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

Wheat genotypes prone to late maturity alpha -amylase (LMA) produced high l evels of germination-type (high pI isozymes) alpha -amylase following expos ure to cool temperature during grain development. Plants grown in the glass house, plants grown in the field and transplanted to the glasshouse after f lowering, and tillers taken from field or glasshouse grown plants all respo nded in a similar manner. Plants or detached tillers can therefore be used in screening tests to identify germplasm with the LMA genotype. The cool te mperature treatment was effective when applied continuously from shortly af ter flowering until near-ripeness, or when limited to the phase of grain de velopment (26-35 days after anthesis) in LMA-prone genotypes that appears t o be most sensitive to cool temperature. Based on these observations, guide lines for screening wheat germplasm are proposed and the advantages of usin g detached tillers discussed. The detached tiller method was successfully a pplied 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 amyl ase) x BD159 (LMA genotype). The preliminary data from this population were consistent with control by a single gene and similar therefore to the mode l proposed previously for cv. Spica.