On Saturday, 17th May, Dr Kirsten Wolff came to speak to Plant Heritage North East about her work at Newcastle University, where she is leading research into profiling plant DNA.
Plant DNA is much the same as human DNA in that each individual (and its clones) has a unique DNA fingerprint. Technology has now advanced to the point where the cultivars of a certain genus or species can be profiled, and comparisons made with other cultivars.
‘So what’s the point of that?’, I hear you ask. Well, in a nutshell, this means that we can now check at the most detailed level that we have correctly identified all of the plants within a national collection.
The collections which Kirsten used for her research were Hesperantha, which are held by Penny and David Ross and Alan Kennedy. She collected 106 named samples (or accessions), covering 61 different cultivars, then proceeded to profile their DNA. The technique she used was, quite frankly, beyond me, but what she managed to do was translate each plant’s DNA into a string of numbers, called a genotype. She then entered these numbers into a spreadsheet and sorted them to see which, if any, were the same and the results were, quite frankly, astounding. After sorting them, Kirsten found there were 58 different genotypes, of which 40 were unique, seven had two or more accessions with same name (which is good), and 11 which had different named cultivars (not good). So some accessions of different names appeared in the same group, and accessions of a single name appeared in multiple groups. Hesperantha ‘Major’, for example, appeared in three groups, so the accessions she had collected were actually three different cultivars. And in one group she found three differently named cultivars: ‘Mary Barnard’, ‘Professor Barnard’ and ‘Speciosa’, proving that these are, in fact, the same plant. The genotypes which included more than one accession can be seen below, where each letter (A to R) denotes a different genotype.
So which of these cultivars is actually the ‘right’ one? That’s a question which is very difficult, if not impossible to answer. Sometimes historical investigation can trace a cultivar back to its earliest appearance, but often there is no way to tell.
And just to add to the confusion, sometimes plants within a group can look slightly different – some pink and some red, such as in group D. It’s possible that this is because the profiling technique used was not quite accurate enough (although there is only a 1 in 100,000 chance that this is the case). The more likely explanation is ‘somatic mutation’, or a random genetic mutation that happens when plants divide. For example, historic records showed that the cv ‘Jennifer’, which is genetically identical to ‘Major’ but a different colour, was actually discovered growing next to ‘Major’.
Although Kirsten’s research is fascinating, does it have any practical application? Indeed it does. If we can correctly identify all cultivars, then we will be one step further towards maintaining genetic diversity. Also, it means that if a plant is lost (such as all the trees we lost during Hurricane Charlie), genetic profiling would allow us to ensure that the lost plant was replaced with exactly the right new plant. And finally, if a plant breeder can prove that his new plant is, indeed, brand new, he could charge a premium for that cultivar.
Lots of food for thought!