanase activity was attributable predominantly to a 2–3 day period in which mRNA transcripts of genes that encode isoenzymes GII and GI accumulated. These genes may therefore be important in the defence responses of barley backcross line BC-200 to pathogen attack. A second scald-resistant backcross line, BC-30, developed levels of (1→3)-β-glucanase similar to BC-200 upon infection, but maximal levels were reached later than in BC-200. The third resistant backcross line, BC-35, showed the same pattern of expression as the susceptible parent cultivar, Clipper. The differences in expression of (1→3)-β-glucanase between the resistant backcross lines clearly show that there are physiologically distinct modes of resistance to the scald fungus in barley, and that at least one of these is accompanied by (1→3)-β-glucanase induction.

Many human activities distort the sample of genes that pass from one generation to the next of a plant population. These activities affect genetic structure either by markedly altering - usually decreasing - the level of genetic diversity, or by causing large changes in specific allele frequencies. The former changes are due to such stochastic evolutionary forces as reduced population size, increased migration and recombination, and the latter changes are due to systematic selection pressure. The leading examples of each are habitat destruction and environmental degradation. Interaction between stochastic and deterministic evolution is well displayed by introduced colonizing weeds. To combat unwanted evolutionary changes in plant population genetic structure, conservation measures - both in situ and ex situ - should employ sampling strategies that meet both stochastic and systematic needs.

The reproductive system determines the way in which gametes are brought together to form new zygotes and thereby exerts the primary level of control on genotypic frequency distributions in populations. Those who seek to improve crop plants genetically through the implementation of various selection strategies begin their task by manipulating genotypic frequency distributions. The success of an improvement program is, in turn, limited by the store of genetic variability available to the breeder. The reproductive system is also a primary determinant of the level of genetic variability within species. As a consequence, the reproductive system interacts with genetic diversity at two levels: first it controls the distribution of genetic diversity in genotypes, and second it determines the extent of genetic diversity through its interaction with the various forces of evolution. The latter interaction involves the integration of evolutionary forces acting over relatively long periods of time. Our purpose here is to explore these interactions.

Allozyme variation as detected by starch gel electrophoresis was used to assess the extent and spatial organization of genetic variation across the entire range of Glycine canescens sensu lato. Eleven enzyme systems were assayed in 116 accessions of this taxon and 102 alleles were detected at a total of 31 loci. Eighty-one percent of loci were polymorphic. Most of this variation occurred between and very little within accessions. Three major groupings were detected. These groupings (groups 1, 2, and 3) also differed with respect to mean seed size and their geographic distribution. A further ten accessions stood out from these distinct groups. These accessions were most closely related to group 3 but were variable among themselves. In general, they were collected from highly dissected terrain, often in the remote interior of the continent. A final group of 18 problematic accessions (group X), originally tentatively identified as G. canescens on morphological grounds, was shown to be isozymically distinct from this species and was reclassified as one form of the polytypic species G. clandestina.

Linkage estimates among 15 isozyme and three seed protein loci in barley (Hordeum vulgare) placed two loci on chromosome 1, three on chromosome 4, eight on chromosome 5, and five on chromosome 6. The markers provided a test of the theory of segmental lengths and residual background genome retention under backcrossing. oThe backcross lines were from the cultivar Clipper, and each was homozygous for an allozyme variant introduced from wild barley (H. spontaneum). The lines were unselected for their genotype at the hordein loci Hor1, Hor2, and Hor3, all on chromosome 5. Among 68 lines selected for allozyme markers not-on chromosome 5, 12 still possessed H. spontaneum hordeins at one or more of the three hordeln loci, whereas among eight lines selected for chromosome 5 markers, four possessed H. spontaneum hordeins.

Plant roots and seed tissues have the capacity for both lactate and ethanol glycolysis. Balanced operation of these two pyruvate utilizing pathways is required for plant survival during oxygen deprivation. According to the Davies-Roberts hypothesis, under low oxygen, pyruvate is initially metabolized to lactate resulting in cytoplasmic acidosis which appears to signal activation of ethanol glycolysis thereby minimizing further potentially toxic cytoplasmic acidosis. We have found that during several days of oxygen deprivation, lactate dehydrogenase (LDH), the enzyme catalyzing pyruvate-lactate interconversion, increases in activity up to 20 fold in root and seed tissues; there are parallel rises in LDH protein synthesis and in the level of translatable LDH mRNA. In hypoxic induced root tissue, however, this increased capacity for lactate glycolysis is not accompanied by increased carbon flux to lactate. Collectively these results imply an as yet unrecognized functional significance for LDH during oxygen deprivation. Barley LDH has been purified to a single band on SDS-PAGE, Mr=40kD, by blue sepharose and oxamate-agarose affinity chromatography. Similar to other plant and animal LDH, barley LDH is a tetramer. Native PAGE resolves barley LDH into 5 closely spaced bands of similar staining activity.

The numerical schemes used to calculate the stationary distributions of Markov chains arising from a genetical problem on inbreeding plant populations with selection are described. Careful treatment is necessary because the distributions are surprisingly ill-behaved analytically. Examples are given, and the moments of the distributions are also derived.

Barley (Hordeum vulgare) and its wild progenitor (H. spontaneum) have three loci for alcohol dehydrogenase (EC 1.1.1.1; ADH). The Adh1 locus is constitutively expressed in seed tissues, whereas expression of the loci Adh2 and Adh3 requires anaerobic induction. The Adh3 gene is well expressed in aleurone and embryo tissues kept under N2 for 2–3 days. Using N2-treated embryos, a diverse collection of H. spontaneum was screened in starch gels for electrophoretic variants at the Adh3 locus. Four variants were found: two were conventional mobility variants (Adh3 S, Adh3 V); one was a null variant (Adh3 n); and the fourth (Adh3 I) variant lacked active homodimers and showed reduced heterodimer activity. The 35S-labeled monomers induced under N2 in the lines homozygous for Adh1, Adh2, or Adh3 variants were immunoprecipitated with antiserum raised against maize ADH. Fluorography after separation by SDS-PAGE and by urea-isoelectric focusing indicated that the Adh3 n allele was CRM- and that the Adh3 I gene product was smaller than normal. The Adh1 and Adh3 variants showed independent segregation.

The study of multilocus systems is claimed as "one the most important unresolved problems of population genetics" (Ginzburg and Braumann 1980). Multilocus organization at the population level means that certain combinations of the allelic variants at different loci are present more frequently than expected, whereas other combinations are infrequent or absent. In a simple example of two alleles at each of two loci, the extremes of organization are random association of alleles into four gametic genotypes on the one hand or their absolute association in two gametic genotypes on the other.

Legumin and albumin are the fractions of pea seed proteins preferred to vicilin because of their high sulfur amino acid contents. The joint inheritance of legumin and albumin contents was studied in a cross between to contrasting lines of peas — one with high legumin and low albumin, and the other with low legumin and medium to high albumin. Single seed determinations were made in the parental, F1; F2 and backcross generations using rocket immunoelectrophoresis. In the non-segregating generations (P1, P2 and F1), legumin and albumin contents were negatively correlated (r=−≅0.50). The estimates of correlation coefficients in the segregating generations (F2, BC1 and BC2) were also about −0.5. However, the two estimates based on the round and on the wrinkled seeds separately in the F2 generation were not significantly different from zero. At least four individual round F2 seeds showed the desired recombination of high legumin with high albumin indicating that the unfavorable correlation can be broken. In this cross legumin content showed predominantly additive genetic variation whereas the dominance variance was the largest component for albumin content. A combined “relative sulfur index”, proposed as a convenient measure for selection, showed a narrow sense heritability of 47%. In general these results support the view that sulfur amino acid content of peas can be improved by breeding, but that the required selection regime must take both legumin and albumin content into account.

Allozyme variation in the tetraploid wild progenitor of wheat, Triticum dicoccoides, was studied for the proteins encoded by about 50 gene loci in 457 individuals representing 12 populations from Israel. Six spikelet morphological traits were measured in the same populations. The results indicate that: (a) 16 loci (= 32%) were monomorphic in all 12 populations, 15 loci (= 30%) were locally polymorphic, and 19 loci (= 38%) were regionally polymorphic. All polymorphic loci (but one) displayed high levels of polymorphism (≧ 10%). In Israel, the proportion of polymorphic loci per population, P, in wild wheat averaged 0.25 (range, 0.16–0.38), and the genetic diversity index, He averaged 0.07, (range, 0.03 – 0.12). (b) Altogether there were 110 alleles at the 50 putative loci tested (c) Genetic differentiation of populations included regional and local patterns: (i) The coefficients of genetic distance between populations were high (mean D = 0.10 range, 0.02 – 0.25), and indicated sharp genetic differentiation over short distances, (ii) Common (≧ 10%) but sporadic and localized alleles were frequent (76%), and (iii) Rare alleles were few (only 5 alleles). (d) The patterns of allozyme and spikelet variation in the wild gene pool were significantly correlated with, and partly predictable by, water factors, including those of precipitation, evaporation, and relative humidity as well as of soil type, (e) All six spikelet characters showed statistically significant variation among localities and (f) Allozymic variation was correlated with spikelet variation.

For the measurements of outcrossing rates in plant populations, current electrophoretic procedures permit many loci to be scored per individual progeny. Given that the total experimental effort or cost is limited, the choice exists then between assaying a large number of loci on a restricted number of individuals, or assaying a large number of individuals at a few loci. Using simple models and the criterion of minimising the variance of the estimate, several factors which affect this choice are considered (levels of polymorphism, heterozygosity, linkage disequilibrium, pollen or outcrossing heterogeneity). The general conclusion is that the actual level of outcrossing is a major factor in determining experimental strategy. Maximum efficiency for estimating outcrossing in predominantly inbreeding plants comes from large samples assayed for few polymorphic loci. In contrast, in predominantly outcrossing plants, more loci should be assayed at the expense of sample size for improved statistical efficiency.

Allozyme variation at 25 genetic loci was assayed in twelve indigenous cultivars (land races) of barley from Iran. For these loci the average probability that two gametes drawn at random from one population would differ at a locus was 0.082. In the collection as a whole, this measure of genetic diversity was 0.161, so that about half the total diversity was distributed between populations. Of the total of 31 allozyme variants, about half were common (frequency >0.10) in only one or two regions. The results were compared with diversity estimates based on spike morphological polymorphisms; with allozyme polymorphism in two composite crosses (CC21 and CC34) of cultivated barley; and with previous results for allozyme polymorphism in Israel populations of wild barley. In the land race samples, the diversity of spike types was a poor index of allozyme diversity. The total allozyme diversity in this collection of land races was intermediate between the moderate levels in composite crosses and the high levels in Hordeum spontaneum from Israel. These results emphasize the role of land races as valuable genetic resources for plant breeding. They support sampling strategies which, by taking samples of moderate size from many sites, emphasize the collection of locally common alleles, as against strategies framed to capture the rare, conspicuous morphological variant by intensive or biased sampling, or strategies based on collecting the extreme ecotypes from a cline. The chromosomal location of 20 of the allozyme loci as deduced from wheat-barley addition lines, is listed in the appendix.

In a high-salt soluble fraction of the total protein from single seeds of Pinus radiata, up to 45 polypeptides were resolved on SDS-polyacrylamide gels. At least one-fifth of these polypeptides showed variation between seeds. In the 27,000–29,000 dalton region, two polypeptides were inherited as codominant alleles at a single locus and were shown to assort independently of another seed protein locus and three allozyme loci. A survey of 120 individuals from the five known native populations of P. radiata in California detected only the 27K and 29K alleles at the locus. In all populations, the 29K allele predominated, and the two island populations were monomorphic for the 29K allele. The 27 and 29 kdalton polypeptides were shown to have very similar amino acid sequences, and the allelic difference at this locus is most probably in the gene sequence for the polypeptide.