Well-established L. chilense plant growing on rocks.
photo courtesy of the Tomato Genetics Resource Center [photo: Rick, Charles M.]

The Lycopersicon peruvianum Complex

those species which are not easily crossed with Lycopersicon esculentum

Lycopersicon chilense Dun.
Lycopersicon peruvianum (L.) Mill.

Lycopersicon chilense

This species is native to parts of Southern Peru and Chile inhabiting arid, rocky sites from sea level to altitudes of 3,000m. It produces small green fruit. This species stigmas exert well beyond the anther cone and are self-incompatible. They are exclusively outbreeders.

Crossing this species with the cultivated tomato, L. esculentum, is extremely difficult due to several barriers which exist. The stigma of L. chilense will not accept pollen from the cultivated tomato and almost always leads to the abortion of the flower. The reciprocal cross, pollen from L. chilense applied to the stigma of L. esculentum, can result in the formation of fruit but few seeds are viable. However, some of the seeds do contain embryos of sufficient size to facilitate embryo rescue.

A wealth of germplasm exists but, due to the difficulty of crossing, this species remains underexploited. The species does exhibit nematode resistance and one important gene has been transferred to L. esculentum, the gene (Tm2² ) which confers resistance to Tobacco Mosiac Virus (TMV). This gene is now found in many commonly available tomato cultivars.

Fruit, foliage and flowers
photo courtesy of the Tomato Genetics Resource Center [photo: Rick, Charles M.]

Lycopersicon peruvianum

L. peruvianum f. glandulosum
L. peruvianum var. humifusum
Like L. chilense, this species also produces green fruit but is somewhat larger in size (~3cm). It is native to Peru and Chile. Several races exist, each of which occupies a different environment. The first is native to coastal areas among moist and brackish areas. The other race is found at higher elevations near mountain streams. There is also a variety which exists L. peruvianum var. humifusum.

Crossing L. peruvianum to L. esculentum is rarely sucessful. Attempts frequently result in embryo or flower abortion. As more lines have been evaluated, a few have produced at least one seed. Fortunately, these hybrids are capable of backcrossing to a L. esculentum parent.

Hybridization between the tomato cultivars and wild species Lycopersicon peruvianum by means of ovule culture. (Imanishi, S. and Chen, L.)

Another method which has been successful at overcoming the incompatibilty between the cultivated tomato and the L. peruvianum is the use of L. chilense as a bridge species (L. peruvianum is crossed to L. chilense and that progeny is crossed to L. esculentum). Although this might seem encouraging, most of the time this methods fails, but does yield better results than a direct cross. Most crosses between the cultivated tomato and the members of the "peruvianum-complex" fail due to some sort of incompatibility.

Resistance of tomato lines from the three-genome hybrid Lycopersicon esculentum - L. chilense - L. peruvianum var. humifusm to the cucumber mosaic virus (CMV) (Stoimenova, E. and Sotirova, V.)

This species has exhibited a number of agriculturally important traits observed by researchers. Here is a sampling of a few:
resistance to:
early blight
leaf mold
fusarium wilt
septoria leaf spot

Introgression and genetics of heat stable nematode resistance from Lycopersicon Peruvianum (Scott, J. W., et.al.)

Fruit, foliage and flowers
photo courtesy of the Tomato Genetics Resource Center [photo: Rick, Charles M.]

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