Study of Population Dynamics of Sugarcane Aphid \u3ci\u3e(Melanaphis sacchari)\u3c/i\u3e in Rio Grande Valley, Texas

Chapter 1: This chapter incorporates detailed information about the biotype concept, aphids, their types and their biotypes, importance of studying insect biotypes and their role in mediating host plant defenses. Chapter 2: This chapter explains in detail about the biology, biotypes, feeding behavior, damage, and economic loss caused due to sugarcane aphid infestation. This chapter further elaborates on the need for studying population level differences and justifies the objectives and significance of this research study. Chapter 3: This chapter provides information about the comprehensive work done on three different populations of sugarcane aphid collected from three different locations in Rio Grande Valley, Texas. This chapter includes detail information on the life history traits and feeding behavior of three different sugarcane aphid populations along with host plant defense responses against post infestation of sugarcane aphids. Chapter 4: This chapter provides an overview of my major findings and possible future directions for research to understand the sugarcane aphids and the potential emergence of new biotype(s)

The Known and Unknowns of Aphid Biotypes, and Their Role in Mediating Host Plant Defenses

Insect species are subjected to disparate selection pressure due to various biotic and abiotic stresses. Management practices including the heavy use of chemical insecticides and introduction of insect-resistant plant cultivars have been found to accelerate these processes. Clearly, natural selection coupled with human intervention have led to insect adaptations that alter phenotypes and genetic structure over time, producing distinct individuals with specialized traits, within the populations, commonly defined as biotypes. Biotypes are commonly found to have better fitness in the new environment and, in the case of aphids, the most commonly studied system for biotypes, have the ability to successfully infest previously resistant host plants and new species of host plants. Although a large number of studies have explored biotypes, the concept for defining biotypes varies among scientists, as we lack a consistency in estimating biotype behavior and their variation within and between biotypes. The concept of biotypes is even more complicated in aphid species (Aphidoidea), as they undergo parthenogenetic reproduction, making it difficult to understand the source of variation or quantify gene flow. In this review, we aim to illuminate the concept of biotype and how it has been used in the study of aphids. We intend to further elaborate and document the existence of aphid biotypes using sugarcane aphid (Melanaphis sacchari) as a model to understand their differences, level of variation, evolution, and significance in pest management

Morphological characterization of intraspecific variation for trichome traits in tomato (Solanum lycopersicum)

Trichomes, the hairlike protuberances in plants, have been well known to act as the first line of defense against herbivores, and abiotic stresses, along with other structural defenses such as spines, thorns, and waxes. We previously reported the tremendous variation in trichome traits among different wild and cultivated Solanum species and demonstrated that trichomes types and density are traditionally miscalculated and often misnamed. However, intraspecific variation in trichome traits is poorly understood, although this has implications for stress tolerance and resistance breeding programs in economically important crop species and can also mediate ecological interactions at multiple trophic levels in their wild congeners. In this study, using tomato as a model, we characterized the trichomes from 10 commonly grown varieties using a minimal sample prep desktop scanning electron microscopy, and followed up with estimating their dimensions across the varieties and trichome types. We hypothesized that although trichome number may vary, the varieties will have similar trichome types, based on current literature. Our results show that there is significant variation for trichome number as well as dimensions of trichome types among these varieties. Furthermore, when we separately analyzed the number and dimensions of commonly found glandular and non-glandular trichomes, the results were consistent with broad assessment of trichomes, showing consistent variation among varieties, suggesting that trichome studies should not be limited to basic classification into glandular and non-glandular, and should accommodate the sub-types and their dimensions

The Known and Unknowns of Aphid Biotypes, and Their Role in Mediating Host Plant Defenses

Insect species are subjected to disparate selection pressure due to various biotic and abiotic stresses. Management practices including the heavy use of chemical insecticides and introduction of insect-resistant plant cultivars have been found to accelerate these processes. Clearly, natural selection coupled with human intervention have led to insect adaptations that alter phenotypes and genetic structure over time, producing distinct individuals with specialized traits, within the populations, commonly defined as biotypes. Biotypes are commonly found to have better fitness in the new environment and, in the case of aphids, the most commonly studied system for biotypes, have the ability to successfully infest previously resistant host plants and new species of host plants. Although a large number of studies have explored biotypes, the concept for defining biotypes varies among scientists, as we lack a consistency in estimating biotype behavior and their variation within and between biotypes. The concept of biotypes is even more complicated in aphid species (Aphidoidea), as they undergo parthenogenetic reproduction, making it difficult to understand the source of variation or quantify gene flow. In this review, we aim to illuminate the concept of biotype and how it has been used in the study of aphids. We intend to further elaborate and document the existence of aphid biotypes using sugarcane aphid (Melanaphis sacchari) as a model to understand their differences, level of variation, evolution, and significance in pest management

Early-Onset Neonatal Meningitis Caused by an Unusual Pathogen‐Moraxella catarrhalis

Introduction. Moraxella catarrhalis are part of the normal flora of the human respiratory tract and are known to have low pathogenic potential. The organism is rarely reported in the literature as the causative agent of meningitis. We report the first case of early-onset neonatal meningitis associated with M. catarrhalis from Nepal. Case Report. A 3-day-old baby with fever and yellowish discolouration of the body since 48 hrs was admitted to the neonatal ward. The baby developed 3 episodes of seizures in the form of uprolling of eyes on the first day of admission during phototherapy course for raised serum bilirubin. Sepsis screen was positive, and meningitis was confirmed as the cerebrospinal fluid culture grew M. catarrhalis. Cranial ultrasound scan was normal. The baby received a 21-day course of intravenous cefotaxime and amikacin. Recovery has been uneventful to date. Conclusion. Neonatal meningitis is a life-threatening infection. This case report presents an uncommon aetiology of neonatal meningitis which can be misidentified in the diagnostic bacteriology laboratory in resource constraints area like ours