rbcL gene based analysis to infer phylogenetic relationships has been extensively used in past and i very well optimized...what you can do is...either used the conserved primers people have used for amplification of these genes or do a multiple alignment of rbcL gene from your system along with other available sequences, identify conserved regions for primer designing and go ahead.....with PCR amplification, sequencing MSA and phylogenetis analysis....if you are not specifically removing chloroplasts at any step...the total genomic DNA should be fine...
PCR condition: 95°C for 1 min, followed by 35 cycles of 95°C for 30 s, (50°C for matK-A, 45°C for matK-B, 51°C for rbcL-A and 48°C for rbcL-B) for 30 s and 68°C for 1 min, followed by an elongation step at 72°C for 5 min.