Cytoplasmic Diversity Research Articles

Polymorphism analysis of the chloroplast and mitochondrial genomes in soybean

BackgroundSoybean is an important protein- and oil-rich crop throughout the world. Much attention has been paid to its nuclear genome, which is bi-parentally inherited and associated with many important agronomical traits. However, less is known about the genomes of the semi-autonomous and essential organelles, chloroplasts and mitochondria, of soybean.ResultsHere, through analyzing the polymorphisms of these organelles in 2580 soybean accessions including 107 wild soybeans, we found that the chloroplast genome is more variable than the mitochondrial genome in terms of variant density. Consistent with this, more haplotypes were found in the chloroplast genome (44 haplotypes) than the mitochondrial genome (30 haplotypes). These haplotypes were distributed extremely unevenly with the top two haplotypes (CT1 and CT2 for chloroplasts, MT1 and MT2 for mitochondria) accounting for nearly 70 and 18% of cultivated soybean accessions. Wild soybeans also exhibited more diversity in organelle genomes, harboring 32 chloroplast haplotypes and 19 mitochondrial haplotypes. However, only a small percentage of cultivated soybeans shared cytoplasm with wild soybeans. In particular, the two most frequent types of cytoplasm (CT1/MT1, CT2/MT2) were missing in wild soybeans, indicating that wild soybean cytoplasm has been poorly exploited during breeding. Consistent with the hypothesis that soybean originated in China, we found that China harbors the highest cytoplasmic diversity in the world. The geographical distributions of CT1–CT3 and MT1–MT3 in Northeast China were not significantly different from those in Middle and South China. Two mitochondrial polymorphism sites, p.457333 (T > C) and p.457550 (G > A), were found to be heterozygous in most soybeans, and heterozygosity appeared to be associated with the domestication of cultivated soybeans from wild soybeans, the improvement of landraces to generate elite cultivated soybeans, and the geographic adaptation of soybean.ConclusionsThe haplotypes of thousands of soybean cultivars should be helpful in evaluating the impact of cytoplasm on soybean performance and in breeding cultivars with the desired cytoplasm. Mitochondrial heterozygosity might be related to soybean adaptation, and this hypothesis needs to be further investigated.

New insights into the intraspecific cytoplasmic DNA diversity, maternal lineages classification and conservation issues of Tunisian pearl millet landraces.

Tunisian pearl millet (Pennisetum glaucum L.) landraces are still growing in contrasting agro-ecological environments and are considered potentially useful for national and international breeders. Despite its genetic potential, the cropping areas of this species are still limited and scattered which increases the risk of genetic erosion. The chloroplast DNA polymorphism and maternal lineages classification of forty nine pearl millet landraces representing seven populations covering the main distribution area of this crop in Tunisia were undertaken based on informative cpSSR molecular markers. A total of 21 alleles combining to 9 haplotypes were detected with a mean value of 3.5 alleles per locus and a haplotype genetic diversity (Hd) of 0.82. The number of chloroplast haplotypes per population ranged from 1 to 4 with an average of 1.28. The haplotypes median-joining network and UPGMA analyses revealed two probable ancestral maternal lineages with a differential pearl millet seed-exchange rate between the investigated areas. Northern and Central populations presented unique genetic backgrounds while historical farmers' practices in the South-East area resulted in the isolation of their own local landraces. The genetic evidences strongly support at least two introduction origins of pearl millet in Tunisia, one in the North and the other in the South followed by distinct local dispersal histories. Complementary in-situ and ex-situ conservation strategies taking into account the conservation of the maternal lineage cytoplasmic diversity are required. The investigated chloroplast SSRs provide useful molecular markers which could be used in further genetic studies and breeding surveys of pearl millet genetic resources.

Cytoplasmic diversity of potato relatives preserved at Plant Breeding and Acclimatization Institute in Poland

Among different types of potato cytoplasmic genomes, some are associated with male sterility or affect agronomic traits. The goal of this study was to analyze types of chloroplast and mitochondrial genomes of selected potato relatives originating from collection of the Institute of Plant Industry, Saint Petersburg, Russia, and preserved in Poland. Using chloroplast and mitochondrial markers the cytoplasm types were determined for 401 genotypes belonging to 43 seed accessions of 28 Solanum species. Among characterized genotypes, 201 (50.1%), 156 (38.9%) and 44 (11%) had cytoplasm types W, D, M, respectively. No accessions with the T, P or A cytoplasm were found. Within cytoplasm W, genotypes with the subtypes: W/α and W/β were identified, but not with W/γ. In S. famatinae, we detected unusual product of the T marker with 65 bp insertion earlier seen exclusively in S. vernei. Among the genotypes of S. leptophyes, two profiles of the ALM_4/ALM_5 marker were observed. S. famatinae and S. vernei come from Argentina, provinces Catamarca and Tucumán. Possibly the insertion in marker T occurred independently in two species, or the accessions were misidentified. Segregation of the ALM_4/ALM_5 marker within S. leptophyes indicates that potato seed accessions are heterogeneous not only due to nuclear DNA polymorphisms but have diversified cytoplasm, too. Our findings are important for exploitation of the tested material in potato breeding. Male-fertile cytoplasm types give a chance of avoiding fertility problems and widening the range of crosses in future generations of breeding materials.

Heterotic Effect of Different Cytoplasmic Combinations in Sunflower Hybrids Cultivated Under Diverse Irrigation Regimes.

The sunflower hybrids hold a narrow cytoplasmic diversity. Besides, the heterotic effect of wild cytoplasmic combinations of sunflower on important traits under water stress has not been explored in detail. Here, we evaluated the different sunflower cytoplasmic combinations in sunflower hybrids using cytoplasmic male sterile (CMS) sources as female parents. We used a total of sixteen sunflower genotypes representing twelve CMS lines from wild and conventional sources along with four restorer lines. Twelve CMS lines were crossed with four restorer lines to develop a total of 48 F1 hybrid combinations. The hybrids were evaluated under two different environments (i.e., regular irrigation and water stress) for morphophysiological, yield, and biochemical traits over two years. Heterotic effect for various CMS sources was evaluated on all of the three possible scales, namely, better-parent heterosis (BPH), mid-parent heterosis (MPH), and heterosis as percent of check (PSH-996). For better-parent and mid-parent heterosis, the CMS sources Helianthus annuus, Helianthus argophyllus, and Helianthus debilis demonstrated positive better-parent heterosis for seed yield, oil content, and oleic acid irrespective of the environment. However, the hybrid combinations of different sources when using the genotype RCR8297 as the restorer parent recorded maximum average returns. Furthermore, chlorophyll meter (SPAD) reading positively correlated with days to 50% flowering, days to maturity, plant height, and number of leaves per plant in both the environments. Overall, this study identified and compared the heterotic effect of the different cytoplasmic combinations in sunflower under water stress as well as under normal irrigation environments.

Differential and interactive effects of cytoplasmic substitution and seed ageing on submergence stress response in wheat (Triticum aestivum L.)

Cytoplasmic genomes affect various phenotypes, including abiotic stress responses, through interaction with nuclear genomes in plants. We focused on the effects of cytoplasmic substitution on germination and seedling growth in combinations with submergence and seed ageing, both of which are known to inhibit these traits posing a challenge in agriculture and seed banking. We carried out comparative phenotypic studies of submergence and seed ageing effects using a series of nucleus–cytoplasm (NC) hybrids of wheat, in which 11 heterologous cytoplasms of Triticum and Aegilops species were combined with a common nucleus. Adopting the test-tube bioassay, germination and seedling growth were studied using aged and non-aged seeds. Imbibed seeds were subjected to 3-days submergence followed by incubation under de-submergence conditions. Seed ageing reduced the germination rates in NC hybrids. Submergence and seed ageing both caused reduction of seedling growth evaluated by shoot length in all or most of the lines. The magnitude of shoot growth inhibition by submergence and seed ageing varied greatly among NC hybrids compared with the nuclear donor, and three distinct response types were recognized. Submergence and seed ageing, in combination, caused leaf chlorosis in most of NC hybrids. Our results suggested that the observed diverse effects of cytoplasmic substitution were exerted through differential interactions with submergence and seed ageing. Further studies are needed to clarify the mechanisms underlying cytoplasmic genome diversity and interaction with nuclear genomes affecting submergence and seed ageing responses in wheat.

Genetic diversity of submergence stress response in cytoplasms of the Triticum-Aegilops complex

Genetic diversity in cytoplasmic and nuclear genomes and their interaction affecting adaptive traits is an attractive research subject in plants. We addressed submergence stress response of wheat that has become increasingly important but remained largely uninvestigated. Our primary aim was to disclose cytoplasmic diversity using nucleus-cytoplasm (NC) hybrids possessing a series of heterologous cytoplasms in a common nuclear background. Effects of submergence on seedling emergence and growth from imbibed seeds were studied and compared with euplasmic lines. Marked phenotypic variabilities were observed among both lines, demonstrating divergent cytoplasmic and nuclear effects on submergence response. NC hybrids with cytoplasm of Aegilops mutica showed a less inhibition, indicative of their positive contribution to submergence tolerance, whereas cytoplasms of Aegilops umbellulata and related species caused a greater inhibition. Superoxide dismutase (SOD) activity showed a marked increase accompanied by retardation of seedling growth in a susceptible NC hybrid. The observation suggested that the elevated SOD activity was resulted from a high level of reactive oxygen species accumulated and remained in susceptible seedlings. Taken together, our results point to the usefulness of NC hybrids in further studies needed to clarify molecular mechanisms underlying the nucleus-cytoplasm interaction regulating submergence stress response in wheat.

Characterization for Drought Tolerance and Physiological Efficiency in Novel Cytoplasmic Male Sterile Sources of Sunflower (Helianthus annuus L.)

Sunflower is sensitive to drought, and furthermore, sunflower hybrids display limited cytoplasmic diversity. In addition, the wild cytoplasmic sources of sunflower are not well explored for their potential to introduce drought tolerance into newly developed hybrids. Therefore here, we carried out a Line × Tester-based genetic study using 19 sunflower genotypes representing, 13 cytoplasmic male sterile (CMS) lines from wild and conventional sources, 2 maintainer lines, and 4 restorer lines. The CMS and maintainer lines were crossed with restorer lines to develop sixty F1 hybrids. The parents and their hybrids were evaluated under two water regimes, normal irrigation and drought stress (i.e., withholding water). A total of twelve important plant descriptors were studied over a period of two years and the significant differences between parents and hybrids are reported here. More specifically, hybrid lines were higher in average values for all the descriptors. The contribution of female parent was more prominent in the expression of traits in hybrids as compared to male parents. The CMS sources varied significantly regarding seed yield per plant and other physiological traits. Proline content in the leaves of all the genotypes was three times higher in the water stress regime. Accession CMS-PKU-2A was identified as the best general combiner for leaf area and specific leaf weight., whereas CMS-234A was the best general combiner for biological yield and photosynthetic efficiency under both conditions. The cross combinations CMS-ARG-2A × RCR-8297, CMS-234A × P124R, and CMS-38A × P124R were found significant for biological yield, seed yield and oil content under both environments. Overall, this study provides useful information about the cytoplasmic effects on important sunflower traits and drought stress tolerance.

Maternal inheritance of male sterility in the progeny of a natural hybrid between Cajanus lineatus and C. cajan

AbstractAdoption of pigeonpea hybrids in central and southern India is showing high impact with on‐farm yield advantages of >30%. The hybrid pigeonpea technology, the first in any legume crop, is based on a cytoplasmic‐nuclear male‐sterility (CMS) system. For a long‐term sustainability of hybrid programme, it is imperative that both nuclear diversity and cytoplasmic diversity are maintained among hybrid parents. In this context, a continuous search for new CMS‐inducing cytoplasms is necessary. This paper reports detection of maternal inheritance of male sterility in the progeny derived from a natural hybrid between a wild relative [Cajanus lineatus (W. & A.) Maesen comb. nov.] of pigeonpea and an unknown pigeonpea [Cajanus cajan (L.) Millsp.] genotype. In the present study, the male sterility was maintained up to BC7F1 generation by an advanced breeding pigeonpea line ICPL 99044. This male sterility inducing cytoplasm of C. lineatus was tagged as A6. In future, this CMS genetic stock can be used to develop a range of new pigeonpea hybrids with high yield and adaptation.

Toward the elucidation of cytoplasmic diversity in North American grape breeding programs

Plants have an intriguing tripartite genetic system: Nuclear genome × Mitochondria × Plastids and their interactions may impact germplasm breeding. In grapevine, the study of cytoplasmic genomes has been limited, and their role with respect to grapevine germplasm diversity has yet to be elucidated. In the present study, the results of an analysis of the cytoplasmic diversity among 6073 individuals (comprising cultivars, interspecific hybrids and segregating progenies) are presented. Genotyping by sequencing (GBS) was used to elucidate plastid and mitochondrial DNA sequences, and results were analyzed using multivariate techniques. Single nucleotide polymorphism (SNP) effects were annotated in reference to plastid and mitochondrial genome sequences. The cytoplasmic diversity identified was structured according to synthetic domestication groups (wine and raisin/table grape types) and interspecific-hybridization-driven groups with introgression from North American Vitis species, identifying five cytoplasmic groups and four major clusters. Fifty-two SNP markers were used to describe the diversity of the germplasm. Ten organelle genes showed distinct SNP annotations and effect predictions, of which six were chloroplast-derived and three were mitochondrial genes, in addition to one mitochondrial SNP affecting a nonannotated open reading frame. The results suggest that the application of GBS will aid in the study of cytoplasmic genomes in grapevine, which will enable further studies on the role of cytoplasmic genomes in grapevine germplasm, and then allow the exploitation of these sources of diversity in breeding.

Cytoplasmic diversity, phylogenetic relationships and molecular evolution of Tunisian Citrus species as inferred from mutational events and pseudogene of chloroplast trnL-trnF spacer

The genus Citrus L. is among the most important fruit trees in the world. In this report, cytoplasmic polymorphism of twenty seven Tunisian Citrus cultivars was explored using the chloroplast trnL-trnF intergenic spacer. Chloroplast sequences showed variation in length and nucleotide content. Haplotype and nucleotide diversity showed low variations. Molecular phylogenetic tree identifies Citrus maternal origins and demonstrates two major groups distinguishing between mandarin and pummelo groups. The trnL-trnF intergenic spacer showed one copy of pseudogene of the original trnF gene in 27 Citrus species at position 275 bp with a size varying from 49 to 63 bp. The anticodon domain was identified as the most conserved element, but one transversion (T−>C) was found in the D-domain. Meanwhile, one transversion (T−>A) and one transition (T−>G) were found in the T-domain. Neutrality tests (Tajima, Fu & Li and Fu) which revealed positive and non-significant values and Pi and θW assume a neutral model of evolution and advocated a constant population size. The study demonstrates the resolving power of trnL-trnF sequence data to prove both pummelo and mandarin gene pool’s contribution in the development of Tunisian secondary species and inferring their genetic and phylogenetic relationships.

Chloroplast DNA analysis of Tunisian cork oak populations (Quercus suber L.): sequence variations and molecular evolution of the trnL (UAA)-trnF (GAA) region.

Sequences of the trnL-trnF spacer and combined trnL-trnF region in chloroplast DNA of cork oak (Quercus suber L.) were analyzed to detect polymorphisms and to elucidate molecular evolution and demographic history. The aligned sequences varied in length and nucleotide composition. The overall ratio of transition/transversion (ti/tv) of 0.724 for the intergenic spacer and 0.258 for the pooled sequences were estimated, and indicated that transversions are more frequent than transitions. The molecular evolution and demographic history of Q. suber were investigated. Neutrality tests (Tajima's D and Fu and Li) ruled out the null hypothesis of a strictly neutral model, and Fu's Fs and Ramos-Onsins and Rozas' R2 confirmed the recent expansion of cork oak trees, validating its persistency in North Africa since the last glaciation during the Quaternary. The observed uni-modal mismatch distribution and the Harpending's raggedness index confirmed the demographic history model for cork oak. A phylogenetic dendrogram showed that the distribution of Q. suber trees occurs independently of geographical origin, the relief of the population site, and the bioclimatic stages. The molecular history and cytoplasmic diversity suggest that in situ and ex situ conservation strategies can be recommended for preserving landscape value and facing predictable future climatic changes.

Cytoplasmic genome types of European potatoes and their effects on complex agronomic traits.

BackgroundVarious wild species germplasm has been used in European potato breeding since the first introduction of potato (Solanum tuberosum L.) to Europe. As the plant cytoplasmic genome including chloroplast and mitochondrial genomes is transmitted only through the maternal parent, cytoplasmic markers are useful tools in breeding programs to determine cytoplasmic genome types and to trace maternal ancestors. The potato cytoplasmic genome can be distinguished into six distinct types (M, P, A, W, T, and D). Male sterility was found in genotypes with S. demissum-derived D-type cytoplasm and S. stoloniferum-derived W/γ-type cytoplasm. These wild species were frequently used to incorporate superior pathogen resistance genes. As a result, the percentage of these two types is increasing unintentionally in the European germplasm pool. Other than cytoplasmic male sterility, little is known about effects of the cytoplasmic genome on complex agronomic traits in potato.ResultThe cytoplasm types of 1,217 European potato cultivars and breeding clones were determined with type specific DNA markers. Most frequent were T- (59.4 %), D- (27.4 %), and W- (12.2 %) type cytoplasm, while A- (0.7 %) and M-type cytoplasm (0.3 %) was rare and P-type cytoplasm was absent. When comparing varieties with breeding clones, the former showed a relatively higher frequency of T-type and lower frequency of D- and W-type cytoplasm. Correlation analysis of cytoplasm types and agronomic data showed that W/γ-type cytoplasm was correlated with increased tuber starch content and later plant maturity. Correlation with quantitative resistance to late blight was observed for D-type and M-type cytoplasm. Both cytoplasm types had a positive effect on resistance.ConclusionThis study revealed and quantified the cytoplasmic diversity in the European potato germplasm pool. Knowledge of cytoplasm type is important for maintaining genetic diversity and managing the male sterility problem in breeding programs. This is the first comprehensive study to show correlations of distinct cytoplasmic genomes with complex agronomic traits in potato. Correlations particularly with tuber starch content and resistance to late blight provided new knowledge on cytoplasmic effects on these important traits, which can be exploited for genetic improvement of potato.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0545-y) contains supplementary material, which is available to authorized users.

Cytoplasmic diversity in potato breeding: case study from the International Potato Center

We analyzed the cytoplasmic diversity of CIP potato breeding germplasm. Cytoplasm types were assigned to 978 genotypes consisting of 265 foreign accessions used as input germplasm, 642 breeding lines developed by CIP, and 71 varieties released from CIP material. We found T (45 %), D (38 %), and W (11 %) to be the most frequent cytoplasm types in CIP breeding germplasm. Comparing the initial input germplasm to CIP breeding lines, the frequency of T-type cytoplasm decreased from 64 to 38 %, while those of D- and W-type cytoplasms increased from 26 to 41 % and from 6 to 14 %, respectively. We conclude that the CIP breeding program, as many others worldwide, has experienced a genetic bottleneck in terms of cytoplasmic diversity due to the unintended and continuous use of cytoplasmic-based male-sterile maternal lineages derived from Solanum demissum and S. stoloniferum in parental line and variety development. Nonetheless, the finding of male-fertile T-type breeding lines must have alleviated the problem to a certain extent, thus enabling CIP breeding progress.

Analysis of Genetic Diversity of Saccharum Complex Using Chloroplast Microsatellite Markers

A basic understanding of the cytoplasmic diversity of Saccharum complex comprising of Saccharum species and related genera is essential for broadening the cytoplasmic base of sugarcane cultivars. In the present study markers generated by nine chloroplast microsatellite primer pairs designed from sugarcane chloroplast genome were used to establish the genetic relationship and phylogeny among 43 accessions belonging to different species of Saccharum and related genera representing the Saccharum complex. The polymorphic primer pairs amplified an average of six alleles per loci and possess relatively high polymorphism information content. Molecular diversity was estimated using 54 polymorphic markers. The overall chloroplast genetic diversity in the Saccharum complex was found to be 53 %. The genetic diversity among Saccharum species was 22 %. Among the Saccharum species S. spontaneum was found to be distinct from other species of Saccharum and cpSSR markers could efficiently distinguish S. spontaneum from rest of the Saccharum spcies. Ripidium, one of the most primitive among the Saccharum complex showed the highest genetic diversity (90 %) with Saccharum. Miscanthus, another primitive genus of Saccharum complex was found to be more closely related to Saccharum than Erianthus. In view of the high genetic diversity, the present study supports the utilization of different species of Erianthus in the sugarcane breeding programmes for broadening the cytoplasmic base of the sugarcane varieties.

Cytoplasmic genome diversity in the cultivated apple - Short Communication

Mikami T., Kitazaki K., Kishima Y. (2015): Cytoplasmic genome diversity in the cultivated apple – Short Com munication . Hort. Sci. (Prague), 42: 47–51. The cultivated apple is one of the most common and important fruit crops in temperate regions. Phylogenetic analysis using a wide array of apple genotypes could give insights into the origin and domestication history of this crop. Ma ternally inherited mitochondrial and chloroplast DNAs have been utilised to characterise the cytoplasmic diversity within the apple germplasm collection and to elucidate the relationships between the cytoplasm types defined. This review focuses on the molecular basis of changes in the mitochondrial genome giving rise to diverse cytoplasm types. The possible maternal lineage of the cultivated apple is also discussed.

Effect of cytoplasmic diversity on post anthesis heat tolerance in wheat

To study the cytoplasmic effects on heat tolerance, the nuclear genomes of ten alloplasmic lines were substituted by four or five backcrosses using ‘Karl 92’, ‘Ventnor’, ‘U1275’ and ‘Jagger’ as the recurrent parent. During the final backcross, reciprocal crosses were made to develop cytoplasmic near isogenic lines. Sixty-eight BC5F1/BC4F1 lines and their parents were evaluated in growth chambers for post anthesis heat tolerance. Plants were grown in the greenhouse and subjected to heat stress in growth chambers 10 days after anthesis for 14 days. Growth chambers were maintained at 35/30 °C for heat stress treatment. To create an optimum temperature treatment, the greenhouse was maintained at 20/15 °C. Effects of high temperature on chlorophyll content and Fv/Fm (photosystem II measuring parameter) were significantly affected by different cytoplasms. Seven cytoplasms showed improved tolerance to heat with at least one recurrent parent. These results indicate that cytoplasmic variations can contribute to an increase in chlorophyll content and quantum efficiency of photosystem II of wheat during heat stress, and also highlight the importance of the interaction between cytoplasmic and nuclear genes. The role of cytoplasm may be considered in wheat breeding programs aimed at improving heat tolerance, but the nature of the interaction between cytoplasm and nuclear gene content warrants further investigation.

Spatial genetic structure in Beta vulgaris subsp. maritima and Beta macrocarpa reveals the effect of contrasting mating system, influence of marine currents, and footprints of postglacial recolonization routes.

Understanding the factors that contribute to population genetic divergence across a species' range is a long-standing goal in evolutionary biology and ecological genetics. We examined the relative importance of historical and ecological features in shaping the present-day spatial patterns of genetic structure in two related plant species, Beta vulgaris subsp. maritima and Beta macrocarpa. Using nuclear and mitochondrial markers, we surveyed 93 populations from Brittany (France) to Morocco – the southern limit of their species' range distribution. Whereas B. macrocarpa showed a genotypic structure and a high level of genetic differentiation indicative of selfing, the population genetic structure of B. vulgaris subsp. maritima was consistent with an outcrossing mating system. We further showed (1) a strong geographic clustering in coastal B. vulgaris subsp. maritima populations that highlighted the influence of marine currents in shaping different lineages and (2) a peculiar genetic structure of inland B. vulgaris subsp. maritima populations that could indicate the admixture of distinct evolutionary lineages and recent expansions associated with anthropogenic disturbances. Spatial patterns of nuclear diversity and differentiation also supported a stepwise recolonization of Europe from Atlantic-Mediterranean refugia after the last glacial period, with leading-edge expansions. However, cytoplasmic diversity was not impacted by postglacial recolonization: stochastic long-distance seed dispersal mediated by major oceanic currents may mitigate the common patterns of reduced cytoplasmic diversity observed for edge populations. Overall, the patterns we documented here challenge the general view of reduced genetic diversity at the edge of a species' range distribution and provide clues for understanding how life-history and major geographic features interact to shape the distribution of genetic diversity.

Genetic Diversity and Classification of Cytoplasm of Chinese Elite Foxtail Millet [Setaria italica (L.) P. Beauv.] Germplasm

ABSTRACTA single cytoplasmic source of foxtail millet male sterile lines has become a major limiting factor for wide utilization of heterosis in foxtail millet. To explore genetic diversity of Chinese foxtail millet cytoplasm, 23 pairs of mitochondrial DNA (mtDNA) primers that showed a high level of polymorphism among selected 14 genetically diverse foxtail millet accessions were identified after screening 34 pairs of consensus mtDNA primers that were derived from various plant species. The 23 pairs of primers were used to analyze genetic diversity of cytoplasm in 111 Chinese elite foxtail millet accessions. Genetic similarity coefficients for differentiation of cytoplasmic types were calculated based on the phylogenetic tree and female‐parent‐derived pedigree graph of all the tested accessions. The results show that the genetic diversity of foxtail millet cytoplasm is low, which makes Chinese foxtail millet germplasm vulnerable to the infection by cytoplasm‐related diseases. The 111 tested accessions can be classified into eight cytoplasmic types: Qinyuanmujizui, Huangruangu, Riben60ri, Dahuanggu, Yingsuigu, Heizhigu, MissingI, and MissingII. The eight cytoplasmic types matched with the geographic and ecological distribution pattern of the most tested accessions. The results provided a scientific foundation for rationally utilizing these germplasm lines, diversifying cytoplasmic types in male sterile lines, and further improving hybrid foxtail millet cultivars.

Effect of wild Helianthus cytoplasms on agronomic and oil characteristics of cultivated sunflower (Helianthus annuus L.)

AbstractSunflower (Helianthus annuus L.) productions reliance on a single source of cytoplasmic male sterility, PET1, derived from H. petiolaris Nutt., makes the crop genetically vulnerable. Twenty diverse cytoplasmic substitution lines from annual and perennial wild species were compared with the inbred line HA89 over four environments. Pairwise comparisons of alloplasmic male fertile (MF) with euplasmic MF lines suggested that cytoplasm of perennial H. angustifolius increased lodging while perennial cytoplasms of H. mollis, H. grosseserratus, and H. divaricatus reduced head size and consequently reduced yield and will need to be used with caution. Lines having annual species, cytoplasms had no effects on agronomic traits. Comparisons of CMS HA 89 with 10 CMS lines suggested yield‐reducing cytoplasmic effects of perennial H. maximiliani and annual H. annuus PI 413178 and PI 413024. Cytoplasmic effects on oil percentage and fatty acid composition were minimal and should not be of concern for sunflower breeders. In general, most cytoplasms of wild annual Helianthus species accommodate cultivated nuclear genes without drastic adverse interactions, and are potential sources of cytoplasmic diversity for sunflower breeding.

Cytoplasmic diversity and possible maternal lineages in apples as revealed by analysis of the mitochondrial cox1 and atp9 loci

In apples, four cytoplasmic groups, ‘Golden Delicious’-, ‘Delicious’-, ‘McIntosh’- and ‘Dolgo Crab’ cytotypes, are differentiated by variation in the mitochondrial cox1 and atp9 loci. The present study builds upon previous reports that (1) ‘Golden Delicious’ and ‘Delicious’ cytotype accessions each contain an intact cox1 (named as G-cox1 and D-cox1, respectively) and a pseudocopy (G-Ψcox1 and D-Ψcox1) at different stoichiometries and (2) the relative copy number of an atp9 pseudocopy (Ψatp9-1) is distinct in each cytotype. Here, the D-cox1 and D-Ψcox1 sequences were found as predominant forms in ‘McIntosh’ type germplasm accessions but as substoichiometric forms in ‘Dolgo Crab’ type accessions. The G-cox1 and G-Ψcox1 sequences were predominant in the ‘Dolgo Crab’ group whereas these two sequences were substoichiometric in the ‘McIntosh’ group. ‘We also detected the presence of predominant form of Ψatp9-1 in ‘McIntosh’ and ‘Dolgo Crab’ groups. Moreover, the four cytotypes could be distinguished from one another by their own chloroplast DNA haplotypes. Using these data and those from our earlier publications, we attempted to construct a network of cytotypes representing possible maternal lineages of apples.