Fungal endophytes of native Gossypium species in Australia

Fungal endophytes of 17 genera were found in stems of four native Gossypium species (G. australe, G. bickii, G. nelsonii, G. sturtianum) collected from inland areas in Queensland, the Northern Territory, and South Australia in 2001. Phoma, Alternaria, Fusarium, Botryosphaeria, Dichomera, and Phomopsis were common, accounting for 58, 18, 11, 3, 1, and 1 % of the 281 recovered isolates, respectively, and occurring in 47, 29, 19, 5, 5, and 4 % of the 79 sampled populations. Among the four Gossypium species in Queensland and the Northern Territory, Alternaria spp. and Fusarium spp. had the greatest recovery frequency in G. bickii stems. The recovery frequencies of Phoma spp. and Alternaria spp. were significantly greater in the G. sturtianum stems collected from South Australia than in those from Queensland and the Northern Territory. Pathogenicity of 42 representative isolates was tested on cultivated cotton (G. hirsutum). All isolates caused some localized discoloration in stem tissue when inoculation was conducted with the stem puncturing method, but none of the isolates could induce any foliar symptoms during the five-week experimental period by either inoculation method (root dipping or stem puncturing), suggesting that the endophytic fungi of native Gossypium species are unlikely sources of cotton pathogens.     

CYTOPLASMIC EFFECTS ON THE DIFFERENTIATION OF ANTHERS AND OVULES OF COTTON

Reciprocal crosses of Upland cotton with a hybrid derived from (Gossypium anomalum × G. thurberi) × G. hirsutum produced progenies differing significantly in anther development and in the production of supernumerary ovules outside the ovary. Plants with G. anomalum cytoplasm produced fewer anthers than the reciprocal hybrids with G. hirsutum cytoplasm, had a higher percentage of sterile anthers, and were far more likely to form external ovules on an abnormally thickened tip of the staminal tube. The number of locules and ovules within the ovary was not significantly affected by cytoplasm.     

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.     

Phylogenetic diversity and relationship among Gossypium germplasm using SSRs markers

Gossypium species represent a vast resource of genetic multiplicity for the improvement of cultivated cotton. To determine genetic diversity and relationships within a diverse collection of Gossypium, we employed 120 SSR primers on 20 diploid species representing seven basic genome groups of the genus Gossypium, five AD allotetraploid cotton accessions while T. populnea served as an outgroup species. Out of 120 SSR primers, 49 pairs are polymorphic, which produced a total of 99 distinct alleles with an average of 2.0 alleles per primer pair. A total of 1139 major SSR bands were observed. Genetic similarities among all the diploid species ranged from 0.582 (between G. herbaceum and G. trilobum) up to 0.969 (between G. arboreum and G. herbaceum). Phylogenetic trees based on genetic similarities were consistent with known taxonomic relationships. The results also indicated that G. raimondii is the closest living relative of the ancestral D-genome donor of tetraploid species and the A-genome donor is much similar to the present-day G. herbaceum and G. arboreum. Ancient tetraploid cotton species were formed by hybridizing and chromosome doubling between them, then different tetraploid cotton species appeared by further geographical and genetic isolation and separating differentiation. The results showed that SSRs could be an ideal means for the identification of the genetic diversity and relationship of cotton resources at the genomic level.     

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.     

Resistant Germplasm in Gossypium Species and Related Plants to Rotylenchulus reniformis

Gossypium hirsutum, G. herbaceum, G. arboreum, G. barbadense, wild Gossypium spp., Hibiscus spp, and other Malvaceae were tested in the greenhouse to identify germplasm resistant to Rotylenchulus reniformis (Rr). Host resistance was based on Rr egg production per gram of root compared with known G. hirsutum susceptible ''Deltapine 16'' as check. G. longicalyx and Sida rhombifolia were nonhosts. High levels of resistance were found in G. stocksii, G. somalense, and G. barbadense ''Texas 110.'' Other cotton lines with potential value in breeding for Rr resistance were G. herbaceum P.I. 408775; G. arboreum P.I. 41895, P.I, 417891, CB 3839; and G. hirsutum 893. All these supported less than 20% of the egg production on the check. Seventy-three percent of the Hibiscus spp. tested were resistant. Female development and egg production reflected host resistance; healthy females and large egg masses were observed on susceptible plants, and degenerated females and small egg masses on resistant plants. Females penetrating nonhost G. longicalyx never matured to kidney shape.     

Breeding for ”low-gossypol seed and high-gossypol plants” in upland cotton. Analysis of tri-species hybrids and backcross progenies using AFLPs and mapped RFLPs

This work aims at breeding upland cotton [Gossypium hirsutum L., 2(AD)₁ genome] with a reduced level of gossypol in the seeds for optimal food and feed uses, and a high gossypol level in the remaining organs for resistance to pests. Two tri-species Gossypium hybrids, (G. thurberi–G. sturtianum–G. hirsutum and G. hirsutum–G. raimondii–G. sturtianum) including G. sturtianum (2C₁) as a donor, G. thurberi (2D₁) and G. raimondii (2D₅) as a bridge species, were created. Recurrent selection initiated with these tri-species hybrids produced backcross (BC) progenies expressing the ”low-gossypol seed and high-gossypol plant” trait at different levels. We used AFLP markers to assess the genetic similarity among the germplasm and RFLP probes to tag the introgression of specific chomosome segments from the parental species. Five pairs of AFLP primers generated 477 fragments, among which 417 (87.4%) were polymorphic. The genetic similarity between the upland cotton and the wild species ranged from 29.5 to 43.2%, while similarity reached 80% between upland cotton and BC3 plants. Introgression of species-specific AFLPs was evident from all the parental species and confirmed the hybrid origin of the analyzed progenies. Southern-blot analysis based on 49 RFLP probes allowed us to trace the introgression of parental DNA segments in the tri-species hybrids and in three generations of backcross. Introgression was evident from 11, 8 and 7 linkage groups of G. sturtianum, G. raimondii and G. thurberi respectively. The types of introgression revealed by RFLP probes are discussed, and breeding schemes to enhance recombination are proposed. The ability to trace DNA segments of known chromosomal locations from the donor G. sturtianum through segregating generations is a starting point to map the ”low-gossypol seed and high-gossypol plant” traits. Received: 5 January 1999 / Accepted: 17 June 1999     

SEGREGATION IN NEW ALLOPOLYPLOIDS OF GOSSYPIUM. IV. SEGREGATION IN NEW WORLD × ASIATIC AND NEW WORLD × WILD AMERICAN HEXAPLOIDS

Phillips , Lyle L. (North Carolina State Coll., Raleigh.) Segregation in new allopolyploids of Gossypium. IV. Segregation in New World × Asiatic and New World × wild American hexaploids. Amer. Jour. Bot. 49(1): 51–57. 1962.—The New World tetraploid cottons, G. hirsutum and G. barbadense, are natural amphidiploids (genome formula, 2 [AD]) combining species of the cultivated Asiatic (2A) and wild American (2D) groups of diploid cottons. Genetic segregation for marker alleles in New World × Asiatic and New World × wild American synthetic hexaploids have been determined. Average segregation for several loci in New World × Asiatic hexaploids is close to the autoploid 5:1 ratio, ranging from 5.1 to 6.8:1. Average segregation for 3 loci (L, Rd, and R₁) common to a series of New World × wild American hexaploids is: New World × G. raimondii, 9.3:1;–× G. harknessii, 16.4:1;–× G. armourianum, 17.4:1;–× G. aridum, 20.3:1;–× G. lobatum, 21.4:1–× G. thurberi, 32.9:1;–× G. gossypioides, 66.5:1. These data are discussed, and the method by which they were derived is compared with other cytogenetical means of discerning phylelic interrelationships among Gossypium species.     

COMPARATIVE ANATOMY OF SOME PARENTS AND HYBRIDS OF THE HAWAIIAN MADIINAE (ASTERACEAE)

Comparative leaf morphology and anatomy was examined in five species and four hybrids involving three genera of Hawaiian Madiinae (Asteraceae). The comparisons included Argyroxiphium grayanum, Dubautia ciliolata subsp. ciliolata, D. knudsenii subsp. knudsenii, D. scabra subsp. leiophylla, D. scabra subsp. scabra, and Wilkesia gymnoxiphium, and the hybrids A. grayanum × D. scabra subsp. leiophylla, D. ciliolata subsp. ciliolata × D. scabra subsp. scabra, D. knudsenii subsp. knudsenii × D. scabra subsp. leiophylla, and W. gymnoxiphium × D. scabra subsp. leiophylla. Foliar morphology, leaf tissue organization, and various characters of stomata and trichomes were compared, using epidermal peels, cross and paradermal sections, and clearings of leaves. Pronounced anatomical differences among these closely related taxa were characterized, and effects of hybridization on the expression of anatomical features were documented. Most comparisons of parents and hybrids revealed statistically significant differences in leaf size, distribution of adaxial and abaxial stomata, and marginal and surface trichomes. In most instances hybrids demonstrated intermediate status in their foliar characters, indicating that these features are inherited from both parents. However, differences in foliar characters were usually of sufficient magnitude to allow recognition of hybrids as well as parents.     

Introgression of the low-gossypol seed & high-gossypol plant trait in upland cotton: Analysis of [(Gossypium hirsutum?×?G. raimondii)2?×?G. sturtianum] trispecific hybrid and selected derivatives using mapped SSRs

In order to select genotypes of Gossypium hirsutum genetically balanced and expressing the low-gossypol seed & high-gossypol plant trait introgressed from the Australian wild diploid species G. sturtianum, the [(G. hirsutum × G. raimondii)2 × G. sturtianum] triple hybrid was backcrossed to G. hirsutum and autopollinated to produce backcross and selfed progenies. Two hundred and six mapped SSR markers of G. hirsutum were used to monitor the introgression of SSR alleles specific to G. sturtianum and G. raimondii in the selected progenies. A high level of heterozygosity, varying from 25 to 100%, was observed for all G. sturtianum-specific SSR markers conserved in the most advanced progenies. These results indicate the existence of segregation distortion factors that are associated with the genes controlling the researched trait. This study represents a starting point to map the genes involved in the expression of the trait and better understand its genetic determinism.     

Evaluation of Gossypium species for resistance to cotton leaf curl Burewala virus

Cotton leaf curl disease (CLCuD), caused by cotton leaf curl Burewala virus (CLCuBV), has emerged as a major threat to cotton production in Pakistan. Resistance to CLCuBV was evaluated in cultivated and wild cotton genotypes representing six Gossypium species by visual symptom scoring and virus assessment using PCR tests. Considerable variation in responses was observed when using whitefly and graft transmission to inoculate Gossypium genotypes with CLCuBV in field and greenhouse experiments. Under field evaluation, all cultivated genotypes of Gossypium hirsutum and three genotypes of G. barbadense were susceptible. Eleven genotypes that represented six wild and cultivated Gossypium species were considered to be highly resistant as they were free from infection. Similar results were obtained when these genotypes were tested using whitefly transmission. To verify these findings, 132 cultivated and wild genotypes were tested by graft inoculation. All G. hirsutum genotypes (116 cultivated, 1 wild, 1 transgenic Coker-312 and 1 non-transgenic Coker-312), three G. barbadense genotypes and one G. thurberi genotype were highly susceptible and exhibited symptoms 9–12 days after grafting. Four genotypes of G. arboreum and one genotype of G. anomalum did not express symptoms but had a detectable level of virus. One genotype of G. herbaceum and three wild genotypes of G. hirsutum showed mild symptoms (severity indexes of 1–2) and exhibited delayed disease development. These genotypes were classified as moderately resistant to resistant. Resistant genotypes that were identified in this study will be useful sources for exploitation of breeding programmes aimed at developing CLCuBV-resistant varieties and increasing genetic diversity.     

Seed esterases,leucine aminopeptidases and catalases of species of the genus Gossypium

Summary Polyacrylamide and starch gel electrophoresis were used to analyze the isozyme makeup of three enzyme systems (esterases, leucine aminopeptidases and catalases) from the dormant seeds of twenty-nine species within the genus Gossypium.Isozyme variation was observed for all three enzymes between the species of the different genome groups. The within species polymorphism noted for the esterases was not observed for the leucine aminopeptidase and catalase patterns. In general, only minor qualitative banding pattern differences distinguished the A and B genome species, whereas, band variations were greatest between the more distantly related species in the C, D and E genomes. Gossypium longicalyx (F genome) showed an overall banding pattern unique to itself. The species of the genomes (C, D, E and F) removed from the postulated area of genetic origin (Southern Africa) also exhibited greater isozyme variability than that of the wild species of the A and B genomes, both located in Southern Africa.Synthetic mixtures of seed extracts from parent species of recently formed synthetic allopolyploids produced additive isozyme patterns for esterase, leucine aminopeptidase and catalase that were closely comparable to the zymograms produced by their hybrids. In contrast all three enzyme systems showed significant qualitative isozyme variations between the three natural allotetraploids, G. tomentosum, G. barbadense and G. hirsutum when compared to the zymograms of the synthetic mixtures of their alleged parental forms.This paper is part of a dissertation by the first author for the degree of Doctor of Philosophy in Genetics. Journal paper 1763 of the Arizona Agricultural Experiment Station.National Research Council Postdoctoral Research Associate.     

The effect of <Emphasis Type="Italic">Gossypium</Emphasis> C-genome chromosomes on resistance to fusarium wilt in allotetraploid cotton

Fusarium oxysporum f. sp. vasinfectum (Fov) has the potential to become the most economically significant pathogen of cotton in Australia. Although the levels of resistance present in the new commercial cultivars have improved significantly, they are still not immune and cotton breeders continue to look for additional sources of resistance. The native Australian Gossypium species represent an alternative source of resistance because they could have co-evolved with the indigenous Fov pathogens. Forty-six BC₃ G. hirsutum × G. sturtianum multiple alien-chromosome-addition-line (MACAL) families were challenged with a field-derived Fov isolate (VCG-01111). The G. hirsutum parent of the hexaploid MACAL is highly susceptible to fusarium wilt; the G. sturtianum parent is strongly resistant. Twenty-two of the BC₃ families showed enhanced fusarium wilt resistance relative to the susceptible G. hirsutum parent. Logistic regression identified four G. sturtianum linkage groups with a significant effect on fusarium wilt resistance: two linkage groups were associated with improved fusarium wilt resistance, while two linkage groups were associated with increased fusarium wilt susceptibility.     

Protein markers for identification of different species and varieties of cotton

Reference electrophoretic spectra that allow compiling electrophoretic formulas of certain cotton species and varieties were obtained on the basis of analysis of the electrophoretic spectrum of water-soluble and barely soluble proteins of seeds of diploid cotton species of genomic group A (Gossypium arboreum var. indicum, G. arboreum ssp. obtusifolum, G. herbaceum ssp. africanum, and G. herbaceum Harga), group C (G. australe, G. bickii, G. nelsone, and G. sturtianum), group D (G. davidsonii, G. harknessii, G. klotzschianum, G. raimondii, G. thurberi, and G. trilobum), and amphidiploid species of group AD (G. mustelinum, G. hirsutum ssp. palmeri, G. tricuspidatum Bagota, G. tricuspidatum Mari Galanta, G. barbadense L., and G. hirsutum L.)     

Duplication,divergence and persistence in the Phytochrome photoreceptor gene family of cottons (<Emphasis Type="Italic">Gossypium</Emphasis> spp.)

Background  

Phytochromes are a family of red/far-red photoreceptors that regulate a number of important developmental traits in cotton (Gossypium spp.), including plant architecture, fiber development, and photoperiodic flowering. Little is known about the composition and evolution of the phytochrome gene family in diploid (G. herbaceum, G. raimondii) or allotetraploid (G. hirsutum, G. barbadense) cotton species. The objective of this study was to obtain a preliminary inventory and molecular-evolutionary characterization of the phytochrome gene family in cotton.     

CYTOGENETIC AND EVOLUTIONARY STUDIES IN SECALE. I. SOME NEW DATA ON THE ANCESTRY OF S. CEREALE

Khush , G. S., and G. L. Stebbins . (U. California, Davis.) Cytogenetic and evolutionary studies in Secale. I. Some new data on the ancestry of S. cereale. Amer. Jour. Bot. 48(8): 723–730. Illus. 1961.—Cultivated rye, Secale cereale, was crossed with all 4 wild species of the genus. It crosses readily with S. montanum, S. africanum, and S. vavilovii, but crossability of S. cereale and S. silvestre is extremely low. Meiosis in the hybrid S. cereale × silvestre is characterized by high frequency of univalents at metaphase I, reduced chiasma frequency at metaphase I, high frequency of PMC's with unequal separations and laggards at anaphase I and II, high frequency of microspores with micronuclei, and extremely low pollen fertility. These abnormalities occurred less frequently in other hybrids, and consequently the pollen fertility is fairly high: 19.1% in the hybrid S. cereale × vavilovii and 31.3% and 31.8%, respectively, in the hybrids S. cereale × montanum and S. cereale × africanum. An interesting cytogenetic feature of all these hybrids, however, was the formation of a translocation configuration of 6 chromosomes at metaphase I of meiosis. In the hybrid, S. cereale × silvestre, a translocation configuration of 8 chromosomes was observed in a few cells. It is evident, therefore, that the genome of S. cereale differs from the genomes of wild species by 2 translocations. Another small translocation may differentiate S. cereale and S. silvestre, in addition. Thus, on the basis of chromosome arrangements, no particular wild species is most likely to be ancestral to S. cereale. Similarly, Stutz's hypothesis of hybrid origin of S. cereale seems highly improbable. After considering ecological preferences, breeding habits, geographical distribution, morphological and cytological affinities of wild species and cultivated rye, it is concluded that S. cereale evolved from S. montanum as a result of progressive cytological and morphological differentiation and that this differentiation was facilitated, probably, by adaptive superiority of translocation heterozygotes and rearrangement homozygotes.     

THE GENOME CONSTITUTION AND PHYLOGENY OF ELYMUS AMBIGUUS

Two Elymus ambiguus Vasey & Scribn. collections from Utah and Idaho were 2n = 28, and the species behaved meiotically as an allotetraploid. The E. ambiguus plants were highly self-sterile, and they hybridized readily with Asian E. junceus Fisch. (2n = 14), E. karataviensis Roshev. (2n = 28), E. multicaulis Kar. & Kir. (2n = 28), and North American E. innovatus Beal (2n = 28). Chromosome pairing at metaphase-I in the E. ambiguus X E. junceus triploid hybrids indicated that one E. ambiguus genome was closely homologous with the E. junceus genome. Chromosome pairing in the tetraploid hybrids indicated that both E. ambiguus genomes were more or less homologous with the genomes of E. karataviensis, E. multicaulis, and E. innovatus. The basic genome formula of E. ambiguus may be written as JJXX, where J is the E. junceus genome and X is a genome of unknown origin. Chromosome pairing in the hybrids indicated that E. ambiguus is more closely related to North American E. innovatus than to the Asian species. The E. ambiguus X E. innovatus hybrids were the only hybrids that set seed. Gene flow between E. ambiguus and E. innovatus is biologically possible, but geographic separation of the species precludes natural introgression.     

MEIOTIC CHROMOSOME BEHAVIOR IN SOME INTERGENERIC HYBRIDS OF THE VANDA ALLIANCE

Tanaka , R., and H. Kamemoto . (U. Hawaii, Honolulu.) Meiotic chromosome behavior in some intergeneric hybrids of the Vanda alliance. Amer. Jour. Bot. 48(7): 573–582. Illus. 1961.—Meiotic chromosome behavior of 11 groups of diploid intergeneric hybrids (2n=38) of the Vanda alliance was investigated. Vanda Miss Joaquim × Luisia teretifolia and Ascocentrum curvifolium × Vanda lamellata usually produced 19 bivalents at metaphase I, indicating good homology of the parental chromosomes. Vanda tricolor var. sanderae × Vandopsis lissochiloides, Vandopsis lissochiloides × Vanda sanderiana, Vandopsis lissochiloides × Vanda Tatzeri and Arachnis flos-aeris × Vandopsis lissochiloides showed fair homology of parental genomes with formation of 12–15 bivalents at metaphase I. Trichoglottis brachiata × Vanda sanderiana, Vanda tricolor var. purpurea × Phalaenopsis denevei, Vanda Tatzeri × Aerides lawrenceae, Renanthera monachica × Vanda luzonica, Renanthera storiei × Vanda Clara Shipman Fisher and Aerides lawrenceae × Saccolabium giganteum, formed an average of 2–7 bivalents, thereby indicating poor homology of parental genomes. The hybrids, Renanthera monachica × Phalaenopsis sanderiana and Arachnis hookeriana × Vanda suavis, lacked chromosome pairing. On the basis of chromosome affinity at meiosis, a cytotaxonomic scheme was developed for the several genera of the Vanda alliance studied. Cytotaxonomy, evolution and breeding behavior in the Vanda tribe were briefly discussed.     

Molecular phylogeny of Gossypium species by DNA fingerprinting

Total genomic DNA from 31 available Gossypium species, three subspecies and one interspecific hybrid, were analysed to evaluate genetic diversity by RAPD, using 45 random decamer primers. A total of 579 amplified bands were observed, with 12.9 bands per primer, of which 99.8% were polymorphic. OPJ-17 produced the maximum number of fragments while the minimum number of fragments was produced with primer OPA-08. Cluster analysis by the unweighted paired group method of arithmetic means (UPGMA) showed six main clusters. Cluster ’A’ consisted of two species and one subspecies of the A-genome, with a 0.78–0.92 Nei’s similarity range. Cluster B, composed of all available tetraploid species and one interspecific hybrid, showed the same sister cluster. Nei’s similarity ranged from 0.69 to 0.84. The B-genome formed the UPGMA sister cluster to the E-genome species. Cluster ’C’ consisted of five Gossypium species of which three belong to the B-genome, with Nei’s similarity values of 0.81 to 0.86. Although there was considerable disagreement at lower infra-generic ranks, particularly among the D- genome (diploid New World species) and C-genome (diploid Australian species) species. The sole F-genome species Gossypium longicalyx was resolved as a sister group to the D-genome species. Gossypium herbaceum and G. herbaceum Africanum showed the maximum Nei’s similarity (0.93). Minimum similarity (0.29) was observed between Gossypium trilobum and Gossypium nelsonii. The average similarity among all studied species was 50%. The analysis revealed that the interspecific genetic relationship of several species is related to their centre of origin. As expected, most of the species have a wide genetic base range. The results also revealed the genetic relationships of the species Gossypium hirsutum to standard cultivated Gossypium barbadense, G. herbaceum and Gossypium arboreum. These results correspond well with previous reported results. The level of variation detected in closely related genotypes by RAPD analysis indicates that it may be a more efficient marker than morphological marker, isozyme and RFLP technology for the construction of genetic linkage maps. Received: 2 January 2000 / Accepted: 12 February 2000