DNA was extracted from leaf tissue with cetylmethylammoniumbromide (CTAB) (Gibb and Padovan, 1994). The aliquots of (10 lg) DNA were digested with appropriate restriction endonucleases (which do not cut the DNA used as the probe, i.e., pha-e coding region) and subjected to electrophoresis on 0.8% agarose gels. 32P-labelled hybridisation probes were prepared using the Megaprime random primer labelling kit (Amersham). Transfer of DNA onto nylon membranes, electrophoresis, and hybridisation were all carried out according to standard procedures