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Cotton is a significant economic crop. It is vulnerable to aphids ( Aphis gossypii Glovers) during the growth period. Rapid and early detection has become an important means to deal with aphids in cotton. In this study, the visible/near-infrared (Vis/NIR) hyperspectral imaging system (376–1044 nm) and machine learning methods were used to identify aphid infection in cotton leaves. Both tall and short cotton plants (Lumianyan 24) were inoculated with aphids, and the corresponding plants without aphids were used as control. The hyperspectral images (HSIs) were acquired five times at an interval of 5 days. The healthy and infected leaves were used to establish the datasets, with each leaf as a sample. The spectra and RGB images of each cotton leaf were extracted from the hyperspectral images for one-dimensional (1D) and two-dimensional (2D) analysis. The hyperspectral images of each leaf were used for three-dimensional (3D) analysis. Convolutional Neural Networks (CNNs) were used for identification and compared with conventional machine learning methods. For the extracted spectra, 1D CNN had a fine classification performance, and the classification accuracy could reach 98%. For RGB images, 2D CNN had a better classification performance. For HSIs, 3D CNN performed moderately and performed better than 2D CNN. On the whole, CNN performed relatively better than conventional machine learning methods. In the process of 1D, 2D, and 3D CNN visualization, the important wavelength ranges were analyzed in 1D and 3D CNN visualization, and the importance of wavelength ranges and spatial regions were analyzed in 2D and 3D CNN visualization. The overall results in this study illustrated the feasibility of using hyperspectral imaging combined with multi-dimensional CNN to detect aphid infection in cotton leaves, providing a new alternative for pest infection detection in plants.

Key messageR2R3 MYB transcription factor GhMYB18 is involved in the defense response to cotton aphid by participating in the synthesis of salicylic acid and flavonoids.R2R3 MYB transcription factors (TFs) play crucial roles in plant growth and development as well as response to abiotic and biotic stresses. However, the mechanism of R2R3 MYB TFs in cotton response to aphid infestation remains largely unknown. Here, an R2R3 MYB transcription factor GhMYB18 was identified as a gene up-regulated from upland cotton (Gossypium hirsutum L.) under cotton aphid (Aphis gossypii Glover) infestation. GhMYB18, which has transcription activity, was localized mainly to nucleus and cell membranes. Transient overexpression of GhMYB18 in cotton activates salicylic acid (SA) and phenylpropane signaling pathways and promoted the synthesis of salicylic acid and flavonoids, which leads to enhancing the tolerance to cotton aphid feeding. In contrast, silencing of GhMYB18 increased the susceptibility of G. hirsutum to aphid. Additionally, GhMYB18 significantly promoted the activities of defense-related enzymes including catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL). These results collectively suggest that GhMYB18 is involved in cotton defense response to cotton aphid attacks through regulating the synthesis of salicylic acid and flavonoids.

Aphis gossypii Glover (Hemiptera: Aphididae) is one of the major pests of okra. Damage severity and high levels of infestation have led to widespread use of chemical insecticides. Okra is ranked fourth in Cameroon among vegetable crops on which chemical insecticides are applied. The objectives of this study were to evaluate resistant okra accessions identified in previous studies, to identify their categories of resistance, and to assess their effects on the non-preference, development, and reproduction of A. gossypii. Results showed that VI041210 was resistant to aphid infestation during the first season, and VI057245 and Gombo caféier were resistant during the second season. Kirikou and VI060794 had the highest yields during the first season, although Kirikou was moderately susceptible to aphid infestation. VI041210 was susceptible to aphid infestation during the second season but produced the highest yield. These results indicate that tolerance occurred in some of the accessions. Aphids did not discriminate between resistant and susceptible accessions, indicating that antixenosis (non-preference) was not a category of resistance found in these accessions. VI041210, VI057245, and Gombo caféier were the most resistant due to lower infestation levels, probably due to their antibiotic properties. Considering constitutive resistance, aphid development was poor, with the longest molting and generation time (To = 15.9) on VI057245 at the vegetative plant growth stage, leading to poor reproduction (lowest intrinsic and finite rates of natural increases: 0.25 and 1.3 aphids, respectively). Considering induced resistance, observed only in VI041210, nymphal development time was longest (14.2 d) leading to one of the lowest net reproductive rates at the vegetative and reproductive plant growth stages, 27.1 and 27.8, respectively. Thus, tolerance and antibiosis were categories of resistance found in these accessions, but antixenosis was not documented.

Powdery mildew, caused by Sphaerotheca fuliginea (Schlecht.) Poll., and melon aphids ( Aphis gossypii Glover) are a typical disease and insect pest, respectively, that affect cucumber production. Powdery mildew and melon aphid often occur together in greenhouse production, resulting in a reduction in cucumber yield. At present there are no reports on the physiological and biochemical effects of the combined disease and pest infection/infestation on cucumber. This study explored how cucumbers can regulate photosynthesis, protective enzyme activity, and basic metabolism to resist the fungal disease and aphids. After powdery mildew infection, the chlorophyll and free proline contents in cucumber leaves decreased, while the activities of POD (peroxidase) and SOD (superoxide dismutase) and the soluble protein and MDA (malondialdehyde) contents increased. Cucumber plants resist aphid attack by increasing the rates of photosynthesis and basal metabolism, and also by increasing the activities of protective enzymes. The combination of powdery mildew infection and aphid infestation reduced photosynthesis and basal metabolism in cucumber plants, although the activities of several protective enzymes increased. Aphid attack after powdery mildew infection or powdery mildew infection after aphid attack had the opposite effect on photosynthesis, protective enzyme activity, and basal metabolism regulation. Azoxystrobin and imidacloprid increased the contents of chlorophyll, free proline, and soluble protein, increased SOD activity, and decreased the MDA content in cucumber leaves. However, these compounds had the opposite effect on the soluble sugar content and POD and CAT (catalase) activities. The mixed ratio of the two single agents could improve the resistance of cucumber to the combined infection of powdery mildew and aphids. These results show that cucumber can enhance its pest/pathogen resistance by changing physiological metabolism when exposed to a complex infection system of pathogenic microorganisms and insect pests.

Cotton aphids ( Aphis gossypii Glover) are important pests of cucurbit crops. Plant defenses at different cell layers, including the leaf surface, mesophyll cells, and phloem, are employed to defend aphids. Here, we assessed differences in aphid resistance among six watermelon varieties and elucidated the defense mechanisms underlying aphid-resistant/susceptible watermelon varieties. The population abundance, offspring number per female, and meantime of phloem-feeding (E2 phase) of aphids were the highest on XiNong (XN), followed by JingXin (JX), TianWang (TW), ZaoJia (ZJ), and MeiFuLai (MFL), and these parameters were the lowest on JinMeiDu (JMD). Further analyses showed that there was no correlation between the aphid resistance of six watermelon varieties and defenses at the leaf surface. For defenses at mesophyll cells, aphid infestation increased salicylic acid (SA) content at 48 h post-infestation (hpi) and ROS accumulation at 6 and 12 hpi in six watermelon varieties. For phloem defenses, aphid infestation increased callose content in JMD plants but decreased callose content in JX, TW, ZJ, MFL, and XN plants at 6, 12, 24, and 48 hpi. Moreover, callose deposition suppressed by 2-deoxy-d-glucose (2-DDG) neutralized the resistance of JMD plants and exacerbated the susceptibility of XN plants to aphids, which exhibited a higher population abundance and E2 phase time. Collectively, phloem defenses regulated by aphid-induced callose deposition were responsible for differences in aphid resistance among the watermelon varieties.

For instance, Pseudomonas is involved in numerous life processes of A. gossypii and exerts a significant influence on its physiological indicators. The results demonstrate that Pseudomonas infection disturbs the normal growth and development of A. gossypii, resulting in a substantial reduction in the number of offspring. Compared with the uninfected control group, the innate rate of increase and the endogenous growth rate are markedly lower. Moreover, RNA-sequencing revealed that genes related to energy synthesis and nutrient metabolism were significantly upregulated in A. gossypii infected with Pseudomonas. Simultaneously, the infection led to a significant downregulation of genes related to alkaline phosphatase in the folate-synthesis pathway and histone proteinase B synthesis in the metabolism pathway of A. gossypii. These experimental findings indicate that Pseudomonas infection disrupts the growth and development of A. gossypii, specifically manifested as a significant upregulation of genes related to energy synthesis and nutrient metabolism and a downregulation of genes related to reproduction. Overall, these results offer support for the study of the interactions between aphids and symbiotic bacteria.

Long non-coding RNAs (lncRNAs) play crucial roles in various plant biological regulatory processes and defense responses to all sorts of biotic and abiotic stresses. However, there are limited studies on the function and mechanism of lncRNAs in plant defense responses to phytophagous insects. In this research, a lncRNA GhlncRNA149.1 was identified from upland cotton (Gossypium hirsutum L.). Depending on the position relationship between lncRNA and mRNA, we identified CC-NBS-LRR family gene GhA01G0129 as the target gene of GhlncRNA149.1. Expression levels of GhlncRNA149.1 and its target gene GhA01G0129 were significantly down-regulated in cotton cotyledons upon cotton aphid infestation. The expression level of GhlncRNA149.1 was significantly down-regulated after the induction of methyl jasmonate and salicylic acid, whereas expression level of its target gene GhA01G0129 was significantly up-regulated. Overexpression of GhlncRNA149.1 in cotton cotyledons enhanced the tolerance of cotton plants to cotton aphid feeding. Expectedly, silencing GhlncRNA149.1 increased susceptibility of cotton plants to cotton aphids. The expression level of GhA01G0129, the target gene of GhlncRNA149.1, was significantly up-regulated in cotton plants overexpressing GhlncRNA149.1, and significantly down-regulated in cotton plants silencing GhlncRNA149.1. The activity and expression levels of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were up-regulated in cotton plants transiently overexpressing GhlncRNA149.1, while opposite results were obtained in cotton plants silencing GhlncRNA149.1. In addition, similar results were obtained in the expression levels of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), enhanced disease susceptibility 1 (EDS1) and non-expression of pathogenesis-related gene 1 (NPR1) in cotton plants transiently overexpressing GhlncRNA149.1 and silencing GhlncRNA149.1. These results collectively suggest that GhlncRNA149.1 improve the plant defense response to aphid attack, and thus has potential for enforcing cotton aphid prevention and control.Key messageLncRNA GhlncRNA149.1 positively regulate the response of cotton to cotton aphid feeding.

The results showed that foliar fertilization with potassium silicate had a clear effect on increasing the thickness of the upper and lower epidermal cuticle layer and increased the thickness of the leaf, as the thickness after the first spray of the upper epidermal cuticle reached 22 microns and the lower epidermal cuticle 11 microns, and the leaf thickness reached 194.8 microns. As for after the second spray, the thickness of the leaf and the upper and lower cuticle layer reached 198.66, 25.33, 16.66 microns, and the third spray was characterized by an increase in the thickness of the leaf compared to the first and second spray, as the thickness of the leaf reached 206.66 microns, and the upper and lower cuticle epidermis was 28.33 and 19 microns, respectively. Compared with the control, the thickness of the paper was 190 microns, and the upper and lower epidermal cuticle layers were 10 and 20 microns, respectively. The results of the study indicated that the treatment of foliar fertilization with silicates with three sprays was superior in reducing the population density of whitefly and aphids on strawberry plant Mergent variety. The effect of the three sprays on the average number of Bemisia tabaci nymphs was 1.16 nymphs / leaf, the first spray had 6.66 nymphs / leaf, and the second spray had 19.66 nymphs / leaf. The effect of the three sprays on nymphs and adults of Aphis gossypii was 0.36 nymphs/leaf and 0.27 adults/leaf. For the second spray, the effect was on nymphs at a rate of 2.33 nymphs/leaf, and on adults at a rate of 1.91 adults/leaf. The first spray had the least effect on reducing the population density, as it reached nymphs at a rate of 8.16 nymphs/leaf. And for adults, 6.33 adults / leaf, with clear significant differences. As for the effect of three sprays of potassium silicate on the numerical density of nymphs and adults of Aphis fabae , the rate of nymphs reached 0.33 nymphs / leaf after the third spray, and for adults, at a rate of 0.27 adults / leaf, which is the most effective compared to the first and second sprays. The average numerical density of nymphs was 9.08 nymphs/leaf and for adults 5.24 adults/leaf after the first spray, while after the second spray the average density was 4.30 nymphs/leaf and for adults 2.16 adults/leaf.

The cotton-melon aphid, Aphis gossypii Glover, is a polyphagous insect pest with many host-specialized biotypes, such as the Cucurbitaceae- and Malvaceae-specialized (CU and MA) biotypes. Bacterial symbionts were reported to determine the host range in some aphids. Whether this is the case in A. gossypii remains unknown. Here, we tested the host specificity of the CU and MA biotypes, compared the host specificity between the wingless and winged morph within the same biotype, and analyzed the composition of the bacterial symbionts. The reproduction of the CU and MA biotypes reduced by 66.67% and 82.79%, respectively, on non-native hosts, compared with on native hosts. The composition of bacterial symbionts was not significantly different between the CU and MA biotypes, with a Buchnera abundance >95% in both biotypes. Meanwhile, the winged morph produced significantly more nymphs than the wingless morph on non-native hosts, and the Buchnera abundance in the winged morph was only about 10% of that in the wingless morph. There seemed to be a relationship between the Buchnera abundance and host specificity. We regulated the Buchnera abundance by temperature and antibiotics, but did not find that a low Buchnera abundance resulted in the high reproduction on non-native hosts. We conclude that the host specificity of A. gossypii is not controlled by specific bacterial symbionts or by Buchnera abundance.

Cotton aphids (Aphis gossypii Glover) cause harm by feeding on phloem sap and spreading plant viruses to lily. Understanding the mechanisms by which aphids infest lily plants is crucial for effective aphid management and control. In this study, we investigated the activity of antioxidants, integrated nontargeted metabolomes and transcriptomes of lilies infested by cotton aphids to explore the changes in lily leaves. Overall, the results indicated that the catalase (CAT) activity in the leaves of the lily plants was greater than that in the leaves of the control plants. A comprehensive identification of 604 substances was conducted in the leaves. Furthermore, the differentially abundant metabolite analysis revealed the enrichment of phenylalanine metabolism and α-linolenic acid metabolism. Moreover, 3574 differentially expressed genes (DEGs), whose expression tended to increase, were linked to glutathione metabolism and phenylpropanoid biosynthesis. In addition, the integrated analysis revealed that the defensive response of lily leaves to aphids is manifested through antioxidant reactions, phenylpropane and flavonoid biosynthesis, and α-linolenic acid metabolism. Finally, the key metabolites were CAT, glutathione, coumaric acid, and jasmonic acid, along with the key genes chalcone synthase (CHS), phenylalanine ammonia-lyase (PAL), and 12-oxo-phytodienoic acid reductase (OPR). Accordingly, the findings of this research elucidate the molecular and metabolic reactions of A. gossypii in lily plants, offering valuable insights for developing aphid resistance strategies in lily farming.