Immunological Studies on the Tuber-bearing Solanums: 1. Techniques and South American Species

Many improvements have been made in recent years in serologicaltechniques which give them a sounder basis and make them morelikely to provide information of taxonomic importance. The Ouchterlonydouble diffusion technique and immuno-electrophoretic analysisare here described, together with new ways of analysing theresults by characterization of the individual antigens. It was shown experimentally with two species that the normalrange of variation in temperature or light intensity duringstorage has no significant effect on the antigen content ofthe tubers. The antigenic proteins of Solanum tuberositm occurchiefly in the phloem and in the peripheral cortex of the tuber.By immuno-electrophoresis and zone electrophoresis, it was shownthat the antigens correspond to the major protein fractionsof the extracts. Organ specificity of antigens was demonstrated, in that withan antiserum to one organ of one species, extracts of otherorgans of the same species reacted weakly, whereas extractsof the same organ of other species reacted strongly. An investigation of the tuber antigens of some South Americanspecies showed a general uniformity, as reported by previousworkers. However some differences common to all clones of bothsubspecies of S.commersoniiybut not to any other species ofthe series Commersoniana, were found.     

Immunological Studies on the Tuber-bearing Solanums III. Variability within S. bulbocastanum and its hybrids with species in series Pinnatisecta

It was shown in the previous paper of this series that the Mexicanspecies Solanum bulbocastanum, S. cardiophyllum subsp. cardiophyllumand subsp. ehrenbergii, S. michoacanum and S. pinnatisectummay be differentiated to some extent by the double diffusiontechnique, and more fully by immuno-electrophoretic analysis.Above all, the relative electrophoretic mobilities of certaincomponents, as expressed by the index have been found to be very constant for each species, with the apparent exception of S. bulbocastanum. A detailed investigation of S. bulbocastanum has now shown thatalthough the many clones of this species appeared similar whenexamined by double diffusion, differences were exposed by immuno-electrophoreticanalysis. In particular, the values fell into two discrete groups, 0.15 to 0.23 and 0.30 to 0.46. Theplants in these groups had been collected from Oaxaca and Guatemala,and from Central Mexico, respectively. Most of the former grouphad been identified as S. bulbocastanum subsp. partitum, andall the latter group as subsp. bulbocastanum and subsp. dolichophyllum.Not only was the wide variation in values of index resolved into two meaningful groups, but it was also found thatall lines within any one collection had almost identical values. The index value for S. cardiophyllum subsp.cardiophyllum is 1.0, and for subsp. ehrenbergii is 0.7. The F₁ hybrids between either ofthese subspecies and S. bulbocastanum had fairly uniform valuesclose to the calculated means of the parental values. The shapesof the leaves of these hybrids were also uniform and more orless intermediate between those of the parents in each case. The F₂ hybrids between S. bulbocastanum and S. pinnatisectum,and also the triple hybrids between these two species and eitherS. cardiophyllum or S. michoacanum, showed a wide range of valuesof index and of leaf shapes, with partial segregation towards the parental types. The serological andmorphological characters segregated independently. S. X sambucinum was found to have a wide variation in serologicaland morphological characters. This variation was consistentwith the theory that S. X sambucinum is a natural hybrid betweenS. pinnatisectum and S. cardiophyllum subsp. ehrenbergii. Within the groups of species investigated, the relative electrophoreticmobilities of certain antigens as displayed by immuno-electrophoreticanalysis were found to vary significantly in different species,in different subspecies of the same species, and in specieshybrids.     

Comparative Studies on S-Glycoproteins Purified from Different S-Genotypes in Self-Incompatible BRASSICA Species II. Immunological Specificities

Antisera were prepared by immunization of apparently purified S-glycoproteins; one from an S allele of Brassica campestris and two from S alleles of B. oleracea. Each antiserum was reactive not only with the homologous S-glycoprotein but also with the heterologous ones, i.e. with the S-glycoproteins of the other S alleles of the same locus. In double diffusion tests, a spur against the heterologous S-glycoproteins suggested heterogeneity of the glycoproteins. The heterogeneity appears to involve a component of the molecule in which the genotypic specificity of an S-glycoprotein resides, probably, for the recognition site. Some molecular components are common to all tested S-glycoproteins and in this respect are like the public antigens of the MHC locus of mammals. The common molecular components were recognized between the S-allele-specific glycoproteins within B. oleracea and also between them and those of B. campestris. No S-specific substances were detected in buffer soluble homogenates of style, ovary or anther. However, these homogenates contained substances that had structures similar to the corresponding common parts of the S-glycoproteins.     

Studies on the crossability relationships of some spinous Solanums

Summary Cytogenetic studies involving six species of spinous Solanums have been made using the parameters of crossability/fertility relationships and chromosome pairing in parental and derived hybrid genomes. These studies have made it possible to integrate hybrid reproductive performance with observed cytological phenomena and draw inferences on concerned intergenomic homeologies. It has been found that species' differences, as they exist, are ascribable to chromosome repatterning, in their divergence and maintenance as distinct taxa. In the light of these studies, the grouping of these species has to be reconsidered.     

Immunological Relationships Among Some Species of Extremely Halophilic Bacteria

Rabbits were immunized with four strains of halobacteria, Halobacterium halobium NRL, H. halobium R-1, H. salinarium NRL-9, and H. cutirubrum NRL-10, that had been fixed with formaldehyde. The antisera obtained detected the presence of an antigen common to the Halobacterium genus and, after absorption, detected three distinct antigenic groups within the Halobacterium genus. A fourth group was agglutinated only by unabsorbed sera.     

Studies on the Relationships Between Moricandia and Brassica Species

Moricandia is the only genus with C3-C4 species within the family of Cruciferae. To provide the basic information of transferring C3-C4 and other important characteristics from Moricandia to Brassica crops, the relationships between Moricandia and Brassica species were studied based on crossability and RFLP fingerprinting. The crossability was very low between the two genera in the experiment. There was no hybrid seed obtained between M. arvensis and B. rapa though 8 000 flowers were crossed. 2 989 cross-pollinated ovaries were cultured and also no hybrid embryo was developed. However, four intergeneric hybrid shoots were generated from 105 cultured ovaries in the combination of M. arvensis x B. napus. The nucleus DNA polymorphism of restriction loci was detected with 23 genic DNA clones of B. napus for the samples of B. napus, B. rapa and B. oleracea, M. arvensis and M. nit, ns. A high homology was found between Moricandia and Brassica species. The similarity between M. nitens and B. rapa was even greater than that between B. rapa and B. napus. The close relationships between Moricandia species and Brassica crops, especially European B. rapa, were also detected with 4 beta mitochondria probes. The intensive homology between Moricandia C3-C4 species and Brassica crops evaluated with the RFLP markers revealed the possibility of transferring some important genes from the C3-C4 species to the domesticated species by sexual hybridization or protoplast fusion followed by recombination of homoeologous chromosomes.     

Species delimitation of North American Nyssa species

The development of next-generation sequencing technologies allows researchers to address complex problems in species delimitation, especially for non-model organisms. The taxonomic status of North American Nyssa species has long been debated and remains controversial. To elucidate the genetic structure and phylogenetic relationships of the five currently recognized North American Nyssa species, we conducted whole-genome sequencing of representative individuals and identified genome-wide single-nucleotide polymorphisms (SNPs) by utilizing the recently released chromosome-level assembly of Nyssa sinensis genome. Population genetic and phylogenetic analyses consistently inferred four well-supported genetic clusters from our sampled individuals, that is, N. aquatica, N. ogeche, N. sylvatica, and N. biflora–N. ursina. Although the identification of N. biflora and N. ursina is primarily based on the morphological characteristics of leaves and drupes, the present evidence, including our principal components analysis of leaf morphological traits, strongly supports the taxonomic designation of N. biflora and N. ursina as a single species. In addition, these four genetic clusters were grouped into two major clades, that is, clade 1 (N. aquatica and N. ogeche) and clade 2 (N. sylvatica and N. biflora–N. ursina). Despite the fact that no evidence of widespread gene flow was found between these two major clades, our analyses revealed the possibility of introgression from N. sylvatica into N. biflora, albeit at a relatively low frequency. This study demonstrates the use of whole-genome sequences as a promising avenue for delimiting species boundaries and further advocates for an integrative approach in the assessment of species delimitation.     

Species diversity in North American temperate forests

Summary Samples from temperate forest communities across the North American continent were analysed for correlations of plant species diversity with environment and community structure.Alpha diversity relationships are complicated by different vegetation patterns and community history. The differences in community diversity patterns may be due to the independent evolution of communities in different regions.Results of analyses were: 1) on a continental scale plant species diversity is related to mean annual temperature, but not precipitation; 2) diversity is substantially greater in continental climates than in maritime regions; 3) diversity-community structure relationships are generally weak, except 4) there is an inverse relationship between diversity and abundance of conifer tree species. Attempts to relate diversity to environmental parameters with multiple regression techniques met with only moderate success.I thank R. H. Whittaker, R. K. Peet and H. G. Gauch, Jr., for their help and comments. I am especially grateful to R. H. Whittaker for making his data available to me. Computation was supported in part by N.S.F. grant No. GB-30679. I was supported by a Nat. Inst. of Health Traineeship during part of this study.     

Relationships between European and North American biological species ofArmillaria mellea

Pairings of monosporous isolates from five European and ten North American biological species ofArmillaria reveal that certain species from Europe are interfertile with certain species from North American. All other pairings between species are intersterile. These pairings of isolates derived from different continents reveal three interactions not observed in earlier studies with isolates exclusively from one continent or the other. One, pairings from species demonstrated to be interfertile have a reduced frequency of compatibility, i.e., some determinant, in addition to mating type, affects the compatibility of specific pairings. Two, the pairing of isolates from intersterile species occasionally results in an unexplained reduction in growth in one or both members of the pairing. Three, in a single case, members of a species from one continent are compatible with members oftwo different intersterile species from the other continent. In fact, individual strains from one European species are compatible with members of two rigorously intersterile North American species.     

A Screen for Swainsonine in Select North American Astragalus Species

Swainsonine is found in several plant species worldwide, and causes severe toxicosis in livestock grazing these plants, leading to a chronic condition characterized by weight loss, altered behavior, depression, decreased libido, infertility, and death. Swainsonine has been detected in 13 North American Astragalus species of which eight belong to taxa in four taxonomic sections, the Densifolii, Diphysi, Inflati, and Trichopodi. These sections belong to two larger groups representing several morphologically related species, the Pacific Piptolobi and the small‐flowered Piptolobi. The objective of this study was to screen the other 31 species for swainsonine in sections Densifolii, Diphysi, Inflati, and Trichopodi previously not known to contain swainsonine. Furthermore, to broaden the scope further, 21 species within the 8 sections of the Pacific Piptolobi and the small flowered Piptolobi were screened for swainsonine. Swainsonine was detected for the first time in 36 Astragalus taxa representing 29 species using liquid and gas chromatography coupled with mass spectrometry. Several taxonomic sections were highly enriched in species that contain swainsonine while others were not. A systematic examination for swainsonine in these species will provide important information on the toxic risk of these species and may be a valuable reference for diagnosticians and land managers.     

Species limits and phylogeography of North American cricket frogs (Acris: Hylidae)

Cricket frogs are widely distributed across the eastern United States and two species, the northern cricket frog (Acris crepitans) and the southern cricket frog (A. gryllus) are currently recognized. We generated a phylogenetic hypothesis for Acris using fragments of nuclear and mitochondrial genes in separate and combined phylogenetic analyses. We also used distance methods and fixation indices to evaluate species limits within the genus and the validity of currently recognized subspecies of A. crepitans. The distributions of existing A. crepitans subspecies, defined by morphology and call types, do not match the distributions of evolutionary lineages recovered using our genetic data. We discuss a scenario of call evolution to explain this disparity. We also recovered distinct phylogeographic groups within A. crepitans and A. gryllus that are congruent with other codistributed taxa. Under a lineage-based species concept, we recognize Acris blanchardi as a distinct species. The importance of this revised taxonomy is discussed in light of the dramatic declines in A. blanchardi across the northern and western portions of its range.