Literature Cited:
Laterrot and Damidaux (1994). TGC REPORT 44 (in this report).
Lefebvre, Palloix and Rives. Euphytica (in press). -
Miller and Tanksley (1990 a). Theor Appl Genet 80 : 385-389.
Miller and Tanksley (1990 b). Theor Appl Genet 80 : 437-448.
Tanksley et al. (1992). Genetics 132: 1141-1160.
Yordanov, Zagorcha and Stoyanova (1977). Genetics and Plant Breeding 10/1 : 13-23.
Molecular cloning of a second S-allele from Lycopersicon peruvianum and assessment of allele frequencies in
populations based on DNA hybridization.
Liang, W., Rivers, B.A. and Bernatzky, R.
Dept. of Plant and Soil Sciences, Univ. Mass. Amherst, MA 01003
A cDNA encoding an S-related stylar protein was cloned from L. peruvianum (LA2163). The corresponding
gene was mapped to the S-locus, sequenced, and used to probe DNA from representatives of 10 populations of L.
peruvianum (Rivers et al., 1993). The cDNA library was further screened using the cloned, mapped S-allele (S7*).
The second S-allele (S6) was cloned and mapped to the S-locus using a backcross population (LA2157 x LA2163)
x LA2163. All seed was provided by C.M. Rick.
The S6 allele was also hybridized to the DNA from the 10 populations of L. peruvianum used in the original
survey (Table 1). In addition, the number of plants from 3 accessions was increased (25 additional plants of
LA2163, 29 additional plants of LA2326, and 7 additional plants of LA1952). Southern hybridization was conducted
under moderate conditions of stringency (68°C, 5X SSC during hybridization, final wash at 68°C, 0.5 X SSC).
It has been reported that the conditions under which the S-probe hybridization was conducted are capable
of detecting alleles sharing between 60% and 70% sequence similarity (Bernatzky et al., 1988). Based on previous
findings (loerger et al., 1990; Rivers et al., 1993), the paucity of homologous DNA fragments among these
populations is not surprising. It is interesting to note the lack of homologous fragments even within the accession
from which these two functional S-alleles were cloned, underscoring the extraordinary sequence diversity
characteristic of this locus. Since sequence divergence at this locus is extreme, absence of hybridization signals
can not be taken as evidence for lack of functional S-alleles.
From this data, it would appear that S6 may be more common than S7, or at least more homologous to a
larger number of alleles. True identity of alleles can only be determined through controlled pollinations and progeny
tests.
Both of these clones are available to interested researchers.
*S7 was formerly reported as S5 (Rivers at al., 1993) but the designation S5 had already been used (Tsai et al.,
1992).
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