Albert-Ludwigs-Universität Freiburg
Iowa State University

Isolation of the new recessive mutant lrt1 deficient in lateral root development
--Hochholdinger, F; Schnable, P; Feix, G

The root system of maize consists of embryogenic primary- and seminal lateral, and postembryonic crown- and brace roots. All of these root types form lateral roots from the pericycle cell layer. A mutant deficient in the formation of lateral roots (designated lrt1 for lateral-rootless1) has been identified in a seedling screen of segregating M2 families derived from an EMS mutagenized B73 population (established in 1994 in Ames). This recessive mutant is completely deficient in lateral root formation on early forming roots as evident from the comparison of 14-day-old wild-type and mutant seedlings shown in the figure. Mutant plants grow slower and are of smaller size than corresponding wild-type plants, but are, however, still fertile. Histological analysis of sections from 14-days-old primary roots of wild-type and mutant plants revealed that, in contrast to the large number of lateral roots already formed at that stage in wild-type plants, only a few lateral root primordia had formed in the primary root of mutant plants. Further, in mutant seedlings none of these primordia had grown out to form lateral roots. An equal number of such rudimentary primordia were also found in the primary root of 14-day-old wild-type plants. Hence, the relationship between these rudimentary primordia and the lrt1 gene remains to be elucidated

Further characterization of this new mutant, including investigations at later stages of development and hormone action studies, are in progress.

Figure. The root system of two 14 day old wt plants (left) in comparison to two lrt1 plants (right), lacking lateral roots.

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