S-allele sequence diversity in natural populations of Solanum carolinense (Horsenettle)

Abstract

S-allele diversity in Solanum carolinense was surveyed in two natural populations, located in Tennessee and North Carolina, with a molecular assay to determine the genotype of individual plants. A total of 13 different S-alleles were identified and sequenced. There is high overlap between the two populations sampled, with 10 alleles shared in common, one allele found only in Tennessee, and two found only in North Carolina. The number of alleles in this species appears to be extremely low compared with other species with gametophytic self-incompatibility. Sequence comparisons show that most alleles are extremely different one from another in their primary sequence and a phylogenetic analysis indicates extensive trans-specific evolution of S-lineages. In addition, some alleles appear to be derived much more recently. The implications of these observations are discussed in the light of recent theoretical results on S-allele population diversity and persistence.

Functional gametophytic self-incompatibility in a peripheral population of Solanum peruvianum (Solanaceae)

“…For all alleles tested, we rejected the null hypothesis of full compatibility; thus, the S-RNase sequences isolated in this study represent unique specificities. Although allelic diversity in our sample is within the range reported for Solanaceae with GSI (Richman et al, 1995;Wang et al, 2001;Lu, 2002;Stone and Pierce, 2005;Savage and Miller, 2006), we recovered fewer alleles than are typically reported. For example, Igic et al, 2007 report 30 alleles from 34 individuals of the closely related species S. chilense, although several factors likely contribute to this discrepancy.…”

“…We used the RT-PCR protocol of Richman et al, 1995 to genotype plants, which were used as parentals in controlled pollinations (see below). Five to ten styles were ground in liquid nitrogen and total RNA was extracted using the RNeasy Plant Mini Kit (Qiagen, Inc., Valencia, CA, USA).…”

“…In particular, the development of reverse-transcriptase PCR methods for amplifying S-alleles using RNA extracted from styles (Richman et al, 1995) has resulted in a number of population surveys of S-RNase variation in several species and genera (Lycium, Savage and Miller, 2006, Miller et al, 2008Nicotiana, Roldán et al, 2010;Petunia, Wang et al, 2001;Physalis, Richman et al 1996, Lu, 2002Solanum, Richman et al, 1995, Igic et al, 2007, Mena-Ali and Stephenson, 2007Witheringia, Stone and Pierce, 2005). Data from studies of SI taxa generally meet expectations; that is, populations contain numerous alleles and allelic lineages persist over millions of years.…”

Allelic diversity of S-RNase at the self-incompatibility locus in natural flowering cherry populations (Prunus lannesiana var. speciosa)

“…In previous studies of Solanaceae, although the total number of alleles maintained among two widely separated populations of Solanum carolinense was not much greater than 14 (Richman et al, 1995), populations of P. crassifolia and Lycium andersonii contained 44 alleles (Richman et al, 1996a) and 36 alleles (Richman, 2000), respectively. The population size required to maintain 20 alleles found in the flowering cherry populations was approximately 1500 individuals, assuming mutation rates (to new specificities) of 10 À8 per generation (see Figure 2 in Wright, 1939).…”

“…Richman et al (1995Richman et al ( , 1996a and Richman (2000) directly determined the putative S-genotypes of plants sampled from Solanaceae by sequence polymorphism at the S-RNase locus. Vieira and Charlesworth (2002) revealed sequence variation at the S-locus in Scrophulariaceae.…”