Vamsi Nalam

Colorado State University | CSU · Department of Agricultural Biology

Background Sugar beets (Beta vulgaris L.) are grown worldwide and suffer economic loss annually due to curly top disease caused by the beet curly top virus (BCTV). The virus is spread by the beet leafhopper (BLH), Circulifer tenellus Baker. Current management strategies rely on chemical control and planting BCTV-resistant sugar beet genotypes. Howe...

The Electrical Penetration Graph (EPG) technique is a well-known specialized tool that entomologists use to monitor and analyze the feeding behavior of piercing-sucking insects, such as aphids, whiteflies, and leafhoppers, on plants. Traditionally, the annotation is conducted by a well-trained technician who uses expert knowledge to compare the tar...

Wheat is a staple crop and one of the most widely consumed grains globally. Wheat yields can experience significant losses due to the damaging effects of herbivore infestation. However, little is known about the effect aphids have on the natural diurnal rhythms in plants. Our time-series transcriptomics and metabolomics study reveal intriguing mole...

Potato virus Y (PVY) is a major economic threat to potato production worldwide. Understanding the prevalent PVY strains and their dynamics is crucial for effective management. This study investigated PVY trends and diversity in the San Luis Valley (SLV), CO, U.S.A. We leveraged the Colorado Seed Potato Certification Program data (2017 to 2022), rev...

Curly top disease, caused by beet curly top virus (BCTV), is among the most serious viral diseases affecting sugar beets in western USA. The virus is exclusively transmitted by the beet leafhopper (BLH, Circulifer tenellus ) in a circulative and non-propagative manner. Despite the growing knowledge on virus-vector interactions, our understanding of...

Diurnal rhythms influence insect behavior, physiology, and metabolism, optimizing their performance by adapting to daily changes in the environment. While their impact on agricultural pests has been briefly explored, our understanding of how these rhythms drive adaptative responses in pest biology and influence host colonization remains elusive. He...

Diurnal rhythms influence insect behavior, physiology, and metabolism, optimizing their performance by adapting to daily changes in the environment. While their impact on agricultural pests has been briefly explored, our understanding of how these rhythms drive adaptative responses in pest biology and influence host colonization remains elusive. He...

The electrical penetration graph (EPG) is a well-known technique that provides insights into the feeding behavior of insects with piercing-sucking mouthparts, mostly hemipterans. Since its inception in the 1960s, EPG has become indispensable in studying plant-insect interactions, revealing critical information about host plant selection, plant resi...

Durable host plant resistance (HPR) to insect pests is critical for sustainable agriculture. Natural variation exists for aphid HPR in sorghum (Sorghum bicolor), but the genetic architecture and phenotype have not been clarified and characterized for most sources. In order to assess the current threat of a sorghum aphid (Melanaphis sorghi) biotype...

Diurnal rhythms influence insect behavior and physiology, driving adaptive responses and synchronizing internal processes with daily light-dark cycles. Aphids are important agricultural pests that feed from phloem sieve elements for prolonged periods by delivering a diverse array of salivary effectors to modulate plant responses. Here, we show that...

Durable host plant resistance (HPR) to insect pests is critical for sustainable agriculture. Natural variation exists for aphid HPR in sorghum ( Sorghum bicolor ) but the genetic architecture and phenotype has not been clarified for most sources. To assess the threat of a sorghum aphid ( Melanaphis sorghi ) biotype shift, we characterized the pheno...

MYZUS PERSICAE-INDUCED LIPASE1 (MPL1) encodes a lipase in Arabidopsis thaliana that is required for limiting infestation by the green peach aphid (GPA; Myzus persicae), an important phloem sap-consuming insect pest. Previously, we demonstrated that MPL1 expression was upregulated in response to GPA infestation, and GPA fecundity was higher on the m...

Autophagy, an intracellular process that facilitates the degradation of cytoplasmic materials, plays a dominant role in plant fitness and immunity. While autophagy was shown to be involved in plant response to fungi, bacteria, and viruses, its role in response to insect herbivory is as yet unknown. In this study, we demonstrate a role of autophagy...

MYZUS PERSICAE-INDUCED LIPASE1 ( MPL1 ) encodes a lipase in Arabidopsis thaliana that is required for controlling infestation by the green peach aphid (GPA; Myzus persicae ), an important phloem sap-consuming insect pest. Previously, we demonstrated that MPL1 expression was upregulated in response to GPA infestation, and GPA fecundity was higher on...

Wheat streak mosaic virus (WSMV) is an economically important viral pathogen that threatens global wheat production, particularly in the Great Plains of the United States. The Wsm2 locus confers resistance to WSMV and has been widely deployed in common wheat varieties adapted to this region. Characterizing the underlying causative genetic variant w...

Wheat streak mosaic virus is an economically important viral pathogen that threatens global wheat production, particularly in the Great Plains region of the United States. The Wsm2 locus confers resistance to WSMV and has been widely deployed in common wheat varieties adapted to this region. Characterizing the underlying causative genetic variant w...

Aphids are the most prolific vectors of plant viruses resulting in significant yield losses to crops worldwide. Potato virus Y (PVY) is transmitted in a non-persistent manner by 65 species of aphids. With the increasing acreage of hemp (Cannabis sativa L.) (Rosales: Cannabaceae) in the United States, we were interested to know if the cannabis aphid...

Pangenome analyses are increasingly being utilized to study the evolution of eukaryotic organisms. While pangenomes can provide insight into polymorphic gene content, inferences about the ecological and adaptive potential of such organisms also need to be accompanied by additional supportive genomic analyses. In this study we constructed a pangenom...

Ash (Fraxinus spp.) is one of the most widely distributed tree genera in North America. Populations of ash in the United States and Canada have been decimated by the introduced pest Agrilus planipennis (Coleoptera: Buprestidae; emerald ash borer), having negative impacts on both forest ecosystems and economic interests. The majority of trees succum...

The soybean aphid (Aphis glycines) continues to threaten soybean production in the United States. A suite of management strategies, such as planting aphid-resistant cultivars, has been successful in controlling soybean aphids. Several Rag genes (resistance against A. glycines) have been identified, and two are currently being deployed in commercial...

Aphid feeding behavior and performance on a given host plant are influenced by the plants’ physical and chemical traits, including structural characters such as trichomes and nutritional composition. In this study, we determined the feeding behavior and performance of soybean aphids (Aphis glycines) on the stem, the adaxial (upper), and the abaxial...

The genus Claviceps has been known for centuries as an economically important fungal genera for pharmacology and agricultural research. Only recently have researchers begun to unravel the evolutionary history of the genus, with origins in South America and classification of four distinct sections through ecological, morphological, and metabolic fea...

• The effects of drought‐induced changes in plant quality on aphid performance and population growth is well‐studied. The response of aphid behaviour to plant water limitation has received less attention. Water limitation may affect host‐plant colonization by altering the attractiveness of plants. Additionally, plant water limitation may inhibit fe...

Feeding location on a plant can affect aphid reproduction and survival, however little is known about factors that influence aphid performance on specific plant parts. We determined performance and feeding behavior of soybean aphid ( Aphis glycines ) on stem, adaxial (upper) and abaxial (lower) leaf surfaces during early vegetative growth of soybea...

Pangenome analyses are increasingly being utilized to study the evolution of eukaryotic organisms, which is often governed by variable gene content. While pangenomes can provide insight into polymorphic gene content, inferences about the ecological and adaptive potential of such organisms also need to be accompanied by additional supportive genomic...

The impact of drought stress on tripartite plant‐pathogen‐vector interactions constitutes a complex and largely understudied field of plant‐insect interaction. A number of studies explored these topics using aphid vectors of plant pathogens, but few have considered the interactions between drought‐stressed plants and pathogen‐transmitting psyllids....

The genus Claviceps has been known for centuries as an economically important fungal genera for pharmacology and agricultural research. Only recently have researchers begun to unravel the evolutionary history of the genus, with origins in South America and classification of four distinct sections through ecological, morphological, and metabolic fea...

Diurnal variation in phloem sap composition has a strong influence on aphid performance. The sugar‐rich phloem sap serves as the sole diet for aphids and a suite of physiological mechanisms and behaviors allow them to tolerate the high osmotic stress. Here, we tested the hypothesis that night‐time feeding by aphids is a behavior that takes advantag...

Nucleobase Cation Symporter 1 proteins are present in bacteria, fungi and among plants. Microbes often contain numerous NCS1 proteins that have evolved specific solute specificity profiles (solute transport and binding). Conversely, most members of Viridiplantae have a unique NCS1 that shows a broad, yet species –specific, solute specificity profil...

Background Ash ( Fraxinus spp.) is one of the most widely distributed tree genera in North America. Populations of ash in the United States and Canada have been decimated by the introduced pest, Agrilus planipennis (Coleoptera: Buprestidae; emerald ash borer), having both negative impacts on forest ecosystems and economic interests. The majority of...

Soybean vein necrosis virus (SVNV) is a newly discovered species of tospovirus infecting soybean plants that is transmitted by the primary vector, soybean thrips (Neohydatothrips variabilis), and two additional secondary vectors, tobacco thrips (Frankliniella fusca) and eastern flower thrips (F. tritici). This study was undertaken to elucidate the...

Aphids constitute a large group of Hemipterans that use their slender stylets to tap into the sieve elements of plants from which they consume copious amounts of phloem sap, thus depriving the plant of photoassimilates. Some aphids also transmit viral diseases of plants. Myzus persicae Sülzer, commonly known as the green peach aphid (GPA), which is...

Aphids are amongst the most damaging pests of plants that use their stylets to penetrate the plant tissue to consume large amounts of phloem sap and thus deprive the plant of photoassimilates. In addition, some aphids vector important viral diseases of plants. Plant defenses targeting aphids are broadly classified as antibiosis, which interferes wi...

Insect endosymbionts (hereafter, symbionts) can modify plant virus epidemiology by changing the physiology or behavior of vectors, but their role in nonpersistent virus pathosystems remains uninvestigated. Unlike propagative and circulative viruses, nonpersistent plant virus transmission occurs via transient contamination of mouthparts, making dire...

The actin cytoskeleton network has an important role in plant cell growth, division and stress response. Actin-depolymerizing factors (ADFs) are a group of actin-binding proteins that contribute to reorganization of the actin network. Here we show that the Arabidopsis thaliana ADF3 is required in the phloem for controlling infestation by Myzus pers...

Insect herbivores from different feeding guilds induce different signaling pathways in plants. In this study, we examined the effects of salicylic acid (SA)- and jasmonic acid (JA)-mediated defenses on performance of insect herbivores from two different feeding guilds: cell-content feeders, soybean thrips and phloem feeders, soybean aphids. We used...

Little is known about how water stress including drought and flooding modifies the ability of plants to resist simultaneous attack by insect feeding and transmission of insect-vectored pathogen. We analyzed insect population growth, feeding behaviors, virus transmission, and plant amino acid profiles and defense gene expression to characterize mech...

Fusarium graminearum causes Fusarium head blight, an important disease of wheat. F. graminearum can also cause disease in Arabidopsis thaliana. Here we show that the Arabidopsis LOX1 and LOX5 genes, which encode 9-lipoxygenases (9-LOXs), are targeted during this interaction to facilitate infection. LOX1 and LOX5 expression were upregulated in F. gr...

The solute specificity profiles (transport and binding) for the nucleobase cation symporter 1 (NCS1) proteins, from the closely related C4 grasses Zea mays and Setaria viridis, differ from that of Arabidopsis thaliana and Chlamydomonas reinhardtii NCS1. Solute specificity profiles for NCS1 from Z. mays (ZmNCS1) and S. viridis (SvNCS1) were determin...

Fusarium graminearum (Fg) causes Fusarium head blight (FHB) disease in wheat and other cereals. Fg also causes disease in Arabidopsis thaliana. In both Arabidopsis and wheat, Fg infection is limited by salicylic acid (SA) signaling. Here we show that in Arabidopsis, the defense regulator EDS1 (ENHANCED DISEASE SUSCEPTIBILITY1) and its interacting p...

Plant response to herbivory is complex and is influenced by insect feeding guilds. Additionally, several insect herbivores vector pathogens resulting in the induction of both pathogen-induced and herbivore-induced plant defenses. There are no studies on plant responses to insect vectors from different feeding guilds. Our study system included the p...

In the U.S., the worst drought conditions in more than 50 years have ravaged major crops such as soybean. Drought stress not only impacts crop yield but also promotes outbreaks of insect pests and pathogens. The physiological and molecular changes occurring in the plant during drought stress is well understood. On the other hand, the impact of drou...

Emerging evidence suggests facultative endosymbiont associations can modify an insect host’s interactions with other trophic levels. Thus far, endosymbionts have been shown to affect insect herbivores via enhanced parasite defense, heat tolerance, and protection from pathogens; but recent findings suggest they may also be tied to plant usage and fa...

Plants have developed sophisticated strategies to protect themselves against insect herbivores. The impact insect herbivores cause on world agriculture has resulted in intense research on plant defense mechanisms against insect herbivory. Roots are increasingly being recognized as important contributors to plant defenses not only against belowgroun...

Soybean (Glycine max) is an important crop due to its versatility as a food source as well as various applications in industries such as biofuel and textiles. Among various environmental stresses that impact soybean productivity, drought stress is a major concern causing reductions in yield of up to 40%. In addition to a direct impact on yield, dro...

Plants have evolved complex biochemical mechanisms to counter threats from insect herbivory. Recent research has revealed an important role of roots in plant responses to above ground herbivory (AGH). The involvement of roots is integral to plant resistance and tolerance mechanisms. Roots not only play an active role in plant defenses by acting as...

Oxylipins derived from lipoxygenase (LOX) activity play important roles in plant growth, development and stress response. In a recent study, we provided evidence that infestation of Arabidopsis thaliana foliage by the green peach aphid (GPA; Myzus persicae), a phloem sap-consuming insect, was promoted by plant LOX5-derived oxylipins. In comparison...

Oxylipins function as signaling molecules in plant growth and development and contribute to defense against stress. Here, we show that oxylipins also facilitate infestation of Arabidopsis thaliana shoots by the phloem sap-consuming green peach aphid (GPA; Myzus persicae), an agronomically important insect pest. GPAs had difficulty feeding from siev...

Abietane diterpenoids are major constituents of conifer resins that have important industrial and medicinal applications. However, their function in plants is poorly understood. Here we show that dehydroabietinal (DA), an abietane diterpenoid, is an activator of systemic acquired resistance (SAR), which is an inducible defense mechanism that is act...

Fusarium head blight (FHB) is a destructive disease of cereal crops such as wheat and barley. Previously, expression in wheat of the Arabidopsis NPR1 gene (AtNPR1), which encodes a key regulator of salicylic acid (SA) signaling, was shown to reduce severity of FHB caused by Fusarium graminearum. It was hypothesized that SA signaling contributes to...

Fusarium graminearum is the principal causative agent of Fusarium head blight (FHB), a devastating disease of wheat and barley. This fungus can also colonize Arabidopsis thaliana. Disease resistance was enhanced in transgenic wheat and Arabidopsis plants that constitutively overexpress the NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1) gene, w...

The spikes of club wheat are significantly more compact than spikes of common wheat due to the action of the dominant allele of the compactum (C) locus. Little is known about the location of C on chromosome 2D and the relationship between C and to other spike-compacting genes. Thus, a study was undertaken to place C on linkage maps and a chromosome...

During the domestication of bread wheat (Triticum aestivum L.), evolutionary modifications that took place in seed dispersal mechanisms enhanced its suitability for agricultural production. One of these modifications involved the evolution of the free-threshing or hulless characteristic. In this study, we studied quantitative trait loci (QTL) affec...

The mature spike rachis of wild emmer [Triticum turgidum L. ssp. dicoccoides (Körn. ex Asch. and Graebner) Thell.] disarticulates spontaneously between each spikelet leading to the dispersion of wedge-type diaspores. By contrast, the spike rachis of domesticated emmer (Triticum turgidum L. ssp. turgidum) fails to disarticulate and remains intact un...