A sexual highly diploidized autotetraploid plant induced from the diploid cytotype of Paspalum chaseanum Parodi

PATRICIA NOVO; CARRIZO, JULIO MARTIN; VILLALBA AUGUSTO IVAN; QUARIN, CAMILO L.; ESPINOZA FRANCISCO

CROP SCIENCE

CROP SCIENCE SOC AMER

Lugar: Baltimore; Año: 2023

0011-183X

aspalumis one of the most commonnative grass genera of the New World grasslands, and it includesmany wild natural forage species and rare domesticated ones. Polyploidy is widespread among the genus. Many species are multiploid, which basically involve two components: a sexual self-incompatible diploid cytotype and a conspecific apomictic tetraploid, pseudogamous and self-compatible cytotype, though other apomictic polyploid levels may occur in the same species. Tetraploid individuals, reproducing exclusively sexualy, have never been identified in a natural apomictic tetraploid Paspalumspecies. Doubling the chromosome number of a 2x cytotype is usedto obtain a sexual autotetraploid to carry outsexual× apomictic crosses in breeding programs for plant improvement. After numerousattempts we generated only one autotetraploid plant of P. chaseanum(I4C) which reproduced sexually and was highly self-incompatible. An unexpected preferential chromosome pairing resulted in the cytological diploidization of I4C. Despite each chromosome havingthree copies in I4C, meiotic chromosome configurations showed just 9.9% chromosomes forming multivalents (trivalents and quadrivalents), 82.1% bivalents plus 7.9% univalents. The possible causes of this preferential pairing were analyzed.Although highly self-incompatible itwas fertile in crosses following intra-andinterspecific pollinations, but with variable seed set, from over 45% when crossed with an apomictic natural tetraploid strain of P. chaseanum, to 0.9% with a strain of P. wrightii. Thus, a novel autotetraploidP. chaseanumwas synthesized with very interesting characteristics: sexual reproduction, high self-incompatibility, variable cross-compatibility, and high cytological diploidization. All valuable attributes for breedingprograms in a forage grass.