富油微藻布朗葡萄藻分子生态学研究进展

分子生态学是研究生命系统与环境系统相互作用机理及其分子机制的科学,可以从宏观和微观结合的角度真实反映生态现象的本质。简述产烃布朗葡萄藻形态与化学种等生理生态特征的基础上,综述了近年来国内外布朗葡萄藻分子生态学研究的新进展,主要包括分子系统发育学及其与化学种、基因组、地理来源等之间的关系。经典分类学上,关于布朗葡萄藻属于绿藻门(Chlorophyta)还是黄藻门(Xanthophyta)存在争议,而基于18S核糖体核糖核酸(18S ribosomal ribonucleic acid,18S rRNA)序列的分子系统发育学研究结果将布朗葡萄藻界定为绿藻门、共球藻纲(Trebouxiophyceae)。依据藻株的产烃种类和化学结构特征,可将布朗葡萄藻划分为A、B和L 3个化学种,而布朗葡萄藻的分子系统学进化关系与化学种间高度统一。在基因组大小上,位于同一大亚聚群中的化学种B与L间却存在明显差异,而进化关系较远的化学种B与A间则更相近。不同地理来源布朗葡萄藻的18S rRNA序列和内部转录间隔区(internal transcribed spacer,ITS)多态性较高,提示不同地缘藻株间存有较高的遗传多样性。探讨了布朗葡萄藻分子生态学研究尚待解决的问题,并对今后相关研究做了展望。     

PHYLOGENETIC PLACEMENT,GENOME SIZE,AND GC CONTENT OF THE LIQUID‐HYDROCARBON‐PRODUCING GREEN MICROALGA BOTRYOCOCCUS BRAUNII STRAIN BERKELEY (SHOWA) (CHLOROPHYTA)1

We report the genome size and the GC content, and perform a phylogenetic analysis on Botryococcus braunii Kütz., a green, colony‐forming, hydrocarbon‐rich alga that is an attractive source for biopetroleum. While the chemistry of the hydrocarbons produced by the B race of B. braunii has been studied for many years, there is a deficiency of information concerning the molecular biology of this alga. In addition, there has been some discrepancy as to the phylogenetic placement of the Berkeley (or Showa) strain of the B race. To clarify its classification, we isolated the Berkeley strain nuclear SSU (18S) rRNA gene and β‐actin cDNA and used these sequences for phylogenetic analysis to determine that the Berkeley strain belongs to the Trebouxiophyceae class. This finding is in agreement with other B races of B. braunii, indicating the Berkeley strain is a true B race of B. braunii. To better understand molecular aspects of B. braunii, we obtained the Berkeley strain genome size as a first step in genome sequencing. Using flow cytometry, we determined the B. braunii Berkeley genome size to be 166.2 ± 2.2 Mb. We also estimated the GC content of the Berkeley strain as 54.4 ± 1.2% for expressed gene sequences.     

Transformation of Lipid Bodies Related to Hydrocarbon Accumulation in a Green Alga,Botryococcus braunii (Race B)

The colonial microalga Botryococcus braunii accumulates large quantities of hydrocarbons mainly in the extracellular space; most other oleaginous microalgae store lipids in the cytoplasm. Botryococcus braunii is classified into three principal races (A, B, and L) based on the types of hydrocarbons. Race B has attracted the most attention as an alternative to petroleum by its higher hydrocarbon contents than the other races and its hydrocarbon components, botryococcenes and methylsqualenes, both can be readily converted into biofuels. We studied race B using fluorescence and electron microscopy, and clarify the stage when extracellular hydrocarbon accumulation occurs during the cell cycle, in a correlation with the behavior and structural changes of the lipid bodies and discussed development of the algal colony. New accumulation of lipids on the cell surface occurred after cell division in the basolateral region of daughter cells. While lipid bodies were observed throughout the cell cycle, their size and inclusions were dynamically changing. When cells began dividing, the lipid bodies increased in size and inclusions until the extracellular accumulation of lipids started. Most of the lipids disappeared from the cytoplasm concomitant with the extracellular accumulation, and then reformed. We therefore hypothesize that lipid bodies produced during the growth of B. braunii are related to lipid secretion. New lipids secreted at the cell surface formed layers of oil droplets, to a maximum depth of six layers, and fused to form flattened, continuous sheets. The sheets that combined a pair of daughter cells remained during successive cellular divisions and the colony increased in size with increasing number of cells.     

Growth and photosynthetic activity of <Emphasis Type="Italic">Botryococcus braunii</Emphasis> biofilms

Botryococcus braunii is a green microalga capable of producing large amounts of external long-chain hydrocarbons suitable as a source of biofuel. There have been several studies indicating that cultures of B. braunii can reduce the energy and water requirement for mass biofuel production, especially if non-destructive extraction methods for milking hydrocarbons are used. Growing microalgae as a raw material for biofuel using conventional liquid-based cultivation (i.e., raceway ponds) has yet to be shown to be economically successful. An alternative solid growth (biofilm) cultivation method can markedly reduce the energy requirements and costs associated with the harvesting and dewatering processes. We evaluated the growth of biofilms of several strains of B. braunii (from races A, B, L and S) and found that three of the four tested races successfully grew to stationary phase in 10 weeks with no contamination. Among all races, B. braunii BOT22 (race B) reached the highest biomass and lipid yields (3.80 mg dry weight cm^?2 day^?1 and 1.11 mg dry weight cm^?2). Irrespective of the race, almost all photosynthetic parameters (F _V /F ₀ , PI_ABS and the OJIP curve) showed that the biofilm cultures were more stressed during lag and stationary phases than in logarithmic phase. We also studied the Botryococcus biofilm profiles using confocal microscopy and found that this method is suitable for estimating the overall biomass yield when compared with gravimetric measurement. In conclusion, the growth characteristics (biomass and lipid) and photosynthetic performance of all races indicated that B. braunii BOT22 is the most promising strain for biofilm cultivation.     

Identification of quantitative trait loci for resistance to <Emphasis Type="Italic">Xanthomonas campestris</Emphasis> pv. <Emphasis Type="Italic">campestris</Emphasis> in <Emphasis Type="Italic">Brassica rapa</Emphasis>

Resistance to six known races of black rot in crucifers caused by Xanthomonas campestris pv. campestris (Pammel) Dowson is absent or very rare in Brassica oleracea (C genome). However, race specific and broad-spectrum resistance (to type strains of all six races) does appear to occur frequently in other brassica genomes including B. rapa (A genome). Here, we report the genetics of broad spectrum resistance in the B. rapa Chinese cabbage accession B162, using QTL analysis of resistance to races 1 and 4 of the pathogen. A B. rapa linkage map comprising ten linkage groups (A01–A10) with a total map distance of 664 cM was produced, based on 223 AFLP bands and 23 microsatellites from a F₂ population of 114 plants derived from a cross between the B. rapa susceptible inbred line R-o-18 and B162. Interaction phenotypes of 125 F₂ plants were assessed using two criteria: the percentage of inoculation sites in which symptoms developed, and the severity of symptoms per plant. Resistance to both races was correlated and a cluster of highly significant QTL that explained 24–64% of the phenotypic variance was located on A06. Two additional QTLs for resistance to race 4 were found on A02 and A09. Markers closely linked to these QTL could assist in the transference of the resistance into different B. rapa cultivars or into B. oleracea.     

DNA addition or deletion is associated with a major karyotype polymorphism in the fungal phytopathogen Colletotrichum gloeosporioides

Summary A 1.2 Mb minichromosome resolved by pulsed-field electrophoresis was present in two independent race 3 isolates of Colletotrichum gloeosporioides causing Type B anthracnose specifically on Stylosanthes guianensis cv. Graham in Australia. This chromosome was absent in duplicate isolates representing races 1, 2 and 4 which infect other S. guianensis cultivars. A gene library was prepared specifically from the 1.2 Mb mini-chromosome and ten independent DNA clones unique to this chromosome were identified by differential hybridisation to whole chromosome probes. All of the ten selected probes hybridised only to the 1.2 Mb minichromosome unique to the race 3 isolates but not to any chromosome in isolates of the other races. These ten probes also hybridised only to restriction-digested DNA of race 3 and were thus both chromosome- and strain-specific for Type B C. gloeosporioides. Hybridisation analysis of NotI fragments of the 1.2 Mb minichromosome with these sequences indicated that they were not tightly clustered on the chromosome. These data demonstrate that the variation in the occurrence of the 1.2 Mb minichromosome did not arise by rearrangement of the genome of a progenitor strain but involved either large scale deletion or addition of DNA. The 1.2 Mb minichromosome did not contain a cloned high-copy-number repeat sequence present on all other mini- and maxichromosomes, suggesting addition from a genetically distinct strain. All ten chromosome-specific DNA probes hybridised to a 2.0 Mb chromosome in all races of C. gloeosporioides causing Type A anthracnose on Stylosanthes spp. including S. guianensis. Restriction fragment length polymorphism analysis demonstrated that only 15% of the hybridising restriction fragments of the Type A 2.0 Mb chromosome and the 1.2 Mb Type B race 3 minichromosome were identical. This indicated that it is unlikely that the 1.2 Mb minichromosome of the race 3 Type B pathogen was recently introgressed from-the Type A pathogen.     

Culture of the green microalga Botryococcus braunii Showa with LED irradiation eliminating violet light enhances hydrocarbon production and recovery

The green microalga Botryococcus braunii (B. braunii), race B, was cultured under light-emitting diode (LED) irradiation with and without violet light. This study examined the effect of violet light on hydrocarbon recovery and production in B. braunii. C34 botryococcene hydrocarbons were efficiently extracted by thermal pretreatments at lower temperatures when the alga was cultured without violet light. The hydrocarbon content was also higher (approximately 3%) in samples cultured without violet light. To elucidate the mechanism of effective hydrocarbon recovery and production, we examined structural components of the extracellular matrix (ECM). The amounts of extracellular carotenoids and water-soluble polymers extracted by thermal pretreatment from the ECM were decreased when the alga was cultured without violet light. These results indicate that LED irradiation without violet light is more effective for hydrocarbon recovery and production in B. braunii. Furthermore, structural ECM components are closely involved in hydrocarbon recovery and production in B. braunii.     

Stiffness and checking of <Emphasis Type="Italic">Eucalyptus nitens</Emphasis> sawn boards: genetic variation and potential for genetic improvement

A trial was undertaken to assess the extent to which variation in sawn-board quality traits of plantation-grown Eucalyptus nitens is under genetic control and amenable to genetic improvement. Five hundred and sixty trees from 129 families and three central Victorian races were sampled from an open-pollinated progeny trial in Tasmania, Australia. Acoustic wave velocity (AWV) was assessed on standing trees and sawlogs. Wedges from disks extracted from sawlogs were assessed for basic density and checking. Processed boards from 496 of the trees were assessed for board stiffness (static modulus of elasticity, MOE), and internal and surface checking. Genetic differences among races were significant for AWV and MOE traits. The Southern race had the highest mean values for these traits. Significant additive genetic variation within races was observed in all traits, demonstrating that the quality of plantation-grown E. nitens boards could be improved through breeding. Estimated narrow-sense heritabilities were 0.85 for standing-tree AWV, 0.71 for log AWV, 0.37 for board MOE, and ranged from 0.20 to 0.52 for checking traits. A strongly positive genetic correlation (r _g = 1.05) was observed between standing-tree AWV and board MOE, indicating that AWV could be used as a selection trait to improve E. nitens board stiffness. The genetic correlation between basic density and board MOE was also positive (r _g = 0.62). However, a significant and adverse genetic correlation (r _g = 0.61) was identified between basic density and surface check length. Wood stiffness and checking traits were more-or-less genetically independent, and genetic correlations between surface and internal checking were positive but only moderate (r _g = 0.48–0.52).     

PHYLOGENETIC PLACEMENT OF BOTRYOCOCCUS BRAUNII (TREBOUXIOPHYCEAE) AND BOTRYOCOCCUS SUDETICUS ISOLATE UTEX 2629 (CHLOROPHYCEAE)1

The phylogenetic placement of four isolates of Botryococcus braunii Kützing and of Botryococcus sudeticus Lemmermann isolate UTEX 2629 was investigated using sequences of the nuclear small subunit (18S) rRNA gene. The B. braunii isolates represent the A (two isolates), B, and L chemical races. One isolate of B. braunii (CCAP 807/1; A race) has a group I intron at Escherichia coli position 1046 and isolate UTEX 2629 has group I introns at E. coli positions 516 and 1512. The rRNA sequences were aligned with 53 previously reported rRNA sequences from members of the Chlorophyta, including one reported for B. braunii (Berkeley strain). Phylogenetic trees were constructed using distance, weighted maximum parsimony, and maximum likelihood, and their reliability was estimated using bootstrap analysis for distance and parsimony and Bayesian inference for likelihood. All methods showed, with high bootstrap or credibility support, that the four isolates of B. braunii form a monophyletic group whose closest relatives are in the genus Choricystis in the Trebouxiophyceae, whereas the previously reported B. braunii sequence is from a member of the Chlamydomonadales in the Chlorophyceae and isolate UTEX 2629 is a member of the Sphaeropleales in the Chlorophyceae. Polyphyly of these sequences was confirmed by Kishino‐Hasegawa tests on artificial trees in which sequences were moved to a single lineage.     

STRUCTURE AND CHEMISTRY OF A NEW CHEMICAL RACE OF BOTRYOCOCCUS BRAUNII (CHLOROPHYCEAE) THAT PRODUCES LYCOPADIENE,A TETRATERPENOID HYDROCARBON1

New strains of the hydrocarbon rich alga Botryococcus braunii Kützing were isolated from water samples collected in three tropical freshwater lakes. These strains synthesize lycopadiene, a tetraterpenoid metabolite, as their sole hydrocarbon. The morphological and ultrastructural characteristics of these algae are similar to those reported for previously described strains which produce either alkadienes or botryococcenes. The pyriform shaped cells are embedded in a colonial matrix formed by layers of closely appressed external walls: this dense matrix is impregnated by the hydrocarbon and some other lipids. We believe the new strains synthesizing lycopadiene form a third chemical race in B. braunii, besides the alkadiene and botryococcene races, rather than a different species. Like the other two types of hydrocarbons, lycopadiene was produced primarily during the exponential and linear growth phases. The major fatty acid in the three races was oleic acid. This fatty acid was predominant in the alkadiene race; palmitic and octacosenoic acid also were present in appreciable amounts in the three races. Cholest-5-en-3β-ol, 24-methylcholest-5-en-3β-ol and 24-ethylcho-lest-5-en-3β-ol occurred in the three races; three unidentified sterols also were detected in the lycopadiene race. Moreover, the presence of very long chain alkenyl-phenols in the lipids of algae of the alkadiene race was not observed in the botryococcene and lycopadiene races. Of the polysaccharides released in the medium, galactose appeared as a primary component: it predominated in the botryococcene race. The other major constituents were fucose for the alkadiene race and glucose and fucose for the lycopadiene race. Although morphologically similar, some important chemical differences exist among algae classified as B. braunii.     

Electrophoretic karyotype of <Emphasis Type="Italic">Flammulina velutipes</Emphasis> and its variation among monokaryotic progenies

 The karyotype of Flammulina velutipes (Curt. : Fr.) Sing. was investigated using contour-clamped homogeneous electric fields (CHEF) gel electrophoresis. A parental dikaryotic stock, JA, was resolved into at least eight chromosomal DNA bands ranging from 1.4- to 4.9-megabase (Mb) pairs. Overall, little size variation was found among monokaryotic strains with a few major exceptions. Among 13 monokaryotic progenies examined, 11 strains were resolved into at least eight chromosomal DNA bands in a manner similar to the parent dikaryon, whereas the other 2 were resolved into at least seven chromosomes lacking the 2.1-Mb chromosome possessed in the former. A slightly larger size variation was found in a chromosome carrying ribosomal DNA. An estimated haploid genome size of this stock was 24.0 Mb or more. Received: October 11, 2001 / Accepted: November 11, 2002 Acknowledgments We thank Professor T. Morinaga, Hiroshima Prefectural University, and Dr. T. Arima for their technical advice regarding CHEF gel electrophoresis. Correspondence to:E. Tanesaka     

The genetics of resistance to five races of downy mildew (Plasmopara halstedii) in sunflower (Helianthus annuus L.)

 These studies were undertaken to determine whether downy mildew resistance genes in sunflower were independent as first reported, or linked as suggested by more recent hypotheses. The segregations for downy mildew reaction of 111 F₃ progenies from a cross between a susceptible line and a line with Pl2 were used to locate this gene on the sunflower consensus RFLP linkage map. It was shown that Pl2 was linked to the same RFLP markers on linkage group 1 as Pl1 and Pl6, mapped earlier, and at a very similar distance. The F₃ progenies showed exactly the same segregation patterns when tested with race 1 and race D. One hundred and fifty four progenies from a cross between a susceptible line and HA335, containing Pl6 (considered as giving resistance to all Plasmopara halstedii races), were tested with the five French downy mildew races, 1, A, B, C and D. Two progenies were observed to show segregation for races 1 and D, while appearing homozygous-resistant to races A , B and C. Tests on F₄ progenies confirmed this separation of resistances with fixation of susceptibility to races 1 and D and resistance to races A, B and C. It is concluded that the Pl6 gene is not a “strong” gene, giving resistance to all downy mildew races, but rather a cluster of genes, each providing resistance to one, or a few, downy mildew races. The genes giving resistance to races 1 and D, on one hand, and to races A, B and C, on the other hand, must be very closely linked, with about 0.6 cM between the two groups. Received: 23 December 1996 / Accepted: 18 April 1997     

Race structure within the Mesoamerican gene pool of common bean (Phaseolus vulgaris L.) as determined by microsatellite markers

Common bean (Phaseolus vulgaris L.) cultivars are distinguished morphologically, agronomically and ecologically into specific races within each of the two gene pools found for the species (Andean and Mesoamerican). The objective of this study was to describe the race structure of the Mesoamerican gene pool using microsatellite markers. A total of 60 genotypes previously described as pertaining to specific Mesoamerican races as well as two Andean control genotypes were analyzed with 52 markers. A total of 267 bands were generated with an average of 5.1 alleles per marker and 0.297 heterozygosity across all microsatellites. Correspondence analysis identified two major groups equivalent to the Mesoamerica race and a group containing both Durango and Jalisco race genotypes. Two outlying individuals were classified as potentially of the Guatemala race although this race does not have a defined structure and previously classified members of this race were classified with other races. Population structure analysis with K = 1–4 agreed with this classification. The genetic diversity based on Nei’s index for the entire set of genotypes was 0.468 while this was highest for the Durango–Jalisco group (0.414), intermediate for race Mesoamerica (0.340) and low for race Guatemala (0.262). Genetic differentiation (G _ST) between the Mesoamerican races was 0.27 while genetic distance and identity showed race Durango and Jalisco individuals to be closely related with high gene flow (N _m) both between these two races (1.67) and between races Durango and Mesoamerica (1.58). Observed heterozygosity was low in all the races as would be expected for an inbreeding species. The analysis with microsatellite markers identified subgroups, which agreed well with commercial class divisions, and seed size was the main distinguishing factor between the two major groups identified.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Alkadiene- and botryococcene-producing races of wild strains of Botryococcus braunii

Samples of the green colonial alga Botryococcus braunii, collected from various localities, were grown in the laboratory and examined for their hydrocarbon content and morphology. Although few differences appeared between the ultrastructures of the samples, the nature of their hydrocarbons, which remains unchanged at any stage of growth, allows the distinction of two physiological races viz algae producing odd-numbered unbranched alkadienes and trienes (C₂₅C₃₁) (the A race) and those producing polymethylated triterpenes C_nH_2n-₁₀ (C₃₀C₃₇), the botryococcenes (the B race). In laboratory culture, the hydrocarbon content of these new strains is very high, from 30 to 60% of the dry biomass. For the two races the greatest hydrocarbon productivity takes place during the active growth phase. The important variability observed in botryococcene distribution could originate both from genetic and environmental factors.     

Cytogenetic characterization of <Emphasis Type="Italic">Hydrangea involucrata</Emphasis> Sieb. and <Emphasis Type="Italic">H. aspera</Emphasis> D. Don complex (Hydrangeaceae)<Emphasis Type="Italic">:</Emphasis> genetic,evolutional, and taxonomic implications

The subsection Asperae of genus Hydrangea L. (Hydrangeaceae) has been investigated for three reasons: several ambiguous classifications concerning Hydrangea aspera have been published, unexpected differences in genome size among seven accessions have been reported Cerbah et al. (Theor Appl Genet 103:45–51, 2001), and two atypical chromosome numbers (2n = 30 for Hydrangea involucrata and 2n = 34 for H. aspera) have been found when all other species of the genus present 2n = 36. Therefore, these two species and four subspecies of Hydrangea in all 29 accessions were analyzed for their genome size, chromosome number, and karyotype features. This investigation includes flow cytometric measurements of nuclear DNA content and bases composition (GC%), fluorochrome banding for detection of GC- and AT-rich DNA regions, and fluorescent in situ hybridisation (FISH) for chromosome mapping of 5 S and 18 S-5.8 S-26 S rDNA genes. In the H. aspera complex, the genome size ranged from 2.98 (subsp. sargentiana) to 4.67 pg/2C (subsp. aspera), an exceptional intraspecific variation of 1.57-fold. The mean base composition was 40.5% GC. Our report establishes the first karyotype for the species H. involucrata, and for the subspecies of H. aspera which indeed present different formulae, offering an element of discrimination. FISH and fluorochrome banding revealed the important differentiation between these two species (H. involucrata and H. aspera) and among four subspecies of the H. aspera complex. Our results are in agreement with the Chinese classification that places the groups Kawakami and Villosa as two different species: Hydrangea villosa Rehder and Hydrangea kawakami Hayata. This knowledge can contribute to effective germplasm management and horticultural use.     

<Emphasis Type="Italic">Blighia unijugata</Emphasis> and <Emphasis Type="Italic">Luffa cylindrica</Emphasis> Seed Oils: Renewable Sources of Energy for Sustainable Development in Rural Africa

Self-sufficiency in energy requirement is critical to the success of any developing economy. Apart from the search for alternatives, there is a need to achieve energy independence, directing much focus on biofuels. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics. Oil was extracted from the seeds of Blighia unijugata and Luffa cylindrica, subjected to chemical characterization and biodiesel production. The oil yield from the seed of B. unijugata was 50.82 ± 1.20% while that of L. cylindrica was 39.10 ± 0.20%. The biodiesel produced had ester content above 98%. The flash point of the biodiesel from B. unijugata and L. cylindrica was above 120°C while the phosphorus content was also below 1 ppm in both cases. The oxidative stability of B. unijugata was 44.30 ± 0.30 h, while that of L. cylindrica was lower than this value due to its high unsaturation. The copper strip corrosion value of the biodiesel was also found to be 1A. This study showed that the high free fatty acid content of B. unijugata and L. cylindrica seed oil can be reduced in a one-step pretreatment of esterification reaction using H₂SO₄ as catalyst thus reducing the problem of soap formation encountered when using oil with high free fatty acid for the production of biodiesel.     

Herbicide-resistant mutants of Botryococcus braunii race B (strain BOT-22)

The freshwater green alga Botryococcus braunii produces long-chain hydrocarbon oil in large quantities and secretes these from the cells. To exploit B. braunii as a source of next-generation biofuel, development of cost-effective cultivation systems are required. One of the most cost-effective methods for large-scale production is to simply grow B. braunii in open ponds. However, trials to cultivate B. braunii in open ponds often fail due to thriving of other green algal and cyanobacterial species because of the relatively slow growth of B. braunii. We previously demonstrated that herbicides are effective in control of contaminating algae. In order to use herbicide-assisted cultivation systems, we generated herbicide-resistant mutants of an oil-rich strain of B. braunii race B (strain BOT-22) by ethyl methanesulfonate mutagenesis. We isolated 44 glufosinate-resistant and 21 methyl viologen-resistant mutant lines. Some of these mutant lines exhibited vigorous growth and oil production in herbicide-containing liquid media, suggesting that they can be directly used in herbicide-containing cultivation systems.     

Relationships between nuclear DNA content and seed and leaf size in soybean

 A correlation between genome size and agronomically important traits has been observed in many plant species. The goal of the present research was to determine the relationship between genome size, seed size, and leaf width and length in soybean [Glycine max (L.) Merr.] Twelve soybean strains, representing three distinct seed size groups, were analyzed. Flow cytometry was used to estimate their 2C nuclear DNA contents. Data on seed size and leaf size of the 12 strains were obtained from 1994 and 1995 field experiments. Variation of 2C nuclear DNA among the 12 soybean strains was 4.6%, ranging from 2.37 pg for a small-seed strain to 2.48 pg for a large-seed strain. Strain seed size was positively associated with leaf width (r=0.92) and leaf length (r=0.93). Genome size was highly correlated with seed size (r=0.97), leaf width (r=0.90) , and leaf length (r=0.93). The results of our study indicate that there is a significant correlation between genome size and leaf and seed size in soybean. It is possible that selection for greater seed size either leads to, or results from, greater genome size. If so, this relationship might be worth exploring at a more fundamental level. Received: 5 April 1997 / Accepted: 9 January 1998