Cotton Breeding Programs Research Articles

INCREASING GENETIC DIVERSITY OF COTTON BREEDING PROGRAMS IN VENEZUELA

There is a steady increase of demands for textile crops, where cotton is the most popular natural fiber, therefore, it is necessary to exploit cotton genetic resources. In order to develop and improve crop populations, a cotton breeding program requires access to new sources of germplasm. With the objectives to evaluate the productivity of local and introduced genotypes from Syria and Brazil, and to expand the genetic base in the Venezuelan Cotton Breeding Program, 16 genotypes were evaluated at three locations in Venezuela during 2013 and 2014 using a randomized complete block design, with three replications. The traits evaluated were plant height, stem diameter, lint yield, boll weight, number of seed per boll, 100-seed weight, and fiber content. Highly significant differences (P≤0.01) were observed among genotypes, environments and their interaction for all traits, except for lint yield and number of seed per boll across environments. ʻC-2955-25ʼ showed high yield (3514.3 kg.ha-1) but was unstable across environments used in the evaluation. ʻL-2955-13ʼ was stable across the environments, suggesting that it would be a good parent. All the genotypes obtained values of lint percent above of 38%. The Syrians genotypes ʻAleppo-11ʼ and ʻAleppo-90ʼ showed high lint yield and good agronomic performance. Genotypes identified in this study could be used as potential sources of germplasm to be introduced in future breeding programs.

Reference genome sequences of two cultivated allotetraploid cottons, Gossypium hirsutum and Gossypium barbadense

Allotetraploid cotton species (Gossypium hirsutum and Gossypium barbadense) have long been cultivated worldwide for natural renewable textile fibers. The draft genome sequences of both species are available but they are highly fragmented and incomplete1–4. Here we report reference-grade genome assemblies and annotations for G. hirsutum accession Texas Marker-1 (TM-1) and G. barbadense accession 3–79 by integrating single-molecule real-time sequencing, BioNano optical mapping and high-throughput chromosome conformation capture techniques. Compared with previous assembled draft genomes1,3, these genome sequences show considerable improvements in contiguity and completeness for regions with high content of repeats such as centromeres. Comparative genomics analyses identify extensive structural variations that probably occurred after polyploidization, highlighted by large paracentric/pericentric inversions in 14 chromosomes. We constructed an introgression line population to introduce favorable chromosome segments from G. barbadense to G. hirsutum, allowing us to identify 13 quantitative trait loci associated with superior fiber quality. These resources will accelerate evolutionary and functional genomic studies in cotton and inform future breeding programs for fiber improvement.

Genome-Wide Association Study Identifies Candidate Genes Related to Seed Oil Composition and Protein Content in Gossypium hirsutum L.

Cotton (Gossypium spp.) is a leading natural fiber crop and an important source of vegetable protein and oil for humans and livestock. To investigate the genetic architecture of seed nutrients in upland cotton, a genome-wide association study (GWAS) was conducted in a panel of 196 germplasm resources under three environments using a CottonSNP80K chip of 77,774 loci. Relatively high genetic diversity (average gene diversity being 0.331) and phenotypic variation (coefficient of variation, CV, exceeding 3.9%) were detected in this panel. Correlation analysis revealed that the well-documented negative association between seed protein (PR) and oil may be to some extent attributable to the negative correlation between oleic acid (OA) and PR. Linkage disequilibrium (LD) was unevenly distributed among chromosomes and subgenomes. It ranged from 0.10–0.20 Mb (Chr19) to 5.65–5.75 Mb (Chr25) among the chromosomes and the range of Dt-subgenomes LD decay distances was smaller than At-subgenomes. This panel was divided into two subpopulations based on the information of 41,815 polymorphic single-nucleotide polymorphism (SNP) markers. The mixed linear model considering both Q-matrix and K-matrix [MLM(Q+K)] was employed to estimate the association between the SNP markers and the seed nutrients, considering the false positives caused by population structure and the kinship. A total of 47 SNP markers and 28 candidate quantitative trait loci (QTLs) regions were found to be significantly associated with seven cottonseed nutrients, including protein, total fatty acid, and five main fatty acid compositions. In addition, the candidate genes in these regions were analyzed, which included three genes, Gh_D12G1161, Gh_D12G1162, and Gh_D12G1165 that were most likely involved in the control of cottonseed protein concentration. These results improved our understanding of the genetic control of cottonseed nutrients and provided potential molecular tools to develop cultivars with high protein and improved fatty acid compositions in cotton breeding programs through marker-assisted selection.

Registration of Arkot 0611, Arkot 0617, and Arkot 0712 Cotton Germplasm Lines

Arkot 0611 (Reg. No. GP‐1035, PI 687864), Arkot 0617 (Reg. No. GP‐1037, PI 687866), and Arkot 0712 (Reg. No. GP‐1036, PI 687865) are conventional germplasm lines of cotton (Gossypium hirsutum L.) released by the Arkansas Agricultural Experiment Station (AAES) in April 2018. The lines were released as part of an ongoing effort to develop improved genotypes with enhanced yield, yield components, earliness, host plant resistance, and fiber properties. They share one common parent, DX25105N, a privately developed line made available to AAES by a Memorandum of Agreement. All three lines produced equal or higher lint yields than ‘DP 393’ and ‘UA48’ over 4 yr and at four test sites in Arkansas. Over all test sites, Arkot 0611 produced 10 and 22% higher lint yields than DP 393 and UA48, respectively. Both Arkot 0617 and Arkot 0712 produced 12% more lint than UA48. Lint percentage, seed per hectare, fibers per seed, and fiber density of each line were greater than UA48 and equal to or greater than DP 393. Compared with the check cultivars, all three lines were earlier maturing, but Arkot 0611 and Arkot 0617 tended to have taller plants. All three lines produced more dense leaf pubescence and bract trichomes than either check cultivar. Fiber quality of Arkot 0611 was inferior to either check, and fiber quality of Arkot 0617 and Arkot 0712 was higher than DP 393 but lower than UA48. The DX250105N parent of these lines increases the genetic diversity with the AAES cotton breeding program and broadens the available cotton germplasm pool.

Evaluation of a multi-parent advanced generation inter-cross (MAGIC) introgressed line population for Verticillium wilt resistance in Upland cotton

Verticillium wilt (VW, caused by Verticillium dahliae Kleb) is a destructive fungal soil-borne disease in Upland cotton (Gossypium hirsutum L.). High levels of VW resistance can be transferred into Upland from Pima cotton (G. barbadense L.) through interspecific introgression breeding. In this greenhouse study, VW resistance was evaluated in a multi-parent advanced generation inter-cross (MAGIC) introgressed line (IL) population, derived from a random mated Barbadense Upland population with five generations of intermating (called RMBUP-C4) between three Upland cotton cultivars and 18 CS-B Upland lines each carrying a pair of G. barbadense chromosome or arm in the TM-1 background. The objectives of this study were to, (1) evaluate VW resistance of 530 MAGIC ILs in the greenhouse; and (2) to identify lines with VW resistance in the MAGIC population based on a total of three replicated greenhouse tests. Approximately 8 plants for each line in each replicate were grown and screened for VW resistance using three parameters i.e., disease leaf severity rating, percentage defoliated leaves, and percentage infected plants, with a total of ~ 25,190 plants evaluated. A correlation analysis indicated that the three parameters were significantly and positively correlated with one another in each test. The disease leaf severity rating was the best parameter to assess VW resistance due to its relatively low coefficient of variation and its higher resolution to differentiate resistant genotypes from susceptible ones. Of the 530 genotypes, 5 showed resistance to VW, namely, NMIL348, NMIL518, NMIL405, NMIL290, NMIL307 and had higher levels of resistance to VW with mean disease leaf severity ratings, percentage of defoliated leaves, and percentage of infected plants across three tests ranging from 0.58–1.46, 9.46–26.74, and 25–95%, respectively. These lines can be used as parental lines to improve VW resistance in cotton breeding programs.

Genome-Wide Mining and Characterization of SSR Markers for Gene Mapping and Gene Diversity in Gossypium barbadense L. and Gossypium darwinii G. Watt Accessions

The present study aimed to characterize the simple sequence repeat markers in cotton using the cotton expressed sequence tags. A total of 111 EST-SSR polymorphic molecular markers with trinucleotide motifs were used to evaluate the 79 accessions of Gossypium L., (G. darwinii, 59 and G. barbadense, 20) collected from the Galapagos Islands. The allele number ranged from one to seven, with an average value of 2.85 alleles per locus, while polymorphism information content values varied from 0.008 to 0.995, with an average of 0.520. The discrimination power ranks high for the majority of the SSRs, with an average value of 0.98. Among 111 pairs of EST-SSRs and gSSRs, a total of 49 markers, comprising nine DPLs, one each of MonCGR, MUCS0064, and NAU1028, and 37 SWUs (D-genome), were found to be the best matched hits, similar to the 155 genes identified by BLASTx in the reference genome of G. barbadense, G. arboreum L., and G. raimondii Ulbr. Related genes GOBAR_DD21902, GOBAR_DD15579, GOBAR_DD27526, and GOBAR_AA04676 revealed highly significant expression 10, 15, 18, 21, and 28 days post-anthesis of fiber development. The identified EST-SSR and gSSR markers can be effectively used for mapping functional genes of segregating cotton populations, QTL identification, and marker-assisted selection in cotton breeding programs.

Assessing the Breeding Potential of Extra‐Long Staple Upland Germplasm in a Cotton Breeding Program

Fiber quality improvement of upland cotton (Gossypium hirsutum L.) is essential to increase the value and competitiveness of cotton fiber. The closely related allotetraploid species G. barbadense L. has long been targeted as a source of beneficial fiber quality alleles. Although interspecific hybridization between G. hirsutum and G. barbadense results in fertile offspring, cultivar development programs have seen little success using this approach. In this study, we evaluated the breeding potential of extra‐long staple (ELS) upland accessions that presumably contain G. barbadense introgressions. As expected, ELS upland accessions produced long fibers with overall excellent mean fiber quality performance. Genetic effects indicated that ELS upland accessions transmitted both additive and nonadditive beneficial alleles for fiber length and micronaire. However, ELS upland accessions also transmitted negative effects for lint percentage, lint yield, and fiber strength. Results suggest that ELS upland accessions are a good source for improving fiber length but also support the idea that linkage drag and skewed chromatin transmission, often seen in progeny derived from interspecific hybridization, may still proliferate in offspring derived from ELS upland accessions.

Historical Datasets Support Genomic Selection Models for the Prediction of Cotton Fiber Quality Phenotypes Across Multiple Environments.

Genomic selection (GS) has successfully been used in plant breeding to improve selection efficiency and reduce breeding time and cost. However, there has not been a study to evaluate GS prediction models that may be used for predicting cotton breeding lines across multiple environments. In this study, we evaluated the performance of Bayes Ridge Regression, BayesA, BayesB, BayesC and Reproducing Kernel Hilbert Spaces regression models. We then extended the single-site GS model to accommodate genotype × environment interaction (G×E) in order to assess the merits of multi- over single-environment models in a practical breeding and selection context in cotton, a crop for which this has not previously been evaluated. Our study was based on a population of 215 upland cotton (Gossypium hirsutum) breeding lines which were evaluated for fiber length and strength at multiple locations in Australia and genotyped with 13,330 single nucleotide polymorphic (SNP) markers. BayesB, which assumes unique variance for each marker and a proportion of markers to have large effects, while most other markers have zero effect, was the preferred model. GS accuracy for fiber length based on a single-site model varied across sites, ranging from 0.27 to 0.77 (mean = 0.38), while that of fiber strength ranged from 0.19 to 0.58 (mean = 0.35) using randomly selected sub-populations as the training population. Prediction accuracies from the M×E model were higher than those for single-site and across-site models, with an average accuracy of 0.71 and 0.59 for fiber length and strength, respectively. The use of the M×E model could therefore identify which breeding lines have effects that are stable across environments and which ones are responsible for G×E and so reduce the amount of phenotypic screening required in cotton breeding programs to identify adaptable genotypes.

Assessment of Genetic Diversity in some Egyptian Cotton Varieties Based on Molecular and Technological Characteristics

Cotton is an economic plant of world importance. It's the world's leading textile fiber crop. The lack of genetic diversity is implicated in the successful breeding program depends on the slowing of progress in developing new cotton cultivars complete knowledge and understanding of the genetic with improved yield and quality potential, as well as diversity within and among genetic resources of the stress resistance. The present study was carried out at the Agricultural Botany Department and Department of Plant production Faculty of Agriculture, Saba Basha, Alexandria University, Egypt. Five commercial varieties representing the two categories of Egyptian cotton were used, namely: Giza 92 and Giza 88 as extra-long staple length and Giza 86, Giza 95 and Giza 90 as long staple length. These studies were conducted during 2015 up to 2018. Fiber properties of the five cotton varieties under study were determined by the High-Volume Instrument (H.V.I.). Ten RAPD primer, were initially screened to determine the suitability of each primer for the study. Isozyme data proved 100% genetic similarity between the extra-long staple cotton, in the other hand 100% between the long staple cotton varieties, although, the cluster was divided by 62%. The results indicated that in all studied cotton varieties, 224 (71%) of the 312 fragments were polymorphic and 88 (29%) were monomorphic. From these data, we can provide that there are high genetic variations between the two-cotton type in Egypt and these found could be useful in breeding program in the future. Cotton productivity and the future of cotton breeding efforts tightly depend on the level of the genetic diversity of cotton gene pools and its effective exploitation in cotton breeding programs. Elucidating the details of genetic diversity is also very important to determine timeframe of cotton agronomy, develop a strategy for genetic gains in breeding, and conserve existing gene pools of cotton.

Diallel analysis in cotton (Gossypium hirsutum L.) for water stress tolerance

Abstract Information about combining ability is important in determining breeding strategies. The objective of this study was to estimate the general (GCA) and specific (SCA) combining abilities among twenty cotton hybrid combinations submitted to water stress, based on agronomic traits. The trails were carried out in semiarid environment (Barbalha, CE), during two years, in dry season under irrigation, and submitted to 23 days of water suppression. Wide variability was verified among parents and their hybrids, with additive effects to seed yield, lint percentage, blooming and boll weight. Dominance effect was found only to plant height. The combinations BRS 286 x CNPA 5M, BRS RUBI x CNPA 5M, FM 966 x CNPA 5M and BRS 286 x BRS Serido showed the best SCAs and averages for the majority of the traits. In addition, at least one of their parents had high CGA. These combinations must be advanced in cotton breeding program.

Genome-wide association study identified genetic variations and candidate genes for plant architecture component traits in Chinese upland cotton.

Thirty significant associations between 22 SNPs and five plant architecture component traits in Chinese upland cotton were identified via GWAS. Four peak SNP loci located on chromosome D03 were simultaneously associated with more plant architecture component traits. A candidate gene, Gh_D03G0922, might be responsible for plant height in upland cotton. A compact plant architecture is increasingly required for mechanized harvesting processes in China. Therefore, cotton plant architecture is an important trait, and its components, such as plant height, fruit branch length and fruit branch angle, affect the suitability of a cultivar for mechanized harvesting. To determine the genetic basis of cotton plant architecture, a genome-wide association study (GWAS) was performed using a panel composed of 355 accessions and 93,250 single nucleotide polymorphisms (SNPs) identified using the specific-locus amplified fragment sequencing method. Thirty significant associations between 22 SNPs and five plant architecture component traits were identified via GWAS. Most importantly, four peak SNP loci located on chromosome D03 were simultaneously associated with more plant architecture component traits, and these SNPs were harbored in one linkage disequilibrium block. Furthermore, 21 candidate genes for plant architecture were predicted in a 0.95-Mb region including the four peak SNPs. One of these genes (Gh_D03G0922) was near the significant SNP D03_31584163 (8.40kb), and its Arabidopsis homologs contain MADS-box domains that might be involved in plant growth and development. qRT-PCR showed that the expression of Gh_D03G0922 was upregulated in the apical buds and young leaves of the short and compact cotton varieties, and virus-induced gene silencing(VIGS) proved that the silenced plants exhibited increased PH. These results indicate that Gh_D03G0922 is likely the candidate gene for PH in cotton. The genetic variations and candidate genes identified in this study lay a foundation for cultivating moderately short and compact varieties in future Chinese cotton-breeding programs.

Genotypic variability among cotton cultivars for heat and drought tolerance using reproductive and physiological traits

Development of rapid and inexpensive screening tools for heat and drought stress tolerance is needed and will be helpful in cotton breeding programs and selecting cultivars for a niche environment. In this study, several pollen-based traits at optimum and high temperatures and physiological parameters measured during the boll-filling period were used to evaluate variability among the cultivars for heat and drought stresses. Principal component analysis and drought stress response index methods were used to categorize cotton cultivars into three heat and drought tolerant clusters. Based on the combined analysis, PX532211WRF has been identified as heat- and drought-tolerant, and would be expected to perform better under both heat- and drought-stressed environments. A poor correlation between reproductive and physiological indices indicates that screening breeders have to use different traits to screen cultivars for reproductive and vegetative tolerance. Identified traits could serve as valuable screening tools in cotton breeding programs aimed at developing genotypes to a changing climate. Moreover, cultivar-dependent relative scores will aid in the identification of cultivars best suited to niche environments to alleviate the influences of abiotic stresses at both vegetative and reproductive stages.

Genetic Map Construction and Fiber Quality QTL Mapping Using the CottonSNP80K Array in Upland Cotton.

Cotton fiber quality traits are controlled by multiple quantitative trait loci (QTL), and the improvement of these traits requires extensive germplasm. Herein, an Upland cotton cultivar from America, Acala Maxxa, was crossed with a local high fiber quality cultivar, Yumian 1, and 180 recombinant inbred lines (RILs) were obtained. In order to dissect the genetic basis of fiber quality differences between these parents, a genetic map containing 12116 SNP markers was constructed using the CottonSNP80K assay, which covered 3741.81 cM with an average distance of 0.31 cM between markers. Based on the genetic map and growouts in three environments, we detected a total of 104 QTL controlling fiber quality traits. Among these QTL, 25 were detected in all three environments and 35 in two environments. Meanwhile, 19 QTL clusters were also identified, and nine contained at least one stable QTL (detected in three environments for a given trait). These stable QTL or QTL clusters are priorities for fine mapping, identifying candidate genes, elaborating molecular mechanisms of fiber development, and application in cotton breeding programs by marker-assisted selection (MAS).

Recent insights into cotton functional genomics: progress and future perspectives.

SummaryFunctional genomics has transformed from futuristic concept to well‐established scientific discipline during the last decade. Cotton functional genomics promise to enhance the understanding of fundamental plant biology to systematically exploit genetic resources for the improvement of cotton fibre quality and yield, as well as utilization of genetic information for germplasm improvement. However, determining the cotton gene functions is a much more challenging task, which has not progressed at a rapid pace. This article presents a comprehensive overview of the recent tools and resources available with the major advances in cotton functional genomics to develop elite cotton genotypes. This effort ultimately helps to filter a subset of genes that can be used to assemble a final list of candidate genes that could be employed in future novel cotton breeding programme. We argue that next stage of cotton functional genomics requires the draft genomes refinement, re‐sequencing broad diversity panels with the development of high‐throughput functional genomics tools and integrating multidisciplinary approaches in upcoming cotton improvement programmes.

History of Cotton Breeding and Genetics at the University of Arkansas

Cotton breeding research was initiated at the University of Arkansas (UA) in early 1900’s. Early work focused on evaluating cultivars and on making plant selections out of established cultivars. J.O. Ware who began breeding cotton in the early 1920’s studied the genetics and interrelationships of several cotton traits, and released several cultivars. In 1935, he became Senior Agronomist at the United States Department of Agriculture (USDA), Beltsville, MD, then returned to UA in 1950. Several breeders followed Ware at UA. L.M. Humphrey and Ware were responsible for a series of Rowden cultivars. From 1948 until 1986, UA maintained two cotton breeding programs, one on the main campus and the other at the Cotton Branch Station, Marianna, AR. The Marianna program, directed by C.A. Moosberg (1948-1972) and C.W. Smith (1974-1986), was responsible for the release of several Rex cultivars, two stripper cultivars, and Arkot 518. Based on the main campus, B.A. Waddle (1951-1986) continued some of Ware work, and focused on early maturity, seedling vigor, host plant resistance (including the Frego bract trait), and naked and tufted seed. J.McD. Stewart filled the position held by Waddle from 1986 until his death in 2012. His work primarily focused on germplasm exploration and introgression, and cotton biotechnology. In 1988, the two traditional breeding programs were merged into one campus-based program. The program was subsequently moved to the Northeast Research and Extension Center, Keiser, AR, in 1997. F.M. Bourland has led the program since 1988, and has been responsible for almost 100 germplasm and cultivar releases and has established methods for evaluating and selecting several cotton traits. The cotton breeding program at UA continues to develop well-adapted lines and concepts that promote profitable cotton production in Arkansas.

History and Current Research in the USDA-ARS Cotton Breeding Program at Stoneville, MS

Cotton breeders have focused mainly on selecting for high yield and early maturity under the impact of the boll weevil (Anthonomus grandis Boh.) in the last century. Selection for high fiber quality was once a less important objective in cotton breeding. With the transition of the U.S. cotton industry from a domestic consumer to a major exporter of raw fibers into the global market and the technology advancements in the textile industry since the 1990s, the need for high fiber quality in cotton cultivars has increased. In recent years, genetic improvement in cultivars for insect resistance, disease resistance, and abiotic stress tolerance has become important for maintaining cotton yield. Under strong competition from other major crops, increasing profit in cotton production has become an urgent task for cotton breeders and increasing economic potential in cottonseed and other economic traits can help promote profits for cotton growers. In this paper, the major research projects related to cotton breeding at the USDA-ARS at Stoneville, MS since the 1960s are reviewed. These research projects reflect the changing needs in cotton production during the period and focus on broadening the genetic base of Upland cotton for improving agronomic traits and fiber quality in cotton cultivars by a group of scientists with different scientific disciplines. A comprehensive review of this research can help develop strategies and identify research fields to strengthen to meet challenges in future.

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.

Genetic Diversity Analysis through Phenotypic Assessment in Bt-Cotton Germplasm

The present research was carried-out to analysis the genetic diversity in a set of 26 Bt-cotton genotypes for seed cotton yield and its associated traits. Results showed that genotypes differed significantly P ≤0.01 for all the traits, registering the significant genetic variability among the genotypes for further evaluation. With regards to mean performance, varieties BH-180 and KZ-389 displayed better performance in terms of plant height, bolls plant-1, seed cotton yield plant-1, monopodial branches plant-1 and sympodial branches length, suggesting that these genotypes can further be exploited for various breeding programs to improve upland cotton genotypes. In cluster analysis, all genotypes divided into nine small clusters, cluster one consisted of five genotypes which were characterized as high yielding genotypes suggesting that genotypes of this cluster could be utilized for future breeding programs in order to get better yielding varieties. In total, first three principal components accounted 75.90% variability, which is considered very high and could be utilized for further breeding programs in cotton. The obtained results may provide a helpful guide for selecting specific genotypes with distinct genetic backgrounds in cotton breeding programs.

Evaluation of genetic divergence, character associations and path analysis in upland cotton genotypes

The present experiment was laid out in randomized complete block design with three replications in order to estimate the genetic divergence, correlation and path analysis in ten upland cotton genotypes. The mean squares revealed highly significant differences (P<0.05) for all the investigated traits among the tested genotypes, proving that used genetic resources showed a great potential for further breeding experiments. On the basis of mean performance, the variety NB-111 displayed desirable performance for variety of traits, unveiling its importance in cotton breeding programs. The results also exhibited that plant height, bolls plant-1, boll weight and seed index developed positive and significant (P<0.05) associations with seed cotton yield plant-1. Pertaining to path analysis, maximum positive direct effects to seed cotton yield palnt-1 was contributed by bolls plant-1, followed by boll weight, GOT% and seed index. This demonstrates that genotypes possessing higher extent of these traits may be chosen in selection for developing high yielding cotton genotypes. Considering genetic distance, diverse parents with broad genetic distance were also identified, signifying their importance for upcoming hybridization programs in cotton crop. Keywords: Genetic distance; Correlation; Path analysis; Upland cotton; Seed cotton yield http://dx.doi.org/10.19045/bspab.2017.600163

Development of superior hybrids for fibre quality based on heterosis and combining ability in upland cotton (Gossypium hirsutum L.)

The cultivated Gossypium spp. represents the most important, natural fibre crop in the world. Breeding for high cotton yield is still the primary goal of cotton breeding programs, but improving fibre quality has become increasingly important. The enhancement of fibre quality traits like fibre length, strength, and fibre fineness is an essential requirement for the modern textile industry. The objective of this study was to facilitate the selection in cotton breeding program and estimate the general combining ability (GCA) of the parents and specific combining ability (SCA) of hybrids considered for the development of high yielding and better fiber quality in early generations. The study was carried out at cotton research area, CCS Haryana Agricultural University, Hisar (India) during 2014 and 2015 kharif season. Fifteen cotton lines (which have maximum diversity) and four testers (which are known as well adapted and high yielding) were crossed in a line x tester mating design in 2014. Nineteen genotypes and 60 F1 hybrids were planted in the randomized complete block design with three replications at the same experimental area in 2015. The ratio of δ2 GCA /δ2 SCA was less than unity for all the nine characters indicating preponderance of non-additive gene action (dominance and epistasis), which is an important in exploitation of heterosis through hybrid breeding. The best general combining ability was detected from the parent H1470 for seed cotton yield, H1464 and H1098-i for fiber quality traits. SCA was significant for AC726 x H1236, ISR12 x H1226, HR1 x H1117 hybrid combinations for yield and fiber quality. The crosses H1470 x H1236 and H1470 x H1098-i were reported good heterosis for seed cotton yield as well as for fibre quality, selected the best hybrids were H1464 x H1098-i and H1463 x H1226. These cross combinations involved at least one parent with high or average GCA effect for a particular trait. The cross combination involving H1470, H1098-i and H1464 parents’ recorded significant positive heterosis with acceptable SCA effect for both yield and fibre quality parameters. This investigation concluded that the parents H1470, H1098-i and H1464 can be used in hybrid development programme with better fibre quality.