Induction of late maturity a-amylase in wheat by cool temperature

Wheat genotypes prone to late maturity α-amylase (LMA) produced high levels of germination-type (high pI isozymes) α-amylase following exposure to cool temperature during grain development. Plants grown in the glasshouse, plants grown in the field and transplanted to the glasshouse after flowering, and tillers taken from field or glasshouse grown plants all responded in a similar manner. Plants or detached tillers can therefore be used in screening tests to identify germplasm with the LMA genotype. The cool temperature treatment was effective when applied continuously from shortly after flowering until near-ripeness, or when limited to the phase of grain development (26–35 days after anthesis) in LMA-prone genotypes that appears to be most sensitive to cool temperature. Based on these observations, guidelines for screening wheat germplasm are proposed and the advantages of using detached tillers discussed. The detached tiller method was successfully applied to a range of genotypes, some of which were known to be prone to LMA, and to a doubled haploid population derived from the cross Janz (low amylase) BD159 (LMA genotype). The preliminary data from this population were consistent with control by a single gene and similar therefore to the model proposed previously for cv. Spica.