Lint Fiber Research Articles

Genetic Analysis of Homozygous-Dominant-Surviving Ligon Lintless Recombinants in Cotton ( Gossypium hirsutum L.)

The Ligon lintless-1 mutant (Li 1) mutant discovered by Griffee and Ligon in 1929 is characterized with its short lint fiber, contorted leaf laminae, and a twisted appearance of branches and stems. The Li 1 mutant has never been observed to produce homozygous phenotype Li 1 by selfing since it was introduced in China. From the cross Li 1 × XZ142 FLM, a recombinant with all distorted leaves and short lint fibers was obtained, and there was no segregation in their F 2 progeny. Thus, the mutation was homozygous of Li 1 gene, which was named as Ligon lintless recombinant (Li-R). Three fibreless mutants, XZ142FLM, MD17, and SL1-7-1, were crossed with Li-R to study the allelic relationship between the fibreless mutant genes and Li 1 gene. Segregation of the 4 F 2s derived from Li-R × XZ142FLM, Li-R × TM-1, Li-R × Hai 7124, and Li-R × Li 1 indicated that the segregation of the homozygous-dominant-surviving phenotype of Li-R fit a 2-locus inheritance model. One locus was the dominant Li 1 and another was a novel recessive locus derived from XZ142 FLM, which was named li a . Therefore, the genotype of homozygous-dominant-surviving plant in Li-R is li ali aLi 1Li 1 , and that of homozygous-dominant-leathal plant of Li 1 is Li aLi aLi 1Li 1 . The genotype of XZ142 FLM is li ali ali 1li 1 , and the genotype of the heterozygous Li 1 mutant found in 1929 is Li aLi aLi 1li 1 . Segregation analysis of F 2-derived F 3 families from Li-R × TM-1 revealed that li a is non-allalic to li 3 and n 2 , both genes leading to fibreless seed phenotype.

Genetic basis of variation for lint color, yield, and quality in cotton (Gossypium hirsutum L.)

Colored cotton produces naturally colored lint, which can help reduce the use of toxic dyes in textile. Four naturally colored lint accessions were crossed with eight white lint varieties of Gossypium hirsutum L. to study the genetic basis of variation of lint color, fiber yield, and quality traits. Various shades of lint appeared in the F1 progenies and the inheritance of lint colors appeared to be controlled by dominant genes with varying degrees of dominance. There was also some indication for the involvement of maternal effects in the manifestation of lint colors. Additive and dominance genetic effects were involved in the inheritance of fiber traits, dominance effects being greater. The estimate of narrow sense heritability was very low for seed cotton yield and therefore direct selection for yield would not be effective in isolating superior genotypes. As non‐additive gene effects predominated in the inheritance of most fiber yield and quality characters, the development of colored cotton hybrids and recurrent crossing and selection would be useful for the genetic improvement of colored cottons.

Spatial and Temporal Variability of Available Nutrient in Cotton Field at Flower and Boll Stage and Its Effect on Lint Yield and Fiber Quality

Flower and boll stage is a key period for lint yield and fiber quality. Studying the spatial and temporal variability of available nutrient in cotton field at flower and boll stage can provide theoretical base for exploring the physiological measurements to improve lint yield and fiber quality. The field experiments were carried out in 2004 at application levels of 0,120,240,360,and 480 kg N ha-1(marked N0,N1,N2,N3,N4 respectively) ,185 kg P ha-1 and 118 kg K ha-1 in Anyang and Nanjing,the typical representatives for ecological regions in Yellow River Valley and the middle lower reaches of Yangtze River Valley in China. The results indicated that,in the process of growth,the content of soil alkali-hydrolyzable nitrogen in 0–60 cm soil layers of N0 treatment presented the trend of decreasing firstly and increasing then. While that of other treatments decreased firstly,increased after topdressing,decreased again,and increased after the beginning of boll opening. Soil available phosphorus and available potassium in 0–60 cm soil layers at two experimental locations presented the similar trends of decreasing firstly and increasing then. Soil available nutrient in 0–60 cm soil layers decreased with the deepening of the layer. Soil alkali-hydrolyzable nitrogen and available phosphorus in the same soil layer of N1,N2,N3,and N4 treatments in Nanjing presented the similar decreasing as the horizontal distance to cotton plant increased,and in N0 treatment,there was no significant variation in alkali-hydrolyzable nitrogen and available phosphorus contents. The spatial and temporal variability for soil alkali-hydrolyzable nitrogen was more significant in Nanjing than in Anyang. While for soil available phosphorus,it was more significant in Anyang than in Nanjing. Soil available potassium in 0–60 cm soil layers in Nanjing and in 20–60 cm soil layers in Anyang presented thesimilar decreasing with the increasing of horizontal distance to cotton plant,while that in 0–20 cm soil layers in Anyang increasing. As a result,at the nitrogen application level of 360 kg ha-1 for Anyang and 240 kg ha-1 for Nanjing,yield components were the relatively optimal,yield was the maximum and the fiber quality of length and strength was better. So,in order to increase lint yield and fiber quality,different ecological regions should follow the spatial and temporal variability of soil available nutrient in cotton field at flower and boll stage to confirm the optimal fertilizer level.

Evaluation of chlorophyll fluorescence as a tool for the identification of drought tolerance in upland cotton

Chlorophyll fluorescence (CF) is one tool used by researchers to quantify plant water status during periods of limited water availability. The research reported herein was designed to evaluate a CF-based protocol as a tool for use in cotton, Gossypium spp. breeding programs for the identification of drought tolerant genotypes. Twenty genotypes were selected to represent diverse and distinct US germplasm pools. Replicated tests were performed in Lubbock and College Station, TX in 2006 and 2007. Dryland and irrigated treatments, as main plots, were applied in a randomized complete block design, split to genotypes. CF measurements were taken at mid-bloom and late bloom growth stages. Source leaf tissue was harvested at predawn and subjected to high temperature incubation with CF measurements subsequently taken hourly for 5 h. Drought stressed plants had not mobilized their carbohydrate reserves from their source leaves overnight and thus maintained cell viability and therefore higher CF values throughout the incubation and measurement period with the opposite being true for non-stressed plants. Fiber lint yield and fiber properties were measured for comparison with the CF data. Genotype × treatment effects complicated the classification of genotypic response to drought. Few and inconsistent correlations were found among CF values and lint yield or fiber properties. Data suggested that this procedure provides little potential in selecting plants for drought tolerance when plants are grown under field culture.

Cotton (Gossypium barbadense L.) Yield and Fiber Properties as Affected by Plant Growth Retardants and Plant Density

ABSTRACT Chemicals may be used to reduce plant size in cotton (Gossypium barbadense L.), which can increase cotton yield by allowing an increased number of plants per unit area. Foliar sprays of growth retardants Cycocel and Alar were applied at concentrations of 250, 500, and 750 ppm 105 days after planting (square and boll setting stage) to Egyptian cotton cultivar Giza 75 planted at three plant densities (166,000, 222,000, and 333,000 plant ha−1). The objectives of this two-year study were to determine if growth retardants may be substituted for plant density, and vice versa, and to investigate their effects on yield and fiber properties. Number of opened bolls plant−1, seed-cotton yield plant−1, and earliness increased as plant density decreased in both years, as did seed-cotton and lint yield ha−1 in the second season. In the first year, the intermediate plant density gave the highest yields. Plant density had no significant effect on lint percentage or fiber properties. Both Cycocel and Alar increased the number of opened bolls plant−1, boll weight, seed and lint indices, seed-cotton yield plant−1, and both seed-cotton and lint yield ha−1, but effects were not always significant and response varied for different traits. Neither Cycocel nor Alar affected lint percentage, yield earliness, or fiber properties at any plant density. The interaction of plant density × growth retardant was significant for the number of opened bolls m−2 and plant−1, seed-cotton yield plant−1 and ha−1, and for lint yield ha−1. The lowest plant densities, combined with application of Cycocel or Alar, gave the highest number of opened bolls m−2 and plant−1, seed-cotton yield plant−1 and ha−1, and lint yield ha−1. This implied that the effect of growth retardants on cotton yield depended essentially on the number of plants per unit area or space available to each plant and that applying growth retardants could enhance the effect of low plant density.

Correspondence of Trichome Mutations in Diploid and Tetraploid Cottons

Quantitative variation for leaf trichome number is observed within and among Gossypium species, varying from glabrous to densely pubescent phenotypes. Moreover, economically important cotton lint fibers are modified trichomes. Earlier studies have mapped quantitative trait loci (QTLs) affecting leaf pubescence in Gossypium using allotetraploids. In this study, we mapped genes responsible for leaf trichome density in a diploid A genome cross. We were able to map 3 QTLs affecting leaf pubescence based on trichome counts obtained from young leaves (YL) and mature leaves (ML). When the F(2) progeny were classified as pubescent versus glabrous, their ratio did not deviate significantly from a 3:1 model, suggesting that glabrousness is inherited in a simple Mendelian fashion. The glabrous mutation mapped to linkage group A3 at the position of major QTL YL1 and ML1 and appeared orthologous to the t1 locus of the allotetraploids. Interestingly, a fiber mutation, sma-4(ha), observed in the same F(2) population cosegregated with the glabrous marker, which indicates either close linkage or common genetic control of lint fiber and leaf trichomes. Studies of A genome diploids may help to clarify the genetic control of trichomes and fiber in both diploid and tetraploid cottons.

Meta-analysis of Polyploid Cotton QTL Shows Unequal Contributions of Subgenomes to a Complex Network of Genes and Gene Clusters Implicated in Lint Fiber Development

QTL mapping experiments yield heterogeneous results due to the use of different genotypes, environments, and sampling variation. Compilation of QTL mapping results yields a more complete picture of the genetic control of a trait and reveals patterns in organization of trait variation. A total of 432 QTL mapped in one diploid and 10 tetraploid interspecific cotton populations were aligned using a reference map and depicted in a CMap resource. Early demonstrations that genes from the non-fiber-producing diploid ancestor contribute to tetraploid lint fiber genetics gain further support from multiple populations and environments and advanced-generation studies detecting QTL of small phenotypic effect. Both tetraploid subgenomes contribute QTL at largely non-homeologous locations, suggesting divergent selection acting on many corresponding genes before and/or after polyploid formation. QTL correspondence across studies was only modest, suggesting that additional QTL for the target traits remain to be discovered. Crosses between closely-related genotypes differing by single-gene mutants yield profoundly different QTL landscapes, suggesting that fiber variation involves a complex network of interacting genes. Members of the lint fiber development network appear clustered, with cluster members showing heterogeneous phenotypic effects. Meta-analysis linked to synteny-based and expression-based information provides clues about specific genes and families involved in QTL networks.

Registration of SJ‐U86 Cotton Germplasm Line with High Yield and Excellent Fiber Quality

Cotton germplasm SJ-U86 (Reg. no. GP-868, PI 642414 and NSSL 441398.01), released in California, USA in 2006, was derived from the cross between cultivars FiberMax 958 and SG 248. SJ-U86 has superior lint yield, fibre length and competitive fibre strength under heat stress environments compared to the Acala cottons of California.

Expression Profiling Identifies Genes Expressed Early During Lint Fibre Initiation in Cotton

Cotton fibres are a subset of single epidermal cells that elongate from the seed coat to produce the long cellulose strands or lint used for spinning into yarn. To identify genes that might regulate lint fibre initiation, expression profiles of 0 days post-anthesis (dpa) whole ovules from six reduced fibre or fibreless mutants were compared with wild-type linted cotton using cDNA microarrays. Numerous clones were differentially expressed, but when only those genes that are normally expressed in the ovule outer integument (where fibres develop) were considered, just 13 different cDNA clones were down-regulated in some or all of the mutants. These included: a Myb transcription factor (GhMyb25) similar to the Antirrhinum Myb AmMIXTA, a putative homeodomain protein (related to Arabidopsis ATML1), a cyclin D gene, some previously identified fibre-expressed structural and metabolic genes, such as lipid transfer protein, alpha-expansin and sucrose synthase, as well as some unknown genes. Laser capture microdissection and reverse transcription-PCR were used to show that both the GhMyb25 and the homeodomain gene were predominantly ovule specific and were up-regulated on the day of anthesis in fibre initials relative to adjacent non-fibre ovule epidermal cells. Their spatial and temporal expression pattern therefore coincided with the time and location of fibre initiation. Constitutive overexpression of GhMyb25 in transgenic tobacco resulted in an increase in branched long-stalked leaf trichomes. The involvement of cell cycle genes prompted DNA content measurements that indicated that fibre initials, like leaf trichomes, undergo DNA endoreduplication. Cotton fibre initiation therefore has some parallels with leaf trichome development, although the detailed molecular mechanisms are clearly different.

Genetic mapping and comparative analysis of seven mutants related to seed fiber development in cotton

Mapping of genes that play major roles in cotton fiber development is an important step toward their cloning and manipulation, and provides a test of their relationships (if any) to agriculturally-important QTLs. Seven previously identified fiber mutants, four dominant (Li (1), Li (2), N (1) and Fbl) and three recessive (n (2), sma-4(h (a)), and sma-4(fz)), were genetically mapped in six F(2) populations comprising 124 or more plants each. For those mutants previously assigned to chromosomes by using aneuploids or by linkage to other morphological markers, all map locations were concordant except n (2), which mapped to the homoeolog of the chromosome previously reported. Three mutations with primary effects on fuzz fibers (N (1), Fbl, n (2)) mapped near the likelihood peaks for QTLs that affected lint fiber productivity in the same populations, perhaps suggesting pleiotropic effects on both fiber types. However, only Li (1) mapped within the likelihood interval for 191 previously detected lint fiber QTLs discovered in non-mutant crosses, suggesting that these mutations may occur in genes that played early roles in cotton fiber evolution, and for which new allelic variants are quickly eliminated from improved germplasm. A close positional association between sma-4(h ( a )), two leaf and stem-borne trichome mutants (t (1) , t (2)), and a gene previously implicated in fiber development, sucrose synthase, raises questions about the possibility that these genes may be functionally related. Increasing knowledge of the correspondence of the cotton and Arabidopsis genomes provides several avenues by which genetic dissection of cotton fiber development may be accelerated.

Molecular dissection of interspecific variation between Gossypium hirsutum and G. barbadense (cotton) by a backcross-self approach: II. Fiber fineness

A backcross-self population from a cross between Gossypium hirsutum and G. barbadense was used to dissect the molecular basis of genetic variation governing two parameters reflecting lint fiber fineness and to compare the precision of these two measurements. By applying a detailed restriction fragment length polymorphism (RFLP) map to 3,662 BC(3)F(2) plants from 24 independently derived BC(3) families, we were able to detect 32 and nine quantitative trait loci (QTLs) for fiber fineness and micronaire (MIC), respectively. The discovery of larger numbers of QTLs in this study than previously found in other studies based on F(2) populations grown in favorable environments reflects the ability of the backcross-self design to resolve smaller QTL effects. Although the two measurements differed dramatically in the number of QTLs detected, seven of the nine MIC QTLs were also associated with fiber fineness. This supports other data in suggesting that fiber fineness more accurately reflects the underlying physical properties of cotton fibers and, consequently, is a preferable trait for selection. "Negative transgression," with the majority of BC(3)F(2) families showing average phenotypes that were poorer than that of the inferior parent, suggests that many of the new gene combinations formed by interspecific hybridization are maladaptive and may contribute to the lack of progress in utilizing G. barbadense in conventional breeding programs to improve upland cotton.

Row configuration as a tool for managing rain-fed cotton systems: review and simulation analysis

Rain-fed cotton production can be a significant proportion (average 17%) of the Australian Cotton Industry. One of the management techniques that rain-fed cotton growers have is to modify row configuration. Configurations that have entire rows missing from the sowing configuration are often referred to as ‘skip row’. Skip configurations are used to: increase the amount of soil water available for the crop, which can influence the potential lint yield; reduce the level of variability or risk associated with production; enhance fibre quality; and reduce input costs. Choosing the correct row configuration for a particular environment involves many, often complex, considerations. This paper presents an examination of how rain-fed cotton production in Australia is influenced by row configuration with different management and environmental factors. Data collated from field experiments and the cotton crop simulation model OZCOT, were used to explore the impact of agronomic decisions on potential lint yield and fibre quality and consequent economic benefit. Some key findings were: (i) soil water available at sowing did not increase the advantage of skip row relative to solid configurations; (ii) reduced row spacing (75 cm) did not alter lint yield significantly in skip row crops; (iii) skip row, rain-fed crops show reasonable plasticity in terms of optimum plant spacing within the row (simular to irrigated cotton); (iv) sowing time of rain-fed crops would appear to differ between solid and skip row arrangements; (v) skip row configurations markedly reduce the risk of price discounts due to short fibre or low micronaire and this should be carefully considered in the choice of row configuration; and (vi) skip configurations can also provide some savings in variable costs. In situations where rain-fed cotton sown in solid row configurations is subject to water stress that may affect lint yield or fibre quality, skip row configurations would be a preferential alternative to reduce risk of financial loss.

Members of a new group of chitinase-like genes are expressed preferentially in cotton cells with secondary walls.

Two homologous cotton (Gossypium hirsutum L.) genes, GhCTL1 and GhCTL2, encode members of a new group of chitinase-like proteins (called the GhCTL group) that includes other proteins from two cotton species, Arabidopsis, rice, and pea. Members of the GhCTL group are assigned to family GH19 glycoside hydrolases along with numerous authentic chitinases (http://afmb.cnrs-mrs.fr/CAZY/index.html), but the proteins have novel consensus sequences in two regions that are essential for chitinase activity and that were previously thought to be conserved. Maximum parsimony phylogenetic analyses, as well as Neighbor-Joining distance analyses, of numerous chitinases confirmed that the GhCTL group is distinct. A molecular model of GhCTL2 (based on the three-dimensional structure of a barley chitinase) had changes in the catalytic site that are likely to abolish catalytic activity while retaining potential to bind chitin oligosaccharides. RNA blot analysis showed that members of the GhCTL group had preferential expression during secondary wall deposition in cotton lint fiber. Cotton transformed with a fusion of the GhCTL2 promoter to the beta -d-glucuronidase gene showed preferential reporter gene activity in numerous cells during secondary wall deposition. Together with evidence from other researchers that mutants in an Arabidopsis gene within the GhCTL group are cellulose-deficient with phenotypes indicative of altered primary cell walls, these data suggest that members of the GhCTL group of chitinase-like proteins are essential for cellulose synthesis in primary and secondary cell walls. However, the mechanism by which they act is more likely to involve binding of chitin oligosaccharides than catalysis.

Soil properties, and cotton growth, yield and fibre quality in three cotton-based cropping systems

The effects of three cotton-based cropping systems on soil properties, black root rot severity, and growth of cotton in a Vertisol were evaluated after a series of floods in eastern Australia. The experimental treatments, which had been imposed since 1985, were conventionally and minimum-tilled continuous cotton, and minimum-tilled cotton–wheat rotation. Frequent rainfall and flooding during the winter of 1998 resulted in near saturated soil at spring sowing in October. Although conventional tillage operations were completed before flooding, minimum tillage operations were not possible due to excessive moisture and cotton was sown onto the old beds with no-tillage. Soil specific volume (electrical conductivity of a 1:5 soil:water suspension) EC 1:5 , exchangeable Na content, pH and organic C were determined for the top 0.6 m of the profile in summer 1998 and again in 1999. Organic C in the surface 0.10 m was also evaluated during 1998–2000. Black root rot severity and mycorrhizal fungal colonisation were evaluated at 6 weeks after sowing. Tissue nutrient concentrations were measured in mature cotton plants. Cotton lint yield and fibre quality were evaluated after picking and ginning. In comparison with either minimum- or conventionally tilled continuous cotton, minimum-tilled cotton–wheat rotation had the lowest exchangeable Na content and severity of bacterial black root rot, best surface structure and the highest crop growth, nutrient uptake and lint yields. Subsoil structure was the best with conventionally tilled continuous cotton. The 1998 floods appear to have decreased exchangeable Na and increased soil pH in all treatments. Surface organic C also decreased between 1998 and 2000. Soil structural damage was minimised by avoiding tillage and trafficking in wet conditions. Compared with 1998, average yield decreases in 1999 were of the order of 43%. Cotton lint fibre quality was also poorer in 1999.

Soil properties, and cotton growth, yield and fibre quality in three cotton-based cropping systems

The effects of three cotton-based cropping systems on soil properties, black root rot severity, and growth of cotton in a Vertisol were evaluated after a series of floods in eastern Australia. The experimental treatments, which had been imposed since 1985, were conventionally and minimum-tilled continuous cotton, and minimum-tilled cotton–wheat rotation. Frequent rainfall and flooding during the winter of 1998 resulted in near saturated soil at spring sowing in October. Although conventional tillage operations were completed before flooding, minimum tillage operations were not possible due to excessive moisture and cotton was sown onto the old beds with no-tillage. Soil specific volume (electrical conductivity of a 1:5 soil:water suspension) EC 1:5, exchangeable Na content, pH and organic C were determined for the top 0.6 m of the profile in summer 1998 and again in 1999. Organic C in the surface 0.10 m was also evaluated during 1998–2000. Black root rot severity and mycorrhizal fungal colonisation were evaluated at 6 weeks after sowing. Tissue nutrient concentrations were measured in mature cotton plants. Cotton lint yield and fibre quality were evaluated after picking and ginning. In comparison with either minimum- or conventionally tilled continuous cotton, minimum-tilled cotton–wheat rotation had the lowest exchangeable Na content and severity of bacterial black root rot, best surface structure and the highest crop growth, nutrient uptake and lint yields. Subsoil structure was the best with conventionally tilled continuous cotton. The 1998 floods appear to have decreased exchangeable Na and increased soil pH in all treatments. Surface organic C also decreased between 1998 and 2000. Soil structural damage was minimised by avoiding tillage and trafficking in wet conditions. Compared with 1998, average yield decreases in 1999 were of the order of 43%. Cotton lint fibre quality was also poorer in 1999.

Effects of foliar applied harpin protein on cotton lint yield, fiber quality, and crop maturity*1

Yield-enhancing compounds are among the many inputs used in cotton (Gossypium hirsutum L.) production systems across the United States Cotton Belt. Some of these products, however, have not been adequately tested in field settings and their impact on cotton yield and quality is unknown. Messenger, marketed by the Eden Bioscience Corporation (Bothell, WA), is a new product containing a protein that may stimulate the hypersensitive response of higher plants, resulting in increased yields. The objective of our investigation was to determine if Messenger applications would result in enhanced cotton crop maturity, lint yield or fiber quality. Messenger studies were conducted in Colquitt, Grady, and Tift Counties in South Georgia and at the University of Georgia Coastal Plain Experiment Station (UGA-CPES) in Tifton in 2000. Plot size at each location ranged from 1.2 ha (Grady County) to 0.01 ha (UGA-CPES). Messenger was applied as a foliar treatment at several stages of crop development at each location with either a John Deere (Moline, IL) high clearance sprayer or a CO2 backpack sprayer. Mid- and late-season plant maps at each location revealed no significant differences in crop maturity among the treatments. Lint yields in Colquitt, Grady, and Tift Counties and the UGA-CPES averaged 1159, 941, 1292, and 1654 kg ha− 1, respectively with no significant treatment differences within a location. Likewise, Messenger did not significantly affect fiber properties at any location. *Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the University of Georgia, the U.S. Department of Agriculture, or other cooperating agencies and does not imply its approval to the exclusion of other products or vendors that may also be suitable. Messenger, Eden, and Eden Bioscience are registered trademarks of the Eden Bioscience Corporation.

Performance of cotton F1 hybrids and its relation to the mean yield of advanced bulk generations

The performance of intraspecific (Gossypium hirsutum) and interspecific (G. hirsutum × G. barbadense) F1 cotton hybrids and its correlation with the mean yield of advanced bulk generations was assessed under Greek environmental conditions. For this, 14 intraspecific and five interspecific cotton F1 hybrids were evaluated at two locations (Sindos and Vardates) during the 1985–88 period. In addition, two interspecific hybrids (5, 6), the three best (8, 7, 11) and two among the worst (4, 10) intraspecific F1s and their F2 bulks were also evaluated at Sindos in 1986. This evaluation was repeated in the following years. In each successive year the new generation (up to the F5 bulk) was included.Intraspecific F1 hybrids outyielded the best variety at both locations. Lint yield of the F1 hybrids ranged from 99 to 158% with a mean value of 122%. Useful F1 heterosis (hybrids with higher values than the best check cultivar) was also expressed for boll weight and Verticillium wilt infestation. The latter was more pronounced in hybrids derived from tolerant parents.All F1 interspecific hybrids were dominated by the barbadense phenotype and had its superior fiber lint quality, lower lint percentage, and resistance to Verticillium wilt. In addition, they expressed positive heterosis for lint yield at Sindos and negative at Vardates, compared with the check variety. The frequency of the hirsutum phenotype progressively increased in the F2 through F5 generations, with plant height, boll weight, earliness, fiber quality and wilt tolerance moving toward the hirsutum values.In the F2 generation yield dropped dramatically (>50%) in the interspecific hybrids, whereas in the intraspecific hybrids inbreeding depression was much less and varied from hybrid to hybrid. The good F1s intraspecific hybrids maintained part of their useful heterosis in the F2. From the F3 onwards the yield improved in the interspecific crosses and stabilized around 75% of the yield recorded in the best check variety. In contrast, the highest yielding F1 intraspecific hybrids yielded progressively less in subsequent generations, and in the F5 they produced the same yield as the best cultivar, whereas the yield of the lowest yielding intraspecific hybrids was stabilized around 95% of the yield recorded in the best cultivar. It was concluded that yield of the F1 did not predict the yield of the bulks in the following generations. Yet, the combined performance of the hybrids in the F1 and F2 generation could be a good indicator to identify the most promising populations to be utilized either as F2 hybrids or as a source population for further selection.

Cotton Response to the Rate and Source of Sulfur on a Sandy Coastal Plain Soil

Cotton acreage in the Coastal Plain of the Southeast has increased in recent years. The soils in this region are sandy and typically have a low retention capacity for sulfate S. A 3-yr (1993-1995) field test was conducted in south Alabama on a Lucy loamy sand (loamy, kaolinitic, thermic Arenic Kandiudults) to evaluate the response of cotton (Gossypium hirsutum L.) to the source, rate, and timing of S fertilizer applications. Sulfur was broadcast preplant as either ammonium sulfate, elemental S, potassium sulfate, potassium thiosulfate, or K-Mg-sulfate at rates of 0, 10, 20 and 40 lb S/acre. Additionally, ammonium sulfate was applied at first square to evaluate timing effects. Lint yields were increased each year and they peaked at a rate of approximately 20 lb S/acre on this Lucy Is soil. Averaged across sources, 20 lb S/acre increased lint yields by an average of 21% as compared with the no S check treatment. Lint yields were not affected by time of S application in 1993 or 1995, but a preplant application of S increased yield compared with S applied at first square in 1994. The response to time of S application was attributed to heavy rainfall that was received soon after the first square application of S. Sources of S did not affect lint yield in 1993 or 1995, but ammonium sulfate and K-Mg-sulfate produced slightly higher yields than those of other sources in 1994, an extremely wet growing season. Lint quality, as measured by high volume instrumentation (HVI), was not affected by any S treatment in 1993 or 1994. In 1995, fiber length increased with S rate, but the differences among sources were inconsistent. Results of this test suggest that cotton produced on sandy Coastal Plain soils that are low in S may require annual applications of 20 lb S/acre to ensure high yields. The S should be applied preplant, although delaying application to first square should not limit yields. For lint production, differences among commercial S fertilizer sources should be minimal.

Economic Analysis of the Harvest-Aid Decision for Cotton in West Tennessee

Economic tradeoffs influence producers' decisions in applying a harvest-aid before a once-over or twice-over harvest for cotton (Gossypium, hirsutum L.). This decision may be affected by responses of first harvest yield and quality to the harvest-aid, cotton prices, harvest-aid treatment costs, cotton harvesting and handling costs, and weather between harvests. The objective of this study was to evaluate how these factors influence net revenues (NR) to alternative harvest-aids. Yields and fiber quality data were from a 1992 to 1994 harvest-aid study at Jackson, TN. Tbe study evaluated 12 treatments including commercial defoliants (Folex [S,S,S,tributyl phosphorotrithioate], Dropp [thidiazuron], Harvade [2,3 Dihydro-5 6-Di-methyyl 1,4-Dithiin], and Defol [sodium chlorate]) with and without a boll opener (Prep [ethephon]). Net revenues for the treatments were estimated using North Delta price quotations, harvest-aid costs, harvesting costs, and handling costs. Dropp (0.05 lb a.i./acre) and Prep (1.0 lb a.i./acre) produced the largest positive influence on effective lint price and NR for farmers interested in once-over or twice-over harvest systems. First harvest NR was significantly higher than for no harvest-aid treatment. However, a once-over harvest using this treatment would have to be delayed from the times in this experiment to allow more bolls to open to minimize second harvest NR foregone. Dropp and Prep also produced the largest two harvest NR. The most important factors influencing NR for Dropp and Prep were a low lint trash content, which resulted in a better LEAF and lower price discounts, and higher first harvest yields.

Soil properties, nutrient uptake and crop growth in an irrigated Vertisol after nine years of minimum tillage

The effects of three contrasting tillage / cropping combinations on soil properties, nutrient uptake, growth, and yield of cotton and cowpea during 1993–1994 were evaluated in a trial running since 1985 in a Typic Pellustert (Vertisol) of north-western New South Wales, Australia. The treatments from 1985 to 1993 were: (a) maximum tillage (disc-ploughing to 0.2 m depth, chisel ploughing to 0.3 m depth followed by ridging every year) sown with continuous cotton ( Gossypium hirsutum L.); (b) minimum tillage (planting on ridges retained intact from previous years with soil disturbance being limited to deepening of the furrows with disc-hillers and shallow cultivation on ridge surfaces, if required) with continuous cotton; and (c) a cotton-winter wheat ( Triticum aestivum L.)-summer (bare) fallow-cotton sequence where cotton was sown with minimum tillage and wheat was sown with no-tillage. Soil was sampled to a depth of 0.6 m in August 1993 and May–June 1994. Soil properties evaluated were organic matter fractions, dispersion index, soil resilience (a measure of the self-mulching ability of the soil), plastic limit, soil strength (as cone index), soil shrinkage indices derived from shrinkage curves, exchangeable Ca, Mg, K and Na, pH, nitrate-N and electrical conductivity. Profile water content and water extraction, nutrient uptake, crop vegetative growth, cotton lint yield and fibre quality were also quantified. In comparison with maximum tillage, values of exchangeable Na, ESP and dispersion index were lower with minimum tillage in 1993 and 1994, and nitrate-N, particulate and total organic matter were greater and pH lower in 1994. Soil compaction (evaluated from shrinkage indices) in ridges was in the order minimum tillage / cotton-wheat-fallow-cotton < minimum tillage / continuous cotton < maximum tillage / continuous cotton, whereas subsoil compaction in maximum tilied plots was less than that in minimum tilled plots. In comparison with published data, however, subsoil compaction was large in all treatments. Nonetheless, water extraction during extended drying cycles was deeper and more extensive with minimum tillage and suggests that “by-pass channels” may have played a significant role in determining water extraction patterns at this site. Nutrient concentrations in plant tissues were not significantly affected by tillage / crop combinations. In comparison with maximum tillage, vegetative growth of cotton and cowpea in January and February (the peak of the summer crop growing season), and cotton lint yield were higher, and cotton lint fibre quality was better with minimum tillage. The highest lint yield and value, and the best fibre quality occurred where minimum tillage / cotton-wheat-summer fallow-cotton had been sown in the past.