Isozymes in the early identification of hybrids and nucellar clones in citrus breeding

One of the problems related to citrus breeding is the polyembryony and the ensuing difficulty in distinguishing nucellar clones from hybrids obtained from controlled crosses. Twelve isozyme systems using starch gel electrophoresis were studied. A procedure for simultaneous resolution of acid phosphatase, anodic and cathodic peroxidase, glutamate oxaloacetate transaminase, phosphoglucoisomerase, phosphoglucomutase and malic enzyme was developed. Thirty one clones with possible use in the Instituto Agronômico de Campinas, State of São Paulo, Brazil breeding program were characterized. Seven loci and twenty five alleles are involved allowing for an early identification of hybrids before transplanting them into the field for agronomic evaluations. Implications in breeding strategies and in the determination of the degree of nucellar embryony of commercial rootstocks are discussed.

citrus; genetics; breeding; isozymes; hybrids; nucellar clones; zygotic embryos

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