Mode of reproduction and amplified fragment length polymorphism variation in purple needlegrass (Nassella pulchra): utilization of natural germplasm sources

A dominant plant of the California grasslands, purple needlegrass [Nassella pulchra (Hitchc.) Barkworth] is an important revegetation species in its n ative range. The amplified fragment length polymorphism (AFLP) method was u sed to elucidate mode of reproduction and nucleotide variation among 11 nat ural populations and three selected natural germplasm releases of N. pulchr a. A total of 12 co-dominant AFLPs, informative within eight populations, f ailed to reveal any heterozygous individuals, indicating very high selfing rates ((S) over bar (H) = 1). Estimates of nucleotide diversity within popu lations ranged from 0 to 0.00069 (0.00035 average), whereas the total nucle otide divergence among populations ranged from 0.00107 to 0.00382 (0.00247 average). Measures of population differentiation (G(S)) in terms of Shannon -Weaver diversity values and estimated nucleotide substitutions were 0.90 a nd 0.86, respectively. Although some of the sample populations contained a mixture of true breeding genotypes, most populations could be distinguished unambiguously. Moreover, geographical distance between the natural source populations was significantly correlated with genetic distance (r = 0.60) a mong the corresponding sample populations. Results indic ate that inbreedin g, combined with founder effects and/or selection, has contributed to the d ifferentiation of N. pulchra populations. Foundation seed populations of th e selected natural germplasm releases were genetically well defined and mos t similar to natural seed collected near the corresponding source populatio ns. Thus, these commercial germplasm sources will be made practically avail able and useful for conservation plantings within the intended areas of uti lization.