COLLEGE STATION, TEXAS

Texas A&M University

COLUMBIA, MISSOURI

University of Missouri

Viviparous-10: a new viviparous mutant in maize

--J. D. Smith and M. G. Neuffer

The viviparous mutants of maize can be classified into subgroups according to their phenotypes and metabolic effects. All known viviparous mutants are recessive and their common characteristic is that embryogenesis and seedling development is a continuous process which results in premature sprouting and seedling lethality unless embryos are rescued. Our classification system is an extension of the system first proposed by Robertson, DS (1955). Classification criteria are based on self-pollinated ears from plants heterozygous for specific mutants in an ACR5855 background (Y; A1 A2 Bz1 Bz2 C1 C2 R Pr Vp1).

    Class I. Viviparous, yellow endosperm, green seedlings, colorless aleurone, normal carotenoids,
                normal abscisic acid (ABA). The only known Class I mutant is vp1.

    Class II. Viviparous, white endosperm, albino seedlings, colored aleurone, carotenoid-deficient,
                reduced ABA. Mutants include vp2, vp5, vp5, vp9, w3, y3 and y9 (y3 is
                temperature sensitive and sectorial, y9 is leaky, and both have pale yellow endosperm).

    Class III. Viviparous, yellow endosperm, green seedlings, colored aleurone, normal carotenoids,
                reduced ABA. The only previously identified Class III mutant is vp8.

We recently identified a new mutant which meets all of the Class III criteria described above. Numerous crosses with vp1 and vp8 have all given negative results, and some F2 ears from vp1 crosses show dihybrid segregation with both colored and colorless viviparous kernels.

We propose to designate this mutant as Viviparous-10 (vp10). Viviparous-10 (previously vp*-86GN5) is one of a number of viviparous mutants induced by EMS treatment of pollen by Neuffer, MG. Rescued embryos are viable, although we have not yet succeeded in producing seed from homozygous vp10 plants. Seedling leaves typically fail to separate at their tips and have a rosette appearance, but growth appears to be normal after leaf tips are mechanically separated. Phenotypic differences in seedling growth patterns suggest that vp10 precedes vp8 in the ABA biosynthetic pathway.


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