FLORAL PIGMENTATION STUDIES IN THE GENUS GOSSYPIUM II CHEMOTAXONOMIC ANALYSIS OF DIPLOID GOSSYPIUM SPECIES

The chromatographic pigment arrays of nine diploid species (G. arboreum, G. anomalum, G. herbaceum, G. stocksii, G. sturtii, G. thurberi, G. gossypioides, G. raimondii and G. klotzschianum) were studied. Among the Old World cottons, G. sturtii of Australia was very different from the species analyzed. The two species of the Herbacea section (G. herbaceum and G. arboreum) were found to have very similar pigment arrays. Both G. anomalum and G. stocksii were more like the Herbacea species than any other species in the genus, but both G. anomalum and G. stocksii had unique pigment characteristics. Although the evidence obtained so far from pigmentation patterns suggests that some pairs of species are closely related, the pigment arrays do not support the classification of the New World diploids into more than one section. From analysis of pigments of interspecific hybrids and their parents, it was found that with a hybrid and one parent species the pigment array of the other parent species could be predicted. Using this approach, the pigment arrays of three New World diploid species were predicted.     

棉属茎,叶表皮毛的研究

棉属植物茎、叶表皮毛的多少及其形态是识别种或品种的主要特征之一,并且与种或品种的抗虫或抗逆性有密切联系。Ramey(1962)研究指出,多毛性状是受 H_1和H_2两个主效基因和一些修饰基因的控制,H_2具有多效性。较系统地研究棉属茎、叶表皮毛的性状报道较少。本文报道利用扫描电镜对棉属植物的茎、叶表皮毛性状观察的结果。     

陆地棉半野生种系的细胞学研究

对原产于墨西哥的8个陆地棉半野生种系进行了核型分析。其根尖细胞的染色体数目均为52。“墨西哥棉”、“阔叶棉”、“帕默尔氏棉”和“尖斑棉”为1B 核型。其中以“墨西哥棉”最为原始,2n=4x=52=44m(6SAT) 8sm。“尤卡坦棉”、“玛利加郎特棉”、“莫利尔氏棉”和“雷奇蒙德氏棉”为2B 核型。其中以后两个种系最进化,2n=4x=52=32m(2或4SAT) 20sm。讨论了各种系之间的可能的演化关系。     

ASSESSMENT OF EVOLUTIONARY AFFINITIES IN GOSSYPIUM BY PROTEIN ELECTROPHORESIS

Protein band patterns from 25 species of Gossypium were obtained by electrophoresis of crude seed extracts on polyacrylamide gel. Band homologies between species were verified by electrophoresis of a mixture of their extracts. The patterns were found to be largely consistent with the conventional classification of the diploids into 6 genomic groups, A–F. However, G. triphyllum and G. bickii showed unique patterns differing respectively from those of the B and C groups, and G. australe showed closer affinity with the Arabian E- than with the Australian C-genome species. Affinities among the D-genome species were different from those implied by their former grouping into taxonomic sections but remarkably similar to those indicated in the most recent taxonomic revision of the genus. They were classifiable into two subgroups, β and ɛ. The clustering pattern of the diploids based on correlation coefficients calculated from densitometer curves of the electrophoretic spectra suggested that the genomic groups were derived from an African progenitor type, and that the American β and ɛ subgroups, most closely related to the African B- and the Arabian E-genome groups respectively, evolved under comparative mutual isolation, possibly separated by the Tertiary Amazonas basin.     

IDENTIFICATION OF MONOSOMES FOR SIX CHROMOSOMES IN GOSSYPIUM HIRSUTUM

Six primary monosomes of the amphidiploid species Gossypium hirsutum have been identified as separate chromosomes of the complement. On the basis of cytogenetic tests involving translocations, a diploid species of the D genome group, and genetic markers, 4 of the 6 monosomes were designated chromosomes 1, 2, 4 and 6 of the A subgenome and 2 were designated chromosomes 17 and 18 of the D subgenome. Fourteen other monosomes were identified as duplicates of 3 of the above 6 primaries.     

FATE MAP OF THE ORGANIZING SHOOT APEX IN GOSSYPIUM

Chimeral seedlings from a “semigametic” strain of cotton were used as the basis for a clonal analysis of events in the progressive organization of the nascent shoot apex. At the time the proembryo becomes a globular stage embryo with a distinct dermatogen, the surface of the embryo contains an eight-celled compartment for each cotyledon, a two-celled compartment for the first leaf, a one-celled compartment for the second leaf, and a three-celled compartment for the apical initials and all subsequent leaves and aerial structures. The developmental history of the first two leaves differs in a fundamental way from that of all the other leaves.     

THE ORIGIN,FERTILITY AND TRANSMISSION OF MONOSOMICS IN GOSSYPIUM

The origin of 51 monosomic plants in Gossypium hirsutum is described, and the great majority are shown to be fertile and transmissible. Both fertility and transmission rate can be increased by outcrossing and selection. Monosomics which have been isolated in a standard hirsutum background can be recognized by distinct morphological characteristics, including modifications of both vegetative and reproductive structures such as smaller or narrower leaves, smaller flowers or flower parts, and smaller, longer, or partially collapsed bolls. Monosomics involving the large chromosomes, i.e., the A genome, are recovered more frequently than are monosomics of the D (small chromosomes) genome. Furthermore, monosomics of certain of the A chromosomes are recovered more frequently than others. Of 20 identified hirsutum monosomics, 7 are chromosome A-2, 7 are A-4, 3 are A-6, and 1 each is A-1, D-17 and D-18.     

CELL DEVELOPMENT DURING EARLY EMBRYOGENESIS IN CAPSELLA AND GOSSYPIUM

The early stages of embryo development in Gossypium hirsutum (cotton) and Capsella bursapastoris were examined with regard to patterns of cell development, embryo and cell size, and distribution of cell divisions. A striking reduction in the total size of the cotton embryo was observed following the first division of the embryo. This decrease in total embryo size continued for several more divisions, and it was not until the embryo contained approximately 75 cells that its total size was larger than the zygote. Distinctive patterns of cell divisions were found in both embryos and indicate that changes in groups of cells undergoing mitosis are of fundamental importance in understanding the development of form in the embryo. A greater degree of variation in development of cell lineages than is generally reported was observed in both embryos.     

棉属种间高代系的过氧化物酶同工酶研究

利用薄层等电聚焦方法,对已稳定遗传２０代的棉属陆地棉（Ｇｏｓｓｙｐｉｕｍ ｈｉｒｓｕｔｕｍ ）×中棉（Ｇ．ａｒｂｏｒｅｕｍ ）种间高代系蕾期真叶及花药中的过氧化物酶同工酶进行研究,结果表明：１．同一棉种的不同品种,其过氧化物酶同工酶基本相同,同一染色体组的不同棉种,其过氧化物酶同工酶存在一定的差异,不同染色体组的棉种,其过氧化物酶同工酶存在显著的差异;２．高代系的同工酶谱与母本“科遗２号”相似,而与父本中棉“完紫”具有较大的差异     

THE CYTOLOGY AND PHYLOGENETICS OF THE DIPLOID SPECIES OF GOSSYPIUM

Meiotic chromosome behavior of 11 inter-genomic hybrids of Gossypium (2n = 26) were investigated. Per cell univalent frequencies at meiotic metaphase I in these hybrids were: A genome × Cgenome—G. herbaceum × sturtianum, 10.53; G. herbaceum × australe, 18.05. A genome × E genome—G. smnalense × arboreum, 21.82. B genome × C genome—G. anomalum × sturtianum, 9.23; G. anomalum × australe, 13.11. B genome × D genome—G. anomalum × klotzschianum, 17.45; G. anomalum × raimondii, 18.83. C genome × D genome—G. robinsonii × davidsonii, 12.77; G. sturtianum (armourianum × thurberi), 8.63. C genome × E genome—G. somalense × australe, 23.78; G. somalense × bickii, 25.58. Trivalent and quadrivalent frequencies were relatively high for those hybrids involving a C genome species, indicating that a reciprocal translocation differentiates the C genome from the A, B, D, and E genomes. The results of this study and the data of similar studies cited from the literature on Gossypium cytogenetics are discussed relative to the phylogenetics and evolution of the major (genome) groups of Gossypium and their constituent taxa.     

FIBER INITIATION ON THE COTTON OVULE (GOSSYPIUM HIRSUTUM)

Cotton ovules at the stage of fiber initiation were studied with a scanning electron microscope. On the day before anthesis the anatropous ovule had many anomocytic stomata, especially on the chalazal end. At anthesis, fibers first appeared at the crest of the funiculus and then around the lateral circumference of the ovule. Fiber initials were delayed for a few hours at the chalazal cap and for 3 or 4 days at the extreme end of the micropylar region. The morphological differentiation of a fiber began when an epidermal cell rounded up and protruded. After a brief period of diametric expansion, the initial began elongation toward the micropylar end. Between 2 and 3 days of age the fibers segregated into small groups, developed tapered tips, and began spiral growth. Fiber density was about 3,300 fibers per mm², and the ratio of fiber initials to total epidermal cells was 1:3.7 at anthesis.     

MOLECULAR EVIDENCE FOR HOMOPLOID RETICULATE EVOLUTION AMONG AUSTRALIAN SPECIES OF GOSSYPIUM

Interspecific hybridization and introgression are important evolutionary processes in plants, but their full significance with respect to speciation at the diploid level remains unresolved. In this study, molecular markers from the plastid and nuclear genomes were used to document an unusual evolutionary history of Gossypium bickii Prokh. (Malvaceae). This species is one of three morphologically similar Australian cottons (along with G. austrate F. Muell. and G. nelsonii Fryx.) in section Hibiscoidea. In contrast to expectations based on previous morphological data, cladistic analysis of maternally inherited cpDNA restriction site mutations unites G. bickii with G. sturtianum J. H. Willis, a morphologically distant species in a different taxonomic section (Sturtia). Few restriction site mutations distinguish the plastomes of G. bickii and G. sturtianum, but these two cpDNAs are differentiated from those of G. australe and G. nelsonii by a minimum of 33 mutations (out of 640 sites scored). These two highly distinct clades are not supported by phylogenetic analyses of allozyme markers (from 58 populations) and restriction site mutations in nuclear ribosomal DNAs. Rather, phylogenies based on 83 nuclear markers indicate that G. bickii shares a more recent common ancestor with G. australe and G. nelsonii than it does with G. sturtianum. We suggest that the striking discrepancy between independent molecular phylogenies from two different genomes indicates a biphyletic ancestry of G. bickii. Our preferred hypothesis involves an ancient hybridization, in which G. sturtianum, or a similar species, served as the maternal parent with a paternal donor from the lineage leading to G. australe and G. nelsonii. Because we detected no G. sturtianum nuclear genes in G. bickii, we suggest that the nuclear genomic contribution of the maternal parent was subsequently eliminated from the hybrid or its descendent maternal lineage. Several possible mechanisms of cytoplasm transfer are suggested, including repeated backcrossing of the hybrid, as female, into the paternal donor lineage, selection against recombinant nuclear genomes and a form of apomixis known as semigamy. This example, and several others in Gossypium as well as other genera, attest to the evolutionary possibility of interspecific cytoplasmic transfer, and perhaps the origin of diploid species via reticulate speciation. In addition, this study offers an example of natural cytoplasmic introgression without long-term survival of nuclear genes from the maternal progenitor.     

棉花花粉发育过程中同工酶和蛋白质的研究

利用超薄胶电泳技术对陆地棉花粉发育各期的酯酶和过氧化物酶的同工酶以及蛋白质的种类及活性变化进行研究。结果发现：在花粉第一次有丝分裂结束之前,存在大量的低分子量酯酶和过氧化物酸酶,花粉成熟后又新出现一些大分子量酯酶和过氧化物酶在花粉第一次有线四分体阶段,了一种特异蛋白,推测具有调控作用。在有丝分裂结束后,出现了一些新的蛋白质,这些蛋白质存在的时间很短。之后大量蛋白质开始合成,并在数量和种类上有逐渐增