JCR | Identification and expression analysis of Tubulin gene family in upland cotton

[Background] Cotton fibers are single-celled extensions of the seed epidermis, a model tissue for studying cytoskeleton. Tubulin genes play a critical role in synthesizing the microtubules (MT) as a core element of the cytoskeleton. However, there is a lack of studies concerning the systematic characterization of the tubulin gene family in cotton. Therefore, the identification and portrayal of G. hirsutum tubulin genes can provide key targets for molecular manipulation in cotton breeding.

[Results] In this study, we investigated all tubulin genes from different plant species and identified 98 tubulin genes in G. hirsutum. Phylogenetic analysis showed that tubulin family genes were classified into three subfamilies. The protein motifs and gene structure of α-, β-tubulin genes are more conserved compared with γ-tubulin genes. Most tubulin genes are located at the proximate ends of the chromosomes. Spatiotemporal expression pattern by transcriptome and qRT-PCR analysis revealed that 12 α-tubulin and 7 β-tubulin genes are specifically expressed during different fiber development stages. However, Gh.A03G027200Gh.D03G169300, and Gh.A11G258900 had differential expression patterns at distinct stages of fiber development in varieties J02508 and ZRI015.

[Conclusion] In this study, the evolutionary analysis showed that the tubulin genes were divided into three clades. The genetic structures and molecular functions were highly conserved in different plants. Three candidate genes, Gh.A03G027200Gh.D03G169300, and Gh.A11G258900 may play a key role during fiber development complementing fiber length and strength.

[Title] Identification and expression analysis of Tubulin gene family in upland cotton

[Authors] CHEN Baojun, ZHAO Junjie, FU Guoyong, PEI Xinxin, PAN Zhaoe, LI Hongge, AHMED Haris, HE Shoupu & DU Xiongming

Journal of Cotton Research 2021, 420


Genotypic variance in 13C-photosynthate partitioning and within-plant boll distribution in cotton

[Background] Photosynthate partitioning and within-plant boll distribution play an important role in yield formation of cotton; however, if and how they interact to mediate yield remains unclear. The objective of this study was to investigate the genotypic variance in photosynthate partitioning and within-plant boll distribution, with a focus on their interactions with regard to yield and yield components. A field experiment was conducted in the Yellow River region in China in 2017 and 2018 using a randomized complete block design with three replicates. Photosynthate partitioning of three commercial cultivars (DP 99B, Lumianyan 21 and Jimian 169), varying in yield potential, to different organs (including bolls) at early flowering, peak flowering, and peak boll-setting stages, as well as within-plant boll distribution at harvest, and their effects on yield formation were examined.

[Results] Lint yield of Jimian 169 was the highest, followed by Lumianyan 21 and DP 99B. Similar differences were observed in the number of inner bolls and boll weight among the three cultivars. J169 partitioned significantly more photosynthate to the fruit and fiber than Lumianyan 21 and DP 99B and allocated over 80% of assimilates to the inner bolls. Additionally, Lumianyan 21 allocated a higher proportion of photosynthate to bolls and fiber, with 12.5%–17.6% more assimilates observed in the inner bolls, than DP 99B.

[Conclusions] Genotypic variance in lint yield can be attributed to differences in the number of inner bolls and boll weight, which are affected by photosynthate partitioning. Therefore, the partitioning of photosynthate to fiber and inner bolls can be used as an important reference for cotton breeding and cultivation.

[Title] Genotypic variance in 13C-photosynthate partitioning and within-plant boll distribution in cotton

[Authors] NIE Junjun, QIN Dulin, MAO Lili, LIU Yanhui, DONG Hezhong, SONG Xianliang and SUN Xuezhen

Journal of Cotton Research 3, Article number: 15 (2020)


Evaluation of the genetic diversity of fibre quality traits in upland cotton (Gossypium hirsutum L.) inferred from phenotypic variations

[Background] Evaluating phenotypic traits is very important for the selection of elite lines in Gossypium hirsutum L. Cotton breeders are interested in using diverse genotypes in hybridization that can segregate for traits of interested with the possibility of selection and genetic gain. Information on phenotypic and molecular diversity helps the breeders for parental selection.

[Methods] In this study, 719 global collections of G. hirsutum L. were evaluated for five fibre-related traits during two consecutive years in eight different environments. A series of phenotypic data for fibre quality traits were obtained and the elite accessions were further screened using principal component analysis and phylogenetic tree construction based on single nucleotide polymorphism markers.

[Results] We found that fibre quality traits showed a wide range of variation among the G. hirsutum accessions over 2 years. In general, accessions from outside China tended to have higher fibre length (FL) and fibre strength (FS) than did Chinese accessions. Among different regional accessions in China, North/Northwest accessions tended to have the highest FL, FS and best fibre macronaire. By assessing five fibre quality traits over 2 years with genotypic data, 31 elite germplasms reaching double-thirty quality values (FL ≥ 30 mm and FS ≥ 30 cN·tex− 1) were selected.

[Conclusions] This study provided a detailed phenotypic diversity description of a population representing a wide range of upland cotton germplasm. Our findings provide useful information about possible elite fibre quality parents for cotton breeding programs.
[Title] Evaluation of the genetic diversity of fibre quality traits in upland cotton (Gossypium hirsutum L.) inferred from phenotypic variations

[Authors] SUN Zhengwen, WANG Xingfen, LIU Zhengwen, GU Qishen, ZHANG Yan, LI Zhikun, KE Huifeng, YANG Jun, WU Jinhua, WU Liqiang, ZHANG Guiyin and MA Zhiying
Journal of Cotton Research2019; 2:22



Response to Pix of cotton varieties in Greece

The climatic conditions in Greece, especially in the north of the country, limit crop duration. Maturing the crop early is frequently needed to avoid the risk of rain and cool temperature at the time of harvest. In these conditions it is important to secure the bottom and the first position bolls on the plants. The studies conducted in Greece during the last three years indicate that among the different techniques inducing earliness, the split use of a plant growth regulator (PGR) namely Pix, not only limits plant height but also induces early fruit set, better bottom boll production and earliness. The plant mapping technique is of great interest to ensure precise field follow up from early plant development to harvest. Preharvest mapping has given a clear indication of the plant production structure with different Pix application regimes. The best results were obtained either with three applications starting at pinhead square, i.e. 60 days after planting (DAP), then first flower (70 DAP) and 7 to 10 days later at the rate of 250, 250, 500 ml per hectare, respectively, or two applications 70 and 80 DAP at the rate of 500, 500 ml per hectare. Higher average yield (25%) and earlier maturity (one week) were obtained on two sites.

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Effect of Salinity on Botanical Characters and Fiber Maturity of Three Egyptian Cotton Cultivars

The objective of this study was to investigate to extent salinity affects the growth and other characters of three Egyptian cotton cultivars: Giza 77, Giza 75 and Giza 80. The salinity levels were 0, 2000, 4000 and 6000 ppm of either NaCl + CaCl2 or NaCl + KCl. Germination speed and capacity were lower as the concentration of various were salts increased. Salinity reduced plant height and the number of the main stem internodes. Salinity reduced cotton lint yield by up to 50%; specific weight of seeds by up to 18%; fiber maturity ratio by up to 8.9%; ovule width by up to 35% and fiber ribbon width by up to 4.9% where 6000 ppm of NaCl alone was applied. The effects of NaCl were greater than the effects of NaCl + CaCl2 or NaCl + KCl. The relationship between fiber maturity and ovule width at two days post anthesis with some other characters are investigated

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Production of High Gossypol Cotton Plants with Low Gossypol Seed from Trispecies Hybrids Including G. sturtianum Willis

Two tri-species hybrids that include G. hirsutum L. (2n=4X=52 (AD genome)) were created to develop upland cotton plants with low gossypol seed and high gossypol aerial parts. G. sturtianum Wil. was used as the donor parent (2n=2x=26, genome C1) and a wild American diploid cotton, G. thurberi Tor. (2n=2x=26, genome D1) or G. raimondii Ulb. (2n=2x=26 genome D5) as bridge species. Both tri-species hybrids were backcrossed to different G. hirsutum varieties, originating from Central and West Africa to produce BC1, BC2, selfed BC2 and BC3 seeds. Growth regulators applications at flowering, in vitro culture of the mature seed embryos and grafting of the more perturbed hybrids on vigorous G. hirsutum seedlings were necessary to obtain a large number of viable hybrid material. A drastic reduction of the gossypol gland density was expressed by at least 25% of the seeds of each backcross generation while the aerial parts of the resulting plants were normally glanded. Mortality rates of germinating seed and young plantlets were very high (76%) for BC1 material but decreased markedly in following generations. Cytogenetic observations confirmed the soundness of the introgression strategy. Both tri-species hybrids and several BC1 and BC2 genotypes issued from nearly totally glandless seeds were fertile and showed high frequencies of multivalent and chiasma formations at metaphase I, indicating important genetic material exchanges.

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Male sterility- New Frontiers in Cotton Breeding

Conventional hybrid cottonseed production is expensive and this has paved the way for intensification of research into male sterility systems in cotton. Histological, morphological differences, yield and fiber properties and changed restorer background were studied to establish facts on male sterility systems. Post meiotic obstruction in pollen development in GMS and pre-meiotic abnormalities in CGMS caused sterility in cotton. Morphologically fertile and sterile counterparts looked alike except for flower traits where significant reductions in ovary size, staminal column, style and anther filament length and anther number in CGMS. This was not apparent with GMS. Despite reports of reduction in yield with CGMS based hybrids compared to conventional hybrids of the same parents, some entirely new combinations of CGMS hybrids proved economically worthwhile. A comparison between two restorer lines, one based on G. hirsutum and the other on G. harknessii backgrounds, the latter proved superior for stable restoration. Among 64 lines converted, eight had a GOT above 40%, 33 had a seed index of 10 g or more and 11 had a halo length above 30 mm. A halo length of 28 mm, seed index up to 12 g and GOT up to 40% was observed in R lines. Hybrids of selected 12 lines and eight R lines exhibited heterosis for yield and boll features compared to the conventional checks. This emphasizes better performance of diversified A and R lines for hybrid production. The possibility of good CGMS lines in G aridum background is predicted.

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Heterosis Component Studies in Upland Cotton

Heterosis is by far the most important and effective tool in the hand of crop breeders for effecting rapid improvement in the yield and others economic attributes. Study of heterosis and inbreeding depression has a direct bearing on the breeding methodology to be employed for genetic improvement. In the present study, four diverse parents present of American Upland Cotton, g Bikaneri Narma, Model, Ganganagar Ageti and DP-16 were crossed to make hybrids. Data were recorded for seed cotton yield per plant and on its contributing traits. From the weighted least square estimates of components of generation means, components of heterosis were calculated. Heterosis in the F1 could be obtained if no mutual cancellation of components of heterosis occur. Over the over dominance as the predominant assignable cause of the heterosis was ruled out by observation of a higher magnitude of dominance (h) and its interaction components than of the additive (d) component.

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Cotton Hybrids and their Role in Indian Economy

India is the pioneer country in the world for cultivating hybrid cotton on a commercial scale. The world’s first intra-hirsutum hybrid i.e. H4 was released in 1970 from Surat (Gujarat) and the world’s first interspecific tetraploid hybrid i.e. “Varalaxmi” was released from Dharwad (Karnataka). Later on, several high yielding hybrids in tetraploid cottons and a few in diploid cottons were released especially for central and southern zones. Recently, some hybrids have been released for north zone also. Hybrid cottons now cover about 40% of the total cotton area and contribute about 50% to the national cotton production. Hybrid cottons have helped India in achieving self sufficiency in cotton production and also in providing employment opportunities to millions of rural people. Now India earns about 420 thousand million rupees of foreign exchange per annum by way of cotton export in the form of lint, yarn and fabrics, half of which comes through hybrids. Besides yield remarkable improvement has been achieved in fiber quality. Various aspects of hybrid cotton such as area under cultivation, types of hybrids, hybrid research centres, practical achievements, hybrid seed production, role of hybrids, limitations and future outlook are discussed.

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Host Suitability and Yield Response of Three Cotton Varieties to Meloidogyne incognita

One susceptible (Deltapine 90) and two resistant (LA 887 and NemX) cultivars were evaluated in field microplots for host suitability and yield loss to an isolate of Meloidogyne incognita. Five replications of seven initial population densities (Pi) of M. incognita (0, 0.5, 1, 10, 50, 100, 500 eggs/500 cm3soil) were established for each cultivar in the 1997 growing season in South Carolina. Deltapine 90 was an excellent host for M. incognita. Severity of galling (G) and reproduction, as measured by the final larvae population density of juveniles in the soil (Pf), responded in a positive linear manner to Pi as predicted by the models G = 1.28 log 10 (Pi + 1) – 0.278, (r 2 = 0.82) and Pf = 822.5 log 10 (Pi + 1) – 253.3, (r 2 = 0.61). NemX and LA 887 were both poor hosts. Severity of galling and Pf for these two varieties responded in a positive linear manner to Pi and could be predicted by the following models: G = 0.239 log 10 (Pi + 1) – 0.013, (r 2 = 0.27) and Pf = 111.78 log 10 (Pi + 1) – 4.80, (r 2 = 0.05) for NemX; G = 0.34 log 10 (Pi + 1) – 0.186, ( r 2 = 0.39) and Pf = 42.62 log 10 (Pi + 1) – 3.51, (r 2 = 0.25) for LA 887. Yield response of the cultivars to Pi did not fit a linear model. In a similar experiment utilizing the same Pi’s, greater yield suppression of DP 90 was observed. The negative linear relationship between Pi and yield fit the model y = – 9.30 log 10 (Pi + 1) + 60.05, (r 2 = 0.13). Generally, LA 887 yielded the highest across Pi’s and had smaller Pf’s at harvest.

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