Commercial Cotton Cultivars Research Articles

Evaluation of Cotton Cultivars and Breeding Lines for Tolerance to Monosodium Methanearsonate (MSMA) Under Field Conditions

Monosodium methanearsonate (MSMA) is an organic arsenical herbicide used to control weeds such as grasses and nutsedges in Upland cotton (Gossypium hirsutum) production. Transient crop injury, yield reduction, and maturity delays have been observed in commercial Upland cotton. It is unknown if genetic variation in MSMA tolerance in cotton exists. In this field study, seven replicated tests were conducted in the same field to compare MSMA tolerance among 212 commercial cotton cultivars and advanced breeding lines. The tests were sprayed over the top at the 4-true-leaf stage, and seedlings were assessed for crop injury severity on a scale of 0 (no injury) to 5 (death). Significant genotypic variation in MSMA tolerance was detected in three tests, and broad-sense heritability estimates for MSMA tolerance ranged from 0.476 to 0.846 with a mean of 0.712, indicating that most phenotypic variation in MSMA tolerance is heritable. Nine tested G. barbadense genotypes, including seven commercial Pima cultivars and two Sea-Island cotton lines, exhibited minimal crop injury with severity ratings of 0.40 to 0.83 (except for one cultivar with 1.33). Among the remaining 203 Upland cotton genotypes with crop injury ratings ranging from 0.90 to 3.67, five commercial transgenic cultivars and 38 public breeding lines exhibited various levels of MSMA tolerance. The results represent the first study in germplasm evaluation for MSMA tolerance and identify a set of tolerant cotton genotypes that can be selected in cotton production or used to develop new cultivars for commercial cotton production.

‘Braun’: the first russian cotton cultivar with naturally colored fiber

Background. Most commercial cotton cultivars have white fiber. Massive energy and water consumption during the production of fabrics from such fiber generates significant problems, so in recent decades more and more cotton cultivars with naturally colored fiber have appeared in the world. In addition to saving natural resources, such fiber has another advantage: it is lowallergenic. Such fiber is much more expensive on the world market.Materials and methods. The research material was cotton line 7C with light brown fiber, produced by individual selection from the hybrid combination Genetic 34 (Turkmenistan, late-maturity, brown fiber) × C2 8101-73 (k-8112, Albania, early-maturity, white fiber). This line was registered in the State Register for Selection Achievements as the cultivar ‘Braun’ in 2019. The authors of the cultivar were M. Sh. Asfandiyarova, L. P. Podolnaya, A. G. Dubovskaya, and R. K. Tuz. The selection achievement was patented (patent No. 10638). The research was conducted at the Caspian Research Institute of Arid Agriculture (now the Caspian Agrarian Federal Research Center of the RAS). 7C was compared to the white-fiber reference ‘AS-5’ for morphological and agronomic traits in 2013–2018 according to VIR’s guidelines.Results and conclusion. ANOVA analysis showed that cv. ‘Braun’ differed significantly from cv. ‘AS-5’ only in fiber length. However, the 5th type to which the fiber cv. ‘Braun’ belongs is used for the production of fabrics on a large scale. The cultivar’s yield of 2.5–3.0 t/ha is comparable to the reference. Variability of the values of the studied traits in cv. ‘Braun’ over the years was less than in the reference cultivar, attesting to its good adaptation to the Northern Caspian environments. The fiber’s natural color would make the products from such fiber notably more attractive. The estimated cost efficiency of its cultivation showed high profitability – up to 132%.

Isolation and characterization of a new imidazolinone‐tolerant mutant in cotton

AbstractCotton (Gossypium hirsutum L.) cultivars resistant to different herbicides have generated important advances in crop management. There is a wide range of cotton resistance to herbicides, however, commercial imidazolinone (IMI)‐tolerant cultivars are not available. In this research, a new mutation that confers tolerance to IMI in cotton was isolated in the M2 generation after seed mutagenic treatments with sodium azide water solutions. The mode of inheritance of the trait was evaluated in the F2 generation by the application of imazethapyr. The inheritance corresponds to a semidominant type with a 1:2:1 distribution of tolerant/intermediate tolerance/not tolerant, in agreement with that observed in most IMI‐tolerant crops. The IMI‐tolerant line behavior was evaluated in the field nursery after the application of the herbicide in the form of foliar and pre‐emergence sprays. The tolerance level was high in pre‐emergence applications and intermediate in foliar applications compared with the nontolerant genotype, which showed a decrease in fiber yield and quality with both methods of application. After sequencing the acetohydroxyacid synthase (AHAS) gene, a point mutation corresponding to Ala205Val in the AHAS enzyme was found, which suggests it could be responsible for the increased IMI tolerance observed in cotton line SP 4172‐32. Based on results from field assays, it can be concluded that this mutant is a promising experimental line that can be used in obtaining IMI‐ tolerant commercial cotton cultivars.

Soil applied potassium improves productivity and fiber quality of cotton cultivars grown on potassium deficient soils.

Cotton (Gossypium hirsutum L.) is considered as the most valuable cash crop of Pakistan. During last decade, its yield has been declined due to various biotic and abiotic factors. Among abiotic factors, improper use of fertilizers is considered very important specially regarding plant defense and yield. This study was conducted to evaluate the effect of different levels (0, 40, 80 and 120 kg ha-1) of K fertilizer (K2O) on different growth parameters of two commercial Bt cotton cultivars (CYTO-301 and IUB-2013) and one non-Bt cultivar (CYTO-142) during 2016 and 2017. Maximum plant height (124–134 cm), dry matter contents (915–1005%), fruiting point (441–462), bolls per plant (96–139), average boll weight (4.2–5.2 g) and seed cotton yield (2524–3175 kg ha-1) and minimum shedding (43–73%) were observed in plots receiving highest dose of K (120 kg ha-1). The CYTO-103 cultivar was found more responsive to K fertilizer as compared to rest of cultivars (CYTO-142 and IUB-2013). Concluding, ideal dose of fertilizer is very important (120 kg ha-1 in our case) for optimum growth and production of good quality fiber with enhanced seed cotton yield.

Morphological description of a novel synthetic allotetraploid(A1A1G3G3) of Gossypium herbaceum L.and G.nelsonii Fryx. suitable for disease-resistant breeding applications.

Wild species of Gossypium ssp. are an important source of traits for improving commercial cotton cultivars. Previous reports show that Gossypium herbaceum L. and Gossypium nelsonii Fryx. have better disease resistance characteristics than commercial cotton varieties. However, chromosome ploidy and biological isolation make it difficult to hybridize diploid species with the tetraploid Gossypium hirsutum L. We developed a new allotetraploid cotton genotype (A1A1G3G3) using a process of distant hybridization within wild cotton species to create new germplasms. First of all, G. herbaceum and G. nelsonii were used for interspecific hybridization to obtain F1 generation. Afterwards, apical meristems of the F1 diploid cotton plants were treated with colchicine to induce chromosome doubling. The new interspecific F1 hybrid and S1 cotton plants originated from chromosome duplication, were tested via morphological and molecular markers and confirmed their tetraploidy through flowrometric and cytological identification. The S1 tetraploid cotton plants was crossed with a TM-1 line and fertile hybrid offspring were obtained. These S2 offsprings were tested for resistance to Verticillium wilt and demonstrated adequate tolerance to this fungi. The results shows that the new S1 cotton line could be used as parental material for hybridization with G. hirsutum to produce pathogen-resistant cotton hybrids. This new S1 allotetraploid genotype will contributes to the enrichment of Gossypium germplasm resources and is expected to be valuable in polyploidy evolutionary studies.

The relationship between commercial cotton cultivars with varying Meloidogyne incognita resistance genes and yield.

Small plot cotton cultivar trials (12 trials) were conducted from 2016 to 2019 in fields infested with Meloidogyne incognita. Entries in these trials included commercial cultivars with partial and high resistance to M. incognita, as well as cultivars with no known resistance. Different resistant groups were created based on different cotton seed companies and their descriptions of the M. incognita resistant cultivars. Groups were none (susceptible); partial resistance found in Stoneville or Fibermax cultivars (PR-FM/ST); partial resistance found in PhytoGen cultivars (PR-PHY); resistance (unknown gene(s)) in Deltapine cultivars (NR-DP); and highly resistant cultivars homozygous for RK1 and RK2 resistant genes in PhytoGen cultivars (HR-PHY). The highest lint yields using a mixed model analysis were found in the PR-FM/ST (1,396 kg lint/ha), HR-PHY (1,327 kg lint/ha), and PR-PHY (1,314 kg lint/ha) groups. Yield for NR-DP (1,234 kg lint/ha) was not different (p > 0.05) than yield for susceptible cultivars (1,243 kg lint/ha). If the older resistant cultivars from Deltapine and PhytoGen (those with only Roundup Ready® herbicide technology) were removed from the analysis, then HR-PHY yields increased by 133 kg of lint/ha to 1,460 kg lint/ha and NR-DP yields remained approximately unchanged (1,227 kg lint/ha). Newer HR-PHY had much improved yield over the first HR-PHY cultivars. Newer HR-PHY averaged 17% higher yield than the susceptible group. LOG10 (M. incognita eggs/500 cm3 soil + 1) were highest for the susceptible cultivars (3.2), followed by PR-FM/ST (2.6), NR-DP (2.4), PR-PHY (2.1), and lowest with HR-PHY (1.4). The newer HR-PHY cultivars (those with ENLIST® herbicide technology) combine excellent yields (17% higher than susceptible cultivars) with high (96%) suppression of M. incognita.

Genome-wide identification of the Dicer-like family in cotton and analysis of the DCL expression modulation in response to biotic stress in two contrasting commercial cultivars

BackgroundDicer-like proteins (DCLs) are essential players in RNA-silencing mechanisms, acting in gene regulation via miRNAs and in antiviral protection in plants and have also been associated to other biotic and abiotic stresses. To the best of our knowledge, despite being identified in some crops, cotton DCLs haven’t been characterized until now. In this work, we characterized the DCLs of three cotton species and analyzed their expression profiles during biotic stress.ResultsAs main results, 11 DCLs in the allotetraploid cotton Gossypium hirsutum, 7 and 6 in the diploid G. arboreum and G. raimondii, were identified, respectively. Among some DCLs duplications observed in these genomes, the presence of an extra DCL3 in the three cotton species were detected, which haven’t been found in others eudicots. All the DCL types identified by in silico analysis in the allotetraploid cotton genome were able to generate transcripts, as observed by gene expression analysis in distinct tissues. Based on the importance of DCLs for plant defense against virus, responses of cotton DCLs to virus infection and/or herbivore attack using two commercial cotton cultivars (cv.), one susceptible (FM966) and another resistant (DO) to polerovirus CLRDV infection, were analyzed. Both cvs. Responded differently to virus infection. At the inoculation site, the resistant cv. showed strong induction of DCL2a and b, while the susceptible cv. showed a down-regulation of these genes, wherever DCL4 expression was highly induced. A time course of DCL expression in aerial parts far from inoculation site along infection showed that DCL2b and DCL4 were repressed 24 h after infection in the susceptible cotton. As CLRDV is aphid-transmitted, herbivore attack was also checked. Opposite expression pattern of DCL2a and b and DCL4 was observed for R and S cottons, showing that aphid feeding alone may induce DCL modulation.ConclusionsAlmost all the DCLs of the allotetraploide G. hirsutum cotton were found in their relative diploids. Duplications of DCL2 and DCL3 were found in the three species. All four classes of DCL responded to aphid attack and virus infection in G. hirsutum. DCLs initial responses against the virus itself and/or herbivore attack may be contributing towards virus resistance.

Using Normalized Difference Red Edge Index to Assess Maturity in Cotton

Temporal remote sensing measurements of plant growth may give breeders a better understanding of crop growth habits, yield, fiber quality, and maturity in cotton (Gossypium hirsutum L.) genotypes. The objective of this research was to derive a spectral index maturity scoring method based on the normalized difference red edge (NDRE) index. Seasonal NDRE measurements were collected from 2015 to 2017. A growth inflection point (GIP) was generated based on a quadratic fit of the NDRE growth curves for nine commercial cotton cultivars under three irrigation treatments. This GIP was the number of heat units associated with the inflection point of the NDRE values during the season. It was compared with manual measurements of crop maturity, including nodes above white flower (NAWF), percentage open boll (POB), and end‐of‐season plant mapping indices. Each year had environmental conditions that changed growth habits and maturity of the cultivars. Cultivar and irrigation affected maturity in all 3 yr. The GIP correlated with each maturity assessment, with the highest correlations found with NAWF (r2 from 0.38 to 0.88) by irrigation. In most cases, the relationship between NAWF and GIP was not cultivar specific, suggesting that GIP may be used across multiple cotton genotypes within multiple growing environments. The GIP method provides a method to more rapidly and objectively evaluate maturity characteristics of cotton cultivars, as well as the effects of management on these characteristics.

Growth, Physiological and Biochemical Responses of two Greek Cotton Cultivars to Salt Stress and their Impact as Selection Indices for Salt Tolerance

Soil salinity is a major constrain of crop productivity. Upland cotton (Gossypium hirsutum L.) is an important fiber crop worldwide and a major agricultural product in Greece. Two commercial cotton cultivars (‘Hersi’ and ‘ST 318’) were studied to compare their response under non-saline and saline conditions in a greenhouse experiment. Salt stress on plants was imposed by two different approaches: a gradual and an initial acclimatization to a non-lethal NaCl concentration (150 mM). To explore salt stress responses, growth (height of plants, roots, shoots and leaves dry weight, reproductive shoots, Salinity Sensitivity Index), gas exchange (Photosynthetic rate, Stomatal conductance, Transpiration rate and Water Use Efficiency) and biochemical parameters (proline, H2O2 and MDA content), were examined as well as ion homeostasis. ‘Hersi’ had significantly higher dry weight of roots, shoots and leaves, lower salinity sensitivity index of roots compared to ‘ST 318’. In this regard, it appears that ‘Hersi’ cultivar performed better than ‘ST 318’ to increased salinity conditions, due to better control of gas exchange parameters and K+/Na+ homeostasis as well as better membrane integrity. Furthermore, the gradual acclimatization to the 150 mM NaCl concentration had a milder effect on both cultivars compared to the initial acclimatization.
 
 *********
 In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
 *********

ОСОБЕННОСТИ СТРУКТУРЫ КОРРЕЛЯЦИЙ У ЛИНИЙ ПРИЗНАКОВОЙ КОЛЛЕКЦИИ ХЛОПЧАТНИКА С ЕСТЕСТВЕННОЙ ОКРАСКОЙ ВОЛОКНА

Background . The overwhelming majority of commercial cotton cultivars have white fiber. Production of fabrics from such fiber has some disadvantages, therefore an increasing number of genotypes of cotton with the naturally colored fiber is being created around the world in the last decades. An investigation of correlations between different traits makes it possible to reveal the degree of influence of fiber color on structural and agronomic characters, and determine the possibility of creating varieties with naturally colored fiber for profitable cultivation in the north of the Astrakhan Province. Material and methods . Fourteen early lines of upland cotton (Gossypium hirsutum L.) from the trait-specific collection, which have naturally colored fiber, were studied in the north of the Astrakhan Province at the Caspian Research Institute of Arid Agriculture (CRIAA). The study employed the techniques developed at VIR and took into account productivity elements and agronomic traits. The lines were created at the Prikumskaya Experiment and Breeding Station of the Stavropol Agricultural Research Institute (Budennovsk) and CRIAA on the basis of hybrids between Turkmen varieties with brown and green fiber and accessions of early white fiber cotton from Albania and Italy. Two lines had beige fiber, 6 light brown, and 6 green. Microsoft Excel 10 was used in the work. Results and Discussion . The analysis of genotypic correlations showed that due to the insufficiency of the total effective temperatures in 2013, no significant links of colored fiber with other signs were discovered. All the correlations were typical for cotton plants. In the more favorable conditions of 2014, the variability of quantitative traits increased and the correlations that were absent in the previous year were revealed. The negative correlation of fiber color with the first generative branch height (r = -0.53), and positive with the fiber yield (r = 0.57) indicate that the lines with brown fiber have a lower height of fruiting branches development (and potentially a shorter growing season) and a larger yield of fiber. By their characteristics, they approach the industrial white fiber cultivars. These results show that the creation of a cultivar with brown fiber in the near future in Russia is quite possible.

Estimations of fibre trait stability and type of inheritance in cotton

Traits affecting fibre quality were evaluated in a multi-location environmental experiment. Four main cotton regions in Greece were selected as different environments. Five commercial cotton cultivars were used for evaluation of 10 fibre quality traits. Each cultivar was sown in 10 different fields in each region. Environmental fluctuations within regions affected each quality trait differently showing a different degree of inheritance. Four traits showed the lowest stability index values indicating quantitative inheritance, further four traits with intermediate values indicated determination by a few genes, while the more stable and thus with qualitative inheritance traits were considered to indicate fibre maturity and uniformity. The mean estimation of stability in multi-location experiments was found the same as in multi-genotype evaluation. Two cultivars (Elsa and Celia) were found to be more stable across the Greek environments and two regions favoured stability for almost all traits. Correlations between regions were high and the same was found between genotypes.

History and Progress in Cotton Breeding, Genetics, and Genomics in New Mexico

The New Mexico Cotton Breeding Program was established in 1926 and has been led by five generations of breeders. The program has released 37 Acala 1517 and one short-staple Upland cotton (Gossypium hirsutum L.) cultivars and numerous germplasm lines. Two Sea-Island G. barbadense L. cultivars have been released for production in the Mesilla Valley, NM. New Mexico germplasm has contributed to the development of 45% of the commercial cotton cultivars including almost all Acala cultivars in California, and has contributed to the improvement in fiber length and strength in U.S. cottons. Many Acala 1517 cultivars are tolerant or resistant to Verticillium wilt and bacterial blight. The recent releases include three transgenic Acala 1517 cultivars, one conventional and two glandless cultivars. The current research program focuses on fiber and seed quality (glandless) to develop elite germplasm with high yields and superior fiber quality and with resistance to Verticillium and Fusarium wilt, thrips, bacterial blight, leaf spot, cotton rust, and tolerance to drought and salinity. Upland × Pima introgression and development of the hybrid seed production system based on cytoplasmic male sterility and the haploid-producing system based on semigamy are also important aspects of the program. Extensive applications of genomic tools and approaches in the program include DNA marker and population development, linkage map construction, and quantitative trait locus mapping. In recent years, reduction in funding and lack of institutional support has hampered the program in delivering solutions to challenging issues such as Fusarium wilt race 4 faced by the cotton farmer.

Correlations between Cotton Characteristics in Greek Multi-environments

Correlations of data provided by AFIS and HVI were performed under a multi-location evaluation of cotton fiber characteristics in the Greek environment. Four main cotton-production Greek regions were selected and the five most cultivated commercial upland cotton (Gossypium hirsutum L.) cultivars were used for evaluation of fiber length and short fiber characteristics by AFIS and HVI instruments. Each cultivar was sown in 16 fields and 80 fields in total were used for all cultivars. Both HVI and AFIS gave reliable data concerning fiber length and short fiber estimations. High positive and statistically significant correlations between the two instruments were found indicating the similarity of final measurements. Fiber length estimations can be performed with higher accuracy than short fiber estimations, because CV values were lower for both instruments. HVI and AFIS showed different advantages in estimating fiber length and short fiber characteristics. Measurements of AFIS on fiber length had a smaller range between maximum and minimum values, but HVI showed lower CV% which is more useful for breeders, since it may indicate gene fixation that ensures easier breeding procedure. For short fibers, AFIS also showed a smaller range between maximum and minimum values and HVI showed lower CV%. Graphical comparisons between HVI and AFIS measurements for fiber length and short fibers showed that HVI had a more pattern with lower fluctuations than AFIS.

Genotype by Environment Interactions on Cotton Fiber Traits and Their Implications on Variety Recommendation

The objective of this study was to evaluate cotton fiber quality traits across diverse environments. This could lead to the selection of the best environment for cotton cultivations and the best adapted commercial cultivars. For this reason four main cotton regions were chosen as different environments: Thessaly, Thrace, Macedonia and Sterea Ellas. Five of the most commercial upland cotton cultivars (DP332, DP377, ST402, CELIA and ELSA) were used for evaluation of their fiber quality traits. Each cultivar was sown in 10 different fields (in order to exploit and evaluate different soil types) in each of the above mentioned regions and (in total) 200 fields were used in total. Four samples from each field were collected in order to analyze fiber quality traits: micronaire, maturity index (%), fiber length as the upper half mean length (mm), fiber strength (gram/tex), uniformity index (%), fiber elongation, short fiber index, yellowness (+b), reflectance index (Rd).Cultivation regions must also be selected in a way that they could promote fiber traits, in order to ensure the highest fiber quality. Cotton fiber quality traits were affected differently from environmental fluctuations, showing that the ranking of cultivars according to environmental fluctuations is important, if proper breeding methods should be applied. Each trait is affected differently by environmental fluctuations and requires precise knowledge of the degree of inheritance i.e., as to how much qualitative or quantitative is the trait, in order to choose and apply the proper breeding method.

Morphogenesis in Tissue Culture of Local Kazakh Cotton Varieties

Callus was initiated from hypocotyl and cotyledon explants of seven of commercial Kazakh cotton cultivars on MS medium supplemented with 0,1 mg L-1 2,4-D and 0,5 mg L-1 kinetin. The percentage of callus formation ranged from 64,0 to 91,0% for cotyledons and from 72 to 90% for hypocotyls. Study of morphological heterogeneity peculiarities of metamorphosis and histological structure of calli of cotton allowed to identifying seven tissues types and selecting the morphologically stable and perspective callus type for embryogenesis. Significant differences between the calli types of cotton were found by histological and morphological comparative analysis.

Stress Responses of Commercial Cotton Cultivars to Reduced Irrigation at Flowering and Maximization of Yields under Sub-Optimal Subsurface Drip Irrigation

The gradual depletion of the Ogallala Aquifer in the Southern High Plains of Texas has resulted in reduced well capacities for cotton (Gossypium spp.) irrigation. This study investigated cotton cultivar responses to reduced irrigation from flowering to harvest (2013); and then evaluated season long water deficits and the impact of the timing and amount of irrigation (2014). In 2013, field-grown cotton irrigated with 5 mm per day irrigation showed relatively low stress levels as exemplified by efficiency of quantum yield values between 0.17 and 0.23. Reducing irrigation levels from 5 mm per day to 2.5 mm per day at flowering produced a range of stress levels of Fv/Fm from 0.28 to 0.54. In 2014, four of the commercial cultivars were grown in replicated plots receiving either 2.5 mm of irrigation per day or 17.5 mm of irrigation once a week. Cultivar differences in plant stress were detected for the daily and weekly irrigation strategies. Changes in plant size, boll production, and timing of cutout were observed. FM 2484B2F and Phytogen 72 exhibited no yield differences between the irrigation regimes, while All-Tex Edge and Phytogen 367 showed yield decreases (20% and 25%) under the 2.5 mm daily irrigation regime. Alteration of the timing for the limited irrigation can impact existing stress sensitivities by reducing stress levels and increasing yields.

Silver nitrate promotes high-frequency multiple shoot regeneration in cotton (Gossypium hirsutum L.) by inhibiting ethylene production and phenolic secretion

The regeneration frequency of cotton (Gossypium spp.) is greatly influenced by its genetic makeup and recalcitrant nature. In particular, phenolic secretion is a major problem in cotton tissue culture. The present study was carried out to develop a rapid and efficient in vitro regeneration method, without phenolic secretion, from cotyledonary node explants of cotton. Multiple shoot induction was achieved after 3 wk of culture on MSB5 medium supplemented with N6-benzyl adenine (BA), kinetin (KN), thidiazuron (TDZ) (each tested at 0.5–3.0 mg L−1), Pluronic F-68 (0.1–0.6% [w/v]), or silver nitrate (AgNO3; 0.5–3.0 mg L−1). AgNO3 at 2 mg L−1 produced the greatest number of shoots (a mean of 22.2 ± 0.21 shoots per cotyledonary node explant), with no phenolic secretion. The induced shoots were healthy with intense green color and multiplied rapidly on the same medium. BA at 2.5 mg L−1 produced 10.3 ± 0.37 shoots/explant with moderate phenolic secretion. Pluronic F-68 at 0.3% produced 7.6 ± 0.28 shoots/explant along with high phenolic secretion. Individual shoots were elongated on MSB5 medium + gibberellic acid (GA3; 0.2 mg L−1; shoot length 7.8 ± 0.31 cm) and rooted on MSB5 medium + α-naphthalene acetic acid (NAA; 0.3 mg L−1; 8.3 ± 0.32 roots/shoot). Rooted plantlets were acclimatized in paper cups inside a plant growth chamber at 25°C and 70% relative humidity with a 70% survival rate. From the present study, AgNO3 was found to be suitable for obtaining a high frequency of multiple shoot production from cotyledonary node explants of cotton without phenolic secretion. The current protocol can be adopted for developing transgenic plants of commercial cotton cultivars through Agrobacterium-mediated genetic transformation.

Field assessment of commercial cotton cultivars for Verticillium wilt resistance and yield

Verticillium wilt is responsible for substantial yield losses in cotton. The use of cultivars with partial resistance to Verticillium wilt is a preferred management strategy. Cotton breeders utilize rating scales based on severity of foliar symptom expression and/or defoliation when making cultivar selections. The objective of this research was to determine the yield relationship with cultivars grouped by both incidence of Verticillium wilt during the boll filling stage, and late season defoliation in fields with a history of Verticillium wilt. Small plot, replicated cultivar trials were conducted over an 11 year period in west Texas. Cultivars were divided into four classes (A–D) based on normalized wilt incidence (NW) and four classes based on normalized defoliation ratings (ND). Classes were determined through a mixed model analysis of cultivars, with T-test comparisons between a partially resistant check (Fibermax 2484B2F) and a susceptible check (Deltapine 0912B2RF). The A and C classes did not differ (P = 0.05) from the partially resistant and susceptible checks, respectively. Classes were used in a mixed model analysis with lint yield. In a model with only NW classes, lint yield decreased significantly as NW increased with least square mean values of 1421, 1385, 1284 and 1204 kg/ha, for classes A, B, C and D, respectively. In a model with both NW and ND classes, the A/A class combination of NW and ND had a significantly (P ≤ 0.05) higher lint yield (1776 kg/ha) than any other combination. NW/ND class combinations of A/B, B/A, B/B, and C/A had intermediate yields, and ND classes of C or D had the lowest yields. Cultivars with both low wilt and defoliation incidences should result in higher yields in fields infested with Verticillium dahliae. Furthermore, these two rating criteria could be used to standardize the process for developing resistant cultivars.

Gossypolhemiquinone, a dimeric sesquiterpenoid identified in cotton (Gossypium)

The report that the cotton leaf perforator, Bucculatrix thurberiella, is one of the few insect herbivores to attack Gossypium thurberi prompted an investigation of the terpenoids present in the leaves of this wild species of cotton. Members of Gossypium produce subepidermal pigment glands in their leaves that contain the dimeric sesquiterpenoid gossypol as well as other biosynthetically related terpenoids. In addition to gossypol, a previously unknown dimeric sesquiterpenoid, gossypolhemiquinone (GHQ), was identified in trace amounts in G. thurberi, a member of the D genome. Other members of the D genome of Gossypium were subsequently found to contain this compound, but GHQ was not detected in commercial cotton cultivars. When fed to Helicoverpa zea in an artificial diet, GHQ delayed days-to-pupation, reduced pupal weights, and survival to adulthood to a lesser or equal extent than gossypol in comparison to the control diet. However, GHQ had a synergistic effect on survival and days-to-pupation when combined with gossypol at the highest dosage tested (0.18%; 15.5:84.5 GHQ:gossypol). Because gossypol exhibits anti-cancer activity, GHQ was also evaluated for its anti-cancer activity against the National Cancer Institute’s 60-Human Tumor Cell Line Screen. Significant inhibitory activity against most of these cell lines was not observed, but the results may offer some promise against leukemia cancer cell lines.

Evaluation of Verticillium wilt resistance in commercial cultivars and advanced breeding lines of cotton

Verticillium wilt (VW), caused by Verticillium dahliae Kleb, is one of the most destructive diseases in cotton (Gossypium spp.). The most efficient and cost-effective method of controlling the disease is the use of resistant cotton cultivars. Most commercial cultivars and elite breeding lines are developed under non-VW conditions and their responses to the disease are currently unknown. This study was conducted to evaluate current commercial cotton cultivars and advanced breeding lines for VW resistance. In 2011–2013, a total of 84 cultivars from major US seed companies, 52 advanced breeding lines from the US public breeding programs, and 87 introgression lines from a cross between Acala 1517-99 × Pima PHY 76 from the New Mexico Cotton Breeding Program, were evaluated for VW resistance in the greenhouse. Cotton cultivars and breeding lines were evaluated in ten separate replicated tests by inoculation with a defoliating-type isolate of V. dahliae. While leaf severity rating and percentages of infected plants, infected leaves and defoliated leaves were found to be significantly and positively correlated with one another, leaf severity rating and percentage of infected leaves were best choices because of their relatively low coefficients of variation and higher resolutions to differentiate resistant genotypes from susceptible ones. The heritabilities for the VW resistance traits ranged from 0.58 to 0.80 with an average of 0.67, indicating that variation in VW resistance is predominantly due to genetic factors. Of the 223 commercial cultivars and advanced lines, six Upland cultivars (FM 9160B2F, FM 9170 B2F, NG 4010 B2RF, Nitro 44 B2RF, DP 1219 B2RF, and ST 4288 B2F), five advanced lines (Ark 0403-3, MD 10-5, MD 25ne, NC11AZ01, and PD 0504), two introgression lines from Upland × Pima (NM11Q1157 and 08N1618), and four Pima cultivars (COBALT, DP 357, PHY 800, and PHY 830) had higher levels of resistance to VW. The resistance shown by most of these cultivars in the greenhouse was consistent with their performance in previous field tests. Based on the initial VW resistance, 19 highly or moderately resistant genotypes were chosen for re-evaluation and 30 genotypes were also assessed more than once for VW resistance in different tests, most of which had concordant performance. These cultivars and advanced lines should be useful resources to improve VW resistance in cotton breeding.