Production of intraspecific aneuploids in the genus Solanum. III. Intraspecific aneuploids

Abstract

The triploids recovered from 4x×2x crosses in three Solanum species were very vigorous and although few seeds/fruit were obtained when the triploids were crossed to diploids, the extensive crossing programme produced sufficient seed of four species cph, chc, pnt and tar. The average seed set for the 3x-2x crosses was an extremely low 3.5 seeds/fruit. Approximately 90% of the progeny of the 3x−2x crosses were aneuploids with chromosome numbers of 2n=25–29. The frequency of the aneuploids in the three species that were studied was chc 93%, pnt 94% and tar 92%. The aneuploids of chc and tar were extremely vigorous and fertile and they were used as females in crosses to the marker stocks. The aneuploids of pnt were vigorous, but the crossability barrier of pnt prevented their use in crosses to the marker stocks. A number of the aneuploids produced seed upon being selfed, but the ability to produce self seed may be related to the pseudo-compatibility of the parental clones. In only 7 aneuploids was there an indication that the self fertility was due to overcoming the self-incompatibility barrier as a result of competition-interaction of the aneuploid gamete. Plants in the families from the triploid-diploid crosses had a tremendous amount of variation in morphological characteristics (leaf shape, size and color; berry shape, color and degree or verrucose spotting: and plant habit and vigor). A large portion of variation exhibited in these families was due to the normal genetic segregation of the heterozygous parents. It was impossible to distinguish the aneuploids from their diploid sibs especially those having only one or two additional chromosomes because they were as vigorous and fertile as the diploids. There were some preliminary indications of the existence of distinct morphological characteristics among the aneuploids (separate petals, long berries, and extreme verrucose berries). However, there was no indication that these traits were due to the dosage effect of the extra chromosome. If it should be determined that this was true, it would be extremely useful in associating genes with chromosomes and determining the phenotypic effects due to the presence of an additional chromosome.