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Summary Cotton seeds are typically covered by lint and fuzz fibres. Natural ‘fuzzless’ mutants are an ideal model system for identifying genes that regulate cell initiation and elongation. Here, using a genome‐wide association study (GWAS), we identified a ~ 6.2 kb insertion, larINDELFZ, located at the end of chromosome 8, composed of a ~ 5.0 kb repetitive sequence and a ~ 1.2 kb fragment translocated from chromosome 12 in fuzzless Gossypium arboreum. The presence of larINDELFZ was associated with a fuzzless seed and reduced trichome phenotypes in G. arboreum. This distant insertion was predicted to be an enhancer, located ~ 18 kb upstream of the dominant‐repressor GaFZ (Ga08G0121). Ectopic overexpression of GaFZ in Arabidopsis thaliana and G. hirsutum suggested that GaFZ negatively modulates fuzz and trichome development. Co‐expression and interaction analyses demonstrated that GaFZ might impact fuzz fibre/trichome development by repressing the expression of genes in the very‐long‐chain fatty acid elongation pathway. Thus, we identified a novel regulator of fibre/trichome development while providing insights into the importance of noncoding sequences in cotton.

Background Cotton production is adversely effected by drought stress. It is exposed to drought stress at various critical growth stages grown under a water scarcity environment. Roots are the sensors of plants; they detect osmotic stress under drought stress and play an important role in plant drought tolerance mechanisms. The seedling stage is very sensitive to drought stress, and it needed to explore the methods and plant characteristics that contribute to drought tolerance in cotton. Results Initially, seedlings of 18 genotypes from three Gossypium species: G. hirsutum, G. barbadense, and G. arboreum, were evaluated for various seedling traits under control (NS) and drought stress (DS). Afterward, six genotypes, including two of each species, one tolerant and one susceptible, were identified based on the cumulative drought sensitivity response index (CDSRI). Finally, growth rates (GR) were examined for shoot and root growth parameters under control and DS in experimental hydroponic conditions. A significant variation of drought stress responses was observed across tested genotypes and species. CDSRI allowed here to identify the drought-sensitive and drought-resistant cultivar of each investigated species. Association among root and shoots growth traits disclosed influential effects of enduring the growth under DS. The traits including root length, volume, and root number were the best indicators with significantly higher differential responses in the tolerant genotypes. These root growth traits, coupled with the accumulation of photosynthates and proline, were also the key indicators of the resistance to drought stress. Conclusion Tolerant genotypes have advanced growth rates and the capacity to cop with drought stress by encouraging characteristics, including root differential growth traits coupled with physiological traits such as chlorophyll and proline contents. Tolerant and elite genotypes of G. hirsutum were more tolerant of drought stress than obsolete genotypes of G. barbadense and G. arboreum. Identified genotypes have a strong genetic basis of drought tolerance, which can be used in cotton breeding programs.

The host plant expansion of host-specialized Aphis gossypii (Glover) has been well studied in the laboratory; however, this phenomenon is poorly understood in the field. Here, we provide a series of laboratory and field experiments to assess the role of zucchini in the host plant expansion of cotton-specialized aphids. We observed that cotton-specialized aphids possessed the ability to expand on a new host plant (cucumber), with individuals first recorded on June 12 and consequently increasing exponentially in number in a field cage. A bioassay experiment showed that aphids from both cotton and cucumber preferred their natal host, but clones from zucchini have a stronger preference for cucumber than cotton or zucchini. A total of 1512 individuals were collected from a cotton field (mixed cotton and cucurbit plot), cotton farmland (cotton alone) and a field cage and sequenced to identify their biotypes. The results for apterous individuals from the cotton field showed that more cucurbit-specialized biotypes occurred on cucumber and more cotton-specialized biotypes occurred on cotton and zucchini. A majority (> 97.0%) of aphids from both the field cage and cotton farmland were cotton-specialized individuals. Consequently, eliminating intermediate host plants may be an effective measure to suppress A. gossypii outbreaks, because cotton and cucumber are often grown together in fields and greenhouses.

The cotton aphid, Aphis gossypii Glover, is an important global pest that sucks sap and transmits viral diseases to host plants, causing serious economic losses in agriculture (Figure 1) (Blackman & Eastop, 2000). It colonizes more than 600 plant species, many of which are important crops (Ebert & Cartwright, 1997). Plant transfer experiments and genetic diversity analysis have highlighted the

Growth-regulating factors-interacting factors (GIFs) are a type of transcription co-activators in plants, playing crucial roles in plants’ growth, development, and stress adaptation. Here, a total of 35 GIF genes were identified and clustered into two groups by phylogenetic analysis in four cotton genus. The gene structure and conserved domain analysis proved the conservative characteristics of GIF genes in cotton. The function of GIF genes was evaluated in two cotton accessions, Ji A-1-7 (33xi) and King, which have larger and smaller lateral root numbers, respectively. The results showed that the expression of GhGIF4 in Ji A-1-7 (33xi) was higher than that in King. The enzyme activity and microstructure assay showed a higher POD activity, lower MDA content, and more giant cells of the lateral root emergence part phenotype in Ji A-1-7 (33xi) than in King. A mild waterlogging assay showed the GIF genes were down-regulated in the waterlogged seedling. Further confirmation of the suppression of GhGIF4 in cotton plants further confirmed that GhGIF4 could reduce the lateral root numbers in cotton. This study could provide a basis for future studies of the role of GIF genes in upland cotton.

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