THE EFFECTS OF TEMPERATURE AND LIGHT-INTENSITY ON EMBRYO NUMBERS IN WHEAT DOUBLED HAPLOID PRODUCTION THROUGH WHEAT X MAIZE CROSSES

Triticum aestivum x Zea mays crosses are now widely used in the produc tion of wheat doubled haploids to produce homozygous lines. Seasonal e ffects are known to influence the number of haploid embryos produced t hrough wheat x maize crosses, but the effects of temperature and light have not been quantified. This study investigated the effect of tempe rature and light intensity on haploid embryo production. New Zealand w heat cultivars were grown in a glasshouse until booting when they were transferred to growth cabinets at three temperatures (day/night; 17/1 2, 22/17 or 27/22 degrees C at an irradiance of 250 mu mol m(-2) s(-1) PAR). In another experiment, wheat lines were transferred to a growth cabinet at one of three light intensities (300, 500 or 1000 mu mol m( -2) s(-1) PAR at 22/17 degrees C day/night, with a photoperiod of 16 h ). The temperature and light intensity at which pollinations were made and subsequent fertilisation and embryo development occurred, signifi cantly (P < 0.01) influenced the frequency of haploid embryo productio n. The optimal temperature for embryo recovery was 22/17 degrees C. Th e greatest number of embryos was produced at a light intensity of 1000 mu mol m(-2) s(-1). These findings will result in improvements in the overall efficiency of the wheat x maize system for wheat doubled hapl oid production. (C) 1998 Annals of Botany Company.