The influence of photoperiod genes on the adaptability of European winter wheats

Abstract

Photoperiod response genes play a major role in determining the climatic adaptability of European wheat varieties. Photoperiod insensitivity, in the vast majority of photoperiod insensitive European wheat varieties, is probably determined by a Ppd1 allele originally derived from the old Japanese variety Akakomugi. Analysis of the pleiotropic effects of a Ppd1 allele from the Italian variety Mara shows that, besides accelerating ear emergence time, Ppd1 also reduces plant height, tillering, and spikelet numbers. Increases in spikelet fertilities more than compensate for reduced spikelet numbers, producing increased numbers of grains per ear. In southern Europe, early flowering Ppd1 genotypes produce larger grain and greater yields. In England and Germany, pleiotropic effects of Ppd1 on yield vary annually, depending on prevailing weather conditions, from +9% to -16%, over a 10 year period in the United Kingdom. A possible alternative Ppd1 allele from the CIMMYT variety Ciano 67 was compared to that from Mara. Differences associated with complete substituted chromosomes were found to be due to linked genes rather than different Ppd1 alleles. Examination of an alternative weaker gene for photoperiod insensitivity, Ppd2, shows this to exert similar but less significant pleiotropic effects to Ppd1. In the UK, in each of three years of trialing, Ppd2 increased yield 6% more than Ppd1. Results of 10 years trialing show that in Central European countries, between areas where photoperiod sensitive or photoperiod insensitive varieties have a clear adaptive significance, the annual variations in climate make it extremely difficult for breeders to produce varieties with good adaptability to changing environmental conditions.