Phylogenetic relationships in the evolution of Solanum scabrum

Abstract

Several cross-pollinations were made between Solanum scabrum (2n = 6x = 72) and S. nigrum (2n = 6x = 72), S. americanum (2n = 2x = 24), and a C3 amphiploid of the cross S. villosum (2n = 4x = 48) × S. americanum (2n = 2x = 24) with a view to determine their phyletic relationship. It was found that the crosses between S. nigrum and S. scabrum, and S. scabrum and a "big-fruited form" were accomplished easily, whereas the cross S. scabrum × S. americanum was successful only when S. scabrum, the higher chromosomal form, was used as the maternal parent. The hybrids (F1) exhibited moderate pollen fertility and vigorous growth, and set fruits and seeds abundantly, even though meiotic abnormalities were encountered in most of the pollen mother cells. From the chromosome pairing behaviour in the hybrids, it is concluded that S. americanum is the diploid ancestor of hexaploid S. scabrum and S. nigrum. The latter two species might have evolved from the sterile triploid hybrids of S. villosum × S. americanum by spontaneous amphiploidy. Key words: Solanum, phylogenetics. polyploidy.

A revision of the Old World Black Nightshades (Morelloid clade of Solanum L., Solanaceae)

“…Modern regional taxonomic treatments of the Old World members of the Morelloid clade have been done for Europe (Hawkes and Edmonds 1972), India (Ganapathi and Rao 1986a, 1988; Schilling and Andersen 1990), Africa and Madagascar (Bitter 1912a, 1912b, 1913a, 1921, 1923; Jaeger 1985; Bukenya and Hall 1988; Bukenya 1993; Bukenya and Carasco 1995; Edmonds and Chweya 1997) and Australia (Henderson 1974). Edmonds and Chweya (1997) remains the most thorough account of the black nightshades in the Old World, but includes only some of the species known to occur in Africa and does not treat species from Asia or those known from Australasia and the Pacific.…”

“…It is thought that most of the polyploids in the Morelloid clade are of alloploid, rather than autoploid origin, because bivalents show regular pairing at meiosis (Edmonds 1977, 1979a; Ganapathi and Rao 1987a; Ojiewo et al 2007). The putative parental origin of these species has been investigated using traditional crossability and hybridisation techniques (Edmonds 1977; Ganapathi and Rao 1985, 1986b, 1986c, 1986d, 1987a, 1987b) and, more recently, using molecular markers (Manoko 2007; Poczai and Hyvönen 2011).…”

“…The putative parental origin of these species has been investigated using traditional crossability and hybridisation techniques (Edmonds 1977; Ganapathi and Rao 1985, 1986b, 1986c, 1986d, 1987a, 1987b) and, more recently, using molecular markers (Manoko 2007; Poczai and Hyvönen 2011). Chromosome painting or GISH (genomic in situ hybridisation) techniques have not been used in determining progenitor genomes in the morelloids as they have with great success in Nicotiana (e.g.…”

“…She suggested that S. sarrachoides (as S. sarachoides ) was a potential diploid parent of S. nigrum , because almost half of the crosses involving it and S. nigrum were successful; she also stated that S. americanum was the “undisputed [diploid] progenitor” of S. nigrum , probably based on the work of Nakamura (1935, 1937). Regular bivalent pairing in hybrids derived from S. nigrum × S. scabrum crosses indicate homology of parental genomes of the two hexaploids (Ganapathi and Rao 1987a). Evidence from other crossing studies suggests that the tetraploid S. villosum , S. retroflexum or one of their close relatives, has also been involved in the parentage of S. nigrum (Ganapathi and Rao 1986b, 1986c) and that S. villosum is one of the parents of S. scabrum (Ganapathi and Rao 1985, 1987a, 1987b).…”

“…General overviews of Black nightshade taxonomy and systematics have been published (Edmonds 1977, 1978, 1979a; Chakrabarti and Sharma 1994), including geographically focused taxonomic treatments for South America (Edmonds 1972), North America (Schilling 1981), Australia (Henderson 1974), Africa (Edmonds and Chweya 1997; Olet 2004; Manoko 2007; Edmonds 2012), Europe (Wessely 1960) and the Indian subcontinent (Schilling and Andersen 1990) and detailed cytological, molecular and morphological studies (Saarisalo-Taubert 1967; Venkateswarlu and Rao 1972; Edmonds 1982, 1983, 1984a; Ganapathi and Rao 1986a, 1986b, 1986c, 1986d, 1987a, 1987b; Nandhini and Paramaguru 2014). These studies have greatly enhanced our understanding of the complex morphological and ploidy level variation present in the group, but much taxonomic work remains within the Morelloids especially in South America, where more than half of the known Morelloid species are found (Barboza et al 2013).…”