Salt Tolerant Gossypium hirsutum L. Cultivars are Mostly Long-Staple Length Cultivars

Background: Cotton is a major cash crop in the global and, in particular, the Indian markets, playing an important economic role in the textile and oil industries. The cotton plant is one of the highly bred plants that is highly sensitive to salt stress. As cotton is a non-food crop, the availability of non-saline terrain and water for the cultivation of cotton plants is only next to other food crops, thereby posing a need to better understand the salt tolerance of this plant. Gossypium hirsutum L. cultivars MCU 5, LRA 5166, and SVPR 2 were selected based on exomorphic traits like staple length and cropping season so that the genotypic responses to salt stress and salt shock can be compared for interpreting the effects of salinity on in vitro germination. Thus, this study aims to establish genotypic dependence on salinity tolerance. Results: The results affirmed genotypic variation in salinity tolerance, with MCU 5 tolerating salt stress better than LRA 5166 and SVPR 2 in all the observed stages of growth of the plant and the parameters measured. Further salt-tolerant cotton varieties were observed to be long-staple length varieties; staple length is the fiber character of the cotton lint. Moreover, salt tolerance in the vegetative growth stage of cotton plants is not independent of the germination stage of the plant.Conclusion: Nevertheless, the correlation of genotypic dependence to morphological characteristics, in particular, staple length (and cropping season), is of agronomic and commercial significance. Further research by screening and investigating a greater number of cultivars using biochemical and molecular techniques will provide a better understanding of this observed phenotypical relationship to the genotypes of cotton cultivars under salt stress.

Effect of host plants on the oviposition preference of pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Pink bollworm (Pectinophora gossypiella (Saunders, 1843)) (Lepidoptera: Gelechiidae) is an important pest of cotton. We aimed to study the effect of different host plants on the oviposition preference of pink bollworm under laboratory conditions. Cotton (Bt and non-Bt), okra and hibiscus plants were used, which vary in morphological characteristics. Significant differences were observed in the density of trichomes and it is positively correlated with oviposition behaviour of pink bollworm. In a no-choice test, we recorded a higher number of eggs on Bt and non-Bt cotton plants. In two-, three- and four-choice experiments, pink bollworm preferred to deposit the maximum number of eggs on non-Bt cotton among other host plants. A substantially higher number of eggs were laid on Bt cotton in combinations with okra and hibiscus and a considerably lower number on non-Bt cotton. We recorded fewer numbers of eggs on hibiscus in all combinations. Overall, pink bollworm moths showed greater affinity towards non-Bt cotton plants and deposited the maximum number of eggs there. From the practical point of view, the development of cotton genotypes which are devoid or have a lesser density of trichomes may be a possible solution to reduce the pink bollworm egg load on cotton.

Aphelenchoides besseyi parasitizing cowpea (Vigna unguiculata) in Brazil

Several species of nematodes are known to cause losses to cowpea (Vigna unguiculata) throughout the world. In Brazil, Aphelenchoides besseyi was recently described causing damages on soybean, cotton, and common bean, but no report was found about the parasitism of this nematode in cowpea. The present study aimed to verify the host reaction of cowpea cultivars to A. besseyi. The experiment was conducted under greenhouse conditions, using as inoculum two A. besseyi populations, obtained from symptomatic soybean and cotton plants collected in naturally infested fields. Cultivars ‘Imponente’, ‘Aracê’, ‘Guariba’, ‘Tumucumaque’, ‘Nova Era’, and ‘Tracuateua’ were inoculated with 500 A. besseyi of each population, separately, into soil and after 30 days from the inoculation nematodes were extracted from shoot systems. Both populations were able to parasitize all the cowpea cultivars. Independently of the cultivar, cowpea plants exhibited symptoms of leaf deformation similar to those described for soybean, cotton, and common bean and, in addition, severe brooming was observed and the interior of the stems was porous and necrotic. To our knowledge, this is the first report of parasitism by A. besseyi of cowpea in Brazil, under greenhouse conditions, increasing the list of hosts of this nematode.

VERTICAL SPINDLE COTTON HARVESTER WITH SYMMETRIC MOVEMENT OF SPINDLE DRUMS

The article deals with the trends in the development of structures, research work on modernization and creation of new vertical spindle cotton harvesting apparatus (CHA). Authors developed new CHA that works as follows: the CHA with a cotton picker moves on the cotton field; the cotton plants getting into the inter-drum slots are processed, that is, the raw cotton be harvested. The CHA are in their original position before picking raw cotton. When a thick cotton plant gets into the inter-drum slot of the front pair of drums, the spindle drums move apart and the inter-drum slot opens, while the connecting rods and the sliders move forward, providing the symmetrical opening of the slot relative to the longitudinal line of the cotton plant row. Further, this thick plant falls into the inter-drum slot of the second pair of drums, while the inter-drum slot of the second drums opens, while the connecting rods and the sliders move along the guides forward, providing the symmetrical opening of the slot relative to the longitudinal line of the cotton plant rows. With such a pairwise symmetric movement of the SD, depending on the thickness of the cotton plant, the force of spindle pressing on the cotton plant from both sides is identical and symmetrical, since the SD move symmetrically to the longitudinal line passing along the cotton plant row.

Silencing of GhKEA4 and GhKEA12 Revealed Their Potential Functions Under Salt and Potassium Stresses in Upland Cotton

The K+ efflux antiporter (KEA) mediates intracellular K+ and H+ homeostasis to improve salt tolerance in plants. However, the knowledge of KEA gene family in cotton is largely absent. In the present study, 8, 8, 15, and 16 putative KEA genes were identified in Gossypium arboreum, G. raimondii, G. hirsutum, and G. barbadense, respectively. These KEA genes were classified into three subfamilies, and members from the same subfamilies showed similar motif compositions and gene structure characteristics. Some hormone response elements and stress response elements were identified in the upstream 2000 bp sequence of GhKEAs. Transcriptome data showed that most of the GhKEAs were highly expressed in roots and stems. The quantificational real-time polymerase chain reaction (qRT-PCR) results showed that most of the GhKEAs responded to low potassium, salt and drought stresses. Virus-induced gene silencing (VIGS) experiments demonstrated that under salt stress, after silencing genes GhKEA4 and GhKEA12, the chlorophyll content, proline content, soluble sugar content, peroxidase (POD) activity and catalase (CAT) activity were significantly decreased, and the Na+/K+ ratio was extremely significantly increased in leaves, leading to greater salt sensitivity. Under high potassium stress, cotton plants silenced for the GhKEA4 could still maintain a more stable Na+ and K+ balance, and the activity of transporting potassium ions from roots into leaves was reduced silenced for GhKEA12. Under low potassium stress, silencing the GhKEA4 increased the activity of transporting potassium ions to shoots, and silencing the GhKEA12 increased the ability of absorbing potassium ions, but accumulated more Na+ in leaves. These results provided a basis for further studies on the biological roles of KEA genes in cotton development and adaptation to stress conditions.

Influence of biopreparation ‘Zamin-M’ on cotton plants (gossypium hirsutum) under soil salinization in Uzbekistan

In this article, a microbial inoculant acting as a biofertilizer is considered as a biostimulant, consisting of three strains of local salt-tolerant strains of rhizobacteria Pseudomonas stutzeri SKB308, Bacillus subtilis SKB309, Bacillus megaterium SKB310. The authors have developed and introduced into agricultural practice an experimental sample of the biological product ‘Zamin-M’, which increases the resistance of cotton to stress conditions of soil salinity. It is proved that the biological product ‘Zamin-M’ increases soil fertility has a beneficial effect on the enzymatic activity of the soil and the development of a population of beneficial microorganisms. The bioproduct ‘Zamin-M’ is presented as a new stimulant in the practice of growing cotton in saline conditions. An agricultural technique for the use of a local biological product in agriculture has been developed. The ‘Zamin-M’ is included by the State Committee of the Republic of Uzbekistan in the list of agrochemicals and pesticides permitted for use in agriculture of the Republic of Uzbekistan (certificate No. 1A1005).

Complete mitochondrial genome sequencing of Oxycarenus laetus (Hemiptera: Lygaeidae) from two geographically distinct regions of India

Oxycarenus laetus is a seed-sap sucking pest affecting a variety of crops, including cotton plants. Rising incidence and pesticide resistance by O. laetus have been reported from India and neighbouring countries. In this study, O. laetus samples were collected from Bhatinda and Coimbatore (India). Pure mtDNA was isolated and sequenced using Illumina MiSeq. Both the samples were found to be identical species (99.9%), and the complete genome was circular (15,672 bp), consisting of 13 PCGs, 2 rRNA, 23 tRNA genes, and a 962 bp control region. The mitogenome is 74.1% AT-rich, 0.11 AT, and − 0.19 GC skewed. All the genes had ATN as the start codon except cox1 (TTG), and an additional trnT was predicted. Nearly all tRNAs folded into the clover-leaf structure, except trnS1 and trnV. The intergenic space between trnH and nad4, considered as a synapomorphy of Lygaeoidea, was displaced. Two 5 bp motifs AATGA and ACCTA, two tandem repeats, and a few microsatellite sequences, were also found. The phylogenetic tree was constructed using 36 mitogenomes from 7 super-families of Hemiptera by employing rigorous bootstrapping and ML. Ours is the first study to sequence the complete mitogenome of O. laetus or any Oxycarenus species. The findings from this study would further help in the evolutionary studies of Lygaeidae.

Regulatory Network of Cotton Genes in Response to Salt, Drought and Wilt Diseases (Verticillium and Fusarium): Progress and Perspective

In environmental conditions, crop plants are extremely affected by multiple abiotic stresses including salinity, drought, heat, and cold, as well as several biotic stresses such as pests and pathogens. However, salinity, drought, and wilt diseases (e.g., Fusarium and Verticillium) are considered the most destructive environmental stresses to cotton plants. These cause severe growth interruption and yield loss of cotton. Since cotton crops are central contributors to total worldwide fiber production, and also important for oilseed crops, it is essential to improve stress tolerant cultivars to secure future sustainable crop production under adverse environments. Plants have evolved complex mechanisms to respond and acclimate to adverse stress conditions at both physiological and molecular levels. Recent progresses in molecular genetics have delivered new insights into the regulatory network system of plant genes, which generally includes defense of cell membranes and proteins, signaling cascades and transcriptional control, and ion uptake and transport and their relevant biochemical pathways and signal factors. In this review, we mainly summarize recent progress concerning several resistance-related genes of cotton plants in response to abiotic (salt and drought) and biotic (Fusarium and Verticillium wilt) stresses and classify them according to their molecular functions to better understand the genetic network. Moreover, this review proposes that studies of stress related genes will advance the security of cotton yield and production under a changing climate and that these genes should be incorporated in the development of cotton tolerant to salt, drought, and fungal wilt diseases (Verticillium and Fusarium).

Fitness costs associated with spinetoram resistance in Spodoptera frugiperda is driven by host plants

Insecticide resistance is usually associated with fitness costs. The magnitude of fitness costs is affected by environmental and ecological factors. Here, we explored how host plants could affect fitness costs associated with insecticide resistance. Initially, spinetoram-resistant (RR) and susceptible (SS) strains of Spodoptera frugiperda were selected using F2 screen from a population collected in Sao Desiderio, Bahia State, Brazil in 2018. Besides de RR and SS strains, fitness costs were also assessed for a heterozygous strain (RS). Life-history traits were evaluated to estimate population growth parameters of neonate larvae of each strain fed on corn, soybean and cotton plants. Compared to the SS strain, the relative fitness of the RR strain, based on intrinsic rate of population increase, was 1.06, 0.84 and 0.67 on plants of corn, soybean and cotton respectively. The relative fitness of the RS strain was similar to the SS strain regardless the host plant, suggesting a recessive fitness cost. No differences were found between the strains fed on corn plants. The larval development time was greater for RR strain fed on soybean and cotton plants compared to RS and SS strain. Low survival rate and fecundity of the RR strain were found when larvae fed on plants of soybean and cotton. The results of this study demonstrated that fitness costs of spinetoram resistance in S. frugiperda depend strongly on the host plants that S. frugiperda larvae fed on. Such information can be used to design resistance management strategies considering the host plants of the agricultural landscape. Keywords: fall armyworm; spinosyns; insect resistance management; relative fitness.