New red flower germplasm lines of cotton selected from hybrid of Gossypium hirsutum × G. bickii

By means of dropping GA₃(50 ppm) and NAA (40 ppm) on the hybrid boll-embryo culturein vitro, one F₁ plant ofG. hirsutum × G. bickii was obtained; when F₁ branches were grafted on upland cotton and then back-crossed with upland cotton under short-day and cooler-night condition, some BC₁ seeds could be harvested. The characteristic segregation was very violent in early generation. Through 3 times of back-crossing and selecting, ten stable hybrid lines with the character of both male parent (viz. red petal-purple spot and strong fibre) and female parent (plant type, earliness, white fibre, lint length, etc.) were established. These lines were assigned as HB red flower lines (HBRL). Transference of character ofG. bickii to upland cotton was proved to be successful for the first time. These new germplasms may play an important role in both the genetic research and new cotton variety breeding.     

New red flower germplasm lines of cotton selected from hybrid of Gossypium hirsutum × G. bickii

By means of dropping GA3 (50 ppm) and NAA (40 ppm) on the hybrid boll-embryo culture in vitro, one F1 plant of G. hirsutum G. bickii was obtained; when F1 branches were grafted on upland cotton and then back-crossed with upland cotton under short-day and cooler-night condition, some BC1 seeds could be harvested. The characteristic segregation was very violent in early generation. Through 3 times of back-crossing and selecting, ten stable hybrid lines with the character of both male parent (viz. red petal-purple spot and strong fibre) and female par-ent (plant type, earliness, white fibre, lint length, etc. ) were established. These lines were assigned as HB red flow-er lines (HBRL). Transference of character of G. bickii to upland cotton was proved to be successful for the first time. These new germplasms may play an important role in both the genetic research and new cotton variety breeding.     

Studies on Chromosome Behaviour of F1 and Fertility Restoration in Hybrid of Gossypium hirtutum ×G. bickii

By means of dripping GAs(50 ppm) and NAA(40 ppm) on the hybrid boll-embryo culture in vitro, one F1 plant of G. hirsuturn × G. bickii was obtained in 1982, the Fx plant flowered profusely but failed to produce any seeds when selfed or back crossed. In meiosis of the pollen mother cell (PMC), mean chromosome coniugation was 33.24 Ⅰ +2.67 Ⅱ +0.095 Ⅲ + 0.048 Ⅳ with high frequence (77.6%) of one chiasma attenuated bivalents. Mean number of chiasmta per bivalents was 1.23. The univalents were scattered over the achromatic figure for most PMCs. Although a few of the bivalents were located in' the equatorial region, but they did not form a definite plate. At the second anaphase the distribution of chromosomes was very irregular. In the majority of cases, multipolar distripution of chromosomes was observed. At the completion of meiosis highly abnormal sporads occurred, which contained from 2 ro 13 spores of various sizes. Thus, all of the pollen grains produced were sterile. When the F1 branches were grafted onto the upland cotton and thence they were backcrossed under short day (12 hours) and cold night(15–18℃) exposure, BC1 seeds could be harvested. BC1 and BC2 plants could grow up later. In the BC, generation, the fertility of the hybrid was restored. By 1988, ten pure lines of hybrid with the characers of both male parent (viz.red petal with purple spot and strong fibre) and female parent (white fibre, high yield, earliness ect.) were selected for the first time.     

Identification of exotic genetic components and DNA methylation pattern analysis of three cotton introgression lines from <Emphasis Type="Italic">Gossypium bickii</Emphasis>

The impact of alien DNA fragments on plant genome has been studied in many species. However, little is known about the introgression lines of Gossypium. To study the consequences of introgression in Gossypium, we investigated ∼2000 genomic and ∼800 epigenetic sites in three typical cotton introgression lines, as well as their cultivar (Gossypium hirsutum) and wild parents (Gossypium bickii), by amplified fragment length polymorphism (AFLP) and methylation-sensitive amplified polymorphism (MSAP). The results demonstrate that an average of 0.5% of exotic DNA segments from wild cotton is transmitted into the genome of each introgression line, with the addition of other forms of genetic variation. In total, an average of 0.7% of genetic variation sites is identified in introgression lines. Simultaneously, the overall cytosine methylation level in each introgression line is very close to that of the upland cotton parent (an average of 22.6%). Further dividing patterns reveal that both hypomethylation and hypermethylation occurred in introgression lines in comparison with the upland cotton parent. Sequencing of nine methylation polymorphism fragments showed that most (7 of 9) of the methylation alternations occurred in the noncoding sequences. The molecular evidence of introgression from wild cotton into introgression lines in our study is identified by AFLP. Moreover, the causes of petal variation in introgression lines are discussed.     

Karyotype Analysis of Gossypium arboreum × G. bickii by Genome in situ Hybridization

By using genome in situ hybridization (GISH) on root somatic chromosomes of allotetraploid derived from the cross Gossypium arboreum × G. bickii with genomic DNA (gDNA) of G. bickii as a probe, two sets of chromosomes, consisting of 26 chromosomes each, were easily distinguished from each other by their distinctive hybridization signals. GISH analysis directly proved that the hybrid GarboreumxG. bickii is an allotetraploid amphiploid. The karyotype formula of the species was 2n = 4x = 52 = 46m (4sat) + 6sm (4sat). We identified four pairs of satellites with two pairs in each sub-genome. FISH analysis using 45S rDNA as a probe showed that the cross G. arboreumxG. bickii contained 14 NORs. At least five pairs of chromosomes in the G sub-genome showed double hybridization (red and blue) in their long arms, which indicates that chromatin introgression from the A sub-genome had occurred.     

Phenotypic Expression of rkn1-Mediated Meloidogyne incognita Resistance in Gossypium hirsutum Populations

The root-knot nematode Meloidogyne incognita is a damaging pest of cotton (Gossypium hirsutum) worldwide. A major gene (rkn1) conferring resistance to M. incognita was previously identified on linkage group A03 in G. hirsutum cv. Acala NemX. To determine the patterns of segregation and phenotypic expression of rkn1, F₁, F₂, F_2:3, BC₁F₁ and F_2:7 recombinant inbred lines (RIL) from intraspecific crosses between Acala NemX and a closely related susceptible cultivar Acala SJ-2 were inoculated in greenhouse tests with M. incognita race 3. The resistance phenotype was determined by the extent of nematode-induced root galling and nematode egg production on roots. Suppression of root galling and egg production was highly correlated among individuals in all tests. Root galling and egg production on heterozygous plants did not differ from the susceptible parent phenotype 125 d or more after inoculation, but were slightly suppressed with shorter screening (60 d), indicating that rkn1 behaved as a recessive gene or an incompletely recessive gene, depending on the screening condition. In the RIL, rkn1 segregated in an expected 1 resistant: 1 susceptible ratio for a major resistance gene. However, within the resistant class, 21 out of 34 RIL were more resistant than the resistant parent Acala NemX, indicating transgressive segregation. These results suggest that rkn1-based resistance in G. hirsutum can be enhanced in progenies of crosses with susceptible genotypes. Allelism tests and molecular genetic analysis are needed to determine the relationship of rkn1 to other M. incognita resistance sources in cotton.     

Genetic diversity analysis of maintainer and restorer accessions in upland cotton (Gossypium hirsutum L.)

Genetic diversity amongst 91 upland cotton accessions (50 maintainer, ‘B’ and 41 restorer ‘R’ lines) and three wild species viz., G. aridum, G. thurberi and G. anomalum was analyzed using SSR and RAPD markers. A total of 53 primers (30 SSR and 23 RAPD) were sampled for screening 94 accessions, of which 26 SSR and 17 RAPD primers were polymorphic. Average polymorphism detected by SSR, RAPD and SSR + RAPD markers was 72.5, 62 and 66.66 per cent, respectively. A unique marker CIR-200₂₆₀ that distinguishes G. thurberi from all upland accessions has been identified. Similarity coefficient values within and between B and R lines ranged from 0.65–0.95, 0.61–0.98 and 0.53–0.93 for SSR and 0.72–0.98, 0.73–0.97 and 0.69–0.98 for RAPD markers. UPGMA cluster analysis was consistent with the pedigree and genotypic background of the accessions. RAPD and SSR matrices showed significant positive product moment correlation (r?=?0.93 and 0.92) with the RAPD + SSR combined data matrix, respectively. The result indicates a moderate level of genetic diversity in B and R accessions of upland cotton. Genetically diverse combinations were identified to further evaluate heterotic performance. The maintainer, AKH-108, AKH-118 and AKH-2173; and restorer AKH-31 and AKH 4943 accession were identified as most distinct and divergent, could be used as candidate parental genotypes in hybrid and varietal development programme and also development of mapping population for trait mapping in cotton.     

Integrated transcript and metabolite profiling reveals coordination between biomass size and nitrogen metabolism in Arabidopsis F1 hybrids

Heterosis refers to the improved agronomic performance of F₁ hybrids relative to their parents. Although this phenomenon is widely employed to increase biomass, yield, and stress tolerance of plants, the underlying molecular mechanisms remain unclear. To dissect the metabolic fluctuations derived from genomic and/or environmental differences contributing to the improved biomass of F₁ hybrids relative to their parents, we optimized the growth condition for Arabidopsis thaliana F₁ hybrids and their parents. Modest but statistically significant increase in the biomass of F₁ hybrids was observed. Plant samples grown under the optimized condition were also utilized for integrated omics analysis to capture specific changes in the F₁ hybrids. Metabolite profiling of F₁ hybrids and parent plants was performed using gas chromatography-mass spectrometry. Among the detected 237 metabolites, 2-oxoglutarate (2-OG) and malate levels were lower and the level of aspartate was higher in the F₁ hybrids than in each parent. In addition, microarray analysis revealed that there were 44 up-regulated and 12 down-regulated genes with more than 1.5-fold changes in expression levels in the F₁ hybrid compared to each parent. Gene ontology (GO) analyses indicated that genes up-regulated in the F₁ hybrids were largely related to organic nitrogen (N) process. Quantitative PCR verified that glutamine synthetase 2 (AtGLN2) was upregulated in the F₁ hybrids, while other genes encoding enzymes in the GS-GOGAT cycle showed no significant differences between the hybrid and parent lines. These results suggested the existence of metabolic regulation that coordinates biomass and N metabolism involving AtGLN2 in F₁ hybrids.     

A glutathione S-transferase GhTT19 determines flower petal pigmentation via regulating anthocyanin accumulation in cotton

Anthocyanin accumulations in the flowers can improve seed production of hybrid lines, and produce higher commodity value in cotton fibre. However, the genetic mechanism underlying the anthocyanin pigmentation in cotton petals is poorly understood. Here, we showed that the red petal phenotype was introgressed from Gossypium bickii through recombination with the segment containing the R₃ ^bic region in the A07 chromosome of Gossypium hirsutum variety LR compared with the near-isogenic line of LW with white flower petals. The cyanidin-3-O-glucoside (Cy3G) was the major anthocyanin in red petals of cotton. A GhTT19 encoding a TT19-like GST was mapped to the R₃^bic site associated with red petals via map-based cloning, but GhTT19 homologue gene from the D genome was not expressed in G. hirsutum. Intriguingly, allelic variations in the promoters between GhTT19^LW and GhTT19^LR, rather than genic regions, were found as genetic causal of petal colour variations. GhTT19-GFP was found localized in both the endoplasmic reticulum and tonoplast for facilitating anthocyanin transport. An additional MYB binding element found only in the promoter of GhTT19^LR, but not in that of GhTT19^LW, enhanced its transactivation by the MYB activator GhPAP1. The transgenic analysis confirmed the function of GhTT19 in regulating the red flower phenotype in cotton. The essential light signalling component GhHY5 bonded to and activated the promoter of GhPAP1, and the GhHY5-GhPAP1 module together regulated GhTT19 expression to mediate the light-activation of petal anthocyanin pigmentation in cotton. This study provides new insights into the molecular mechanisms for anthocyanin accumulation and may lay a foundation for faster genetic improvement of cotton.     

QTL mapping for fiber quality traits across multiple generations and environments in upland cotton

Identification of quantitative trait loci (QTL) for fiber quality traits that are stable across multiple generations and environments could facilitate marker-assisted selection for improving cotton strains. In the present study, F₂, F_2:3, and recombinant inbred lines (RILs, F _6:8 ) populations derived from an upland cotton (Gossypium hirsutum L.) cross between strain 0-153, which has excellent fiber quality, and strain sGK9708, a commercial transgenic cultivar, were constructed for QTL tagging of fiber quality. We used 5,742 simple sequence repeat primer pairs to screen for polymorphisms between the two parent strains. Linkage maps of F₂ and RILs were constructed, containing 155 and 190 loci and with a total map distance of 959.4 centimorgans (cM) and 700.9?cM, respectively. We screened fiber quality QTL across multiple generations and environments through composite interval mapping of fiber quality data. Specifically, we studied F₂ and F_2:3 family lines from Anyang (Henan Province) in 2003 and 2004 and RILs in Anyang in 2007 and Anyang, Quzhou (Hebei Province), and Linqing (Shandong Province) in 2008. We identified 50 QTL for fiber quality: 10 for fiber strength, 10 for fiber length, 10 for micronaire, eight for fiber uniformity, and 12 for fiber elongation. Nine of these fiber quality QTL were identified in F₂, F_2:3 and RILs simultaneously. Two QTL for fiber strength on chromosomes C7 and C25 were detected in all three generations and all four environments and explained 16.67?C27.86% and 9.43?C21.36% of the phenotypic variation, respectively. These stable QTL for fiber quality traits could be used for marker assisted selection.     

Inheritance of Semidwarfism in Rice, ORYZA SATIVA L

The inheritance of plant height was investigated in a ten-parent diallel cross of diverse rice cultivars. Parents included two tall japonica lines and eight semidwarf lines. Data from parent, F₁, F₂ , and F₃ generations indicated that the majority of height variation among the ten parents could be accounted for by three major genes with additive loci effects. D51, 72/2234–11, and G33 (derived from the known major-gene indica semidwarf Dee-geo-woo-gen) all were found to possess an allelic, partially recessive semidwarfing gene (sd₁). Additional semidwarfing genes were detected in D66 (sd₂, fully recessive) and in CI 9858 (sd₃, partially to fully recessive). Relative magnitudes of additive effects were sd₁ > sd₂ ≥ sd₃. Hokuriki 76, Tedoriwase, and IV 29–4 were found to be dwarfed by a multiple-gene system. Hayman-Jinks diallel cross analysis on parent and F₁ information (1974 and 1975) and on parent and F₂ information demonstrated the presence of significant additive and dominance variation, but epistasis was not detected. A preponderance of dominant alleles with partial dominance for increased plant height was observed. Since diallel statistics reflect properties of genes with larger effects, the genetic model proposed from segregation analysis was in substantial agreement with predictions of the Hayman-Jinks analysis.     

Breeding Potential of Introgression Lines Developed from Interspecific Crossing between Upland Cotton (Gossypium hirsutum) and Gossypium barbadense: Heterosis,Combining Ability and Genetic Effects

Upland cotton (Gossypium hirstum L.), which produces more than 95% of the world natural cotton fibers, has a narrow genetic base which hinders progress in cotton breeding. Introducing germplasm from exotic sources especially from another cultivated tetraploid G. barbadense L. can broaden the genetic base of Upland cotton. However, the breeding potential of introgression lines (ILs) in Upland cotton with G. barbadense germplasm integration has not been well addressed. This study involved six ILs developed from an interspecific crossing and backcrossing between Upland cotton and G. barbadense and represented one of the first studies to investigate breeding potentials of a set of ILs using a full diallel analysis. High mid-parent heterosis was detected in several hybrids between ILs and a commercial cultivar, which also out-yielded the high-yielding cultivar parent in F₁, F₂ and F₃ generations. A further analysis indicated that general ability (GCA) variance was predominant for all the traits, while specific combining ability (SCA) variance was either non-existent or much lower than GCA. The estimated GCA effects and predicted additive effects for parents in each trait were positively correlated (at P<0.01). Furthermore, GCA and additive effects for each trait were also positively correlated among generations (at P<0.05), suggesting that F₂ and F₃ generations can be used as a proxy to F₁ in analyzing combining abilities and estimating genetic parameters. In addition, differences between reciprocal crosses in F₁ and F₂ were not significant for yield, yield components and fiber quality traits. But maternal effects appeared to be present for seed oil and protein contents in F₃. This study identified introgression lines as good general combiners for yield and fiber quality improvement and hybrids with high heterotic vigor in yield, and therefore provided useful information for further utilization of introgression lines in cotton breeding.     

Quantitative trait loci mapping and genetic dissection for lint percentage in upland cotton (Gossypium hirsutum)

Lint percentage is an important character of cotton yield components and it is also correlated with cotton fibre development. In this study, we used a high lint percentage variety, Baimian1, and a low lint percentage, TM-1 genetic standard for Gossypium hirsutum, as parents to construct a mapping populations in upland cotton (G. hirsutum). A quantitative trait locus/loci (QTL) analysis of lint percentage was performed by using two mapping procedures; composite interval mapping (CIM), inclusive composite interval mapping (ICIM) and the F_2:3 populations in 2 years. Six main-effect QTL (M-QTL) for lint percentage (four significant and two suggestive) were detected in both years by CIM, and were located on chr. 3, chr. 19, chr. 26 and chr. 5/chr. 19. Of the six QTL, marker intervals and favourable gene sources of the significant M-QTL, qLP-3(2010) and qLP-3(2011) were consistent. These QTL were also detected by ICIM, and therefore, should preferentially be used for marker-assisted selection (MAS) of lint percentage. Another M-QTL, qLP-19(2010), was detected by two mapping procedures, and it could also be a candidate for MAS. We detected the interaction between two M-QTL and environment, and 11 epistatic QTL (E-QTL) and their interaction with environment by using ICIM. The study also found two EST-SSRs, NAU1187 and NAU1255, linked to M-QTL for lint percentage that could be candidate markers affecting cotton fibre development.     

Analysis of [Gossypium capitis-viridis × (G.hirsutum × G.australe)2] Trispecific Hybrid and Selected Characteristics

Speciation is always a contentious and challenging issue following with the presence of gene flow. In Gossypium, there are many valuable resources and wild diploid cotton especially C and B genome species possess some excellent traits which cultivated cotton always lacks. In order to explore character transferring rule from wild cotton to upland tetraploid cotton, the [G. capitis-viridis × (G. hirsutum × G. australe)²] triple hybrid was synthesized by interspecies hybridization and chromosome doubling. Morphology comparisons were measured among this hybrid and its parents. It showed that trispecific hybrid F₁ had some intermediate morphological characters like leaf style between its parents and some different characters from its parents, like crawl growth characteristics and two kind flower color. It is highly resistant to insects comparing with other cotton species by four year field investigation. By cytogenetic analysis, triple hybrid was further confirmed by meiosis behavior of pollen mother cells. Comparing with regular meiosis of its three parents, it was distinguished by the occurrence of polyads with various numbers of unbalanced microspores and finally generating various abnormal pollen grains. All this phenomenon results in the sterility of this hybrid. This hybrid was further identified by SSR marker from DNA molecular level. It showed that 98 selected polymorphism primers amplified effective bands in this hybrids and its parents. The genetic proportion of three parents in this hybrid is 47.8% from G. hirsutum, 14.3% from G. australe, 7.0% from G. capitis-viridis, and 30.9% recombination bands respectively. It was testified that wild genetic material has been transferred into cultivated cotton and this new germplasm can be incorporated into cotton breeding program.     

Genetic analysis of hybrid seed formation ability of Brassica rapa in intergeneric crossings with Raphanus sativus

A hybridization barrier leads to the inability of seed formation after intergeneric crossings between Brassica rapa and Raphanus sativus. Most B. rapa lines cannot set intergeneric hybrid seeds because of embryo breakdown, but a B. rapa line obtained from turnip cultivar ‘Shogoin-kabu’ is able to produce a large number of hybrid seeds as a maternal parent by crossings with R. sativus. In ‘Shogoin-kabu’ crossed with R. sativus, developments of embryos and endosperms were slower than those in intraspecific crossings, but some of them grew to mature seeds without embryo breakdown. Intergeneric hybrid seeds were obtained in a ‘Shogoin-kabu’ line at a rate of 0.13 per pollinated flower, while no hybrid seeds were obtained in a line developed from Chinese cabbage cultivar ‘Chiifu’. F₁ hybrid plants between the lines of ‘Shogoin-kabu’ and ‘Chiifu’ set a larger number of hybrid seeds per flower, 0.68, than both the parental lines. Quantitative trait loci (QTLs) for hybrid seed formation were analyzed after intergeneric crossings using two different F₂ populations derived from the F₁ hybrids, and three QTLs with significant logarithm of odds scores were detected. Among them, two QTLs, i.e., one in linkage group A10 and the other in linkage group A01, were detected in both the F₂ populations. These two QTLs had contrary effects on the number of hybrid seeds. Epistatic interaction between these two QTLs was revealed. Possible candidate genes controlling hybrid seed formation ability in QTL regions were inferred using the published B. rapa genome sequences.     

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.     

GhPSY,a phytoene synthase gene,is related to the red plant phenotype in upland cotton (Gossypium hirsutum L.)

Carotenoids are important accessory pigments in plants that are essential for photosynthesis. Phytoene synthase (PSY), a rate-controlling enzyme in the carotenoid biosynthesis pathway, has been widely characterized in rice, maize, and sorghum, but at present there are no reports describing this enzyme in cotton. In this study, GhPSY was identified as a candidate gene for the red plant phenotype via a combined strategy using: (1) molecular marker data for loci closely linked to R1; (2) the whole-genome scaffold sequence from Gossypium raimondii; (3) gene expression patterns in cotton accessions expressing the red plant and green plant phenotypes; and (4) the significant correlation between a single nucleotide polymorphisms (SNP) in GhPSY and leaf phenotypes of progeny in the (Sub16 × T586) F₂ segregating population. GhPSY was relatively highly expressed in leaves, and the protein was localized to the plastid where it appeared to be mostly attached to the surface of thylakoid membranes. GhPSY mRNA was expressed at a significantly higher level in T586 and SL1-7-1 red plants than TM-1 and Hai7124 green plants. SNP analysis in the GhPSY locus showed co-segregation with the red and green plant phenotypes in the (Sub16 × T586) F₂ segregating population. A phylogenetic analysis showed that GhPSY belongs to the PSY2 subfamily, which is related to photosynthesis in photosynthetic tissues. Using a reverse genetics approach based on Tobacco rattle virus-induced gene silencing, we showed that the knockdown of GhPSY caused a highly uniform bleaching of the red color in newly-emerged leaves in both T586 and SL1-7-1 plants with a red plant phenotype. These findings indicate that GhPSY is important for engineering the carotenoid metabolic pathway in pigment production.     

田间条件下海岛棉和陆地棉花铃期叶片光保护的机制

研究海岛棉(Gossypium barbadense)和陆地棉(G. hirsutum)两个棉花栽培种的光合作用特性, 探讨两个栽培种光合机构的光抑制以及防御保护机制, 以期为新疆棉花高光效品种选育和高产高效栽培实践提供理论基础。在新疆生态气候条件下, 系统测定了海岛棉和陆地棉的叶片运动、叶片接受光量子通量密度(PFD)、叶片温度、叶绿素荧光参数、气体交换参数和光呼吸速率的日变化。研究结果表明: 陆地棉叶片的“横向日性”较强而海岛棉较弱, 导致海岛棉叶片接受PFD较低, 但其叶片温度较高。海岛棉叶片的光合速率和气孔导度均显著低于陆地棉。在8:00-10:00 (北京时间, 下同)海岛棉叶片的光呼吸速率略低于陆地棉, 其余时间段海岛棉和陆地棉叶片的光呼吸速率相似。不同栽培种间, 叶片的最大光化学效率和实际光化学效率的日变化均无明显差异。除14:00-16:00以外, 海岛棉叶片的表观电子传递速率和光化学猝灭系数均显著低于陆地棉。8:00以后, 海岛棉叶片的非光化学猝灭显著高于陆地棉。因此, 在新疆生态气候条件下, 海岛棉和陆地棉叶片“横向日性”运动能力和气孔导度的差异导致叶片所处的光温环境不同, 同时造成海岛棉叶片的碳同化能力较低。为阻止光合电子传递链的过度还原, 减轻光合机构的光抑制, 陆地棉叶片主要通过光合机构的电子流途径耗散激发能, 而海岛棉叶片通过热耗散途径和相对较高的光呼吸能力来耗散激发能。     

Morphological,chemical, and cytogenetic characters of F1 hybrids betweenParthenium argentatum (Guayule) andP. fruticosum var.fruticosum (Asteraceae) and their potential in rubber improvement

Interspecific hybrids betweenParthenium argentatum, the guayule rubber plant, andP. fruticosum var. fruticosum were evaluated for their potential rubber content and quality. Fifteen-mo-old field-grown plants ofP. fruticosum var.fruticosum measured four times more in height and spread than those ofP. argentatum, but contained less than 0.05% rubber of low mol wt.Parthenium argentatum showed 2% rubber content, with a mol wt of about one million. Resin contents varied little among parents or hybrids. The same age F₁ hybrids were intermediate in height and spread and had low rubber content, but showed presence of high mol wt rubber like the guayule parent. This indicates that high mol wt rubber is expressed over the low mol wt rubber in F₁ hybrids. Despite low rubber content but favorable biomass production, F₁ hybrids revealed irregular meiotic chromosome behavior and low pollen and seed germination. These results suggest that interspecific F₁ hybrids may be used in backcross programs to increase biomass and rubber content in guayule.     

Improved versions of rice maintainer line,APMS 6B,possessing two resistance genes, <Emphasis Type="Italic">Xa21</Emphasis> and <Emphasis Type="Italic">Xa38</Emphasis>, exhibit high level of resistance to bacterial blight disease

APMS 6B is the stable maintainer of the CMS line APMS 6A, which is the female parent of the popular Indian rice hybrid DRRH 3. APMS 6B has good combining ability and plant stature but is highly susceptible to bacterial blight (BB) disease. In order to improve the BB resistance of APMS 6B, we pyramided two major, dominant BB resistance genes, Xa21 and Xa38, through marker-assisted backcross breeding (MABB). Improved Samba Mahsuri (ISM) was used as the donor for Xa21 while PR 114 (Xa38) served as the donor for Xa38. Individual crosses [APMS 6B/ISM and APMS 6B/PR 114 (Xa38)] were performed, and true F₁ plants were then backcrossed with APMS 6B and the MABB process was continued till BC₃. A single positive BC₃F₁ plant identified from both the crosses with maximum genotypic and phenotypic similarity with APMS 6B was selfed to generate BC₃F₂s. At BC₃F₂ generation, plants homozygous for either Xa21 or Xa38 were identified and further confirmed for the absence of two major fertility restorer genes, Rf3 and Rf4. A single such homozygous BC₃F₂ plant, each from both the crosses, was then inter-mated to generate ICF₁s (inter-cross F₁s). Selected ICF₁ plants possessing both the BB resistance genes were selfed to generate ICF₂s. A total of 42 ICF₂ plants homozygous for both Xa21 and Xa38 were identified and screened with parental polymorphic SSR markers to identify the best F₂ plants having the maximum recurrent parent genome recovery. Twelve best ICF₂ plants were advanced up to ICF₅. The ICF₅ lines displayed very high level of BB resistance and were similar to APMS 6B in terms of agro-morphological characters. Further, most of these lines also showed complete maintenance ability and such lines are being advanced for conversion to WA-CMS lines.