Theses and Dissertations

Date of Award

5-1-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Teresa Patricia Feria Arroyo

Second Advisor

Madhurababu Kunta

Third Advisor

Mamoudou Sétamou

Abstract

The Texas citrus industry has a long history of resilience, rebounding from environmental and economic disasters. Over the last decade it has endured several hurricanes, freezes, pests and diseases. Huanglongbing (HLB), a graft-transmissible disease caused by Gram-negative bacterium Candidatus Liberibacter asiaticus which is vectored by the Asian citrus psyllid (ACP) (Diaphorina citri Kuwayama), is an endemic citrus disease posing serious threat to the long-term viability of the industry. Rapid production of high quality nursery trees and effective protection of young citrus transplants from HLB are critical for long term sustainability of citriculture in this region. Studies were performed to improve Sour Orange (Citrus × aurantium L.) (SO) rootstock seedling production and optimizing the budding technique of ‘Rio Red’ grapefruit (Citrus x paradisi Macfad) on SO rootstock plants. Furthermore, different aperture size of individual protective covers (IPC) used to protect individual young citrus trees by mechanical exclusion of ACP and develop HLB-free trees for the first few years before they become bearing trees were also tested. Results showed that sowing SO seeds vertically with micropyle oriented downward yields significantly less seedlings with an undesirable crooked stem. Reducing apical dominance through bending or cutting off significantly enhanced scion growth compared to non-forced method. However, the optimal budding technique must balance physiological performance with nursery operational efficiency. Under South Texas conditions, IPCs with an aperture of <0.7 mm2 showed optimal performance to exclude ACP and to protect transplants in the field. Together, these nursery and field strategies may help strengthen citrus production under HLB endemic conditions.

Comments

Copyright 2026 Ruth Lilia Galan. All Rights Reserved. https://proquest.com/docview/3371135118

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