Articles
Citrus rootstock breeding in an HLB-endemic environment with an industry in crisis
Article number
1448_20
Pages
171 – 178
Language
English
Abstract
The Florida Citrus Industry is in crisis due to now endemic HLB (huanglongbing or citrus greening disease). This season, only 15% of the juice processed in Florida was from Florida trees; whereas 5 years ago, 85% came from Florida trees.
Thus, developing a solution to HLB is the primary research objective of our breeding program.
The ultimate solution to HLB is an HLB-resistant rootstock that can transfer its tolerance/resistance to any grafted scion.
Such a rootstock would bring all susceptible scion cultivars, including the ‘Early Valencia’, ‘Hamlin’, all grapefruit, and the ‘Honey Murcott’ (now nearly seedless selections available), etc., back into play HLB-risk free! Rootstock breeding for Florida was already difficult due to the many attributes required for an improved rootstock.
These include resistance to blight, CTV, nematodes, the Diaprepes/Phytophthora complex, high salinity; adaptation to challenging soil types and tree size control for high density plantings.
Due to our success with somatic hybridization, we now breed rootstocks at both the diploid and tetraploid levels; and tetraploid rootstocks have shown good potential for tree size control.
We have developed a high-throughput method to screen new rootstock hybrids for ability to transmit HLB tolerance to susceptible scions.
With the advancement of tissue culture micropropagation of citrus rootstocks, nucellar polyembryony is no longer a required trait.
This has greatly expanded the germplasm base available for rootstock improvement.
Several promising new rootstock candidates have been identified from this research, including a few that suppress CLas (bacterium that causes HLB) replication.
Some of these selections have parents previously selected for abiotic stress tolerance (salinity tolerance). We are also identifying HLB tolerant rootstock candidates from other sources, and a few examples will be discussed (including a putatively more HLB-tolerant mutant of x639). We are confident that our progress with citrus rootstock improvement will contribute substantially to the recovery of the Florida citrus industry.
Thus, developing a solution to HLB is the primary research objective of our breeding program.
The ultimate solution to HLB is an HLB-resistant rootstock that can transfer its tolerance/resistance to any grafted scion.
Such a rootstock would bring all susceptible scion cultivars, including the ‘Early Valencia’, ‘Hamlin’, all grapefruit, and the ‘Honey Murcott’ (now nearly seedless selections available), etc., back into play HLB-risk free! Rootstock breeding for Florida was already difficult due to the many attributes required for an improved rootstock.
These include resistance to blight, CTV, nematodes, the Diaprepes/Phytophthora complex, high salinity; adaptation to challenging soil types and tree size control for high density plantings.
Due to our success with somatic hybridization, we now breed rootstocks at both the diploid and tetraploid levels; and tetraploid rootstocks have shown good potential for tree size control.
We have developed a high-throughput method to screen new rootstock hybrids for ability to transmit HLB tolerance to susceptible scions.
With the advancement of tissue culture micropropagation of citrus rootstocks, nucellar polyembryony is no longer a required trait.
This has greatly expanded the germplasm base available for rootstock improvement.
Several promising new rootstock candidates have been identified from this research, including a few that suppress CLas (bacterium that causes HLB) replication.
Some of these selections have parents previously selected for abiotic stress tolerance (salinity tolerance). We are also identifying HLB tolerant rootstock candidates from other sources, and a few examples will be discussed (including a putatively more HLB-tolerant mutant of x639). We are confident that our progress with citrus rootstock improvement will contribute substantially to the recovery of the Florida citrus industry.
Publication
Authors
J.W. Grosser, F.G. Gmitter, J. Chater, M. Dutt, A.A. Omar, L.M. Cano
Keywords
citrus rootstock, disease resistance, genetic variation, huanglongbing, micropropagation
Groups involved
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