High proportion of diploid hybrids produced by interspecific diploid × tetraploid Sorghum hybridization

• Published in: Genetic resources and crop evolution Vol. 65; no. 2; pp. 387 - 390
• Main Authors: Cox, Stan, Nabukalu, Pheonah, Paterson, Andrew H., Kong, Wenqian, Auckland, Susan, Rainville, Lisa, Cox, Sheila, Wang, Shuwen
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-02-2018; Springer Nature B.V
• Subjects: Agriculture; Biomedical and Life Sciences; Chromosomes; Genetic crosses; Germplasm; Grain; Hybridization; Hybrids; Inbreeding; Interspecific; Life Sciences; Metaphase; Phenotypes; Plant Genetics and Genomics; Plant Physiology; Plant Sciences; Plant Systematics/Taxonomy/Biogeography; Pollen; Progeny; Short Communication; Soil degradation; Sorghum; Sorghum bicolor bicolor; Sorghum halepense; Tillage; Tips; Sorghum breeding; Ploidy; Genetic resource; Perennial; Interspecific hybridization; Chromosome; Germplasm enhancement
• ISSN: 0925-9864; 1573-5109
• DOI: 10.1007/s10722-017-0580-7

A perennial version of grain sorghum [
S. bicolor
(L.) Moench] would create opportunities for greatly reducing tillage and preventing soil degradation. Efforts to select for perenniality and grain production among progeny of hybrids between
S. bicolor
(2n = 20) and the weedy tetraploid perennial
S. halepense
(L.) Pers. (2n = 40) are complicated in that F
1
hybrids produced by diploid × tetraploid sorghum crosses are usually tetraploid. In 2013, a set of random pollinations between 19 diploid cytoplasmic male-sterile inbred lines and 43 tetraploid perennial plants produced 165 F
1
hybrid plants, more than 75% of which had highly atypical plant, panicle, and seed phenotypes. Phenotypic segregation in F
2
populations derived from atypical hybrids was also anomalous. Examination of mitotic metaphase cells in F
1
or F
2
root tips revealed that 129 of the 165 hybrids were diploid. Parentage of the diploid progenies was confirmed using simple-sequence repeat analysis. The mechanism by which diploid hybrids arise from diploid × tetraploid crosses is unknown, but it may involve either production of monohaploid (n = 10) pollen by the tetraploid parent or chromosome elimination during early cell divisions following formation of the triploid zygote. The ability to produce diploid germplasm segregating for
S. bicolor
and
S. halepense
alleles could have great utility, both for the development of perennial sorghum and for the improvement of conventional grain sorghum.