Articles
Citrus rootstock breeding at the University of California Riverside
Article number
1448_23
Pages
191 – 194
Language
English
Abstract
The UCR citrus rootstock breeding program develops new rootstocks by hybridization-selection.
These selections and those from other programs are trialed in California.
We target traits important for California because the program is primarily funded by California citrus growers.
Parents expected to have complementary traits are crossed, and progeny are evaluated for target traits.
New hybrids are typically field-planted on their own roots and selected for adequate vigor.
Seedlings from each hybrid are visually evaluated for uniformity and polyembryony.
Some are now also tested with KASP SNP markers to evaluate percent nucellar seedlings.
We recently tested rooted cuttings of some hybrids that have insufficient nucellar embryony, but success is relatively genotype-specific.
Phytophthora root rot tolerance is tested by growing inoculated seedlings.
We test for Citrus tristeza virus (CTV) tolerance by growing inoculated grafted trees in a greenhouse, a PCR test to quantify citrus nematodes on seedling roots, and a greenhouse test of calcareous soil tolerance.
The order of evaluation of different traits is a difficult strategic issue involving trait value, cost, throughput, and accuracy of tests.
Rootstock trials are conducted with scions important in California.
Most trials have been with grower-cooperators, but some are on field stations where the collection of yield records is more reliable.
Most trials have about 10-12 single-tree replications of 15-25 rootstocks.
Some trials target specific traits, such as tolerance to calcareous soils, and do not include yield records, but may include fruit quality evaluation.
The collection of yield records from trials with growers is among the greatest challenges.
It is not possible to conduct field trials for HLB tolerance in California, but we are evaluating whether tests in containment facilities will be useful.
These selections and those from other programs are trialed in California.
We target traits important for California because the program is primarily funded by California citrus growers.
Parents expected to have complementary traits are crossed, and progeny are evaluated for target traits.
New hybrids are typically field-planted on their own roots and selected for adequate vigor.
Seedlings from each hybrid are visually evaluated for uniformity and polyembryony.
Some are now also tested with KASP SNP markers to evaluate percent nucellar seedlings.
We recently tested rooted cuttings of some hybrids that have insufficient nucellar embryony, but success is relatively genotype-specific.
Phytophthora root rot tolerance is tested by growing inoculated seedlings.
We test for Citrus tristeza virus (CTV) tolerance by growing inoculated grafted trees in a greenhouse, a PCR test to quantify citrus nematodes on seedling roots, and a greenhouse test of calcareous soil tolerance.
The order of evaluation of different traits is a difficult strategic issue involving trait value, cost, throughput, and accuracy of tests.
Rootstock trials are conducted with scions important in California.
Most trials have been with grower-cooperators, but some are on field stations where the collection of yield records is more reliable.
Most trials have about 10-12 single-tree replications of 15-25 rootstocks.
Some trials target specific traits, such as tolerance to calcareous soils, and do not include yield records, but may include fruit quality evaluation.
The collection of yield records from trials with growers is among the greatest challenges.
It is not possible to conduct field trials for HLB tolerance in California, but we are evaluating whether tests in containment facilities will be useful.
Publication
Authors
Z. Thomas, C.T. Federici, M.L. Roose
Keywords
cultivar trials, SNP markers
Groups involved
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