Pollen fertility differences in the progenies obtained from a cross between eggplant (Solanum melongena L.) as a seed parent and eggplant cytoplasmic substitution lines as pollen parents

To the best of our knowledge, there is no report about pollen fertility of the progenies developed using eggplant (Solanum melongena L.) as a seed parent and eggplant cytoplasmic substitution lines as pollen parents. Pollen fertility of these progenies is very important to use as restorer line in the eggplant’s hybrid breeding program. In this study, pollen fertility was investigated for the progenies which were produced using S. melongena ‘Uttara’ as a seed parent and the eggplant cytoplasmic substitution lines as pollen parents. To assess pollen fertility, pollen stainability and in vitro germination ability were investigated. Although the nuclear and the cytoplasmic genome of the progenies were almost identical to eggplant ‘Uttara’, a clear difference was observed in the pollen fertility due to the difference in the pollen parents having different wild Solanum cytoplasms. The progenies produced using the functional cytoplasmic male sterile (CMS) lines as a pollen parent, whose cytoplasm donor were S. kurzii, S. violaceum and S. virginianum, showed pollen release type and high pollen fertility almost equal to eggplant ‘Uttara’. It is considered that the characteristics of these progenies were almost the same as eggplant. On the other hand, the progenies that produced using the fertility restored lines of the pollen non-formation type CMS lines as a pollen parent, whose cytoplasm donors were S. aethiopicum, S. anguivi and S. grandifolium, showed pollen release type and low pollen fertility, i.e., pollen staining ability was about 54% and pollen germination ability were about 35%. It is considered that the cause of this low pollen fertility was the incompatibility between the eggplant cytoplasm and the eggplant nuclear genome, which seems to be modified in the process of continuous backcrossing under the wild Solanum cytoplasms. It is suggested that complete nuclear substitution is difficult by continuous backcrossing with eggplant in the alloplasmic lines with S. aethiopicum, S. anguivi and S. grandifolium cytoplasm donors. Incompatibility between the normal eggplant cytoplasm and the modified eggplant nuclear genomes of the alloplasmic lines with S. aethiopicum, S. anguivi and S. grandifolium cytoplasms might be a cause for the low pollen fertility of the investigated progenies

Ethylene Differentially Modulates Hypoxia Responses and Tolerance across Solanum Species

The increasing occurrence of floods hinders agricultural crop production and threatens global food security. The majority of vegetable crops are highly sensitive to flooding and it is unclear how these plants use flooding signals to acclimate to impending oxygen deprivation (hypoxia). Previous research has shown that the early flooding signal ethylene augments hypoxia responses and improves survival in Arabidopsis. To unravel how cultivated and wild Solanum species integrate ethylene signaling to control subsequent hypoxia acclimation, we studied the transcript levels of a selection of marker genes, whose upregulation is indicative of ethylene-mediated hypoxia acclimation in Arabidopsis. Our results suggest that ethylene-mediated hypoxia acclimation is conserved in both shoots and roots of the wild Solanum species bittersweet (Solanum dulcamara) and a waterlogging-tolerant potato (Solanum tuberosum) cultivar. However, ethylene did not enhance the transcriptional hypoxia response in roots of a waterlogging-sensitive potato cultivar, suggesting that waterlogging tolerance in potato could depend on ethylene-controlled hypoxia responses in the roots. Finally, we show that ethylene rarely enhances hypoxia-adaptive genes and does not improve hypoxia survival in tomato (Solanum lycopersicum). We conclude that analyzing genes indicative of ethylene-mediated hypoxia acclimation is a promising approach to identifying key signaling cascades that confer flooding tolerance in crops.