Analysis of apospory transmission through reduced female gametes in tetraploid Paspalum notatum

VEGA MS; LEBLANC O; VEGA JM; SIENA LA; QUARIN CL; ORTIZ JPA

Mendoza

Congreso; ALAG 2019; 2019

Sociedad Argentina de Genética

P. notatum forms an agamic complex composed by sexual self-sterile diploid and aposporous apomictic self-fertile tetraploid plants. Apospory (a component of apomixis) is transmitted by male gametes as a single-dominant factor with distorted segregation ratios (6-3 sex:1 apo). Most natural apomicts are obligate, however highly-sexual apomictic genotypes were experimentally obtained and used as female parents in crosses with apomictic donors. Here, we analyzed the transmission of apospory by female reduced gametes. To achieve this, three populations were developed: Pop_S (n=6) derived from self-pollination of Q3664, a highly-sexual facultative apomictic plant with white (recesive) stigmas; Pop_C (n=12) from the cross between Q3664 and C4-4x, a fully sexual plant with purpura (dominant) stigmas; and, Pop_A (n=20) from open pollination of Q4117, a natural apomictic accession. Progeny origin (hybrid/maternal clone) was determined by observation of stigmas color and molecular analysis. The reproductive mode was assessed by observation of ovules at anthesis (meiotic vs. aposporous embryo sacs). Phenotypic and molecular analyses showed that all Pop_S and Pop_C plants but one of Pop_S derived from sexuality, while all plants of Pop_A resulted from apomixis. Pop_S showed 5 aposporous and 1 sexual plants (χ21 3:1 apo:sex=0.22) and Pop_C comprised 3 aposporous and 9 sexual individuals (χ21 1:1=3.0). Apospory expressivity in hybrids range 3-13%. Our results indicate that apomixis is transmitted by reduced female gametes, although maternal inherited apospory showed low expressivity.