Wrinkled auricle (rough sheath?)
--Duncan, DR and Widholm, J
In 1988, a large plant regeneration effort was conducted to examine the type of somaclonal variation that might arise in the H99 genotype. R0 plants from approximately 9 month old cultures (initiated in the summer of 1987) were planted on the South Farm of the University of Illinois in Urbana. These plants were self pollinated and the R1 progeny were planted again on the South Farm in the summer of 1989. Five of eight progeny of a single R0 plant produced a heritable phenotype which we have called wrinkled auricle. Plants expressing the phenotype show varying degrees of folds or waves (wrinkles) of excess tissue in the region of the auricle. A normal H99 leaf has a distinct white to translucent auricle that does not extend completely around the stem. In the wrinkled auricle phenotype the auricle and leaf are wrapped around the stem. Consequently, as the girth of the stem increases the wrinkles often tear leaving tattered tissue with browning edges at the base of each leaf. The phenotype is first noticed at the V4 or V5 leaf stage and does not appear to be expressed in any manner in more juvenile tissue. In extreme cases, the plants "buggy whip" as they mature and are highly contorted but fertile. The leaf blade, per se, does not show any signs of abnormality.
We have attempted over the past several years to do genetic analysis of the trait, with little success. We know the trait is heritable but its expression is extremely sensitive to environmental conditions. H99 grows well in a greenhouse and the trait is expressed well in that environment. Space limitations have forced us, however, to attempt to work with this trait under field conditions. Under the hot and rather dry conditions of Jerseyville, Illinois we have seldom seen the trait expressed in field grown plants. Plants from remnant seed from the field plantings, when grown in a greenhouse, do express the trait.
Plants grown in the field during 1993 expressed the trait. The field
conditions in 1993 were extremely wet and relatively cloudy with record
levels of rainfall (the season was so wet that this field planting ended
up somewhere in the Gulf of Mexico as a result of flooding). The 1993 field
observation and the fact that the trait is expressed well under greenhouse
conditions, suggests that the water status of a plant containing the wrinkled
auricle mutation may regulate the expression of the phenotype. We also
cannot rule out a role for heat in regulating the expression of the trait,
although the summer greenhouse conditions are as hot or hotter than our
field conditions. It is possible that wrinkled auricle is akin to one of
the rough sheath genotypes, but we have not pursued this possibility.
Presently, we do not have the facilities or commitable time to continue studying this somaclonal variant. We would be more than happy to supply seed to anyone interested in studying this material further.
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