POLYEMBRYONY INHERITANCE IN TWO EXPERIMENTAL MAIZE POPULATIONS

Abstract

In this work it is postulated that polyembryony (PE) occurring in two maize populations (Zea mays L.) is under the control of two epistatic loci, where a dominant allele at either gene pair produces the normal seedling trait (duplicate gene action), so that polyembryony is shown only by the double homozygous recessive genotype. The genetic analysis was based on the F₁, F₂ and BC₁ progenies from crosses among the populations IMM-UAAAN-BAP (D) and IMM-UAAAN-NAP (C) with eight non related germplasm sources, which were six commercial hybrids, one experimental simple hybrid and a population from CIMMYT. The 16 F₁ crosses were done in 2007 in Tepalcingo, Mor; the F₂ during 2008, in Buenavista, Coah., and The back crosses (BC₁) were generated in 2009, in Buenavista. The PE evaluation for F₁ and F₂ was done under both greenhouse and field conditions using a complete block design, with 4 or 5 replicates; the BC₁ evaluations were performed only under greenhouse. The PE segregation in F₂ was tested under the hypothesis of two recessive hypostatic loci, ratio 15:1 (No-PE vs PE progenies); for the BC₁ the hypothesis was for the 12:4 ratio. As expected, the PE was not shown in F₁ progenies, but it was observed in F₂ and BC₁, with proportions of 3 to 7 % and 13 to 22 %, respectively. These results are compatible with the proposed hypothesis, considering a joint effect with incomplete penetrance; this phenomenon was present in amounts of 10 to 50 %, varying according to the exotic germplasm in use. The applied χ² tests to the two types of hypothesis support the proposed inheritance pattern for PE in the two studied maize populations.