Agriculture Commons^™

Soil Moisture Dynamics In Cover Cropping Systems: From Local To Global Scales, Manish Gautam

Theses and Dissertations

Cover cropping systems, which have gained recognition for their ability to enhance soil health and promote sustainability are also associated with potential risks related with declining soil moisture and pose a dilemma for farmers considering the adoption of cover crops in water deficit semi-arid settings worldwide. To address this pressing issue, we conducted a participatory cover cropping trial in the Lower Rio Grande Valley (LRGV) region, encompassing four different farms and supplemented this experiment with a meta-analysis to answer our soil moisture and climate parameters and quantify the impact of cover crops on soil moisture levels. The findings revealed that …

Morphological Characterization Of Intraspecific Variation For Trichome Traits In Tomato (Solanum Lycopersicum), Satinderpal Kaur, Neetu Khanal, Robert K. Dearth, Rupesh R. Kariyat

Biology Faculty Publications and Presentations

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 …

Greenbug Feeding-Induced Resistance To Sugarcane Aphids In Sorghum, Heena Puri, Edith Ikuze, Jessica Ayala, Isabella Rodriguez, Rupesh R. Kariyat, Joe Louis, Sajjan Grover

Biology Faculty Publications and Presentations

Plants are attacked by multiple insect pest species and insect herbivory can alter plant defense mechanisms. The plant defense responses to a specific herbivore may also contribute to the herbivore growth/survival on plants. Feeding by one insect species can modulate the plant defenses, which can either facilitate or hamper the colonization of subsequent incoming insects. However, little is known about the effect of sequential herbivory on sorghum plants. In this study, we demonstrate that a specialist aphid, sugarcane aphid (SCA; Melanaphis sacchari) grows faster on sorghum than a generalist aphid species, greenbug (GB; Schizaphis graminum). We also determined …

Effective Farm Management Promotes Native Amf And Benefit Organic Farming Systems, Pushpa Soti, Rupesh R. Kariyat, Alexis Racelis

Biology Faculty Publications and Presentations

Highlights

• Agricultural practices have significant influence on the AMF community dynamics.

• Soil nutrients regulate AMF spore abundance and diversity.

• Using grass cover crops can promote native AMF in farms.

Abstract

Using soil inoculants containing naturally occurring beneficial microorganisms has become a popular practice in sustainable agriculture. However, an understanding of the environmental variables that affect plant-microbe interactions and the benefit of using commercial inoculum is relatively sparse. To address this, we examined the efficiency of three different methods to inoculate AMF (Arbuscular Mycorrhizal Fungi) in organic vegetable farms in south Texas: cover cropping, application of farm-produced (indigenous) AMF inoculum, …

Winners And Losers In Dryland Reforestation: Species Survival, Growth, And Recruitment Along A 33-Year Planting Chronosequence, Clifton Albrecht, Zarek Contreras, Kimberly Wahl-Villarreal, Mitch Sternberg, Bradley O. Christoffersen

Biology Faculty Publications and Presentations

Reforestation in the Lower Rio Grande Valley (LRGV) of Texas began in the 1960s and to date over 6,475 ha of land has been reforested. However, there has been minimal assessment to understand differential species success, compositional trends, and the aboveground C sequestration potential of these developing forests. We coupled quantitative planting information of >50 native woody tree and shrub species with surveys of 5,223 stems of 4,606 individuals in a chronosequence of restored forests ranging in age from 1 to 33 years to estimate species-specific mortality rates, biomass accumulation and recruitment, as well as compositional trends in the herbaceous …

A Sugarcane G-Protein-Coupled Receptor, Shgpcr1, Confers Tolerance To Multiple Abiotic Stresses, Manikandan Ramasamy, Mona B. Damaj, Carol Vargas-Bautista, Victoria Mora, Jiaxing Liu, Carmen S. Padilla, Sonia Irigoyen, Tripti Saini, Nirakar Sahoo, Jorge A. Dasilva, Kranthi K. Mandadi

Biology Faculty Publications and Presentations

Sugarcane (Saccharum spp.) is a prominent source of sugar and serves as bioenergy/biomass feedstock globally. Multiple biotic and abiotic stresses, including drought, salinity, and cold, adversely affect sugarcane yield. G-protein-coupled receptors (GPCRs) are components of G-protein-mediated signaling affecting plant growth, development, and stress responses. Here, we identified a GPCR-like protein (ShGPCR1) from sugarcane and energy cane (Saccharum spp. hybrids) and characterized its function in conferring tolerance to multiple abiotic stresses. ShGPCR1 protein sequence contained nine predicted transmembrane (TM) domains connected by four extracellular and four intracellular loops, which could interact with various ligands and heterotrimeric G …

Civic Agriculture In Review: Then, Now, And Future Directions, Allison Kaika, Alexis Racelis

Biology Faculty Publications and Presentations

"Civic agriculture," a term first coined by rural sociologist Thomas Lyson, refers to forms of agriculture that occur on a local level, from production to consumption, and are linked to a community's social and economic development. Sixteen years since its original articulation, the term "civic agriculture" has taken on greater significance in research, political activism, and community organizing. Grown from the roots of civic community theory, civic agriculture functions as a new branch of civic community theory that is ripe for theorization. In revisiting the foundations of the term, this review paper seeks to consolidate current and future research in …

Weeds As Hosts Of Plant Parasitic Nematodes In Subtropical Agriculture Systems, Habraham F. Lopez, Pushpa Soti, Ganpati B. Jagdale, Parwinder Grewal, Alexis Racelis

Biology Faculty Publications and Presentations

With a nearly year-round growing season, tropical and subtropical regions are plagued with a myriad of agro-nomic challenges, including near-continuous weeds and invertebrate pests including plant-parasitic nematodes (PPNs). A poor understanding of the presence and geographical distributions of these pests complicate their man-agement, especially in organic farming systems. This work attempts to document the interaction of PPNs with the major weeds in the semi-arid region of south Texas. Five organically managed farms were surveyed for four weeds of regional agronomic importance including silverleaf nightshade (Solanum elaeagnifolium), common sunflower (Helianthus annuus), false ragweed (Parthenium hysterophorus), and London rocket (Sisymbrium irio). Soil …

Discerning Competitive Vs. Facilitative Relationships Of Weeds On Forest Restoration Efforts At La Sal Del Rey, Tx, Mylen A. Arias

Theses and Dissertations

Dryland ecosystems need effective restoration strategies to address severe degradation. It is often assumed that voluntary forb weeds either compete with or have no effect on native seedlings. In contrast, theory and empirical work suggest a potential facilitative role for such forb weeds. We conducted a manipulative weed exclusion experiment at a semi-arid site in South Texas targeted for large scale forest restoration and subsequently dominated by early successional forb weeds to discern the net effect of these weeds on the growth and survival of target thornscrub tree and shrub seedlings. Overall, weed presence did not significantly affect seedling mortality …

Developing Methods To Survey, Collect, Process, And Screen Endemic Entomopathogenic Fungi Against The Asian Citrus Psyllid In The Lower Rio Grande Valley, Jonathan Cisneros

Theses and Dissertations

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), vectors “Candidatus Liberibacter spp.”, the causative agent of Citrus Greening Disease. Managing ACP is imperative given the continuous increase in HLB positive trees. An aspect of integrated pest management (IPM) is the use of entomopathogenic fungi for the biological control of D. citri.

In order to identify endemic entomopathogenic fungi actively infecting D. citri, ACP were collected from local residential areas, surface sterilized, and plated on a semi-selective agar medium. Collection of over 9,300 samples from 278 sites throughout the LRGV led to the positive identification of …

Examining The Efficacy Of Cover Crops As An Integrated Pest Management Tool In Organic Farms In The Lower Rio Grande Valley, Lili M. Martinez

Theses and Dissertations

The Lower Rio Grande Valley (LRGV) consists of a mix in subtropical and costal habitats, a combination that provides a favorable environment for the animals and plants that inhabit it. This is a problem for organic farmers as they refrain from using synthetic chemicals and therefore led them to seek other methods of dealing with insect herbivory. Of the many alternative methods available, we looked specifically at integrated pest management methods (IPM) to determine their efficacy in reducing insect herbivory among cash crops. Chapter II discusses an experiment performed in an organic farm in Edinburg, Texas consisting of a two-year …

Impact Of Cover Crops On Insect Community Dynamics In Organic Farming, Lili Martinez, Pushpa Soti, Jasleen Kaur, Alexis Racelis, Rupesh R. Kariyat

Biology Faculty Publications and Presentations

Manipulating cover crops as an integrated pest management strategy has recently gained popularity in both traditional and organic agroecosystems. However, little information is available for producers to make informed decisions about cover crop selection, management, and their potential use as a pest management tool. To address this, we conducted a two-year, four-season field experiment on the potential of various cover crops during the summer seasons of both years, followed by monocultures of cash crops during winters. We hypothesized that the cover crop treatments would attract beneficial insects and repel damaging herbivores in a species-specific manner, and the insect community dynamics …

Comparing Novel And Traditional Sampling Methodologies To Analyze The Population Status Of The Rio Grande Cooter (Pseudemys Gorzugi), Amy P. Bogolin

Theses and Dissertations

The Rio Grande Cooter, Pseudemys gorzugi, is an understudied aquatic turtle species of conservation concern in the Rio Grande, Pecos, and Devils river systems. Traditional sampling methodologies for aquatic turtle species face numerous challenges, but novel sampling methodologies, such as drone-based surveys and environmental DNA analysis, may address these issues. This study compared novel sampling methodologies to traditional sampling methodologies in mean detections and identifications of aquatic turtle species, developed and implemented an environmental DNA assay to detect P. gorzugi, and characterized P. gorzugi habitat. Following an introductory chapter, each task is addressed by chapter and formatted to …

Polyphenol-Rich Purple Corn Pericarp Extract Adversely Impacts Herbivore Growth And Development, Mandeep Tayal, Pavel Somavat, Isabella Rodriguez, Tina Thomas, Bradley O. Christoffersen, Rupesh R. Kariyat

Biology Faculty Publications and Presentations

Plant secondary metabolites such as terpenes, phenolics, glycosides, and alkaloids play various functional roles including pigmentation, foliar and floral volatile synthesis, hormonal regulation, and direct and indirect defenses. Among these, phenolic compounds are commonly found in plants, but vary in the distribution of their specific compounds among plant families. Polyphenols, including anthocyanins and tannins, are widely distributed and have been well documented for their roles- primarily in plant pigmentation and also in plant defenses. However, commercialization of such compounds for use in insect pest management is severely hampered by expensive, inefficient, and time-consuming extraction protocols. Using a recently developed inexpensive …

Review Of Major Crop And Animal Arthropod Pests Of South Texas, Holly N. Davis, John A. Goolsby, Donald B. Thomas, Ismael Badillo, Rupesh R. Kariyat, Christopher Vitek, Danielle Sekula

Biology Faculty Publications and Presentations

The Lower Rio Grande Valley is an area in Texas that consists of the four southern-most counties. This area contains a diverse range of agriculture and land-use including vegetable, row-crop and livestock production. The year-around cool to hot subtropical climate means that green vegetation is continually present, including many crops. Geographically, it shares an international border, making it a region vulnerable to new invasive species and the re-introduction of pests that have been previously eliminated in the United States. These combined factors lead to an array of arthropod pests that may have serious impacts on the crops, animals, and people …

Genetic Variation In Two Economically Important Arthropod Vectors Of Citrus Diseases, Alejandra Fuentes

Theses and Dissertations

Arthropod vectors are agriculturally and ecologically important because they transmit numerous plant pathogens. Commonly, control strategies for vector-borne plant pathogens focus on suppression of vector populations. Genetic variation studies in pest populations provide useful information for biological control, understanding pesticide resistance, and inferring global movement patterns. In chapter I, genetic variation of worldwide populations of Diaphorina citri, the vector of Citrus greening disease, was examined to assess potential sites of origin of invasive populations. The results showed population structure at regional levels, suggesting limited gene flow and revealing patterns of invasion. In chapter II, I explored the community of …

Multifunctionality Of Cover Crops On Organic Vegetable Farms In South Texas, Savannah M. Rugg

Theses and Dissertations

Situated in deep South Texas, the Lower Rio Grande Valley (LRGV) is considered one the most productive agricultural regions in the southern US. With the highest concentration of organic farms in the state (Hidalgo county), finding management practices that comply with organic certification is increasingly pertinent. Cover cropping can serve multiple functions in an agroecosystem such as: suppressing weeds, increasing soil organic matter (SOM), increasing soil nitrates, and enhancing soil biodiversity. The four cover crops (lablab, sunn hemp, sudangrass, and pearl millet) were assessed to see their potential to increase soil nitrogen, to increase soil organic matter, and to suppress …

Management Of Silverleaf Whitefly, Bemisia Argentifolii Bellows And Perring (Hemiptera: Aleyrodidae), Using Non-Crop Companion Plants In Organically-Managed Cantaloupe Systems In South Texas, Ruth Renee Colyer

Theses and Dissertations - UTB/UTPA

Field trials in three separate phases of research were carried out from March, 2010, to August, 2012, to determine the effects of inter-cropping cantaloupe (Cucumis melo var. inodorus) with select non-crop companion plants in an effort to develop organic production strategies for melons in South Texas without the use of pesticides. A research program was designed and initiated to assess the effects of the companion plants and their ability to: 1) attract insect pollinators, and 2) repel or suppress pest species without affecting beneficial natural enemy complexes. The hypotheses were: 1) that organically-managed cantaloupe systems grown with non-crop companion plants …

A Survey Of Heavy Metals In Water, Soil And The Surrounding Plants In The Lower Rio Grande Valley, Erving W. Morelius

Theses and Dissertations - UTB/UTPA

Heavy metal pollution of the environment in recent years has become a major issue of importance for both human and environmental health. Samples were investigated for the potential pollution of the area as it is a vital produce producing area. During the study plant, soil and water samples were collected from the Donna Reservoir and Canal System to test the concentration of various heavy metals. The heavy metals tested included both potentially toxic and micronutrients in the samples which included arsenic, cadmium, chromium, copper, iron, lead, nickel and sulfur. During the study, a sixty day sampling period was used to …

Comparison Of Soil Chemistry And Microbial Communities That Inhabit The Rhizosphere Of Native And Non-Native Grasses Of The Lower Rio Grande Valley, Jacqueline Valencia

Theses and Dissertations - UTB/UTPA

Non-native grasses can modify the soils they invade. This study investigated microbial variation among native and non-native grasses in the Lower Rio Grande Valley. We hypothesized that rhizospheres of non-native grasses would support a higher density of microorganisms; therefore microbial communities of invasive plants would exploit more carbon sources than those of native plants. A second hypothesis stated that Streptomyces bacteria from the rhizosphere of non-native grasses would be better competitors. Samples of grasses, and soil from their respective rhizospheres were obtained in Arroyo City, TX. Results indicated a higher bacterial colony density, total activity and number of substrates utilized …