| Seed Dormancy and Tissue Culture Response in Wheat. Crop Science 35:1324-1329 |
| Morris,C.F. and DeMacon,V. |
| High levels of seed dormancy in
wheat (Triticum aestivum L. em Thell) effect tolerance to pre-harvest sprouting
conditions. An inverse relationship between the level of seed dormancy at maturity
and growth of calli derived from mature embryo explants was previously observed
among a small group of wheat genotypes. In this study, 24 genotypes representing
a diverse genetic base were used to examine the relationship between seed dormancy
and tissue culture response in wheat. Immature embryo explants were cultured
on a modified Murashige and Skoog medium. Increase in callus fresh weight and
subjective callus rating were determined after 30 and 60 d. Cumulative germination
curves, percentage germination, a modified Promptness Index, and time to reach
50% germination were evaluated as methods of characterizing the relative level
of dormancy among the genotypes. Visual assessment of cumulative germination
curves categorized the genotypes into four dormancy groups. Numerical reduction
of these curves indicated that genotypes differed most in percent germination
and modified Promptness Index after 6 d(PG6 and MPI6, respectively). PG6 and
MPI6 were highly correlated (r = 0.98). Median germination produced a similar
ranking of genotypes for seed dormancy with predicted population midpoints of
2.3 to 56 d. After 60d in culture, calli ranged from an average of 0.29 to 1.00g,
and watery, loose and translucent to friable, compact and yellow-white in appearance.
Callus ratings and weights were all significantly correlated. Wheat genotypes
with good tissue culture response exhibited a wide range in mature seed dormancy
and no correlation between the two biological phenomena was evident. Therefore,
the level of mature seed dormancy and tissue culture response in wheat are largely
independent traits, and wheat breeding programs may use tissue culture to develop
sprouting-resistant cultivars.
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