By Lamiaa Mahmoud and Manjul Dutt
Utilizing tolerant rootstocks to combat HLB is a long-term management strategy that can help sustain productivity and enhance tree survival, especially when implemented alongside other HLB management approaches.
Australian limes are tolerant to HLB, and their DNA can be incorporated into HLB-susceptible citrus using conventional breeding methods to enhance tolerance to HLB. Over the last decade, citrus breeders at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center (UF/IFAS CREC) have developed a large population of HLB-tolerant hybrids by making crosses between different Australian lime species. Some of the trees exhibit improved tolerance to HLB in the field, and many have remained HLB-negative even in endemic HLB conditions.
Cuttings from several of these hybrids were rooted in a mist bed, and the resulting trees were grafted with Valencia budwood. HLB progression in trees infected with CLas was observed over time. A recently published greenhouse study highlighted the potential of these field-tolerant hybrids to enhance tolerance to HLB in Valencia sweet orange. Among the evaluated hybrids, a select mandarin × finger lime (MFL1–98) and a HLB-tolerant pummelo × finger lime (PFL2–61) hybrid demonstrated excellent graft success rates and scion vigor, comparable to the Swingle rootstock control. PCR analysis of the DNA from the Valencia scion revealed a low infection rate in Valencia scions grafted onto these hybrids, and the root tissues of the hybrids remained free of CLas infection.
Continued research and development will enhance the use of these rootstocks commercially. Field trials using this germplasm are scheduled to examine the impact of these rootstocks on tree growth and fruit quality. Please reach out to manjul@ufl.edu if you are interested in assessing any of these germplasms.
Lamiaa Mahmoud is a postdoctoral researcher, and Manjul Dutt is an assistant professor, both at the UF/IFAS CREC.
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