Location: Sunflower and Plant Biology ResearchTitle: Triploid production from interspecific crosses of two diploid perennial Helianthus with cultivated sunflower Author
Submitted to: Genes, Genomes, Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2017
Publication Date: 4/1/2017
Citation: Liu, Z., Seiler, G.J., Gulya, T.J., Feng, J., Rashid, K.Y., Cai, X., Jan, C. 2017. Triploid production from interspecific crosses of two diploid perennial Helianthus with cultivated sunflower. Genes, Genomes, Genetics. 7(4):1097-1108. Interpretive Summary: Wild perennial Helianthus species have been less exploited for the improvement of cultivated sunflower (Helianthus annuus L.), because of the crossing difficulty and the low fertility of F1 hybrids. We are reporting the discovery and characterization of a unique high frequency of triploid production unexpectedly observed while crossing a group of wild diploid perennial H. nuttallii and H. maximiliani accessions, collected near Morden, Manitoba, Canada, with cultivated sunflower. Genomic in situ hybridization (GISH) analyses indicated that the triploid F1 plants had two genomes from the wild pollen sources and only one from the cultivated line. Mitotic chromosome number analyses confirmed that the high frequency (overall 93%) of triploid F1 progenies was only obtained from the crosses of cultivated lines × N102, rather than those using other wild diploid or tetraploid perennial species as the female parents or in the reverse crosses. By comparison, the progenies with abnormal chromosome numbers derived from five other wild perennial species was less than 1% Pollen stainability of 22 wild sunflower accessions revealed the existence of unreduced gametes in some accessions, especially N102 and H. maximiliani M1113. Since the cross-incompatibility between wild perennial species and cultivated lines are high, the higher frequency of triploids above what would be expected for diploid F1 progenies could be due to the preferred fertilization of the low frequency of 2n male gametes with the female gametes of the cultivated sunflower. The triploids have been successfully used to produce amphiploids and aneuploids. Our results provide the confirmation of this ultra-rare genetic alteration in these accessions leading to the abnormal whole genome transmission while crossing to the female parent cultivated sunflower. This discovery is novel and unique for sunflower and is expected to have significant implications for sunflower evolution of its higher ploidy species.
Technical Abstract: Wild Helianthus species are a valuable genetic source for the improvement of cultivated sunflower. We report the discovery and characterization of a unique high frequency production of triploids when cultivated sunflower was pollinated by specific accessions of diploid Helianthus nuttallii T. &. G. and H. maximiliani Schr. Genomic in situ hybridization (GISH) analyses indicated that the triploid F1s had two genomes from the wild pollen sources and one from the cultivated line. Mitotic chromosome analyses indicated that the frequency of triploid progenies from the crosses of cultivated lines × H. nuttallii accession 102 (N102) was significantly higher than those of unexpected polyploid progenies from the crosses of wild perennial species × N102, and no unexpected polyploids were obtained from the reverse crosses. Pollen stainability analysis suggested the existence of a low percentage of unreduced gametes in some accessions, especially N102 and H. maximiliani accession 1113 (M1113). The triploid F1s could be the results of preferred fertilization of the low frequency of 2n male gametes with the female gametes of the cultivated sunflower, due to the dosage factors related to recognition and rejection of foreign pollen during fertilization. The triploids have been used to produce amphiploids and aneuploids. Future studies of the male gametes’ fate from pollination through fertilization will further uncover the mechanism of this whole genome transmission. Studies of the genetic control of this trait will facilitate research on sunflower polyploidy speciation and evolution, and the utilization of this trait in sunflower breeding.