Showing papers in "Theoretical and Applied Genetics in 1979"

Identification of a high-molecular-weight subunit of glutenin whose presence correlates with bread-making quality in wheats of related pedigree.

Abstract: The subunit composition of glutenin was analysed by SDS-polyacrylamide-gel electrophoresis using two varieties of contrasting pedigrees. ‘Maris Widgeon’, a variety of good bread-making quality, was shown to contain 2 glutenin subunits not present in ‘Maris Ranger’, a much higher yielding variety that is unsuitable for making bread. A third subunit was only found in ‘Maris Ranger’ glutenin. To determine if any of these subunits are directly related to bread-making quality, 60 randomly-derived F2 progeny from a ‘Maris Widgeon’ x ‘Maris Ranger’ cross were analysed for bread-making quality and for glutenin subunit composition. A strong correlation was demonstrated between the presence of one of the two subunits inherited from ‘Maris Widgeon’, and quality. This subunit (termed subunit 1 glutenin) had an approx. mol. wt. of 145,000. It was also found in ‘Maris Freeman’, a bread-making variety selected from the same cross previously made in 1962. In further crosses involving ‘Maris Widgeon’ or its descendants, more bread-making varieties have been produced in the last decade at the Plant Breeding Institute, Cambridge and all but one have inherited glutenin subunit 1. The subunit has been traced back through ‘Holdfast’ to ‘White Fife’, a Canadian hard spring wheat of excellent breadmaking quality. Some 67 varieties were screened for the presence of glutenin subunit 1 and it was found in 31% of them. Several unrelated varieties of good bread-making quality did not contain subunit 1 glutenin.

Seed protein electrophoresis in taxonomic and evolutionary studies.

Abstract: Seed protein electrophoresis is increasingly being utilized as an additional approach for species identification and as a useful tool for tracing back the evolution of various groups of plants. This paper summarizes the main features of the seed protein profile — stability, uniformity and additive nature. In addition, the significance of this approach for resolving specific taxonomic and evolutionary problems is pointed out.

Comparison of single cell culture derived Solanum tuberosum L. plants and a model for their application in breeding programs.

Abstract: The techniques of microspore and protoplast regeneration starting from dihaploid Solanum tuberosum plants has been improved to such an extent that the production of more than 2000 microspore derived A1 plant lines and of several hundred protoplast derived plantlets has become possible. Further, from the dihaploid Solanum species S. phureja the regeneration of microspores to plants, and from the species S. infundibuliforme, S. sparsipilum and S. tarijense the regeneration of protoplasts to calluses, has been achieved. The plants descending from the two single cell culture systems are compared with reference to phenotypic markers and economic qualities. Some principles characteristic for either microspore or protoplast derived plants are examined and their significance is discussed. The results are compiled into an extended analytical synthetic breeding scheme based on a stepwise reduction of the autotetraploid to the monohaploid level and a subsequent controlled combination to a new synthetic completely heterozygous tetraploid potato.

Callus formation from cell culture protoplasts of corn (Zea mays L.).

Abstract: Routine procedures for the isolation of large numbers of protoplasts from an established cell culture of Zea mays and for the induction of sustained divisions leading to secondary cell cultures have been developed. The critical factors seem to be associated with neither specific enzymatic conditions for the isolation nor specific culture conditions for the protoplasts but with the ‘quality’ of the culture used for protoplast isolation.

Selection of potato callus for resistance to culture filtrates of Phytophthora infestans and regeneration of resistant plants.

Abstract: Dihaploid calli from Solanum tuberosum were selected, which were resistant to the culture filtrate of Phytophthora infestans. Each of the resistant calli was resistant to all four pathotypes of Phytophthora used in these experiments. The resistance was not lost through regeneration and the induction of new callus.

Stimulation of embryogenesis and haploid production in Brassica campestris anther cultures by elevated temperature treatments.

Abstract: Culture of Brassica campestris anthers at 35°C for one or three days prior to culture at 25°C significantly stimulated the yield of microspore-derived embryos. More than 100 plants were regenerated from cultured embryos and haploids were identified amongst them. The haploid frequency was greater than 70% if all small-flowered sterile plants were considered to be haploid. The yield of microspore-derived plants in B. campestris is approaching the level where anther culture may be utilized as a practical breeding tool.

Basic studies on hybrid wheat breeding : VIII. A new male sterility-fertility restoration system in common wheat utilizing the cytoplasms of Aegilops kotschyi and Ae. variabilis.

Abstract: The nuclei of 12 common wheats (genome constitution AABBDD) were placed into the cytoplasms of Aegilops kotschyi and Ae. variabilis (both CuCuSvSv) by repeated backcrosses. Using these nucleus-cytoplasm hybrids, male sterility-fertility restoration relationship was investigated. Male sterility was expressed by these cytoplasms only in Slm, Splt and Mch. The other nine common wheat nuclei gave normal fertility against these cytoplasms. These cytoplasms were compared with the Triticum timopheevi cytoplasm that is now widely used in the hybrid wheat breeding program in order to investigate their effects on important agronomic traits of the 12 common wheats: The kotschyi and variabilis cytoplasms were as good as the timopheevi cytoplasm in this respect.

Genetics of incompatibility inCorylus avellana L.

Abstract: Diallele crosses of sibs and parents of 3 parental combinations demonstrated sporophytic type of incompatibility inCorylus avellana L. One gene with multiple alleles was indicated. All 6 alleles present in the 4 parental cultivars and in their progeny exhibited dominance in pollen and independent action in the pistil. Individuals homozygous for S-alleles appeared in progeny of parents having one allele in common. Reciprocal differences occurred in some crosses. The stigmatic surface is the site of the incompatibility reaction. Incompatible pollen germinated abundantly but failed to penetrate into the stigma cells.

An efficient plating system for rapid isolation of mutants from plant cell suspensions

Abstract: A plating system for cell suspensions of soybean, SB-1, (Glycine max L. cv. ‘Mandarin’) and Datura innoxia D.I. (Mill) was developed using feeder cells. The characteristics of the system are: a) the efficiency of plating (EOP) is high (0.5–0.6), b) over a range of 10–300 plated clumps the EOP is constant, c) the growth rate of plated cells resembles that of suspension cultures (generation time 24 hr.). Clumps with few or with many cells have similar plating efficiencies. Employing the plating system, a mutant resistant to 8 azaguanine (8AG) was isolated from SB-1 in 7 days and purified and tested within an additional 3 weeks. Feeder plates were used to selectively re-isolate 8 AG resistant and maltose utilizing mutants from a 1000-fold excess of wild type cells. The plating technique also can be utilized to isolate auxotrophic mutants since free amino acids are not produced by the feeder suspension. Other applications of this plating technique are discussed.

Use of amino acid analogue-resistant cell lines for selection of Nicotiana sylvestris somatic cell hybrids.

Abstract: Nicotiana sylvestris cell lines resistant to the amino acid analogues S-2-aminoethyl-cysteine (AECR), or 5-methyl-tryptophan (5MTR), were isolated in suspension culture. Assuming these resistances to be dominant, we have attempted to determine if such variant cell lines can be used to select double resistant somatic cell hybrids. A total of 1.8 × 104 control calli from mixed AECR and 5MTR protoplasts, and AECR and 5MTR homokaryotic fusions were placed on double analogue selection, but none survived. Eight somatic hybrid calli (0.8%), able to grow without inhibition on the double analogue selection medium, were obtained after AECR + 5MTR protoplast fusion. These were further determined as hybrids on the basis of resistance level, chromosome number, and chlorophyll content, all characteristics differing in the parental cell lines.

Gene-centromere mapping by 4x-2x matings in potatoes.

Abstract: Two of the four strands of a bivalent are recovered together in tetraploid progeny arising from 4x-2x matings. This provides a method for gene and centromere mapping. The cross pppp x Pp produced 62 nulliplex tetraploid individuals in a total of 951, i.e., 6.5%. The diploid clone was found to produce diplandrous gametes through first division restitution (FDR). The map distance P-centromere was estimated as 13.0 units, the limiting values at the 95% binomial confidence interval being 10.1 and 16.3. The mapping method is explained in detail and a formula is deduced to obtain genotypic series of 2n gametes under particular assumptions. The direction 4x×2x is advantageous, since high seed set diploid clones which give 99% tetraploid progeny, and whose method of diplandroid formation is known are already available. Diploid clones heterozygous for many markers and tetraploids nulliplex for the same markers are needed to fully exploit this method.

Linnaeus' Peloria: The history of a monster

Abstract: The so-called Peloria case has been discussed repeatedly in world literature since the discovery of the five-spurred Linaria in 1742 and its description by Linnaeus in 1744. In 1742 a young Uppsala botanist found a peculiar specimen of the common toad-flax (now named Linaria vulgaris L.) on an island in the Stockholm archipelago. The plant, which had spread vegetatively, possessed five spurs instead of one spur, a characteristic of the common toad-flax. The material was presented to Linnaeus, who became quite excited. The finding was contrary to his concept that genera and species had universally arisen through an act of original creation and remained unchanged since then. In a famous thesis of 1744, Linnaeus called the deviating plant ‘Peloria’, Greek for ‘monster’. The case of pelorism was discussed later on by a great number of famous writers and scientists including, for example, Goethe, Darwin, Naudin, De Vries and Stubbe. Parallel types were found in numerous species of other genera and families. Such aberrant forms are caused by spontaneous mutation. The history, mode of origin, morphology, inheritance and distribution of different Peloria mutants are discussed in the paper.

The Deficiency of Soluble Proteins and Plastid Ribosomal RNA in the Albino Pollen Plantlets of Rice

Abstract: The components of soluble protein and ribosomal RNA in green and albino pollen plantlets of rice were studied by means of polyacrylamide gel electrophoresis. The results were as follows: (1) Soluble protein: the soluble proteins in green pollen plantlets may be fractionated into 15 bands of varying intensities in which the highest content and the most prominent one is band 3 (fraction I protein). Band 3, however, is nearly absent in albino pollen plantlets. (2) Ribosomal RNA (rRNA): rRNA of high molecular weight in green pollen plantlets may be fractionated into 4 bands, i.e. 25S RNA and 18S RNA in cytoplasmic ribosomes, and 23S RNA and 16S RNA in plastid ribosomes. Little or no 23S RNA and 16S RNA, however, is found in albino pollen plantlets. Together with the evidence obtained by other workers, it is suggested that albino forms of pollen plantlets is caused by the impairment of DNA.

‘Nucleolar dominance’ as observed in barley translocation lines with specifically reconstructed SAT chromosomes

Abstract: Diploid homo- and heterokaryotypes of barley translocation lines with only one satellite chromosome pair containing two nucleolus organizer regions (NORs) in opposite arms were found to show repressed nucleolus formation by the transposed NOR as evident from the formation of only micronucleoli. The same was true for auto-tetraploid homokaryotypes and for translocation lines with all NORs tandemly arranged into the same chromosome arm. When NORs were transposed to chromosomes without NOR in the standard karyotype, the normal pattern of nucleolus formation remained unaffected. The modified mode of nucleolus formation after the combination of all NORs in one chromosome pair is interpreted to be due to intrachromosomal nucleolar dominance analogous to interchromosomal nucleolar dominance observed in certain interspecific hybrids.

Sex determination in Sarotherodon (tilapia) : Part 2: the sex ratio as a tool for the determination of genotype - a model of autosomal and gonosomal influence.

Abstract: The simplest possible model of the sex determination process adding autosomal influence to a minimal number of sex chromosomes was developed to explain matings of Tilapia (Sarotherodon) species. Eighteen different genotypes, each having two autosomes (AA, Aa, or aa) and two sex chromosomes (WX, WY, WW, XY, XX or YY) involved in sex determination, are predicted by the theory. Their sex (10 males and 8 females) were determined using a series of directed graphs, showing the relative strength of the chromosome pairs, developed on the basis of Chen's sex ratio results (Chen 1969). This theoretical model predicts eight different sex ratios (0∶1, 1∶3, 3∶5, 1∶1, 9∶7, 5∶3, 3∶1, 1∶0 ♀∶♂); three of them are not predicted by the WXYZ theory. The greatest part of these sex ratios have been obtained experimentally in extensive series of crosses between related species of Tilapia and their hybrids, carried out by several authors. The theory succeeds in explaining all of Chen's results, including those ratios 5∶3 and 0∶1 seen in certain crosses but not predicted by the WXYZ theory. The importance of the autosomes is seen in comparisons of the genotype pairs (AaWY, aaWY), (AaXY, aaXY) and (AAWW, AaWW) in which the first genotype in each case is male while the second is female as proven by the sex ratio results. The members of the pair differ only in the substitution of one autosome for the other. To test the theory, experiments consisting of hormonal sex reversion and a series of crosses are proposed. Finally, theoretical and practical implications of the theory are discussed.

Isolation of a recessive barley mutant resistant to S-(2-aminoethyl)L-cysteine.

Abstract: S-(2-aminoethyl)L-cysteine (AEC) inhibits the growth of mature barley (Hordeum vulgare L vars. 'Bomi' and 'Maris Mink') embryos grown on sterile medium. This inhibition is relieved by lysine and, to a lesser extent, arginine and ornithine. In order to try and select plants which accumulate lysine, 8200 M2 embryos of sodium azide mutagenised barley were screened for growth in the presence of 0.25 mM AEC. One line, R906 was selected for further characterisation. Progeny of the originally selected plant after selfing were all resistant to AEC. In a reciprocal cross with a sensitive barley the resistant trait was inherited as a single recessive nuclear gene which we designate aec-1.

Nucleotide polymorphism in chloroplast dna of Nicotiana debneyi.

Abstract: EcoR1 restriction endonuclease analysis of chloroplast DNA isolated from several distinct populations of Nicotiana debneyi has revealed a naturally occurring polymorphism. The chloroplast DNA of seven of the nine populations analysed possessed an additional EcoRl site. The origin of the additional restriction endonuclease fragments was confirmed by hybridisation of [32 P]-cRNA to fractionated EcoRl restricted chloroplast-DNA fragments adsorbed to nitrocellulose filters. Reciprocal f1 hybrids between plants carrying the variant chloroplast-DNA's confirmed maternal inheritance of chloroplast-DNA.

Somatic hybrids between unilateral cross-incompatible Petunia species.

Abstract: Somatic hybrid plants regenerated following the fusion of leaf mesophyll protoplasts of Petunia parodii with those isolated from a cell suspension of albino P. inflata. These two species exhibit a unilateral cross-incompatability with a pre-zygotic mode of reproductive isolation preventing hybridizations with P. inflata as the maternal parent. Selection of somatic hybrids relied on the fact that unfused or homokaryon protoplasts of P. parodii did not develop beyond the cell colony stage while those of the putative somatic hybrids and albino P. inflata parent produced callus. Green somatic hybrid calluses were readily identified against the white background of P. inflata following complementation to chlorophyll synthesis proficiency and continued growth in hybrid cells. Shoots, and ultimately flowering plants, were identified as somatic hybrids based on their floral morphology and colour, chromosome number and the fact that they segregated for parental characters. The frequency of somatic hybrid production was comparable to that previously established for two sexually compatible Petunia species.

An effective chemical mutagenesis procedure for Petunia hybrida cell suspension cultures.

Abstract: By using mercury(II)-chloride (HgCl2) and Dl-6-fluorotryptophan (6FT) as positive selection conditions we were able to show that N-methyl-N′-nitro-N-nitrosoguanidine (NG) is an effective mutagen for Petunia hybrida suspension cells.

Fertilization and early embryo development in reciprocal interspecific crosses of Phaseolus.

Abstract: Fertilization and early embryo and endosperm development were examined in Phaseolus vulgaris x P. acutifolius, P. vulgaris x P. lunatus crosses and their reciprocals. The number and length of pollen tubes were not different between selfings and interspecific crosses. Fertilization was completed in all matings and the time of fertilization was maternally dependent which may reflect the degree of maturation of embryo sacs at pollination. A large difference between reciprocal crosses was found in the time of endosperm and embryo division in relation to the time of fertilization. When P. vulgaris was the female parent and P. acutifolius the male parent, endosperm division occurred at the same time as in P. vulgaris upon selfing, while in P. vulgaris x P. lunatus crosses the time of endosperm division was intermediate as compared with the two parents. The time lapse between fertilization and endosperm and embryo division in P. acutifolius x P. vulgaris crosses was longer than in either parent upon selfing. In P. lunatus x P. vulgaris crosses, endosperm division occurred in only 7–12% of the ovules at 72 hours after pollination. Embryo development in these ovules was limited to the four cell stage although the endosperm was at the free nuclei stage. The severe delay in embryo and endosperm divisions may be the major cause of early pod abscission in P. lunatus x P. vulgaris crosses.

Combining ability analysis over F1-F5 generations in diallel crosses of bread wheat

Abstract: Combining ability studies for grain yield and its primary component traits in diallel crosses involving seven diverse wheat cultivars of bread wheat (Triticum aestivum L.) over generations F1-F5 are reported. The general and specific combining ability variances were significant in all generations for all the traits except specific combining ability variance for number of spikes per plant in the F5. The ratio of general to specific combining ability variances was significant for all the traits except grain yield in all the generations. This indicated an equal role of additive and non-additive gene effects in the inheritance of grain yield, and the predominance of the former for its component traits. The presence of significant specific combining ability variances in even the advanced generations may be the result of an additive x additive type of epistasis or evolutionary divergence among progenies in the same parental array. The relative breeding values of the parental varieties, as indicated by their general combining ability effects, did not vary much over the generations. The cheap and reliable procedure observed for making the choice of parents, selecting hybrids and predicting advanced generation (F5) bulk hybrid performance was the determination of breeding values of the parents on the relative performance of their F2 progeny bulks.

Direct infection of embryogenic tissue cultures of haploidBrassica napus with resting spores ofPlasmodiophora brassicae.

Abstract: A direct infection of cultured tissue with resting spores of the obligate endoparasitePlasmodiophora brassicae has been made possible by using stem embryo cultures of haploid rape. The fungus develops and completes its lifecycle in the cultured cells. The results are discussed in connection with the possibility of using this system to select for resistance to the pathogen.

The chromosomal location of peroxidase isozymes of the wheat kernel.

Abstract: The analysis of the individual parts of the Triticum aestivum L. kernel yields a total of 11 peroxidase isozymes: m, n, a, c, d1, d, d2, e, f, g and h (in order from faster to slower migration). Isozymes a, c and d are found in the endosperm (Ed) and seed coats (C), while m, n, d1, d2, e, f, g and h are peculiar to the embryo and scutellum (E + S). The use of the nullitetrasomic and ditellosomic series of ‘Chinese Spring’ wheat allows peroxidase isozymes to be associated with specific chromosome arms. Isozymes a, c and d (Ed) are associated with chromosome arms 7DS, 4BL and 7AS; whereas isozymes m, d2, e and f are associated with chromosome arms 3DS, 3BL, 3DL and 3DL, respecitvely. Thus, the E + S isozymes are associated with homoeology group 3 and the Ed isozymes with homoeology groups 7 (a and d isozymes) or 4 (c isozymes).

Interactions of S alleles in sporophytically controlled self incompatibility of Brassica.

Abstract: The expressed activity in pollen and stigma was determined for both S alleles of sixteen S-aliele heterozygous genotypes and for one of the two S alleles of two additional heterozygotes. Activities were measured using pollen tube penetration and seed set data from reciprocal crosses between each S-allele heterozygote and its two corresponding S-allele homozygotes. In pollen the S-allele activities ranged from zero to 100% inhibition of pollen tube penetration and seed set, and in the stigma they ranged from 8 to 100% inhibition. Of the sixty-eight S-allele activities measured, thirty-three (48%) were 90 to 100% inhibition, nine (13%) were 80 to 89% inhibition and one to five were within each ten-unit range below 80% inhibition. In an S-allele heterozygote, each subset of two S alleles had an activity for each allele in both pollen and stigma which was highly repeatable among duplicate pollinations within and among successive years. Each subset of two S alleles had a specific S-allele interaction in the pollen, and the same or another specific interaction in the stigma. In pairings with six other S alleles, allele S 2 had four calculated levels of activity in pollen that ranged from 88 to 94%, and five levels in the stigmas between 15 and 94%. When paired in a heterozygote, alleles S 3 and S 5 had activities ranging between 42 and 59%, representing mutual weakening of S-allele activity. Also, heterozygote S 15 S 3 had pollen activities, respectively, of 25 and 6%, i.e. mutual weakening in the pollen. These results indicate that in heterozygous combination with a series of other S alleles, each S-allele may have activity in pollen and also in stigma that potentially is between zero and 100% inhibition. They further indicate that the defined sexual-organ X S-allele-interaction Types I, II, III and IV are extremes; all intermediate variations including complete weakening of both alleles are possible. Recessiveness is weakening of the activity of but one of the two S alleles. The pollen tube penetrations into the style and seed set were highly correlated.

Incompatibility alleles in Corylus avellana L. cultivars.

Abstract: Pollen-stigma compatibility relationships are reported for 55 filbert cultivars (cvs) (Corylus avellana L.). A total of 11 S-alleles have been identified amongst 36 cvs for which one or both S-alleles have been established. For the 20 cvs with only one known allele and the 17 for which neither allele have been identified further information is provided as to which alleles can be excluded as possibilities.

The effects of selection for different combinations of weights at two ages on the growth curve of mice

Abstract: The weights of mice in lines selected for different combinations of high and low body weights at 5 and at 10 weeks of age were recorded from 3 to 21 weeks of age. The average growth curve for each line was computed using the Gompertz function. The growth curves of lines selected for high or low weight at a single age (ST lines) showed large differences in estimates of mature size and small differences in estimates of maturing rate, i.e. of the relative rate of growth to maturity. The growth curves of lines selected by independent culling for divergent combinations of deviations of opposite sign in 5- and 10-week weights (ICL lines) showed little difference in estimates of mature size and a large difference in estimates of maturing rate. The growth curves of lines selected by index for divergence in 5-week weight with no change in 10-week-weight or for divergence in 10-week-weight with no change in 5-week weight showed large differences in estimates of mature size and large differences in estimates of the maturing rate. The relationship between mature size and maturing rate was affected in different ways by the three types of selection.

Yield stability and population diversity in oats (Avena sp.).

Abstract: The relationship between yield stability and populations containing various numbers and combinations of diverse homozygous and homogeneous lines was examined in an environment in which considerable variability occurs among and within growing seasons. Two groups (1,2), each containing 15 populations (4 pure lines grown singly and 11 multilines consisting of mechanical mixtures of all possible 2,3 and 4 way combinations of these 4 pure lines) were tested in each of 5 consecutive years. The pure lines in group 1 and 2 were selected on the basis of previous yield and yield variability respectively. In group 1, no significant differences were found among the 5 year means or the deviation mean squares of the 15 populations but highly significant differences among regression coefficients were present. The regression coefficients of the 4 pure lines differed considerably, indicating that this stability parameter was genetically influenced. The regression coefficients of the multilines tended towards unity regardless of the regression coefficients of the pure lines involved. In group 2, highly significant differences were found among the 5 year means, regression coefficients and deviation mean squares of the 15 populations. No consistent, predictable pattern was apparent between the mean and stability values of the pure lines and the multilines in which they were included. Differences between the 2 groups suggest that higher yield and greater stability result in the multilines if relatively high yielding pure lines are selected for inclusion. In general, the results indicated that multilines containing a number of diverse homozygous and homogeneous pure lines have satisfactory yields and enhanced yield stability. However, adequate testing of the pure lines and potential multilines over a broad range of environments is essential to determine desirable combinations.

Reproductive system and pattern of genetic variation in two Limnanthes species.

Abstract: Several populations of two species of the genus Limnanthes, (L. alba, an outbreeder and L. floccosa, an inbreeder) were examined with respect to variability of fifteen quantitative characters, allozyme variation at 11 loci, and response to different pollination conditions and moisture stress. Nearly equal amounts of phenotypic variability were found in the two species. L. alba had higher within-family variability than L. floccosa, but this result was highly heterogeneous among characters. A study of between- and within-population variance estimates did not reject the null hypothesis that L. alba and L. floccosa are similar with regard to the partitioning and amount of variability for quantitative characters. However, allozyme variation at 11 loci in a large number of populations showed L. alba to be highly polymorphic in contrast to the virtual monomorphism within L. floccosa populations. The average number of alleles per locus in L. alba and L. floccosa was 1.97 and 1.02, respectively, and on an average, L. alba and L. floccosa populations had 63% and 3% loci with polymorphism, respectively. Three groups of allozyme allelic combinations emerged which correlated well with the taxonomic delineation of allogamous L. alba, three semi-autogamous L. floccosa forms and two autogamous L. floccosa forms.All taxa showed a significant reduction in the seed output per plant due to moisture stress. L. alba suffered a further loss of fecundity under the paucity of pollinators, L. floccosa ssp. floccosa showed no significant effect from this factor, whereas L. floccosa ssp. grandiflora exhibited a curvilinear response which peaked at 'partial pollination' and decreased to a lower level at 'full pollination.'The geographic distribution of the two species with regard to the temperature and rainfall distribution did not suggest L. floccosa to be living in drier marginal areas. Patterns of variation in flowering time showed L. alba to be less variable than L. floccosa. Overall, there seemed to be little direct support for the thesis that inbreeding species originated from outcrossing taxa in marginal environments as a direct adaptation to a shortened growing season of xeric environments and to the lack of pollinators. Alternative hypotheses suggest that autogamy in L. floccosa might have evolved as a reproductive isolating barrier acting through either cleistogamy or divergence in flowering times.

Procedures for identifying S-allele genotypes of Brassica.

Abstract: Procedures are described for efficient selection of: (1) homozygous and heterozygous S-allele genotypes; (2) homozygous inbreds with the strong self- and sib-incompatibility required for effective seed production of single-cross F1 hybrids; (3) heterozygous genotypes with the high self- and sib-incompatibility required for effective seed production of 3- and 4-way hybrids. From reciprocal crosses between two first generation inbred (I1) plants there are three potential results: both crosses are incompatible; one is incompatible and the other compatible; and both are compatible. Incompatibility of both crosses is useful information only when combined with data from other reciprocal crosses. Each compatible cross, depending on whether its reciprocal is incompatible or compatible, dictates alternative reasoning and additional reciprocal crosses for efficiently and simultaneously identifying: (A) the S-allele genotype of all individual I1 plants, and (B) the expressions of dominance or codominance in pollen and stigma (sexual organs) of an S-allele heterozygous genotype. Reciprocal crosses provide the only efficient means of identifying S-allele genotypes and also the sexual-organ x S-allele-interaction types. Fluorescent microscope assay of pollen tube penetration into the style facilitates quantitation within 24–48 hours of incompatibility and compatibility of the reciprocal crosses. A procedure for quantitating the reciprocal difference is described that maximizes informational content of the data about interactions between S alleles in pollen and stigma of the S-allele-heterozygous genotype. Use of the non-inbred Io generation parent as a ‘known’ heterozygous S-allele genotype in crosses with its first generation selfed (I1) progeny usually reduces at least 7 fold the effort required for achieving objectives 1, 2, and 3, compared to the method of making reciprocal crosses only among I1 plants. Identifying the heterozygous and both homozygous S-allele genotypes during the I1 generation facilitates, during subsequent inbred generations, strong selection for or against modifier genes that influence the intensity of self- and sib-incompatibility. Selection for strong self and sib incompatibility can be effective for both homozygous inbreds and also for the S-allele heterozygote, thus facilitating production of single-cross F1 hybrids and also of 3-and 4-way hybrids.

Doubled haploids for estimating genetic variances and a scheme for population improvement in self-pollinating crops.

Abstract: An analysis is derived for a diallel experiment in which each cross is represented by a number of homozygous Unes developed by the doubled haploid method. Both additive and additive x additive genetic variances can be estimated with this analysis. A population-improvement scheme involving the doubled haploid or single seed descent methods is also proposed.