[Objective] This study aimed to map the fuzzless mutant (i.e., naked seed) gene n2 in XZ142w cotton plants. [Method] An F2 population of upland cotton (Gossypium hirsutum L.) was generated from a cross between XZ142 and the lintless-fuzzless mutant XZ142w. First, 108 simple sequence repeat (SSR) markers were used for mapping. High resolution melting (HRM) technology was then applied to screen 50 single nucleotide polymorphism (SNP) primer pairs designed based on a comparative transcriptomic analysis of the two parents. The SNP markers were used for genotyping. [Results] The n2 gene was first mapped to a 20.2-cM region on chromosome 26 based on 108 SSR markers. Nine pairs of SNP markers from the HRM screening were used to genotype the F2 progeny. Using the linkage map based on SSR markers, the genetic interval of n2 was finally narrowed to a 19.5-cM region. At a genetic distance of 5.5 cM, the closest marker was Cricaas20158 (an SNP marker). The linkage map was mostly consistent with an in silico physical map based on a sequenced upland cotton genome. [Conclusion] The application of HRM technology is useful for detecting cotton SNPs and mapping the n2 gene.
[Objective] The aim of this study was to finely map and clone the photoperiod-sensitive male sterility gene in upland cotton. [Method] Eleven male parents were crossed with CCRI 9106 (i.e., a novel Gossypium hirsutum L. photoperiod-sensitive male sterile mutant derived from CCRI 040029 using space mutation breeding technology) to evaluate heterosis. The F1 and F2 populations generated from the cross between CCRI 9106 and G. hirsutum L. cv. Letu 603 were used for genetic analyses. A bulked segregant analysis combined with simple sequence repeat (SSR)-based techniques were used to detect markers linked with the male sterility gene. An F2 population (186 plants) from the CCRI 9106 × Letu 603 cross was used for gene mapping analyses. [Results] All F1 plants were fertile, and the segregation ratio of fertility phenotypes in the F2 population was consistent with the 3:1 ratio of Mendelian inheritance. This indicated that male sterility was controlled by a recessive gene. Out of 16 544 SSRs, 18 were linked with the gene. The genetic linkage map suggested that the gene was located on chromosome D12 of the upland cotton genome within markers NAU3442 and CGR6339 , with a 0.2-cM genetic distance to them. This photoperiod-sensitive male sterility gene was named ys-1. [Conclusion] The mapping results for ys-1 may be applicable for the fine-mapping and positional cloning of the photoperiod-sensitive male sterility gene.
[Objective] Ascorbate peroxidase (APX) is a type of peroxidase, which can scavenge reactive oxygen species. The objective of this study was to further characterize the APX gene families. [Method] Using bioinformatics methods, we identified 14 members of the APX gene family using the Gossypium hirsutum L. genomic sequence provided by the Institute of Cotton Research of the Chinese Academy of Agricultural Sciences. Systematic analyses focused on chromosome locations, subcellular localizations, evolutionary relationships, physicochemical properties, structure, and the presence of signal peptides and conserved motifs. Preliminary expression analyses were completed for selected genes related to fiber development. [Results] The APX gene family members were distributed on almost all chromosomes. Most of the encoded hydrophilic and lipid-soluble enzymes were localized to the cytoplasm. They had three conserved motifs, and the associated gene sequences were highly conserved. The origin and evolution of the APX genes was complex. Additionally, the predicted secondary structures of the main motifs consisted of α-helices and random coils. Genes in the first and second subgroups were speculated to affect different cotton fiber development stages. [Conclusion] These results may be useful for future studies of the structures and functions of APX family members.
[Objective] The aim of this study was to reveal the genetic basis of drought tolerance traits and detect major quantitative trait loci (QTLs) by mapping drought tolerance QTLs on the Gossypium tomentosum genome. This information may be useful for developing drought-tolerant cotton cultivars. [Method] The present study examined the genetic basis of drought tolerance in 188 F2 lines and 149 F2:3 lines developed from an interspecific cross between a wild cotton species, Gossypium tomentosum, and an upland cotton variety (CCRI 12). Five morpho-physiological traits (i.e., height, number of leaves, and chlorophyll, malondialdehyde, and proline contents) were assessed under water-limited (W1) and well-watered (W2) conditions during the seedling stage. Additionally, the composite interval mapping method was used for QTL mapping of drought resistance coefficients for the abovementioned traits. [Results] Sixteen significant QTLs were detected on 13 chromosomes in the F2:3 population. We detected five QTLs for plant height, one for the number of leaves, three for chlorophyll content, three for leaf malondialdehyde content, and four for proline content. The qSHDC-19-1, qSHDC-19-2, qSLNDC-5-1, qMDADC-24-1, and qMDADC-24-2 alleles were derived from G. tomentosum, and explained 9.4%-25.8% of the phenotypic variation. [Conclusion] These results may help elucidate the genetic basis of drought tolerance in cotton, and may be important for breeding programs involved in marker-assisted development of new cultivars with improved tolerance to drought stress.
[Objective] The objective of this study was to reveal the mechanism underlying potassium (K+) uptake in cotton. [Method] We used virus-induced gene silencing to examine the functions of the K+ channel (GhAKT1) and K+ transporter (GhKT2) genes in two cotton cultivars, namely Guoxin 3 and CCRI 41. [Results] The silencing of these two genes decreased K+ levels by about 15% and more than 25% at low (0.1 mmol·L-1) and sufficient (2.5 mmol·L-1) K+ concentrations, respectively. Regarding the parameters affecting K+ uptake kinetics, the silencing of GhAKT1 and GhKT2 decreased Imax (per root dry weight), but increased Km to varying levels. Additionally, the results of pharmacological tests indicated that the contribution of a high-affinity K+ uptake system to the absorption of K+ is greater than that of K+ channels in cotton at external K+ concentrations below 250 μmol·L-1. Furthermore, GhAKT1 activity may be sensitive to NH4+. [Conclusion] These results suggest that GhAKT1 and GhKT2 are associated with low- and high-affinity K+ uptake in cotton. These genes may be useful for increasing cotton K+ contents.
[Objective] The purpose of this investigation was to systematically study the standard techniques used to identify and evaluate Verticillium wilt resistance in cotton to solve the traditional methods or develop a new one. [Method] Fourteen nationally recommended cotton varieties in 2014 were used to systematically study the importance of inoculum concentration, sample number, disease level, and evaluation method. We also used the relative area under the disease progress curve and the related disease index at the disease peak to evaluate Verticillium wilt resistance in cotton in two consecutive years. [Results] The ideal concentrations for plot and column inoculations were 60 g·m-2 and 10 g·m-1 based on the real-time monitoring of the disease index of susceptible variety (Jimian 11) plants. To improve the reliability of the data, the minimum number of investigated plants was set as 50 according to the divergence rate analysis. The new disease grading standard related to cotton yield was based on the foliar disease rate and included the following levels: 0 level (0%), first level (1%-33%), second level (34%-66%), third level (67%-99%), and fourth level (100%). And disease resistance evaluation results in two consecutive years showed applying the relative area under the disease progress curve produced 100% consistent results between years. [Conclusion] The present study provides potentially useful data for improving the techniques used to evaluate cotton variety disease resistance, and may stimulate the breeding, authorization and promotion of new cotton varieties.
[Objective] Phosphorus is one of the three most essential macronutrients required by plants, and is important for plant growth and development. Phosphate (Pi) transporter proteins in the Pht1 family play important roles in Pi uptake and translocation in plants. However, few systematic studies have been performed on this topic. In this study, we aimed to identify the Pht1 family members in the upland cotton genome and analyze their expression patterns. [Method] The gene structure, chromosomal localization, gene duplication, and expression of Pht1 family members in upland cotton, as well as the structure of the encoded protein, were analyzed using bioinformatics methods. [Results] (1) A total of 17 GhPT genes were identified in the upland cotton genome, with eight and nine GhPT genes distributed on the A and D subgenomes, respectively. (2) The GhPT protein sequences were highly similar, and included 12 transmembrane regions. (3) The GhPT proteins were divided into Groups I and II based on phylogenetic analyses. Most GhPT genes within the same group had similar exon and intron organizations. (4) The chromosomal distribution pattern revealed that GhPT genes were unevenly distributed on five chromosomes of the A and D subgenomes. Segmental and tandem duplications were the major contributors to the increase in the number of GhPT genes in upland cotton. (5) The GhPT expression patterns revealed that GhPT6 and GhPT14 were highly expressed in roots. Moreover, the expression levels of these genes were up-regulated under low phosphorus and low potassium conditions. [Conclusion] These results may help to elucidate the functions of GhPT genes and the molecular mechanisms underlying the cross-talk among ion signals in plants.
[Objective] 1,1-dimethyl-piperidinium chloride (DPC) has been widely used for cotton (Gossypium hirsutum) production. Fortified DPC (DPC+) is a slowly released emulsion (i.e., oil and DPC prepared in water) that is more active than normal soluble DPC powder. The role of DPC+ in cotton treatments was determined using different amount of water provided in a drip irrigation system. The results may be useful for improving chemical toppings involving DPC+. [Method] Cotton variety Xinluzao 53 plants were grown using a drip irrigation system (i.e., 3000, 4800, or 6600 m3·hm-2), and DPC+ (i.e., 450, 750, or 1050 mL·hm-2) was applied in early July with manual toppings. Agronomic traits, some physiological traits, yield, and fiber quality were analyzed. [Results] Plant height and the number of fruit branches per plant decreased with increasing DPC+ doses. The plants treated with low (450 mL·hm-2), moderate (750 mL·hm-2), and high (1050 mL·hm-2) DPC+ doses were 9.4, 6.2, and 2.2 cm taller than the control plants, respectively. Additionally, the number of fruit branches per plant increased by 4.8, 3.9 and 2.6, respectively. The moderate irrigation treatment (i.e., 4800 m3·hm-2) resulted in the highest yields, which were about 20% and 5% greater than that of low (3000 m3·hm-2) and high irrigation (6600 m3·hm-2) treatments, respectively. Regarding yield, there was a significant interaction between the amount of water and DPC+ dose. The low, moderate, and high DPC+ doses produced the highest yields with low, moderate, and high irrigation treatments, respectively. The low DPC+ dose produced greater yields with the lowest irrigation treatment mainly because of the relatively high above-ground plant biomass. The high yield obtained with a high DPC+ dose and high irrigation treatment was associated with the large proportion of dry mass in plant reproductive parts. The moderate DPC+ dose and irrigation treatment produced the highest yield among all treatments because of ideal dry mass accumulation and plant biomass distribution. [Conclusion] Manual toppings of DPC+ may be replaced by the application of an ideal combination of DPC+ and water in a drip irrigation system.
[Objective] The study objective was to improve the accuracy of root length density measurements for a wheat and cotton intercropping system or monocultures using a method that combines field root auger sampling and computer image analysis. [Method] Following field root auger sampling, root length density was measured using an imaging method (DT-SCAN image analysis software) or a ruler (conventional measurement method). The accuracy of the imaging method was assessed using 3423 pairs of root length density data collected from 2002 to 2013. The consistency between the imaging method data (simulated data) and ruler measurements was assessed according to the root mean square error. [Results] The results of the imaging method were correlated with the ruler measurements, although the imaging method was more accurate. Subsequent analyses revealed that in the wheat and cotton intercropping system or monocultures, the accuracy of the imaging method was higher for wheat monocultures than cotton monocultures. Additionally, the accuracy was higher for cotton monocultures than the wheat and cotton intercropping system. Furthermore, the accuracy of the imaging method improved as increasing depths. For the intercropping of wheat and cotton, the accuracy of the imaging method improved from wheat to cotton rows. More accurate data showed: the imaging method accuracy of the wheat rows were higher than the between-wheat rows for wheat monocultures, and that of the between-cotton rows were higher than the cotton rows in cotton monocultures. Regarding the influence of cotton growth periods, the imaging method data for cotton monocultures were more accurate than the data for the wheat and cotton intercropping system before flowering. However, the opposite trend was observed after flowering. [Conclusion] The accuracy of the root length density measurements for the wheat and cotton intercropping system or monocultures increased by combining field root auger samples and an imaging method. This improved method is inexpensive, fast, and enables more accurate analyses of fine lateral roots.
[Objective] This article aims to study how cotton nitrogen metabolism changes with the density and sowing date change in simplified cultivation fields. [Method] The distribution of nitrate reductase (NR) activity was measured in cotton’s main leaves and roots of Huamian 3109 using a field split-plot design with sowing date (S1: 30th May and S2: 14th June) as the main plot and density (plant·m-2) (D1: 7.5, D2: 9.0 and D3: 10.5) as the subplot. [Results] 1) The sowing date and planting density had significant effects on the average NR activities in the main leaves and roots. No difference was observed in the average NR activity distributions in leaves and roots after the sowing date was delayed in the squaring period, whereas an increase in the plant density had an inhibitory effect on the average NR activity in leaves. However, during the first and peak bloom periods, delayed sowing dates significantly decreased the average NR activity in leaves, whereas the effect of delayed sowing on the average NR activity in the roots was controlled by lateral root NR activity. Increasing the planting density initially improved NR activity and then subsequently decreased it, indicating that delayed sowing promoted under-ground root nitrogen metabolism instead of reducing above-ground leaf nitrogen metabolism. The optimum density increased nitrogen metabolism in leaves and roots. 2) The average NR activity in leaves decreased as the growth period progressed, namely squaring> first bloom> peak bloom, whereas the NR activity in the roots initially rose prior to the first bloom period and then subsequently decreased. 3) During the three periods, the NR activity decreased in the main leaves from the top to the bottom, and fluctuated mainly in the top 1st to 3rd leaf with no significant differences in the remaining leaves lower than the 4th leaf. This implied that the intensity of the nitrogen metabolism in young leaves was higher than in mature leaves, whereas the intensity of the nitrogen metabolism in mature leaves remained constant. [Conclusion] Sowing date for cotton planting in the Yangtze River region (mainly in the Hubei Province) should not be later than 14th June, and the optimum planting density is 9.0 plant·m-2.
[Objective] This study investigated the genetic relationship between wild-type diploid and cultivated allotetraploid cotton species, and explored the origin and evolution of each species. [Method] Genomic in situ hybridization (GISH) was performed on chromosomes of Gossypium hirsutum var. CCRI 16 and G. barbadense var. Xinhai 7 as representative species of wild-type diploid cotton B, E, and F genome species using G. anomalum, G. somalense, and G. longicalyx genomic DNA as probes. [Results] The fluorescent signals were mainly distributed on A sub-genome chromosomes and were accompanied by three pairs of strong GISH-nucleolar organizer regions (NORs), one pair on the A sub-genome chromosomes and two pairs on the D sub-genome chromosomes. GISH-NOR signal intensities and distribution were similar for all diploid D genome gDNA probes. These results indicate that the G. anomalum, G. somalense, and G. longicalyx genome species have a closer genetic relationship with the tetraploid A sub-genome, which is consistent with their geographic distribution, while their 45S rDNA repeat sequences show higher homology with those of the D genome. Using G. sturtianum (C1) and G. bickii (G1) gDNA as probes, fluorescent signals were distributed on all 26 pairs of chromosomes, the A and D sub-genomes were unable to be discriminated. This phenomenon was also observed using the D6 genome species as a probe when three pairs of strong GISH-NOR signals were also detected. These findings suggest that the C and G genomes are highly homologous with the A and D sub-genomes of allotetraploid cotton species, or that they both contain A and D genome components leading to genome heterozygosity. However, their 45S rDNA repeat sequences appear to belong to the D genome type. [Conclusion] These findings provide useful information for cotton hybrid breeding and researches on the origin and evolution of Gossypium species.
The applications received and approved by the General Program, Young Scientists Fund, and the Fund for Underdeveloped Regions of the National Natural Science Foundation from 1995 to 2014 were used to analyze the current status and development trends in cotton genetics and breeding, cultivation, and physiology. They were also used to assess the deficiencies in cotton studies, which may be relevant for future developments in this research area.
