MILAN, ITALY
1DIFCA and Dept. of Genetics and Microbiology
University of Milan

The fused leaves mutant in maize is altered in the embryo and juvenile leaf morphology
--Frascarolo, P, Landoni, M, Dolfini, S1, Gavazzi, G, Consonni, G

The "fused leaves" (fdl) mutant was originally isolated by Dr. Jane Langdale in a genetic line carrying an active Spm; it behaves as a single gene recessive mutant and its phenotype is recognizable shortly after germination. In comparison to wild-type siblings, homozygous Fdl seedlings show a delay in germination; they also exhibit curly initial leaves that develop precociously while still enclosed in the coleoptile. Frequently, among mutant seedlings, fusion of the leaf surface is also observed: the first and the second leaves or, alternatively, the coleoptile and the first leaf are fused together. Later on in the development, the plant acquires a normal phenotype with expanded and discrete leaves. Homozygous mutant plants at four leaves stage are indistinguishable from wild type plants; they can be grown to maturity and selfed to obtain homozygous progeny seedlings.

Histological analysis reveals that fusion occurs between the epidermis of the leaves. The epidermis of the curly leaf is also altered in the cell morphology: the presence of a series of cells with larger diameter and irregular shape is observed where the fusion occurs. Development of the mutant embryo is delayed in comparison to the wild type embryo, particularly at the level of the shoot primordia. At maturity, the plumule comprises five leaf primordia whose morphology is altered, anticipating leaf morphology of the mutant seedling.


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