Abstract Enhancing genetic diversity to breed cotton ( Gossypium hirsutum L.) for water‐limited production in the Texas High Plains is one objective of the Texas A&M AgriLife Research breeding program in Lubbock. CA 4008 (Reg. no. GP‐1099, PI 698821) was derived from TX 307 (PI 165390) and 07‐A‐05, an unreleased breeding line. TX 307, wild material of species Gossypium hirsutum , was used as a parent based on performance in hydroponic salinity characterization of 290 accessions conducted at Texas A&M AgriLife Research in Lubbock from 2006 to 2009. Performance testing for yield, fiber quality, and other agronomic properties was conducted at six site‐years from 2014 to 2017 with check cultivars ‘FM 958’ (PI 619096), a high‐yield and fiber quality regional standard, and ‘DP 491’ (PI 618609), which historically produced good yield and quality under water stress in the Texas High Plains. CA 4008 produced similar yield and fiber quality, lower lint percentage, and taller plants across site‐years compared with checks. CA 4008 was tested at 11 locations across the United States in the 2017 Regional Breeder Testing Network and showed low leaf defoliation under Verticillium wilt pressure. In previous studies, CA 4008 had less germination reduction under salinity than 27 of 31 Texas A&M AgriLife Research in Lubbock lines but equal to cultivar ‘FM 989’ (PI 603956). CA 4008 had less root dry weight reduction under salinity in hydroponic studies but equal to FM 989 in shoot and leaves dry weight reduction. CA 4008 is adapted to Texas High Plains stress conditions developed from a wild accession.
ABSTRACT The upland cotton ( Gossypium hirsutum L.) industry in the United States has shifted from a domestic market to an export‐based market that mandates simultaneous improvements of yield and various fiber traits to maintain competitiveness. Fiber elongation (ability to stretch before breaking) is one of the key fiber parameters in determining yarn quality. It is a trait that is largely understudied due to an absence of monetary incentives for growers to produce high‐elongation cotton fibers. Five upland genotypes were selected as representatives of major upland cotton germplasm pools in the United States. These genotypes and their 10 F 1 progenies were grown in College Station, TX, in 2010 and 2011, and fiber properties were tested in a diallel analysis. Overall, general combining ability was greater than specific combining ability for fiber elongation, suggesting the predominance of additive gene action. Two parental lines, cultivar PSC 355 and germplasm line Dever Line 8, were identified as good combiners for fiber elongation when fibers were measured with the High Volume Instrument (HVI) and the Stelometer. A highly significant negative correlation was observed between fiber upper‐half mean length and elongation, whereas a slight negative correlation was observed for elongation and strength. Stelometer and HVI readings for elongation were correlated with r value of 0.69.
Abstract Fusarium oxysporum f. sp. vasinfectum Race 4 (FOV4) causes high seedling mortality in pima cotton ( Gossypium barbadense L.) grown in the western and southwestern U.S. Cotton Belt. The objectives of this study were to analyze the combining abilities and genetic basis of FOV4 resistance in pima cotton using a half‐diallel mating design. Thirty‐six biparental F 3 and F 4 generations were derived from six commercial cultivars and three elite lines and artificially inoculated with FOV4 for screening for FOV4 resistance in four replicated tests, with two tests for each generation. Disease severity rating (DSR) at 28 d after inoculation (DAI) and the area under the disease progress curve (AUDPC) across 7, 14, 21, and 28 DAI were analyzed via Griffing's Method 2 and Hayman's diallel analysis. ‘Pima S‐6’, ‘PHY 76’, and ‘8810’ (resistant parents) were heterogeneous in their responses to FOV4 infections with 20 to 50% disease incidence and mortality rate; and they had significantly lower DSR and AUDPC with negative general combing ability effects compared with the susceptible parents. Variances caused by specific combining ability and nonadditive effects were higher than those caused by additive effects for FOV4 resistance, consistent with the estimates for broad‐sense heritability. The results indicated a predominant nonadditive effect for FOV4 resistance within these genotypes of pima cotton. A minimum of one or two genes was estimated for FOV4 resistance based on Hayman analysis. The results represented the first study applying a diallel analysis to investigate the quantitative genetic basis of FOV4 resistance in pima cotton.
Virus-induced gene silencing (VIGS) offers a powerful approach for functional analysis of individual genes by knocking down their expression. We have adopted this approach to dissect gene functions in cotton resistant to Verticillium wilt, one of the most devastating diseases worldwide. We showed here that highly efficient VIGS was obtained in a cotton breeding line (CA4002) with partial resistance to Verticillium wilt, and GhMKK2 and GhVe1 are required for its resistance to Verticillium wilt. Arabidopsis AtBAK1/SERK3, a central regulator in plant disease resistance, belongs to a subfamily of somatic embryogenesis receptor kinases (SERKs) with five members, AtSERK1 to AtSERK5. Two BAK1 orthologs and one SERK1 ortholog were identified in the cotton genome. Importantly, GhBAK1 is required for CA4002 resistance to Verticillium wilt. Surprisingly, silencing of GhBAK1 is sufficient to trigger cell death accompanied with production of reactive oxygen species in cotton. This result is distinct from Arabidopsis in which AtBAK1 and AtSERK4 play redundant functions in cell death control. Apparently, cotton has only evolved SERK1 and BAK1 whereas AtSERK4/5 are newly evolved genes in Arabidopsis. Our studies indicate the functional importance of BAK1 in Verticillium wilt resistance and suggest the dynamic evolution of SERK family members in different plant species.
A survey of 100 cotton fields selected randomly in 1995 and 1996 was conducted in the High Plains of Texas to determine the incidence and potential severity of Meloidogyne incognita and Thielaviopsis basicola. Information was obtained from producers for each field on their nematicide application rates and fungicide seed treatments. The percent of squares and bolls set was evaluated for 20 plants in each field during late July 1995 and early August 1996. Thielaviopsis basicola was identified in 55% of the fields in 1995 and 73% of the irrigated fields in 1996. Meloidogyne incognita was found in 39% and 43% of the fields in 1995 and 1996, respectively. Both M. incognita and T. basicola were found together in approximately 30% of the fields. The average rate of aldicarb used in 1995 and 1996 was higher when fields were infested with both T. basicola and M. incognita than for fields infested with none or only one of the pathogens. However, there was no relationship between the use of fungicide treatments active against T. basicola and the potential for root necrosis, or presence of either or both pathogens (T. basicola and M. incognita). Aldicarb rates and usage of fungicide seed treatments were chosen by producers before fields were surveyed (i.e., the survey did not influence grower practices). In 1995, but not in 1996, the association of M. incognita and potential root necrosis (based on a bioassay from soil samples) was negatively correlated with the number of squares, percentage of squares set, and percentage of bolls set. The association between M. incognita and T. basicola, or potential severity of root necrosis, could not be correlated with fruit attributes in 1996 under warm spring conditions but was negatively correlated with fruit attributes in 1995 under cool spring conditions.
This study explored the flame resistance and physical properties of two naturally colored cotton fabrics in order to determine their acceptance for passenger vehicle and airplane seat upholstery. The sample included two 306.7 g/m 2 twill fabrics each of Coyote and Buffalo brown. Testing of the fabrics was conducted before and after (a) application of U6P flame-retardant (12.5% and 25%) and (b) drycleaning. Untreated fabrics met requirements of the Motor Vehicle Safety Standard No. 302, while treated fabrics (25% concentration) met the Federal Aviation Airworthiness Standard. Physical strength was reduced by flame-retardant application as well as drycleaning and was reduced in Coyote more than in Buffalo. Naturally colored cotton fabrics were judged to be suitable for upholstery use in passenger vehicles and airplanes. End use will determine physical strength requirements.
Hybrids (F 2 ) of cotton ( Gossypium hirsutum L.) reportedly offer improved seedling vigor, disease tolerance, and yield for this major crop of the Texas High Plains but raise concern about increased fiber property variability. Our objective was to compare fiber variability in the F 2 generation with that in pure lines and in F 1 hybrid cultivars. A four‐parent complete diallel mating system using lines with similar and divergent fiber types resulted in 28 treatments: 4 parents, 12 F 1 hybrids, and 12 F 2 hybrids. The variance (converted to base 10 logarithm) of 10 plants in each treatment was analyzed by a randomized block design analysis of variance with three blocks. Subsets of the treatments (parents, F 1 's, and F 2 's) and orthogonal contrasts (parents vs. F 1 and F 2 , F 1 vs. F 2 ; parents and F 1 vs. F 2 , wide F 1 vs. wide F 2 [fineness]; wide F 1 vs. narrow F 1 , wide F 2 vs. narrow F 2 [fineness]; wide F 1 vs. narrow F 1 , wide F 2 vs. narrow F 2 [length/strength]) were analyzed. When environmental influence is high, strength and standard fineness show more variability in the F 2 than in the F 1 hybrid. The higher variability for strength and standard fineness disappears when environmental influence is minimal; the variability that does occur, both in the F 1 hybrid and in the F 2 hybrid, appears to be a function of original parental variability, especially for fiber fineness or agronomic properties. When original parental variability was low and the strength and standard fineness of the two parents were similar, fiber variability in the F 2 hybrid was not greater than variability on a single plant in any generation.
Thrips (Thysanoptera: Thripidae) are common pests of cotton ( Gossypium spp.) worldwide, typically causing economic damage within the first few weeks after planting of a cotton crop. With the loss of granular aldicarbs and resistance development to other insecticides in recent years, host plant resistance could play an important role in the integrated management of thrips. Two breeding lines originally developed for cold tolerance in the Texas A&M AgriLife Research cotton improvement program at Lubbock, TX, exhibited characteristics associated with thrips tolerance. These G. hirsutum lines, CA 4005 (Reg. No. GP‐1023, PI 681593) and CA 4006 (Reg. No. GP‐1024, PI 681594), are germplasm lines that were subsequently evaluated for potential resistance to thrips feeding injury. Both lines were evaluated in field and greenhouse tests from 2012 to 2014. CA 4005 and CA 4006 consistently displayed greater resistance to thrips feeding injury than the commercial and susceptible checks at the field level. Greenhouse evaluations, however, revealed that these lines are only partially resistant and can be overcome at high thrips densities. Yield potential, high‐volume instrument (HVI) fiber quality, and other agronomic characteristics of CA 4005 and CA 4006 were comparable to the evaluated commercial checks. These germplasm lines exhibited improved thrips resistance and competitive agronomic potential for the Texas High Plains and would be valuable sources of partial thrips resistance in adapted G. hirsutum germplasm.
