Assessment of Gossypium sturtianum and G. australe as potential sources of Fusarium wilt resistance to cotton

When challenged with Fusarium oxysporum f. sp. vasinfectum (Fov) from vegetative compatibility groups (VCGs) 01111 and 01112 in glasshouse tests, Gossypium australe Mueller and Gossypium sturtianum Willis accessions showed a variety of disease responses ranging from highly resistant to highly susceptible. Under high disease pressure G. sturtianum accession Gos-5275 was significantly more resistant than the commercial G. hirsutum cultivars that are designated standards for Fusarium resistance by Australian cotton breeders. Under low disease pressure G. sturtianum accession Gos-5250 was more susceptible than a highly susceptible commercial cultivar. A series of glasshouse tests was performed at two locations (Indooroopilly, QLD. and Canberra, ACT), and under low and high disease pressure. In these tests, a hexaploid cross (Gos-5271) generated from a Fusarium-resistant G. sturtianum (Gos-5275) and a Fusarium-susceptible G. hirsutum L. (CPI-138969) was significantly more resistant to Fusarium wilt than its G. hirsutum parent. Thus G. sturtianum, with a diploid genome and a range of responses to Fov challenge, has the potential to provide the basis for the elucidation of the genetic basis of resistance to Fusarium wilt in cotton species. In addition, resistant accessions of G. sturtianum are identified as a potential source of Fusarium wilt resistance genes for cotton breeding. In the glasshouse tests used to assess the resistance of various Gossypium accessions to Fusarium wilt disease, the scoring of vascular browning was found to give a more reliable indication of disease severity than the scoring of foliar symptoms. This revised version was published online in August 2006 with corrections to the Cover Date.     

Interspecific hybridization in Gossypium L.: characterization of progenies with different ploidy‐confirmed multigenomic backgrounds

Cytological and molecular investigations were undertaken for parent and progeny derived from a trispecific line [2(Gossypium arboreum × G. anomalum) × G. hirsutum var. BWR], which was crossed with G. hirsutum var. JLH168. Cytomorphological analysis of the F₁ (G. arboreum × G. anomalum), its amphidiploid and progeny from trispecies hybrid showed distorted ploidy segregation with monovalents to hexavalents and high intergenomic (small A₂ and large B₁) allosynthetic chromosome pairing. Microsatellite analysis identified three fragments associated with G. arboreum and G. anomalum and six fragments associated with G. hirsutum in derivates of the trispecies line × G. hirsutum var. JLH168. Inter‐Retrotransposon Amplified Polymorphism (IRAP) analysis revealed fragments of G. arboreum and G. anomalum, only in F₁ and amphidiploid. Chromosomal association and microsatellite analysis of three progeny genotypes (i.e. haploid, hexaploid and tetraploid no. 1) confirmed that they share multigenomic background from the three cotton species (A₂, A_hD_h and B₁ genome). The interspecific hybrid cotton genotypes studied are likely to be useful for the introgression of genes from diploid species to commercial upland cultivars.     

Cytogenetics of a new trispecies hybrid in cotton: [(Gossypium hirsutum L. × G. thurberi Tod.)2 × G. longicalyx Hutch. & Lee]

A three‐species hybrid named HTL including Gossypium hirsutum L. [2n = 4 x = 52, (AD)₁ genome] was created using the pseudophyletic introgression method with G. longicalyx Hutch. & Lee (2n = 2x = 26, F₁ genome) as donor parent and G. thurberi Tod. (2n = 2x = 26, D₁ genome) as bridge species. The new hybrid was totally self‐sterile and its interspecific status was confirmed using simple sequence repeat markers and cytogenetic analysis. Cytogenetic studies showed that its chromosome configuration was 2n = 52 = 14.13 I + 15.10 II + 1.03 III + 0.9 IV + 0.03 V + 0.13 VI (where I, II, III, IV, V and VI are univalents, bivalents, trivalents, tetravalents, pentavalents and hexavalents, respectively). Prospects for successfully exploiting the HTL hybrid in breeding programmes are discussed.     

Introgression of a gene for delayed pigment gland morphogenesis from Gossypium bickii into upland cotton

The presence of gossypol and its derivatives above the WHO/FAO standards (0.02–0.04%) in cotton seed oil and meal limits its usage as food and feed. To the contrary, the presence of pigment glands filled with gossypol and its derivatives helps to protect cotton plants from phytophageous pests. Thus a desirable cultivar would have glandless seeds on a glanded plant. This paper describes results on the successful introgression of this trait from Gossypium bickii into cultivated upland cotton. Five different tri‐specific hybrids (ABH1, ABH2, ABH3, ABH4 and ABH5) were obtained by crossing the amphidiploid F₁ (G. arboreum × G. bickii) with different gland genotypes of G. hirsutum as male parent. The hybrids were highly sterile, and their chromosome configuration at meiosis metaphase 1 (M1) in pollen mother cell (PMC) was 2n = 52 = 41.04 I + 4.54 II + 0.57 III + 0.04 IV. All five hybrids were similar in morphological characters, except for the gland expression and gossypol contents. The hybrid (ABH3) derived from genotype Gl₂Gl₂gl₃gl₃ of upland cotton (a single gene dominant line) had completely introgressed the target trait of G. bickii. While ABH1 and ABH2, which derived from recessive (gl₂gl₂gl₃gl₃) or dominant (GlGl) glandless upland cotton genotypes, had glandless seeds too, but the density and size of the glands on the plant were reduced significantly.     

Prefertilization barriers to interspecific hybridization involving Gossypium hirsutum and four diploid wild species

Interspecific hybridization among species of cotton has lead to improvement in productivity, earliness, fibre quality and resistance to pests and diseases. However, wide crosses is often limited by the operation of either pre‐ or/and post‐fertilization barriers. An investigation on pollen tube behaviour of four wild species in the pistils of Gossypium hirsutum was taken up. Pollen germination was normal in crosses involving Gossypium triphyllum and Gossypium armourianum and markedly inhibited in the crosses involving Gossypium davidsonii and Gossypium thurberi. Pollen tubes reached the pistils and fertilization was accomplished within 8 h after pollination (HAP) in control cross. Even though delay in pollen tube was a common phenomenon in all the four crosses successful fertilization was observed in crosses involving G. triphyllum and G. armourianum, as they reached the ovary at 24 HAP. In crosses with G. davidsonii and G. thurberi, pollen tubes failed to reach the ovary even at 24 HAP indicating the presence of strong stylar and ovarian incompatibility. Measures to overcome such barriers to interspecific hybridization in the incompatible crosses are discussed.     

Production of fertile hybrid germplasm with diploid Australian Gossypium species for cotton improvement

The 17 wild Australian Gossypium species are distant diploid relatives of the commercial tetraploid cottons, G. barbadense L. and G. hirsutum L. They interest cotton breeders as a source of terpenoid-aldehyde-free seeds, a trait only found in five Australian Gossypium species. They elicit further interest because some species grow near current and projected cotton growing areas in Australia and thus could serve as unintentional recipients of transgenes from genetically engineered cotton cultivars. The utility of the wild Australian Gossypium species in cotton breeding depends on the ability to generate fertile hybrids, and to the extent this is possible under glasshouse conditions, it allows predictions regarding the probability that fertile hybrids between the transgenic cottons and spatially associated populations of wild species will arise without human manipulation. The Australian Gossypium species fall into three morphologically and cytologically distinct groups designated the C, G, and K genomes, The G-genome species hybridize most readily with G. arboretum (a diploid A-genome cultivated cotton), while the C- and K-genome species are more compatible with G. hirsutum (a tetraploid AD-genome cultivated cotton). These intergenomic hybrids are sterile, and the chromosome complement of the hybrids must be doubled prior to backcrossing to G. hirsutum. The only exceptions were four G. hirsutum × K-genome triploids, which exhibited limited female fertility when backcrossed to G. hirsutum. Two of the three diploid species geographically associated with commercial cotton fields (G. australe F. Mueller & G. rotundifolium Fryxell, Craven & Stewart) failed to produce hybrid progeny when pollinated with G. hirsutum pollen; the third species (G. sturtianum J.H. Willis) produced only 5 sterile triploids from 25 pollinations. Thus, the probability that wild species could serve as recipients of transgenes is functionally zero, especially in conjunction with the profound prezygotic barriers that separate the cultivated tetraploid cottons from their wild Australian relatives. Eighteen new fertile synthetic polyploids and 23 self-fertile derivatives of two synthetic hexaploids were produced. Synthetic tetraploids require greater effort to backcross than do synthetic hexaploids. These fertile hybrids represent a new avenue of introgression of genes from wild Australian Gossypium species into commercial cotton cultivars, an avenue limited only by the level of recombination. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relationship between molecular marker heterozygosity and hybrid performance in intra- and interspecific hybrids of cotton

The present study was conducted to investigate the relationship between parental molecular marker diversity and hybrid performance in both intra‐ and interspecific hybrids of cotton to evaluate the feasibility of predicting hybrid performance using molecular markers. Three cytoplasmic male sterile (CMS) lines were crossed with 10 restorer lines to produce 22 F₁ hybrids during 2003. Of 22 F₁s, 14 hybrids were intraspecific (Gossypium hirsutum × G. hirsutum) and eight interspecific (G. hirsutum × G. barbadense). These 22 F₁ hybrids and their parents were evaluated for yield and fibre quality traits at Zhejiang University, Hangzhou, China during 2004 and 2005. Genetic distances (GD) among the parents were calculated from 56 random‐amplified polymorphic DNAs (RAPD) and 66 simple sequence repeat (SSR) marker data, and their correlation with hybrid performance and heterosis were analysed. The parents could be discriminated into G. hirsutum and G. barbadense clusters by cluster analysis based on both RAPD and SSR markers data. The correlation (r = 0.503, P ≤ 0.05) was calculated between GD_rapd (GD based on RAPD markers) and GD_ssr (GD based on SSR markers). Correlation of GD with hybrid performance and heterosis differed considerably between intra‐ and interspecific hybrids. The correlation between GD and hybrid performance was non‐significant for most of traits within the hybrids of G. hirsutum species. However, it was significantly and positively correlated for fibre length, fibre strength and elongation in interspecific hybrids. The relationship between GD and heterosis was observed to be positively significant for boll weight within hybrids of G. hirsutum with significant and negative correlations for fibre length and elongation. In conclusion, the power of predicting hybrid performance using molecular markers in cotton is low. But, the relationship between SSR marker heterozygosity and hybrid performance can be used to predict fibre length during interspecific hybrid cotton breeding.     

QTL mapping of fiber quality in an elite hybrid derived-RIL population of upland cotton

Xiangzamian 2 (XZM2) was the most widely cultivated cotton hybrid planted as F₁ hybrids and as selfed F₂ seeds in China before the release of transgenic Bt hybrids. By crossing two parents of XZM2, Gossypium hirsutum cv. Zhongmiansuo12 (ZMS12) and G. hirsutum acc. 8891, and through subsequent selfings, we obtained F₈ and F₉ populations of 180 recombinant inbred lines (RILs). A RIL population was cultivated in two cotton-growing regions in China for 2 years. The purpose of the present research was to detect quantitative trait loci (QTL) for fiber quality and provide information applicable to cotton breeding. A genetic map was constructed mainly using SSR markers. QTL controlling fiber quality traits were determined at the single-locus and two-locus levels, and genotype-by-environment interactions were analyzed. Among the main-effect QTL, a fiber length QTL qFL-D2-1 and a reflectance QTL qFR-D2-1 were simultaneously detected at two growing regions in 2 years, which suggested a high degree of stability in different environments, and might be of particular value for a marker-assisted selection (MAS) program. The results suggested that epistatic effects, as well as additive effects, of QTL play important roles in fiber quality in these RILs. In our research, the phenomenon of QTL clusters was detected in the cotton genome.     

QTL mapping for economic traits based on a dense genetic map of cotton with PCR-based markers using the interspecific cross of Gossypium hirsutum × Gossypium barbadense

A high-density molecular marker linkage map of cotton based entirely on polymerase chain reaction-based markers is useful for a marker-assisted breeding program. Four kinds of markers—simple sequence repeats (SSRs), sequence-related amplified polymorphism (SRAP), random amplified polymorphic DNA (RAPD), and retrotransposon-microsatellite amplified polymorphism (REMAP)—were used to assay an F₂ population from a cross between “Handan208” (Gossypium hirsutum) and “Pima90” (Gossypium barbadense). Sixty-nine F₂ plants were used for map construction using 834 SSRs, 437 SRAPs, 107 RAPDs, and 16 REMAPs. Linkage analysis revealed that 1,029 loci could be mapped to 26 linkage groups that extended for 5,472.3 cM, with an average distance between 2 loci of 5.32 cM. The corresponding 69 F_2:3 families were grown, arranged in two replicates, and scored for eight phenotypes. Quantitative trait loci (QTL) analysis was performed by means of composite interval mapping using WinQtlCart ver 2.0. A total of 52 distinct QTLs were detected: 4 QTLs for lint index, 8 for seed index, 11 for lint yield, 4 for seed cotton yield, 9 for number of seed per boll, 3 for fiber strength, 5 for fiber length, and 8 for micronaire value. The present map and QTL analysis may provide a useful tool for breeders to transfer desirable traits from G. barbadense to the mainly cultivated species, G. hirsutum.     

Electron Transport Through Photosystem II Is Not Limited By A Wide Range of Water Deficit Conditions In Field‐Grown Gossypium hirsutum

Despite exhaustive literature describing drought stress effects on photosynthesis in Gossypium hirsutum, the sensitivity of photosynthetic electron flow to water deficit is heavily debated. To address this, G. hirsutum plants were grown at a field site near Camilla, GA under contrasting irrigation regimes, and pre‐dawn water potential (Ψ_PD), stomatal conductance (g_s), net photosynthesis (P_N), actual quantum yield of photosystem II (Φ_PSII) and electron transport rate (ETR) were measured at multiple times during the 2012 growing season. Ψ_PD values ranged from ?0.3 to ?1.1 MPa. Stomatal conductance exhibited a strong (r² = 0.697), sigmoidal response to Ψ_PD, where g_s was ≤0.1 mol m^?2 s^?1 at Ψ_PD values ≤ ?0.86 MPa. Neither Φ_PSII (r² = 0.015) nor ETR (r² = 0.010) was affected by Ψ_PD, despite exceptionally low Ψ_PD values (?1.1 MPa) causing a 71.7 % decline in P_N relative to values predicted for well‐watered G. hirsutum leaves at Ψ_PD = ?0.3 MPa. Further, P_N was strongly influenced by g_s, whereas ETR and Φ_PSII were not. We conclude that photosynthetic electron flow through photosystem II is insensitive to water deficit in field‐grown G. hirsutum.     

Meiotic studies of spontaneous hybrids of Amaranthus: genome analysis

The meiotic behaviour of 13 spontaneous interspecific F₁ hybrids of Amaranthus was studied. The hybrids between species with n= 16 chromosomes had 16 bivalents but varied considerably in pollen stainability (0–55%). These results suggest the existence of cryptic structural hybridity. The hybrids involving A. cruentus (n = 17) and species with n = 16 (A. caudatus and A. quitensis) always formed 15II+1 III with very low pollen stainability (5–7%). Further observations indicated that Amaranthus species are allotetraploids with basic numbers of x= 8 and x= 9 but exhibit x= 16 and x= 17 as secondary basic numbers, as demonstrated by (a) the frequent presence of 811 + 171 in the meiosis of the hybrid A. spinosus (n = 17) × A. hybridus (n= 16); and the occurrence of secondary associations between bivalents in MI. Genomic formulae are proposed for each species, on the basis of the meiotic behaviour of the hybrids studied.     

Hybridization between diploid (Gossypium arboreum) and tetraploid (Gossypium hirsutum) cotton through ovule culture

Summary With in vitro culture of ovules, interspecific hybrids have been obtained in an otherwise incompatible cross between a diploid (Gossypium arboreum) and a tetraploid (G. hirsutum) cultivated cotton. The early abortion of the embryo was prevented by repeated treatment of the flowers, immediately after pollination with a solution of gibberellic acid and naphthalene acetic acid. The ovules excised three days after pollination and cultured in a liquid medium underwent profuse proliferation, whereas on an agar-solidified medium supplemented with casein hydrolysate, indoleacetic acid and kinetin they germinated to form hybrid plants.     

Using molecular markers and field performance data to characterize the Pee Dee cotton germplasm resources

Knowledge of genetic relationships in crop breeding programs provides valuable information that can be used by plant breeders as a parental line selection tool. In Upland cotton (Gossypium hirsutum L.), the Pee Dee germplasm program represents one of the most historically significant Upland cotton breeding programs and is known as a key source of fiber quality genes for commercial cultivars. The foundation of the Pee Dee germplasm is known to represent an array of genetic diversity involving the hybridization of G. hirsutum L., G. barbadense L., and triple hybrid strains (G. arboreum L. × G. thurberi Todaro × G. hirsutum L.). In this study, we characterized genetic relationships within the Pee Dee germplasm collection using molecular marker and field performance data. Molecular marker and field performance data showed the Pee Dee germplasm collection still maintains useful amounts of genetic diversity. The methods described provide plant breeders of cotton and other crops a strategy to develop a parental line selection tool based on genotypic and phenotypic information. Cotton breeders can directly use the information provided to select specific Pee Dee germplasm parental line combinations based on genotypic (molecular marker) and phenotypic (field performance) information rather than relying on pedigree and phenotypic information alone.     

A microsatellite-based genome-wide analysis of genetic diversity and linkage disequilibrium in Upland cotton (Gossypium hirsutum L.) cultivars from major cotton-growing countries

To better understand the genetic diversity of the cultivated Upland cotton (Gossypium hirsutum L.) and its structure at the molecular level, 193 Upland cotton cultivars collected from 26 countries were genotyped using 448 microsatellite markers. These markers were selected based on their mapping positions in the high density G. hirsutum TM-1 × G. barbadense 3-79 map, and they covered the whole genome. In addition, the physical locations of these markers were also partially identified based on the reference sequence of the diploid G. raimondii (D₅) genome. The marker orders in the genetic map were largely in agreement with their orders in the physical map. These markers revealed 1,590 alleles belonging to 732 loci. Analysis of unique marker allele numbers indicated that the modern US Upland cotton had been losing its genetic diversity during the past century. Linkage disequilibrium (LD) between marker pairs was clearly un-even among chromosomes, and among regions within a chromosome. The average size of a LD block was 6.75 cM at r ² = 0.10. A neighbor-joining phylogenic tree of these cultivars was generated using marker allele frequencies based on Nei’s genetic distance. The cultivars were grouped into 15 groups according to the phylogenic tree. Grouping results were largely congruent with the breeding history and pedigrees of the cultivars with a few exceptions.     

Cytomorphological studies in an intergeneric hybrid between Gossypium hirsutum L. (2n=52) and Hibiscus panduraeformis Burm.

Summary An intergeneric hybrid (2n=38) between Gossypium hirsutum L. (2n=52) × Hibiscus panduraeformis Burm. (2n=24) was obtained by pollinating about 2000 flower buds of G. hirsutum var. Gregg Male Sterile with pollen from H. panduraeformis. The F₁ hybrid was intermediate in plant habit, but possessed gossypol glands and nectaries on the leaves, bolls containing seeds with fuzz and lint as dominant characters of G. hirsutum. Flowers with yellow corolla and anthers; purple petal spot, profuse growth of epidermal hairs on all plant parts including the boll sutures, and jassid tolerance were dominant characters of H. panduraeformis. The partial fertility of the F₁ indicated the possibilities of combining jassid and drought tolerance of H. panduraeformis with the desired economic characters of G. hirsutum for rainfed cultivation.The F₁ hybrid showed various meiotic irreguarities and about 40% pollen sterility. Formation of the normal bivalents occurred quite frequently suggesting a close relationship between the parental species. The sterility observed in the hybrid may be due to small structural differences between the chromosomes of the two genera and meiotic abnormalities.     

Relevance of unilateral and bilateral sexual polyploidization in relation to intergenomic recombination and introgression in <Emphasis Type="Italic">Lilium</Emphasis> species hybrids

Sexual polyploids were induced in diploid (2n = 2x = 24) interspecific F1 hybrids of Longiflorum × Asiatic (LA) and Oriental × Asiatic (OA) Lilium hybrids by backcrossing to Asiatic (AA) parents as well as by sib-mating of the F1 LA hybrids. A majority of the BC1 progenies were triploid and the progenies from sib-mating were tetraploid or near tetraploids. Genomic in situ hybridization (GISH) technique was applied to assess the intergenomic recombination in the BC1 populations of LA and OA hybrids obtained after unilateral sexual polyploidization. A total of 63 LA (LA × AA and AA × LA) and 53 OA hybrids were analysed. LA hybrids were originated through the functioning of 2n gametes either as 2n eggs or 2n pollen while those of OA hybrids originated through functional 2n pollen of diploid OA genotype. In both type of crosses, a majority of the progenies had originated through First Division Restitution (FDR) mechanism of functional 2n gamete either with or without a cross over. However, there were nine LA- and four OA-genotypes where Indeterminate Meiotic Restitution (IMR) was the mechanism of 2n gamete formation. Based on GISH, total amount of introgression of Longiflorum and Oriental genome into Asiatic genome was determined. Most of the BC progenies exhibited recombination and the amount of recombination was higher in LA hybrids as compared to OA hybrids. Intergenomic recombination was also determined cytologically in the 16 plants of sib-mated LA hybrids where both parents had contributed 2n gametes. Based on these results the nature of interspecific lily hybrids obtained from uni- and bilateral sexual polyploidization leading to allotriploid and allotetraploid formation is discussed in the context of introgression and intergenomic recombination.     

Stability analysis for bollworm complex in <Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.

One approach to improve cotton (Gossypium hirsutum L.) yield is to identify stable genotypes for low or no bollworms damage as it accounts low cost of cultivation to a considerable extent. The objective of the study was to identify stable genotypes for low bollworms damage under protected and unprotected experiments. Fifty cotton (Gossypium hirsutum L.) genotypes were evaluated for open bollworms damage percent (spotted, pink and Heliothis bollworms) for 3 years during 2003–2005 under protected and unprotected conditions. Variance due to genotypes, environments, genotype × environment and genotype × environment (linear) components were highly significant for the trait in protected and unprotected experiments. Under protected experiment, genotypes CSH 3020 and 3045 were found to be desirable and stable while genotype CSH 3058 was suited for poor environments. Fourteen genotypes viz. CSH 3034, 3035, 3043, 3044, 3047, 3051, 3053, 3058, 3059, 3094, 3106, 3114, 3123 and CSH-3157 were fairly stable under unprotected environments. The study lead to the conclude that in general for the two experiments the genotypes differed for stability for low bollworms damage.     

Morphological,cytological and reproductive characterization of tri-species hybrids (GOS) between <Emphasis Type="Italic">Pennisetum glaucum</Emphasis>, <Emphasis Type="Italic">P. orientale</Emphasis> and <Emphasis Type="Italic">P. squamulatum</Emphasis>

New tri-species hybrids (GOS) in the genus Pennisetum involving the cultivated species pearl millet (P. glaucum L.) and two wild species, viz. P. squamulatum Fresen and P. orientale L. C. Rich, are reported. Six hybrid plants were recovered after crossing a backcross hybrid (2n = 3x = 23, GGO) between P. glaucum (2n = 2x = 14, GG) and P. orientale (2n = 2x = 18, OO) with F₁s (2n = 6x = 42, GGSSSS) between P. glaucum (2n = 4x = 28, GGGG) and P. squamulatum (2n = 8x = 56, SSSSSSSS). The hybrids were perennial, morphologically intermediate to their parents, and represented characters from the three contributing species. The hybrids contained 2n = 44 chromosomes (GGGSSO) representing 21, 14 and nine chromosomes from P. glaucum, P. squamulatum and P. orientale, respectively. Meiotic and flow-cytometric analysis suggested origin of these hybrids from unreduced female and reduced male gametes. Average chromosome configuration (8.42_I + 14.32_II + 1.62_III + 0.52_IV) at Meiosis showed limited inter-genomic pairing indicating absence of significant homology between the three genomes. The hybrids were male sterile (except one) and highly aposporous. P. orientale was identified to induce apospory in hybrid background with P. glaucum at diploid and above levels, though it was quantitatively affected by genomic doses from sexual parent. A case of inducible and recurrent apospory is presented whereby a transition from Polygonum-type sexual embryo-sacs to Panicum-type aposporous embryo-sacs was observed in diploid interspecific hybrids. Results supported independent origin and partitioning of the three apomixis-components (apomeiosis, parthenogenesis, and functional endosperm development), reported for the first time in Pennisetum. Potential utilization of GOS hybrids in understanding genome interactions involved in complex traits, such as perenniality and apomixis, is discussed.     

Novel interspecific hybridization between sweetpotato (<Emphasis Type="Italic">Ipomoea batatas</Emphasis> (L.) Lam.) and its two diploid wild relatives

Interspecific hybridization is an important approach to broaden the genetic base and create novel plant forms in breeding programs. However, interspecific hybridization in Ipomoea is very difficult due to the cross incompatibility. Here we report two novel interspecific F₁ hybrids between I. batatas (L.) Lam. (2n = 6x = 90) and two wild species, I. grandifolia (2n = 2x = 30) and I. purpurea (2n = 2x = 30). Hybridization was stimulated by applying plant growth hormones. Morphological, molecular and cytological tests were conducted to confirm their hybridity. We found that the two hybrids were quite distinctive in leaf color and morphology, and yielded intermediate sizes of storage roots compared to their respective parents. Inter-simple sequence repeat analysis showed that the unique DNA bands from the wild parents could be detected in these two hybrids. The cluster analysis also showed that the two F₁ hybrids were closer to I. batatas in phylogeny relationship. The number of chromosomes of the two hybrids was both 60, indicating that the hybrids were tetraploid. The meiotic configuration analysis of the H₁ of I. batatas × I. grandifolia revealed the occurrence of 17.58I + 14.28II + 1.36III + 2.48IV at metaphase I in average chromosome association per pollen mother cells (PMCs), 4.26I + 18.32II + 2.56III + 3.12IV was average meiotic configuration in the H₂ of I. batatas × I. purpurea. Both hybrids appeared to be polyads and multi-microcytes at tetrad phase and differed in their pollen fertility.     

PCR-RFLP analysis of the whole chloroplast DNA from three cultivated species of cotton (Gossypium L.)

Variations of the chloroplast DNA (cpDNA) from three of the four cultivated species of cotton (Malvaceae); Gossypium barbadense L., Gossypium hirsutum L., Gossypium arboreum L. and its synonym Gossypium nanking Meyen., were analyzed. Using specific set of primers, the whole circular cpDNAs from the four test species were amplified. These were subsequently digested with the use of seven restriction enzymes. The amplified fragments of the whole cpDNAs of the diploid cultivated cotton G. arboreum and its synonym G. nanking did not show any differences. However, the allotetraploid cultivated cottons G. barbadense and G. hirsutum, showed some fragment length differences directly visible after amplification and two types of restriction fragment length polymorphism (RFLP), the first appeared as slightly lengthened bands and the other as gain or loss of a restriction site. The results also showed that the chloroplast genomes of the allotetraploid cultivated cottons are highly similar to the diploid cultivated cottons tested in terms of length and digestion patterns. The detected amplified length differences, RFLPs and the restriction sites can be considered as species specific markers for the allotetraploid cultivated cottons, which could be a useful tool for future studies of the cpDNA of the genus Gossypium L.