Variation among progenies of diploid plants regenerated from haploid, microspore-derived cell-suspension protoplasts of rice (Oryza sativa L.)

Progenies of 110 diploid R₀ plants regenerated from haploid protoplasts derived from microspore callus cell suspension culture of rice (cv. Miara) were evaluated for 6 traits, along with control lines, in a replicated field trial. Complementary post-harvest observations were carried out for four panicle or grain characters. A wide range of variation was observed for all traits under study among the protoclonal lines. The mean of the protoclonal population was significantly different from that of the control for most traits and 64.5% of the lines differed from the control for at least one field-evaluated trait. A unidirectional shift towards later-maturing, taller, and lower-tillering lines was observed. Of all the lines, 39% were taller than the control by at least 10 cm, 31 % had flowering delayed by at least 5 days, and 13% exhibited significantly longer panicles (P = 0.05). As to the agronomical value of the lines, the variation resulted in a global negative drift although favourable variations were found in a few lines. All but two lines were homogeneous, suggesting that most variations existed in a homozygous form in the R₀ plants. R₂ lines grown from seeds of 17 R₁ protoclonal lines stably inherited the changes and did not segregate, thereby confirming that variations are fixed.