In this report we present the results of a complementation test involving nine emp (empty pericarp) mutants of maize that represent single gene mutants, isolated as independent events.
These mutants are embryo lethal at maturity and drastically reduced in their endosperm size. They can be subdivided in two major subgroups: those with a flat appearance of the kernel and those with a wrinkled pericarp.
By crossing inter-se plants heterozygous for emp mutants, we identified those non-complementing (that means allelic) and those complementing (that means not allelic) in the F1 generation. Most results in the F1 were concordant to those obtained in the F2 generation with the exception of four cases where the F1 results suggest allelism (i.e. one gene) whereas those in the F2 segregation of two genes.
This intriguing result seems to suggest an interaction between different emp mutants due to second site non-complementation (SSNC).
In addition while scoring ears segregating for a single emp mutant, in different genetic backgrounds, we noticed that some mutant seeds exhibited a more abundant endosperm tissue and occasionally an embryonic axis. About 10% of these seeds germinate yielding slow growing seedlings. This observation could be explained by assuming that emp mutants introduced in different genetic backgrounds uncover a cryptic variability. This point needs to be further investigated but if confirmed, emp mutants could be used as a tool for the detection of genetic factors contributing to the amount of endosperm in the maize kernel to exploit in breeding programs
