Thrips are major early season insect pests that cause significant economic damage in Upland cotton in the U.S. Development and deployment of resistant cultivars is the most effective and ecologically sustainable means of reducing thrips damage in cotton. Interspecific hybridization and backcrossing were performed to introgress thrips resistance from Pima cotton (Gossypium barbadense L.) accession Coastland 320 into Upland cotton (Gossypium hirsutum L.) cultivars Acala Maxxa (AM) and Fiber Max 966 (FM966). Backcross populations were screened for thrips resistance in thrips screening summer field nurseries in North Carolina. Thirty-two BC2F2 plants with thrips resistance were identified and backcrossed further to develop BC3F2 plants. Eleven AM derived BC2F2 resistant plants and 21 FM966 derived BC2F2 resistant plants were genotyped using CottonSNP63K array to identify the Pima chromatin in the introgression lines (ILs). In the ILs, introgressed Pima chromatin was detected on chromosomes A01, A08, A09, A10, A11, D10, D11, D12, and D13. Of these, four ILs, two each in AM and FM966 background, showed overlapped introgressed Pima chromatin on chromosomes A10 and D11. Further, four introgression lines, two each in AM and FM966 background, shared a common Pima introgression on chromosome D13. Characterization of thrips species in the screening nursery showed that predominant thrips species were tobacco thrips (Frankliniella fusca (Hinds)) followed by western flower thrips (Frankliniella occidentalis (Pergande)). The identified ILs with thrips resistance should be a useful source of genetic variability for developing Upland cotton cultivars with pest resistance.

Thrips are major early season insect pests that cause significant economic damage in Upland cotton in the U.S. Development and deployment of resistant cultivars is the most effective and ecologically sustainable means of reducing thrips damage in cotton. Interspecific hybridization and backcrossing were performed to introgress thrips resistance from Pima cotton ( Gossypium barbadense L.) accession Coastland 320 into Upland cotton ( Gossypium hirsutum L.) cultivars Acala Maxxa (AM) and Fiber Max 966 (FM966). Backcross populations were screened for thrips resistance in thrips screening summer field nurseries in North Carolina. Thirty-two BC2F2 plants with thrips resistance were identified and back- crossed further to develop BC3F2 plants. Eleven AM derived BC2F2 resistant plants and 21 FM966 derived BC2F2 resistant plants were genotyped using CottonSNP63K array to identify the Pima chromatin in the introgression lines (ILs). In the ILs, introgressed Pima chromatin was detected on chromosomes A01, A08, A09, A10, A11, D10, D11, D12, and D13. Of these, four ILs, two each in AM and FM966 background, showed overlapped introgressed Pima chromatin on chromosomes A10 and D11. Further, four introgression lines, two each in AM and FM966 background, shared a common Pima introgression on chromosome D13. Characterization of thrips species in the screening nursery showed that predominant thrips species were tobacco thrips ( Frankliniella fusca (Hinds)) followed by western flower thrips ( Frankliniella occidentalis (Pergande)). The identified ILs with thrips resistance should be a useful source of genetic variability for developing Upland cotton cultivars with pest resistance.

Two conventional upland cotton (Gossypium hirsutum L.) germplasm lines, NC18-05 (Reg. no. GP-1082, PI 697272) and NC18-06 (Reg. no. GP-1083, PI 697273), were developed by the Department of Crop and Soil Sciences at North Carolina State University. The lines were bred for fiber elongation within yield-competitive phenotypes. The two lines were derived from a randomly mated population using multiple parental lines. Both NC18-05 and NC18-06 produced equivalent or higher lint than commercial cultivars 'DP393', 'SG747', and 'UA48' during 2 yr in Clayton, NC. Germplasm line NC18-05 produced 1507.2 kg ha(-1) of lint, which was 36.2% higher than DP393 and 29.4% higher than UA48 (p < .05). Germplasm line NC18-06 produced 1428.6 kg ha(-1) of lint, which was 29.1% higher than DP393 and 22.6% higher than UA48 (p < .05). However, neither line yielded more lint per hectare than SG747 or the average of the parental lines (p > .05). Both NC18-05 and NC18-06 exhibited equal or higher fiber elongation values (6.0-49.2%) than the commercial cultivar controls. These two lines had higher lint percentages than UA48 (p < .05). NC18-06 also demonstrated stronger fiber than DP393 and SG747 (p < .05). These two germplasm lines offer breeders a new source of exceptional fiber elongation before break within a high-yielding background.

Private and public cotton breeders in the U.S.A. make around 100 genetic combinations annually. In the first segregating generation (F2), an average of 1000 plants are examined. This number then doubles in the next generation. With cotton having 52 chromosomes, are 1000 F2 plants sufficient to begin selection? Will there be a great probability that a transgressive segregate is identified? Is linkage so tight that small numbers of progeny is sufficient or does that dictate very large numbers of progeny? In other words, is the current approach of making large numbers of genetic combinations with few progeny per cross the most efficient breeding method for upland cotton? If we assume that we have information on the breeding value of the parents, e.g. yield performance, then we may make fewer genetic combinations and look at larger progeny numbers. If we assume we have no information on breeding value then we may want to make more crosses and look at fewer progeny per cross. The probability of producing a transgressive segregate is proportional to the number of loci involved, linkage, and crossing over rates. The data suggests that populations much larger than 1000 F2 plants are required or that selection begin in the F3 or later generation when the population number can be expanded and homogeneity

Four upland cotton (Gossypium hirsutum L.) lines, NC18‐07 (Reg. no. GP‐1052, PI 690767), NC18‐08 (Reg. no. GP‐1053, PI 690768), NC18‐09 (Reg. no. GP‐1054, PI 690769), and NC18‐10 (Reg. no. GP‐1055, PI 690770), were developed by the Department of Crop and Soil Sciences at North Carolina State University. The four upland cotton lines have improved yield production and some good fiber quality traits. All four lines were derived from a random mated population using multiple parental lines. These four lines were compared with commercial check cultivars ‘DP393’, ‘Sure‐Grow 747’, and ‘UA48’ over 2 yr in Clayton, NC. NC18‐07 produced 7.6 to 34.2% greater lint yields than that of the checks and had 15.2% greater elongation value than that of UA48. NC18‐08 produced 5.9 to 32.1% greater lint yield than the checks. NC18‐09 yielded 2.2 to 27.5% greater lint than checks and showed 44.7 and 22.3% greater elongation values than that of UA48 and parental lines, respectively. Germplasm line NC18‐10 produced 1.0 to 26.0% greater lint yield than the commercial checks and also displayed 26.5 and 7.0% greater elongation values than that of UA48 and parental lines, respectively. These lines could be valuable sources for cotton breeding and programs focusing on improving yield as well as fiber elongation.

Four upland cotton (Gossypium hirsutum L.) germplasm lines, NC18‐11 (Reg. no. GP‐1056, PI 690771), NC18‐12 (Reg. no. GP‐1057, PI 690772), NC18‐13 (Reg. no. GP‐1058, PI 690773), and NC18‐14 (Reg. no. GP‐1059, PI 690774), were developed by the Department of Crop and Soil Sciences at North Carolina State University. These four cotton lines had improved fiber quality traits and exhibited 915.5 to 1180.9 kg ha−1 lint yield. All four lines were derived from a random mated population using multiple parental lines. The four lines were compared with commercial cultivars ‘DP393’, ‘Sure‐Grow 747’, and ‘UA48’ over 2 yr using a replicated randomized complete block design in Clayton, NC. Lines NC18‐11, NC18‐12, and NC18‐13 had significantly (p = 0.05) better micronaire values than the checks and significantly higher strength values (8.3–25.3%) than DP393, Sure‐Grow 747, and the parental lines. These three lines also had significantly (p = 0.05) greater upper half mean length values (4.9–11.6%) than DP393 and Sure‐Grow 747. Germplasm line NC18‐14 had a 15.4 to 62.5% significantly (p = 0.05) higher fiber elongation value than all checks and parental lines and showed 5.0 to 12.8% more lint fraction than the checks. These lines could be additional sources of genetic variability for cotton breeding programs focusing on improving fiber quality traits while still producing more than 900 kg ha−1 of lint.

Three hundred and ninety-one Gossypium hirsutum and 34 Gossypium barbadense accessions were screened for thrips resistance under field conditions at the Upper Coastal Plain Research Station in Rocky Mount, North Carolina in years 2014 and 2015. Visual damage ratings, thrips counts, and seedling dry weights were recorded at 2.5, 3.5, and 4.5 wk after planting, respectively. Population density and thrips arrival times varied between years. Data from the three separate damage scoring dates provided a better estimate of resistance or susceptibility to thrips than ratings from the individual dates over the season. Tobacco thrips [Frankliniella fusca (Hinds) (Thysanoptera: Thripidae)], followed by western flower thrips [Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)], were the dominant thrips species observed in the study. Five resistant G. barbadense accessions and five moderately resistant upland cotton accessions were identified from field evaluations. Greenhouse experiments were conducted in Fall 2015 and Spring 2016 to determine if plant height, growth rate, leaf pubescence, and leaf area were significantly different in resistant and susceptible groups of G. hirsutum and G. barbadense accessions identified from the field screenings. Leaf pubescence and relative growth rate were significantly higher in resistant accessions compared with susceptible accessions in absence of thrips. There was no difference for plant height and leaf area between resistant and susceptible groups. Results suggest thrips-resistant plants have a possible competitive advantage through faster growth and higher trichome density, which limits thrips movement.

Leaf shape is spectacularly diverse. As the primary source of photo-assimilate in major crops, understanding the evolutionary and environmentally induced changes in leaf morphology are critical to improving agricultural productivity. The role of leaf shape in cotton domestication is unique, as breeders have purposefully selected for entire and lobed leaf morphs resulting from a single locus, okra ( L-D 1 ). The okra locus is not only of agricultural importance in cotton ( Gossypium hirsutum L.), but through pioneering chimeric and morphometric studies it has contributed to fundamental knowledge about leaf development. Here we show that the major leaf shapes of cotton at the L-D 1 locus are controlled by a HD-Zip transcription factor most similar to Late Meristem Identity1 (LMI1) gene. The classical okra leaf shape gene has133-bp tandem duplication in the promoter, correlated with elevated expression, while an 8-bp deletion in the third exon of the presumed wild-type normal leaf causes a frame-shifted and truncated coding sequence. Virus-induced gene silencing (VIGS) of this LMI1-like gene in an okra variety was sufficient to induce normal leaf formation. An intermediate leaf shape allele, sub-okra , lacks both the promoter duplication and the exonic deletion. Our results indicate that sub-okra is the ancestral leaf shape of tetraploid cotton and normal is a derived mutant allele that came to predominate and define the leaf shape of cultivated cotton.

Measuring maturity in Upland cotton (Gossypium hirsutum L.) cultivar trials is a simple calculation of percentage of first harvest to total harvest when most trials are harvested twice. This provides a rough estimate of maturity. Today, cotton trials are rarely harvested twice because of the use of synthetic boll-opening agents. Breeding programs in states such as Arkansas and North Carolina have estimated maturity by either visually estimating percentage bolls open or actually counting open and closed (green) bolls. This study was conducted to determine the optimum combination of replicates, years, and locations of data needed to show 1 d difference in maturity between cultivars. Data were used from the Arkansas testing program for years 2005 through 2012 and from North Carolina for years 2007 through 2012. Arkansas program estimates percentage bolls open visually in all replicates and North Carolina program counts number of open and closed bolls in a short section of each plot in two replicates. For the Arkansas method, we would need to collect data from four replicates, 2 yr, and five locations or four replicates, 3 yr, and three locations. For North Carolina we would need 3 yr, four replicates, and three locations; or 3 yr, three replicates, and five locations; or 3 yr, five replicates, and two locations to provide the same level of precision. Single-year data could detect a 2 d difference in maturity using the Arkansas method and a 4 d difference in maturity using the North Carolina method. The Arkansas method is quicker and provides fairly accurate data on maturity and would be the recommended method to follow.

An 18-environment field study was undertaken to observe the mean and coefficient of variation (as a measure of stability) for cotton (Gossypium hirsutum L.) lint yield components in population types that differed for lint yield stability to determine which yield components contributed to yield stability. Hybrids and blends of hybrids (heterozygous populations) were more stable than the parents and blends of parents (homozygous populations) for lint yield. No within-boll yield component showed convincing evidence of differences between population types with respect to stability. Stability observed for bolls/hectare followed the same trend as lint yield in which the heterozygous populations were more stable than homozygous populations. Heterosis for boll production was not consistent across locations and declined with increasing environmental mean. Ultimately, the difference between population types, with respect to yield and stability, was attributed to the heterozygous entries producing more bolls in the low-yielding environments while producing numbers that were similar to the homozygous populations in the high-yielding environments. This reduced the range of lint yield, reduced the variation across locations, and resulted in increased lint yield stability. Manipulating within-boll components might not increase lint yield stability.

There exist four major leaf shape alleles in tetraploid cotton: normal, sub-okra/Sea-Island, okra, and super-okra. This allelic series has long served as a model genetic locus both in cotton and the broader leaf development research community. Over the years, numerous studies have attributed various production advantages to specific leaf shapes. The objective of this study was to provide a comprehensive review of this literature in order to provide a definitive report on the true benefits of these leaf shapes. In addition, a history of the genetic dissection of the major leaf shape locus was compiled. Leaf shape was found to have consistent effects on boll rot resistance, earliness, flowering rate, chemical spray penetration, lint trash, and yield. Reported effects on various insect resistances, photosynthetic rate, water use efficiency, and fiber quality were not consistent across studies. An ideal cotton cultivar would produce normal leaves up until the point canopy closure is obtained and then it would switch over to an open canopy of okra or super okra. Major leaf shapes of Upland cotton are a multiple allelic series of a single incompletely dominant genetic locus L-D1 on chromosome 15-D1 (Chr15). Genetic analysis studies have precisely mapped the major effect leaf shape genes in cotton and deciphered the causal nucleotide and gene expression changes leading to leaf shape phenotypic diversity in cotton. Recent advances in understanding the molecular processes underlying leaf shape phenotypic changes could help open new avenues for developing cotton cultivars with ideal leaf shape and could enhance sustainable and profitable cotton production.

One of the most important functions of agriculture research stations is the conduct of comparative yield performance trials. How data are reported is critical in how that data are used and interpreted. This review paper looks at various aspects of data reporting using surveys and scientific articles on the subject. Surveys covered wheat (Triticum aestivum L.), corn (Zea mays L.), and soybeans (Glycine max (L.) Merr.). Many report data with more significant digits than necessary; the number of digits should be based on the precision of the data. Regarding what statistics to report we recommend reporting a minimum of mean and Least Significant Difference (LSD) choosing a significance level preferably between 0.20 and 0.40. Several studies have shown that individual location data are not as predictive as across location data and should only be reported when a clear interaction is evident. It is critical that multi-location by year and multi-year across locations be reported. There are varied ways that the data are formatted but all are available on websites and in electronic form. We recommend formatting tables to show columns of across locations singleyear, two-year, and three-year data. The common practice of ranking by yield on two-year data is appropriate. Some measurements provide little useful information or can be misleading such as moisture at harvest for small grains or grain sorghum. We hope this review will stimulate discussions on how crop performance data are reported and initiate any needed changes so that the end user will be better

The three principles of experimental design-randomization, replication, and blocking-have been followed routinely in field experiments. This paper addresses issues of blocking in conducting cultivar performance trials. Most agronomists design (block) their trials by considering the slope of the field at most. However, the direction of field variation might not always follow the slope of the field. Blocking in the direction of field operations is advocated. The objective of this study was to compare precision between three years of horizontal blocking with three years of vertical blocking in North Carolina Official Cotton Variety Trials. No significant difference in precision was found between the two blocking arrangements. However, the standard analysis of variance of a randomized complete block design revealed that vertical blocking produced a larger standard error than when the tests were blocked horizontally. Although vertical blocking results in increased spatial distance, the use of a spatial analysis package should mitigate this problem.

Crop performance trials are conducted in nearly every state as part of the land-grant mission. These trials have been conducted for flue-cured tobacco in the southeastern United States since 1954 and continue today. Even though the trials are conducted in a scientific manner, they are subject to variability caused by management and natural causes like diseases and insects. This article looks at the variability of 3 measurements from the North Carolina Official Flue-Cured Tobacco Variety Trials from 1981 through 2001. Yield, grade index, and dollar value per hectare ($/ha) were examined with the use of a procedure developed for other crops. First the relationship between error and mean was established. For these 3 traits there were no relationships between error and mean. A pooled (average) variance was calculated and then a maximum allowable variance was determined by multiplying the pooled variance by 2. Six out of 112 environments had questionable accuracy for yield; there were 7 questionable environmen...

Key message A major leaf shape locus (L) was mapped with molecular markers and genomically targeted to a small region in the D-genome of cotton. By using expression analysis and candidate gene mapping, two LMI1 -like genes are identified as possible candidates for leaf shape trait in cotton.Leaf shape in cotton is an important trait that influences yield, flowering rates, disease resistance, lint trash, and the efficacy of foliar chemical application. The leaves of okra leaf cotton display a significantly enhanced lobing pattern, as well as ectopic outgrowths along the lobe margins when compared with normal leaf cotton. These phenotypes are the hallmark characteristics of mutations in various known modifiers of leaf shape that culminate in the mis/over-expression of Class I KNOX genes. To better understand the molecular and genetic processes underlying leaf shape in cotton, a normal leaf accession (PI607650) was crossed to an okra leaf breeding line (NC05AZ21). An F-2 population of 236 individuals confirmed the incompletely dominant single gene nature of the okra leaf shape trait in Gossypium hirsutum L. Molecular mapping with simple sequence repeat markers localized the leaf shape gene to 5.4 cM interval in the distal region of the short arm of chromosome 15. Orthologous mapping of the closely linked markers with the sequenced diploid D-genome (Gossypium raimondii) tentatively resolved the leaf shape locus to a small genomic region. RT-PCR-based expression analysis and candidate gene mapping indicated that the okra leaf shape gene (L (o) ) in cotton might be an upstream regulator of Class I KNOX genes. The linked molecular markers and delineated genomic region in the sequenced diploid D-genome will assist in the future high-resolution mapping and map-based cloning of the leaf shape gene in cotton.

NC05AZ21 (Reg. No. GP‐966, PI 667659) is an okra‐leaf line and NC05‐11 (Reg. No., GP‐965, PI 667658) is a normal‐leaf line of Upland cotton (Gossypium hirsutum L.). NC05AZ21 was developed from a cross of NC 72 and an unknown okra leaf, red stem line from Louisiana while NC05‐11 was developed from a cross of NC 72 and Fiber Max 989 (FM 989). NC 72 is a normal and smooth leaf line. FM 989 is a commercial, normal‐leaf cultivar. A pedigree breeding method was followed in developing these lines. Both lines were compared with two commercial cultivars across multiple environments for agronomic traits. Line NC05AZ21 was also compared with a commercial okra‐leaf cultivar FM 832 for agronomic performance. NC05AZ21 showed superior lint yield and lint percentage to and comparable fiber length as FM 832. It had a lower lint yield but longer fibers than Deltapine 455BG/RR (DP 455BG/RR) and Stoneville 5327B2RF (ST 5327B2RF) and comparable fiber strength. It has good resistance to Fusarium wilt [caused by Fusarium oxysporum Schlet.f.sp. vasinfectum (Atk.) Snyd. &Hans.] as well. It could be a good source of earliness and Fusarium wilt resistance and perhaps tolerance to boll rot (caused by numerous organisms)—the latter because of its okra‐leaf shape. NC05‐11 had comparable lint yields as DP 451BG/RR and DP 455BG/RR with superior fiber length and strength. It also had good resistance to Fusarium wilt. Both NC05AZ21 and NC05‐11 could prove to be valuable sources of additional genetic variability for cotton breeding programs having an emphasis on improving Fusarium wilt resistance and fiber quality.

During the past 9 yr, a new race of Fusarium (Fusarium oxysporum f. sp. vasinfectum [FOV Race 4]) has increasingly impacted cotton (Gossypium spp.) in the San Joaquin Valley of California. To assess the vulnerability of upland cotton (G. hirsutum L.) in California to FOV disease, elite upland germplasm lines from 13 U.S. public breeding programs across the Cotton Belt and commercial cultivars were evaluated for disease resistance to FOV Races 1 and 4. Ten independent replicated field trials were conducted: three in 2008, four in 2010, and three in 2011. Significant differences (P ≤ 0.05) were observed for disease severity index of leaves, vascular root staining, and plant survival values among the elite germplasm lines in all 3 yr for the levels of resistance–response to FOV Races 1 and 4. Also, significant interactions among germplasm lines, FOV races (1 and 4), and evaluation sites indicated that germplasm lines differed in mechanisms of plant‐defense response for the two FOV races. Selected lines from programs in the states of Alabama, Arkansas, Louisiana, and Mississippi showed at least a moderate level of tolerance to both FOV races; however, several of these lines produced weak and coarse fibers. Based on these evaluations, many of the entries in public breeders’ current elite upland germplasm pools may be more susceptible than expected to some FOV races, and sources of acceptable levels of resistance may be limited when tested under infestation levels that resulted in only 5 to 35% plant survival in susceptible check cultivars.

Upland cotton (Gossypium hirsutum L.) hybrids display commercially useful levels of heterosis for lint yield. Cotton lint yield is primarily a multiplicative product of boll number and lint per boll, both of which can be further dissected into sub-components. Relationships among the yield components are complex where they further interact with the environment. To identify different yield components of hybrid cotton lint yield and their relationship with environment, three cotton varieties, DP51, STV474 and LA887 and, their respective hybrids were evaluated for lint yield components across five environments. Heterosis was observed for lint yield as well as yield components. The relationship between heterosis and mean environmental yield was negative for two hybrid combinations, whereas one hybrid showed increased heterosis from low to high yielding environments. Boll number was the major yield component contributing to lint yield. However, yield components contributing to the change in heterosis from low to high yielding environments were different for the three hybrids. The change in lint yield heterosis across environments was correlated with lint per boll and lint per seed for DP51 × STV474 and LA887 × DP51. Whereas, bolls number and boll retention were the main yield components contributing to higher lint yield heterosis of STV474 × LA887 in low yielding environments. Results also reveal effects of parental entries on lint yield as well as relationship of heterosis and environment.