Report Tomato Genetics Cooperative 33: 3-4. (1983)
Use of pollen mixture technique in interspecific cross between Lycopersicon esculentum and L. peruvianum.
The breeding value of L. peruvianum is well known but crosses with the tomato remains difficult. Different methods are used by breeders to obtain Fl hybrids and plants of the first backcross.
We have successfully used the technique of pollen mixture to facilitate hybridization.
Emasculated flowers, of a tomato line bearing a recessive seedling marker gene, are pollinated with a 1:1 mixture of tomato and L. peruvianum pollen.
Many seeds are obtained, however, only seedlings without the marker gene are hybrids. This technique, but without the marker gene, was first used in 1965, to obtain the first backcross from which the PEROU line (Tm-2 without nv) was developed; the FI hybrids had been obtained by in vitro culture of immature seeds.
The pollen mixture technique, with a tomato line bearing a recessive marker gene as female parent, was used in 1978 to obtain Fl hybrids and again in 1980 to realize the first backcross in the CMV partial resistance program (marker genes aa for the Fl and c for the backcross). On the same Fl hybrids we have obtained the first backcross for Tomato Yellow Leaf Curl Virus (TYLCV) resistance with ag as marker.
With this technique, 1 to 5 hybrids per 100 pollinated flowers are obtained. It is probably possible to improve this technique by using a male sterile line to eliminate emasculation of the female parent. In this case the tomato pollen comes from a male-fertile line bearing the same marker gene as the female line. Efficiency of the method might also be enhanced by double pollination; the first by L. peruvianum and the second a short time later, with tomato pollen.
The screening for tomato varieties and of environmental conditions resulting in a higher percentage of interspecific hybrids with L. peruvianum could be interesting.