The success obtained in plant regeneration from maize tissue culture
by means of organogenesis or somatic embryogenesis and the possibility
of obtaining somaclonal variants from regenerated plants stimulated us
to test some genetic stocks for regeneration capacity and the obtainment
of mutants of somaclonal origin. The genetic constitution of the two stocks
used in this study is reported in the Table. The background of the first
was originally W23 x K55 and it was reproduced by selfing while the second
is an inbred line (A188). Calli induced on Murashige and Skoog medium (1962)
were then transferred to regeneration medium, according to a procedure
described by Armstrong and Green (1985). The yield of embryogenic calli
differed in the two stocks as shown.
|Genotype||Origin||Number of embryos explanted||Embryogenic calli (%)||Number of R1 plants|
|A1 A2 C1 C2 R-g||W23 + K55||120||13.5%||180|
|A1 A2 c1 C2 r-r||A188||140||2.5%||56|
Different morphological variants were observed among regenerated (RI) plants, including abnormal leaf and auricle development, white stripes on leaves, and tassel seed. Regenerated plants were often asynchronous in their male and female inflorescence maturation; accordingly they were outcrossed and the progeny grown and selfed.
The resulting ears were then scored for appearance of nonparental phenotypes
and the results obtained are the following:
|Number of R1 plants tested||Number of selfed ears||Ears with nonparental phenotypes|
*dek: defective kernel; et: etched; up: viviparous; ss: semisterility.
The frequency of these presumed mutants was in most cases lower than the expected one-quarter except for viviparous, which segregates as a monogenic recessive mutant; one of the seven dek and the three cases of semisterility exhibited a ratio of about 1:1. We are planning to ascertain the genetic basis of these presumed mutants through progeny tests, and to characterize them further in relation to their somaclonal origin.
M.L. Racchi and M. Pontoglio
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