Novel inter-series hybrids in Solanum, section Petota

Abstract

Sexual hybrids between distantly related Solanum species can undergo endosperm failure, a post-zygotic barrier in inter-species hybridizations. This barrier is explained by the endosperm balance number (EBN) hypothesis, which states that parents must have corresponding EBNs for viable seed formation. Tests for inter-crossability were made involving the Mexican species Solanum pinnatisectum Dunal. (series Pinnatisecta, ApiApi, 1EBN), autotetraploids of this species, Solanum verrucosum Schlechtd. (series Tuberosa, AA, 2EBN), haploids (2x, 2EBN) of the South American S. tuberosum L. (series Tuberosa, A1A1A2A2, 4EBN), and F2 haploid-species hybrids with South American species (AA, 2EBN) S. berthaultii Hawkes, S. sparsipilum (Bitter.) Juz. and Bukasov and S. chacoense Bitter. The development of hybrid endosperms was investigated for these combinations by confocal microscopy with regard to cell-division timing and tissue collapse. Novel sexual diploid (AApi) and triploid (AApiApi) inter-series hybrids were generated from S. verrucosum x S. pinnatisectum crosses by using post-pollination applications of auxin. F1 embryos were rescued in vitro. The hybrid status of recovered plants was verified by microsatellite marker analysis, and the ploidy was determined by chromosome counting. The application of phytohormones in inter-ploidy S. pinnatisectum x S. tuberosum crosses, however, did not delay endosperm collapse, and embryos were not formed. Other diploid, 1EBN species tested in remote hybridizations with Group Tuberosum were S. cardiophyllum Lindl., S. trifidum Correll, and S. tarnii Hawkes and Hjert., series Pinnatisecta, and S. bulbocastanum Dunal., series Bulbocastana. Based on the analysis of post-zygotic reproductive barriers among isolated species of section Petota, we propose strategies to overcome such incompatibilities.

Production and characterisation of the intergeneric hybrids between Dendranthema morifolium and Artemisia vulgaris exhibiting enhanced resistance to chrysanthemum aphid (Macrosiphoniella sanbourni)

“…But the percentage of successfully rescued ovules was very low indeed. This rather low proportion could perhaps be improved by the imposition of a variety of physical and/or chemical treatments, for example, bud pollination (Trindade et al 2001), in vitro pollination (Van Tuyl et al 1991) and phytohormone treatment (Dinu et al 2005).…”

Propagating the pale‐flowered kumarahou (Pomaderris hamiltonii) and kumarahou (Pomaderris kumeraho) from seeds

“…An imbalance in the ploidy level of the endosperm and embryo or in the ratio of maternal and paternal nuclei making up the endosperm can affect successful seed formation and germination (Dinu et al 2005;Recupero et al 2005), although this usually results in complete endosperm failure and death of the embryo. Harvey & Braggins' (1985) study of one population found that fertilisation is not involved in the production of the endosperm in P. hamiltonii, which may be derived from one or both of the polar nuclei and is triploid, the same chromosome number as the embryo and parent plant.…”

Unilateral and bilateral hybridization barriers in inter-series crosses of 4x 2EBN Solanum stoloniferum, S. pinnatisectum, S. cardiophyllum, and 2x 2EBN S. tuberosum haploids and haploid-species hybrids

“…pinnatisectum and S. cardiophyllum are primitive 2x species from Mexico and the southwest United States that are reproductively isolated from 4x cultivated potato and their 2x haploids (Novy and Hanneman 1991;Kuhl et al 2002;Ramon and Hanneman 2002;Dinu et al 2005). Several approaches for direct introgression into cultivated potato have been used to overcome reproductive barriers between potato species.…”