| Vernalization response in autumn-sown spring wheat
R.G. FLOOD* and G.M. HALLORAN School of Agriculture and Forestry, University of Melbourne Parkville, victoria 3052, Australia Vernalization response appears to be present in most temperate agricultural plants and in many species according to the strength of response, it causes strong differentiation of growth habit into spring and winter forms. Spring habit in wheat is conferred by the condition of little or no vernalization response while winter habit is conferred by a strong response. The adaptive value of strong vernalization response, or winter habit, is of obvious significance in preventing precocious floral initiation and freezing injury to the apex in autumn-sown wheat in environments with prolonged below-freezing temperatures during winter. However, the possible adaptive value of low levels of response in many spring wheats is not as immediately apparent. Many autumn-sown spring wheats, as in Australia, possess moderate to low levels of vernalization response (HALSE & WElR 1970, MARCELLOS & SINGLE 1971, PUGSLEY 1971, Syme 1973, Halloran 1975, 1977). While there has been no deliberate selection for the inclusion of vernalization response in the breeding of Australian wheat its general occurrence in these wheats indicates that selection for optimum flowering time or yield has most likely involved indirect selection for this character. Therefore, in breeding autumnsown spring wheats for increased adaptability and yield, knowledge of the significance of changes to be effected in vernalization response towards this end, appear to be important. The aim of this study was to examine a number of Australian autumn-sown spring wheats for the quantitative and qualtaitive nature of their vernalization responses. In this evaluation they were to be compared with vernalization responses in a set of near-isogenic lines of Triple Dirk which differ for vernalization response (vrn) genes (PUGSLEY 1968, 1970, 1972). Materials and Methods Sixteen Australian wheats, comprising current and superceded commercial cultivars, the Canadian cultivar Thatcher, plus a set of four near-isogenic lines of Triple Dirk (differing in vernalization response genes) (Table 1) were used in this study (Table 2). Seed of the 21 wheats was imbibed for 48 hours at room temperature and sown into pots of a sterile soil mixture of loam, sand and ligna peat (3:2:1 by volume) with adequate nutrients and placed in a cold room at 3C for vernalization. On emergence, the seedlings were given a 12 h photoperiod for the duration of the vernalization treatment provided by two 60 W incandescent lamps 40 cm above them. Separate batches of seed of each line were vernalized for 4, 6 and 8 weeks, such that the vernalization periods were completed simultaneously. After vernalization the seedlings were kept at room temperature for three days to prevent possible devernalization. |
| * Present address: Victorian Crops Research Institute, Private Mailbag 260, Horsham, Victoria 3400, Australia. |
| --> Next |