Origins of weedy rice revealed by polymorphisms of chloroplast DNA sequences and nuclear microsatellites

Conspecific weeds that permanently infest worldwide agroecosystems are evolved from their crop species. These weeds cause substantial problems for crop production by competing for resources in agricultural fields. Weedy rice represents such a conspecific weed infesting rice ecosystems, and causing tremendous rice yield losses owing to its strong competitiveness and abundant genetic diversity, likely resulted from its complex origins. Here, we report the use of chloroplast DNA (cpDNA) fingerprints to determine whether weedy rice is evolved from its wild (exo‐feral) or cultivated (endo‐feral) rice progenitor as the maternal donor in recent hybridization events. In addition, we also applied nuclear simple sequence repeat (SSR) markers to confirm the exo‐feral or endo‐feral origins of weedy rice accessions determined by the cpDNA fingerprints. We found that the studied weedy rice accessions evolved either from their wild or cultivated rice progenitor, as the maternal donor, based on the cpDNA network and structure analyses. Combined analyses of cpDNA and nuclear SSR markers indicated that a much greater proportion of weedy rice accessions had the endo‐feral origin. In addition, results from the genetic structure of nuclear SSR markers indicated that weedy rice accessions from the endo‐feral pathway are distinctly associated with either indica or japonica rice cultivars, suggesting their complex origins through crop–weed introgression. The complex pathways of origin and evolution could greatly promote genetic diversity of weedy rice. Therefore, innovative methods should be developed for effective weedy rice control.     

Assessment of gene flow from a herbicide-resistant indica rice (Oryza sativa L.) to the Costa Rican weedy rice (Oryza sativa) in Tropical America: factors affecting hybridization rates and characterization of F1 hybrids

Herbicide-resistant rice cultivars allow selective weed control. A glufosinate indica rice has been developed locally. However, there is concern about weedy rice becoming herbicide resistant through gene flow. Therefore, assessment of gene flow from indica rice cultivars to weedy rice is crucial in Tropical America. A field trial mimicking crop–weed growing patterns was established to assess the rate of hybridization between a Costa Rican glufosinate-resistant rice line (PPT-R) and 58 weedy rice accessions belonging to six weedy rice morphotypes. The effects of overlapping anthesis, morphotype, weedy accession/PPT-R percentage, and the particular weedy accession on hybridization rates were evaluated. Weedy rice accessions with short overlapping anthesis (4–9 days) had lower average hybridization rates (0.1%) than long anthesis overlapping (10–14 days) accessions (0.3%). Hybridization also varied according to weedy rice morphotype and accession. Sativa-like morphotypes (WM-020, WM-120) hybridized more readily than intermediate (WM-023, WM-073, WM-121) and rufipogon-like (WM-329) morphotypes. No hybrids were identified in 11 of the 58 accessions analyzed, 21 accessions had hybridization rates from 0.01% to 0.09%, 21 had rates from 0.1% to 0.9%, and 5 had frequencies from 1% to 2.3%. Another field trial was established to compare the weedy rice-PPT-R F₁ hybrids with their parental lines under noncompetitive conditions. F₁ hybrids had a greater phenotypic variation. They had positive heterosis for vegetative trait and reproductive potential (number of spikelets and panicle length) traits, but negative heterosis for seed set. This study demonstrated the complexity of factors affecting hybridization rates in Tropical America and suggested that the phenotype of F₁ hybrids facilitate their identification in the rice fields.     

Sequence variation of non-coding regions of chloroplast DNA of soybean and related wild species and its implications for the evolution of different chloroplast haplotypes

Soybean chloroplast DNAs (cpDNAs) are classified into three types (I, II and III) based on RFLP profiles. Type I is mainly observed in cultivated soybean (Glycine max), while type II and type III are frequently found in both cultivated and wild soybean (Glycine soja), although type III is predominant in wild soybean. In order to evaluate the diversity of cpDNA and to determine the phylogenetic relationship among different chloroplast types, we sequenced nine non-coding regions of cpDNA for seven cultivated and 12 wild soybean accessions with different cpDNA types. Eleven single-base substitutions and a deletion of five bases were detected in a total of 3849 bases identified. Five mutations distinguished the accessions with types I and II from those with type III, and seven were found in the accessions with type III, independently of their taxa. Four species of the subgenus Glycine shared bases that were identical to those with types I and II at two of the five mutation sites and shared bases that were identical to those with type III at the remaining three sites. Therefore, the different cpDNA types may not have originated monophyletically, but rather may have differentiated from a common ancestor in different evolutionary directions. A neighbor-joining tree resulting from the sequence data revealed that the subgenus Soja connected with Glycine microphylla which formed a distinct clade from Clycine clandestina and the tetraploid cytotypes of Glycine tabacina and Glycine tomentella. Several informative length mutations of 54 to 202 bases, due to insertions or deletions, were also detected among the species of the genus Glycine. Received: 16 December 1999 / Accepted: 12 February 2000     

Effect of seed depth on germination and growth of velvetleaf (Abutilon theophrasti Medic.)

Importance of several weed species has been considerably increased during the last few decades in Hungary. Velvetleaf (Abutilon theophrasti Medic.) belongs to this spreading weed group as well. This weed species was in the 27th position in the course of the fourth Hungarian weed survey, but at the time of the fifth weed survey in 2007-2008 it stepped forward to the 10th position in the cornfields of Zala County. Requiring a warm climate, global climate warming plays a significant role in its rapid spread. Moreover, its effective reproduction strategy supports its occurrence and continuous spread in almost all field crops. Protection against velvetleaf can only be successful, if we know its biological and ecological characteristics. Comprehensive knowledge of the plant and selection of a proper application of weed control methods together can result velvetleaf free crop fields. The experiment was set up on the 29th of April 2009 at Keszthely where fifty seeds were sown into 50 litres volume plastic pots, in four replications with fifty pieces of seed per each plot. Germination percent of velvetleaf seeds and several growth indexes of seedlings (stem- and root length, leaf area, number of leaves, stem- and root fresh and dry weight) were measured on three different sampling dates.     

A chloroplast DNA phylogeny of lilacs (Syringa, Oleaceae): plastome groups show a strong correlation with crossing groups

Phylogenetic relationships and genomic compatibility were compared for 60 accessions of Syringa using chloroplast DNA (cpDNA) and nuclear ribosomal DNA (rDNA) markers. A total of 669 cpDNA variants, 653 of which were potentially phylogenetically informative, was detected using 22 restriction enzymes. Phylogenetic analyses reveal four strongly supported plastome groups that correspond to four genetically incompatible crossing groups. Relationships of the four plastome groups (I(II(III,IV))) correlate well with the infrageneric classification except for ser. Syringa and Pinnatifoliae. Group I, which includes subg. Ligustrina, forms a basal lineage within Syringa. Group II includes ser. Syringa and Pinnatifoliae and the two series have high compatibility and low sequence divergence. Group III consists of three well-defined species groups of ser. Pubescentes. Group IV comprises all members of ser. Villosae and has the lowest interspecific cpDNA sequence divergences. Comparison of cpDNA sequence divergence with crossability data indicates that hybrids have not been successfully generated between species with divergence greater than 0.7%. Hybrid barriers are strong among the four major plastome groups, which have sequence divergence estimates ranging from 1.096 to 1.962%. In contrast, fully fertile hybrids occur between species pairs with sequence divergence below 0.4%. Three regions of the plastome have length variants of greater than 100 bp, and these indels identify 12 different plastome types that correlate with phylogenetic trees produced from cpDNA restriction site data. Biparentally inherited nuclear rDNA and maternally inherited cpDNA length variants enable the identification of the specific parentage of several lilac hybrids.     

Introgression between wild and cultivated soybeans of Japan revealed by RFLP analysis for chloroplast DNAs

Wild soybeans collected in Japan were surveyed for RFLPs of chloroplast DNA. Three haplotypes were detected in RFLPs with a cpDNA clone which contains a LSC region adjacent to the left member of IR. Most of the plants tested possessed haplotype III, and a few plants, collected mostly in southern Japan, had haplotype II. Haplotype I, which is the predominant form in modern cultivars, was detected at six sites from four widely separated regions. Our results indicate that haplotype III is predominant in wild soybean of Japan. Some of the plants having haplotype I were phenotypically intermediate between wild and cultivated soybeans, while the others possessed a seed morphology and plant architecture typical of ordinary wild soybean. The plants having haplotype I appear to be either derivatives of hybridization between wild and cultivated soybeans or relics of a direct progenitor of soybean cultivars with the haplotype I chloroplast genome.     

Identification of sequence variations by PCR-RFLP and its application to the evaluation of cpDNA diversity in wild and cultivated soybeans

The diversity and maternal lineage in wild and cultivated soybeans have previously been assayed using restriction fragment length polymorphism (RFLP) and sequencing analyses of chloroplast DNA (cpDNA). Here we describe a method based on PCR-RFLP for the identification of nucleotides at four mutation sites in non-coding regions of cpDNA. Of the four sites, two were located in restriction enzyme sites and two were not. For the latter two sites, new primers were designed to artificially create restriction sites that spanned them. The PCR-RFLP method enabled us to identify nucleotides at each of the four mutation sites easily and reliably. Fifty-seven wild and sixty-seven cultivated soybeans of different origins and different cpDNA types (types I, II, and III) were assayed. All of the samples tested could be classified into four haplotypes. All of the type-I and -II accessions had the same nucleotides at each of the four mutation sites, while all of the type-III accessions, except for 3 wild ones, had nucleotides that were different from those of types I and II. A sequencing analysis revealed that the 3 wild accessions possessed other single-base variations in the non-coding regions of trnH-psbA and trnT-trnL. The results of this study suggest that the type-I and type-II chloroplast genomes form a group that is distinct from the type-III chloroplast genome. Received: 14 April 2000 / Accepted: 11 July 2000     

Independent segregation of the plastid genome and cytoplasmic male sterility in Petunia somatic hybrids

Summary The chloroplast genomes of three sets of Petunia somatic hybrids were analyzed to examine the relationship between chloroplast DNA (cpDNA) composition and cytoplasmic male sterility (CMS). Chloroplast genomes of somatic hybrid plants were identified either by restriction and electrophoresis of purified cpDNAs or by hybridization of total DNA digests with cloned cpDNA probes that distinguish the parental genomes.The chloroplast genomes of a set of seven somatic hybrids derived from the fusion of Petunia CMS line 2423 and fertile line 3699 were analyzed. All seven plants were fertile, and all exhibited the cpDNA restriction pattern of the sterile cytoplasm. Similarly, four fertile somatic hybrids derived from the fusion of CMS line 3688 and fertile line 3677 were found to contain the CMS chloroplast genome. The cpDNA compositions of four fertile and two sterile somatic hybrids derived from the fusion of CMS line 3688 and fertile line 3704 were determined by restriction analysis of purified cpDNAs; all six plants exhibited the cpDNA restriction pattern of line 3704. Thus the CMS phenotype segregates independently of the chloroplast genome in Petunia somatic hybrids, indicating that CMS in Petunia is not specified by the chloroplast genome.     

基于叶绿体DNA变异的湖北梨属种质系统进化及遗传多样性分析

利用trnL intron、trnL-trnF、trnS-psbC和accD-psa I等4个叶绿体DNA片段对来自湖北省的88份梨属种质资源进行系统进化和遗传多样性分析。结果表明,4个cpDNA片段共检测到变异位点11个,其中单一突变位点6个,插入/缺失(Indel)位点5个。acc D-psa I多态性最高,其变异位点数、核苷酸多态性和单倍型多样性均为最高。供试梨种质的核苷酸多样性和单倍型多样性分别为0.00112和0.769;Tajima's D检验值在P0.10水平上均不显著,表明所检测的4个区域以及合并后的片段均遵循中性进化模型;4个序列合并共检测到叶绿体单倍型10个,其中兴山梨种质中检测到的单倍型最多,荆门其次;Hap2和Hap5是2个主要单倍型,分别占总样本数的31.82%和30.68%;中介邻接网络图显示东方梨和西洋梨独立进化,而较为原始的稀有单倍型Hap8和Hap9均位于荆门,暗示该地区可能为砂梨的起源中心或多样性中心之一。     

苘麻挥发油对小麦、玉米和大豆萌发及幼苗生长的化感作用

苘麻是旱田常见杂草,可造成作物减产,化感作用是造成减产的可能原因之一。本研究分析了苘麻挥发油成分对3种旱田作物小麦、玉米和大豆种子萌发和幼苗生长的化感作用。结果表明: 应用气相色谱-质谱(GC-MS),从苘麻挥发油中鉴定出26种化学成分,占总峰面积的98.1%,其中,低分子量萜类成分有α-蒎烯、桉树醇、α-松油烯、β-松油烯、反式α-紫罗兰酮、反式β-紫罗兰酮。苘麻挥发油饱和水溶液能通过滤纸和土壤2种基质抑制3种作物种子萌发。苘麻挥发油能通过空气、滤纸和土壤3 种基质抑制3种作物幼苗生长,对小麦的抑制作用最强,玉米和大豆次之。苘麻挥发油对小麦生长的抑制作用以空气载体最强,滤纸和土壤载体次之。挥发油中低分子量的萜类成分可能是重要的化感成分。     

Hybridization between European and Asian dandelions ( Taraxacum section Ruderalia and section Mongolica)2. Natural hybrids in Japan detected by chloroplast DNA marker

Natural hybridization in Taraxacum between native sexual diploids and introduced agamospermous triploids occurring in Japan was studied by means of chloroplast DNA (cpDNA) marker. We first determined the nucleotide sequences between trnT (UGU) and trnF (GAA) of cpDNA for 22 plants obtained from Japan and Europe. The sequences analyzed were about 1,574 base pairs long. Among all accessions, the total numbers of polymorphic characters were 56 nucleotide substitutions, three insertions/deletions (ins/dels), and one repeat number polymorphism of mononucleotide motif. Of these polymorphic characters, four nucleotides and one ins/del were applicable in the discrimination between Japanese and European taxa of dandelions. We selected the ins/del in an intergenic region between trnL (UAA) 3′ exon and trnF (GAA) as a cpDNA marker. Using a newly developed cpDNA marker, 225 plants of putative Taraxacum officinale collected from 11 populations in Niigata City were investigated. Eighty-two percent of them showed a Japanese haplotype of cpDNA, and they were regarded as hybrids. Compared with the previous studies, it is likely that the prevalence of the hybrid plants is a general phenomena at least in urban areas in Japan. The validity of the cpDNA marker for screening Taraxacum hybrids is discussed. Electronic Publication     

Italian weedy rice—A case of de‐domestication?

Weedy rice is a representative of the extensive group of feral weeds that derive from crops, but has returned to the lifestyle of a wild species. These weeds develop either from a hybridization of crops with wild relatives (exoferality), or by mutation of crops to weedy forms (endoferality). Due to the close relation of weed and crop, the methods for weed‐targeted containment are limited to date. A deeper understanding of the development of such weeds might help to design more efficient and sustainable approaches for weed management. Weedy rice poses a serious threat to rice yields worldwide. It is widely accepted that weedy rice has originated independently in different regions all over the world. However, details of its evolution have remained elusive. In the current study, we investigated the history of weedy rice in northern Italy, the most important rice‐growing area in Europe. Our approach was to analyze genes related to weedy traits (SD1, sh4, Rc) in weedy rice accessions compared to cultivars, and to integrate these results with phenotypic and physiological data, as well as historical information about rice farming in Italy. We arrive at a working model for the timeline of evolution of weedy rice in Italy indicating that both exoferality and endoferality acted as forces driving the development of the diverse weedy rice populations found in the region today. Models of weed evolution can help to predict the direction which weed development might take and to develop new, sustainable methods to control feral weeds.     

Worldwide phylogeny and biogeography of Cardamine flexuosa (Brassicaceae) and its relatives

Phylogenetic relationships, biogeography, and taxonomy of a group of taxa putatively related to the tetraploid Cardamine flexuosa were explored using sequences of the internal transcribed spacer region of nrDNA (ITS) and the trnL-trnF region of cpDNA. Taxon sampling focused on eastern Asia, North America, and Europe, and included 19 taxa represented by 177 and 182 accessions for each data set, respectively. Our analyses provided unequivocal evidence that Asian weedy populations traditionally assigned to C. flexuosa form an independent evolutionary lineage and represent a distinct taxon from European C. flexuosa. The allopolyploid origin of this common weed in paddy fields, its origin, and/or spread associated with the establishment of suitable man-made habitats are suggested. It is also found as an introduced weed in Australia and North America. Phylogenetic relationships and the associated taxonomic implications are presented and discussed for the group as a whole. Contrasting patterns of genetic variation (particularly in cpDNA) among different species were revealed. While very little haplotype diversity was found in widespread C. hirsuta and C. flexuosa, greater variation, showing phylogeographic structure, was observed in the tetraploid C. scutata within a relatively small area of Japan.     

Physiological determinants of growth rate in response to phosphorus supply in wild and cultivated Hordeum species

Summary Under favorable nutrition, accessions of the weedy barleygrass (Hordeum leporinum and H. glaucum) had a higher relative growth rate (RGR) than did accessions of cultivated barley (H. vulgare) or its wild progenitor (H. spontaneum). RGR was not positively correlated with the presumed level of soil fertility at the collection site of an accession either within or among species. RGR was reduced more strongly by low-P supply in the progenitor than in the crop or weed, indicating that selection of cultivars to grow in fertile soils had not reduced their potential to grow effectively under low-P conditions. Seed and embryo masses were more important than RGR in determining plant size. Relative differences among assessions in plant size declined with time, because (1) accessions with small seeds had a higher RGR, and (2) RGR of large-seeded accessions declined with time. Absolute growth rate correlated positively with leaf area and negatively with photosynthetic rate per unit leaf area. Under favorable nutrition, maximum photosynthetic rate correlated negatively with leaf length and therefore was higher in the weeds than in the crop or progenitor accessions. P absorption potential did not differ consistently among species but generally increased in response to P stress. Cultivars produced a few tall tillers, whereas weeds and progenitors produced many small tillers. The cultivar had a larger proportion of reproductive tillers, allocated a larger proportion of biomass to grain, and produced larger grains than did the weedy accession. By contrast, the weed began maturing seeds sooner, produced more reproductive tillers, and produced more grains per car and per plant than did the cultivar. The study suggests two major conclusions: (1) A low RGR is not an adaptation to low P supply in annual Hordeum species. (2) Seed size is the major determinant of early plant size between accessions in these Hordeum species under favorable nutrition. However, large seed size indirectly results in a low RGR because of the inverse relationship between plant size and RGR and results in a low photosynthetic rate because of the inverse relationship between leaf size and photosynthesis.     

Impact of interspecific hybridization between crops and weedy relatives on the evolution of flowering time in weedy phenotypes

Background

Like conventional crops, some GM cultivars may readily hybridize with their wild or weedy relatives. The progressive introgression of transgenes into wild or weedy populations thus appears inevitable, and we are now faced with the challenge of determining the possible evolutionary effects of these transgenes. The aim of this study was to gain insight into the impact of interspecific hybridization between transgenic plants and weedy relatives on the evolution of the weedy phenotype.

Methodology/Principal Findings

Experimental populations of weedy birdseed rape (Brassica rapa) and transgenic rapeseed (B. napus) were grown under glasshouse conditions. Hybridization opportunities with transgenic plants and phenotypic traits (including phenological, morphological and reproductive traits) were measured for each weedy individual. We show that weedy individuals that flowered later and for longer periods were more likely to receive transgenic pollen from crops and weed×crop hybrids. Because stem diameter is correlated with flowering time, plants with wider stems were also more likely to be pollinated by transgenic plants. We also show that the weedy plants with the highest probability of hybridization had the lowest fecundity.

Conclusion/Significance

Our results suggest that weeds flowering late and for long periods are less fit because they have a higher probability of hybridizing with crops or weed×crop hybrids. This may result in counter-selection against this subset of weed phenotypes, and a shorter earlier flowering period. It is noteworthy that this potential evolution in flowering time does not depend on the presence of the transgene in the crop. Evolution in flowering time may even be counter-balanced by positive selection acting on the transgene if the latter was positively associated with maternal genes promoting late flowering and long flowering periods. Unfortunately, we could not verify this association in the present experiment.     

Chloroplast DNA variation in Populus. III. Novel chloroplast DNA variants in natural Populus x canadensis hybrids

A rare phenomenon of the occurrence of novel non-parental chloroplast DNA (cpDNA) variants in natural sexual interspecific hybrids between Populus deltoides var deltoides and P. nigra, P. x canadensis is described. Restriction fragment variation of cpDNA in 17 P. x canadensis cultivars was examined and compared with that of representative samples of P. deltoides and P. nigra using 83 combinations of 16 restriction enzymes and six Petunia hybrida cpDNA probes. Twelve cultivars had one to five novel non-parental cpDNA fragments in the chloroplast genome region homologous to the 9.0-kb PstI cpDNA fragment of Petunia from the large single-copy region.     

Patterns and relative rates of nucleotide and insertion/deletion evolution at six chloroplast intergenic regions in new world species of the Lecythidaceae

Insertions and deletions (indels) in chloroplast noncoding regions are common genetic markers to estimate population structure and gene flow, although relatively little is known about indel evolution among recently diverged lineages such as within plant families. Because indel events tend to occur nonrandomly along DNA sequences, recurrent mutations may generate homoplasy for indel haplotypes. This is a potential problem for population studies, because indel haplotypes may be shared among populations after recurrent mutation as well as gene flow. Furthermore, indel haplotypes may differ in fitness and therefore be subject to natural selection detectable as rate heterogeneity among lineages. Such selection could contribute to the spatial patterning of cpDNA haplotypes, greatly complicating the interpretation of cpDNA population structure. This study examined both nucleotide and indel cpDNA variation and divergence at six noncoding regions (psbB-psbH, atpB-rbcL, trnL-trnH, rpl20-5'rps12, trnS-trnG, and trnH-psbA) in 16 individuals from eight species in the Lecythidaceae and a Sapotaceae outgroup. We described patterns of cpDNA changes, assessed the level of indel homoplasy, and tested for rate heterogeneity among lineages and regions. Although regression analysis of branch lengths suggested some degree of indel homoplasy among the most divergent lineages, there was little evidence for indel homoplasy within the Lecythidaceae. Likelihood ratio tests applied to the entire phylogenetic tree revealed a consistent pattern rejecting a molecular clock. Tajima's 1D and 2D tests revealed two taxa with consistent rate heterogeneity, one showing relatively more and one relatively fewer changes than other taxa. In general, nucleotide changes showed more evidence of rate heterogeneity than did indel changes. The rate of evolution was highly variable among the six cpDNA regions examined, with the trnS-trnG and trnH-psbA regions showing as much as 10% and 15% divergence within the Lecythidaceae. Deviations from rate homogeneity in the two taxa were constant across cpDNA regions, consistent with lineage-specific rates of evolution rather than cpDNA region-specific natural selection. There is no evidence that indels are more likely than nucleotide changes to experience homoplasy within the Lecythidaceae. These results support a neutral interpretation of cpDNA indel and nucleotide variation in population studies within species such as Corythophora alta.     

Biosystematics and agronomic potential of some weedy and cultivated amaranths

Summary Three weedy amaranths (Amarantkus hybridus, A. retroflexus and A. powellii) from nine California sites, three domesticated species (A. caudatus, A. hypochondriacus and A. cruentus) from the USDA plant inventory as well as other sources and a naturally-occurring crop-weed hybrid were studied for numerical taxonomy using morphological and allozyme variation data. The crop and weedy species groups were easily separated and the hybrid populations were found to be intermediate. Surprisingly, very little intraspecific variation was present. Crop, weed and hybrid amaranths were also compared for their yielding ability, harvest index, seed efficiency of grain production and protein, popping quality and other agronomic traits. Although field plot yields were similar among the three groups of species (700 Kg/ha seed without fertilizer treatment and water, ranging to 3000 Kg/ha with fertilizer applications of 170 Kg N/ha, and abundant water), the harvest index of the weedy group was much higher (25–40%) than the domesticated species (10–15%). The allocation of biomass to seed production is positively correlated with seed yield in the domesticated but not in the weedy types, whereas the percentages of biomass as stem material and as seeds are negatively correlated. Several weedy and crop characteristics together should provide the basis of new improved cultivars through genetic recombination and selection.     

Chloroplast and mitochondrial DNA composition of triploid and tetraploid somatic hybrids between Lycopersicon esculentum and Solanum tuberosum

The chloroplast (cp) DNA type and mitochondrial (mt) DNA composition of 17 somatic hybrids between a cytoplasmic albino tomato and monoploid potato (A7-hybrids) and 18 somatic hybrids between a nitrate reductase-deficient tomato and monoploid potato (C7-hybrids) were analyzed. Thirteen A7-hybrids and 9 C7-hybrids were triploids (with one potato genome); the other hybrids were tetraploid. As expected, all A7-hybrids contained potato cpDNA. Of the C7-hybrids 7 had tomato cpDNA, 10 had potato cpDNA and 1 hybrid contained both tomato and potato cpDNA. The mtDNA composition of the hybrids was analyzed by hybridization of Southern blots with four mtDNA-specific probes. The mtDNAs in the hybrids had segregated independently from the cpDNAs. Nuclear DNA composition (i.e. one or two potato genomes) did not influence the chloroplast type in the C7-hybrids, nor the mtDNA composition of A7- or C7-hybrids. From the cosegregation of specific mtDNA fragments we inferred that both tomato and potato mtDNAs probably have a coxII gene closely linked to 18S+5S rRNA genes. In tomato, atpA, and in potato, atp6 seems to be linked to these mtDNA genes.     

Identification of genetic variations of cultivated and weedy types of Perilla species in Korea and Japan using morphological and SSR markers

To better understand the genetic diversity and relationships of the two cultivated types of Perilla crop and their weedy types in Korea and Japan, we evaluated the genetic variations of 56 accessions by assessing five morphological characteristics and 18 SSR markers. The two cultivated types of var. frutescens and var. crispa were clearly distinguished by seed size, whereas most accessions of cultivated and weedy types of var. crispa cannot be distinguished strictly by seed characteristics. A total of 165 alleles with the SSR analysis were detected with an average number of 9.2 alleles per locus among the 56 Perilla accessions. The number of alleles per locus ranged from two for KWPE-56 and KWPE-39 to 21 for GBPFM-204. Additionally, the genetic diversity of each locus ranged from 0.497 at KWPE-56 and KWPE-39 to 0.959 at GBPFM-204, with an average of 0.692. The average genetic diversity values were 0.549, 0.685, 0.451 and 0.557 for cultivated and weedy types of var. frutescens and for cultivated and weedy types of var. crispa, respectively. The weedy type accessions of var. frutescens and var. crispa evidenced greater variation than the corresponding cultivated type accessions. The accessions of the cultivated and weedy types of var. frutescens and var. crispa from Korea exhibited greater SSR diversity than those of Japan. An UPGMA phylogenetic tree revealed three major groups, which was congruent with their morphological characteristics except for a few odd accessions. SSR markers clarified the genetic relationships between var. frutescens and var. crispa and helped improve our understanding of the genetic diversity of the two cultivated types of P. frutescens and their weedy types in Korea and Japan.