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4. GENETIC DIVERSITY...
RAPD and ISJ polymorphism
A total of 119 polymorphic bands were detected among eight populations of L. multiflorum
and 12 populations of L. perenne. In both species the ISJ markers revealed higher
polymorphism than RAPD (Table 4.1) measured as the percentage of polymorphic loci. Similarly,
the number of scorable bands per a primer was almost twice greater for ISJs (13.8)
than for RAPDs (7.1). Italian and perennial ryegrass appeared to have the similar level of
polymorphism as estimated by RAPD (75 and 77%, respectively) and ISJ markers (93 and
96%). They did not differ in the average number of RAPD alleles over all loci (A). In opposite,
this parameter was lower in L. multiflorum than in L. perenne when estimated from ISJ
markers. This probably resulted from the very low polymorphism observed in ecotypes of
L. multiflorum. Otherwise, cultivars of Italian ryegrass had the polymorphism comparable to
both cultivars and ecotypes of perennial ryegrass.
In general, L. multiflorum and L. perenne shared the same bands with similar frequencies.
None of identified bands was a species specific i.e., present in all individuals of one
species but absent in another. It was only possible to find two “semi-diagnostic alleles” i.e.,
alleles that are generally present in one species and rarely found in the other. Both alleles
were generated by the RAPD primer, OPA02. They were observed with significantly higher
frequency in L. multiflorum in comparison with L. perenne, namely 0.423 and 0.242 for
OPA02-4 and 0.399 and 0.163 for OPA02-4. Interestingly, the latter was present in all individuals
of L. multiflorum cultivars but it was very rare (frequency equal to 0.069) in ecotypes
of this species.