PRELIMINARY RESULTS ON THE USE OF FLOW CYTOMETRY AS A DIAGNOSTIC TOOL FOR THE IDENTIFICATION OF POLYEMBRYONIC CITRUS ROOTSTOCK HYRBIDS

K.F. Hannweg, G. Visser , A. Sippel
Citrus rootstock breeding and development is hindered by the polyembryonic nature of the majority of citrus rootstocks. Seeds of polyembryonic cultivars or selections contain numerous embryos which are nucellar in origin with the zygotic embryo dying due to lack of nutrients and over-crowding within the developing seed. Since nucellar seedlings are genetically the same as the female parent, this makes it almost impossible to breed with polyembyonic rootstocks unless in vitro embryo rescue is carried out. A study was undertaken whereby embryo development was followed over time (40 days post pollination to 120 days post pollination) for a number of parental crossings to determine if zygotic embryos could be isolated and rescued at an early enough developmental and identifiable stage, in order to produce hybrid plantlets from the in vitro rescued embryos. Although there were differences between the various crossing combinations in terms of embryo development (developmental stage and number), this visual technique alone could not be used to identify the zygotic embryos resulting from controlled pollinations with certainty. Although various molecular methods including the use of RAPDs, SSRs, etc. have been used to identify hybrid seedlings, flow cytometry was investigated as a possible technique for the identification of hybrids for its simplicity and economy. Three replicates for each sample (one each of each parent and ‘hybrid’) were analysed using flow cytometry and the DNA content determined using a standard of known DNA content (Tahiti Lime). Data were analysed using the Student’s t-test. The results of the investigation indicated that if the DNA contents of the parental crossings are significantly different from each other, flow cytometry provides an efficient and cost-effective means of determining hybridity of seedlings produced from controlled pollinations of polyembryonic citrus rootstock crosses.
Hannweg, K.F., Visser , G. and Sippel, A. (2013). PRELIMINARY RESULTS ON THE USE OF FLOW CYTOMETRY AS A DIAGNOSTIC TOOL FOR THE IDENTIFICATION OF POLYEMBRYONIC CITRUS ROOTSTOCK HYRBIDS. Acta Hortic. 1007, 733-738
DOI: 10.17660/ActaHortic.2013.1007.85
https://doi.org/10.17660/ActaHortic.2013.1007.85
citrus rootstocks, flow cytometry, hybrid identification
English

Acta Horticulturae