After obtaining somatic hybrids between these two species by protoplast fusion (Adams and Quiros, Pl. Sci. 40 (1985) :209-219) , we now report their sexual hybrids. We crossed the same two plants used for the somatic hybridization experiment. The cross succeeded only when using L. peruvianum as pistilate parent. A few seeds were obtained and germinated in Nitch and Nitch culture medium. Embryo rescue was not necessary. Two hybrid plant develped; one moderately sterile (48% pollen stainability) and very vigorous, and another highly fertile (88% pollen stainability) but smaller in size. Both plants were heterotic with respect to the two parents. Chromosome counts revealed that the former was a triploid hybrid, most likely a sesquidiloid originated by fertilization of L. pennellii 2n pollen, judged by its closer resemblance to this species.The second was a diploid hybrid, highly self-compatible, setting spontaneously many fruits with viable seeds. This behavior was in agreement with the observations of Chmielewski (TGC 18:9). A few seeds were obtained when this hybrid was backcrossed as staminate parent to L. peruvianum. The reciprocal crosses and backcrosses in any direction to L. pennillii were unsuccessful. Self-incompatibility (SI) from green fruited species is dominant over self-compatibility (SC) of red fruited species. When species of these two groups are hybridized, as a rule the self-compatible species have to be used as pistilate parents due to a strong unilateral incompatibility (Rick, Biol. Zbl. 101(1982):185-198). The SC of L. pennellii (LA 716). however, is the exception to this rule. It is dominant over SI and its unilateral incompatibility reaction is reversed. Crosses with this accession will succeed only when using the self-incompatibility species as pistilate parents. This unusual behavior was examined by Hardon (Genetics 57 (1967) :795-808) in L. pennellii hybrids between SC and SI accessions, and in L. pennellii/L. esculentum hybrids. He postulated that SC in L. pennellii is determined by a dominant allele (S^P^ ), at the S locus.
Allozyme segregations for seven loci in the hybrid F2 progeny are summarized in Table 1. Segregations for loci Prx-1, Skd-1, both on chromosome 1, and Pgi-I on chromosome 12, deviated from the expectd 1:2:1 ratio. An excess of pennellii and a deficiency of peruvianum alleles was evident in the hybrid progeny. The same deviations for the first two loci was reported by Tanksley and Loaiza-Figueroa (PNAS 82(1985):5093-5096) in L. peruvianum intraspecific hybrids. Deviations for other loci have been reported by several other authors for various Lycopersicon interspecific crosses. This is believed to be due to pollen competition, and selection acting during germination and at seedling stage. Our data confirms the linkage between Tpi-2 and Pgm-2 (chromosome 4). but we could not detect the linkage between Prx-1 and Skd-1 (chromosome 1). We found significant associations between Prx-1 and Tpi-2, and Prx-1 and Pgm-2. Linkage calculations, however, indicated that the recombination fraction for these two sets of loci was above 50%. Most likely, the significant associations observed were an artifact due to the significant departure from the 1:2:1 ratio found for Prx-1. We will study linkages between the segregating allozyme loci, SI and unilateral incompatibility in this F2 progeny. It is expected to segregate for self-incompatibility in a 3:1 (SC:SI) ratio. This shall confirm Hardon's report indicating that S^P^ is located at the S locus, and Tanksley and Loaiza--Figueroa's report that S locus is on chromosome 1, linked to Skd-1 and Prx-1. Furthermore, by backcrossing F2 plants to both parents, it will be possible to detect segregations between SI and unilateral incompatibility, if any.
Table 1. Segregating ratios for 7 isozyme loci.
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Loci Alleles X^2^ P
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PN PN/PV PV
Prx-1 23 34 5 11.03* <0.01
Skd-1 23 33 1 18.40** <0.01
Aps-1 13 19 11 0.77 0.74
Tpi-2 12 29 15 0.40 0.82
Pgm-2 12 28 15 0.34 0.83
Mdh-2 13 28 13 0.08 0.99
Pgi-l 28 23 4 25.71 (0.01
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