Papers by Prayan Pokharel
Nepalese Horticulture, 2023
Plum is a temperate stone fruit widely adapted and is by far the most diverse of all the 'Prunus'... more Plum is a temperate stone fruit widely adapted and is by far the most diverse of all the 'Prunus' species. However, fruit and flower phenology and pomological characteristics differ among varieties. Phenological and pomological characteristics of six plum varieties ('Soldam,' 'Mirabelle,' 'Quetsche,' 'Methley,' 'Santa Rosa,' and 'Local') during September 2021-August 2022 in the fruit orchard of Temperate Horticulture Development Center, Mustang, Nepal, were studied. The phenological study revealed the Local as early and Quetsche as late among the tested varieties. However, the average flowering duration was lowest in Methley (10.6 days) and highest in Soldam (15.2 days). Linear dimensions of the fruits were maximum in Soldam and minimum in Mirabelle. The fruit shape of all the varieties was round except for Quetsche, which was elliptic. The stone share was highest in Mirabelle (7.82%) and lowest in Soldam (1.86%). The ripening index was highest for Mirabelle (29.11) and lowest for Methley (7.20). The organoleptic evaluation revealed that Soldam was the most preferred while Quetsche was the least.
In conclusion, our study showcased a significant diversity in plum varieties, with implications for orchard management and variety selection to cater to various preferences and needs in the local market and beyond.
Biology Open
Plants produce chemicals (or plant specialised/secondary metabolites, PSM) to protect themselves ... more Plants produce chemicals (or plant specialised/secondary metabolites, PSM) to protect themselves against various biological antagonists. Herbivorous insects use plants in two ways: as a food source and as a defence source. Insects can detoxify and sequester PSMs in their bodies as a defence mechanism against predators and pathogens. Here, I review the literature on the cost of PSM detoxification and sequestration in insects. I argue that no-cost meals might not exist for insects feeding on toxic plants and suggest that potential costs could be detected in an ecophysiological framework.
Herbivorous insects encounter diverse plant specialized metabolites (PSMs) in their diet, that ha... more Herbivorous insects encounter diverse plant specialized metabolites (PSMs) in their diet, that have deterrent, anti-nutritional, or toxic properties. Understanding how they cope with PSMs is crucial to understand their biology, population dynamics, and evolution. This review summarizes current and emerging cutting-edge methods that can be used to characterize the metabolic fate of PSMs, from ingestion to excretion or sequestration. It further emphasizes a workflow that enables not only to study PSM metabolism at different scales, but also to tackle and validate the genetic and biochemical mechanisms involved in PSM resistance by herbivores. This review thus aims at facilitating research on PSM-mediated plant-herbivore interactions.
Insects, 2020
Predators and parasitoids regulate insect populations and select defense mechanisms such as the s... more Predators and parasitoids regulate insect populations and select defense mechanisms such as the sequestration of plant toxins. Sequestration is common among herbivorous insects, yet how the structural variation of plant toxins affects defenses against predators remains largely unknown. The palearctic milkweed bug Lygaeus equestris (Heteroptera: Lygaeinae) was recently shown to sequester cardenolides from Adonis vernalis (Ranunculaceae), while its relative Horvathiolus superbus also obtains cardenolides but from Digitalis purpurea (Plantaginaceae). Remarkably, toxin sequestration protects both species against insectivorous birds, but only H. superbus gains protection against predatory lacewing larvae. Here, we used a full factorial design to test whether this difference was mediated by the differences in plant chemistry or by the insect species. We raised both species of milkweed bugs on seeds from both species of host plants and carried out predation assays using the larvae of the l...
Sequestration, i.e., the accumulation of plant toxins into body tissues for defence, is primarily... more Sequestration, i.e., the accumulation of plant toxins into body tissues for defence, is primarily observed in specialised insects. Sequestration was frequently predicted to incur a physiological cost mediated by increased exposure to plant toxins and may require resistance traits different from those of non-sequestering insects. Alternatively, sequestering species could experience a cost in the absence of toxins due to selection on physiological homeostasis under permanent exposure of sequestered toxins in body tissues. Milkweed bugs (Heteroptera: Lygaeinae) sequester high amounts of plant-derived cardenolides. Although being potent inhibitors of the ubiquitous animal enzyme Na+/K+-ATPase, milkweed bugs can tolerate cardenolides by means of resistant Na+/K+-ATPases. Both adaptations, resistance and sequestration, are ancestral traits shared by most species of the Lygaeinae. Using four milkweed bug species and the related European firebug (Pyrrhocoris apterus) showing different combi...
Teaching Documents by Prayan Pokharel
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Papers by Prayan Pokharel
In conclusion, our study showcased a significant diversity in plum varieties, with implications for orchard management and variety selection to cater to various preferences and needs in the local market and beyond.
Teaching Documents by Prayan Pokharel
In conclusion, our study showcased a significant diversity in plum varieties, with implications for orchard management and variety selection to cater to various preferences and needs in the local market and beyond.