Agronomic value and adaptation across climatically contrasting environments of Italian red clover landraces and natural populations

This study aimed to support red clover (Trifolium pratense L.) breeding programmes by investigating germplasm adaptive variation. Four landraces representative of the former commercial ecotypes from northern and central Italy, thirteen natural populations collected in Italy across a wide latitudinal and altitudinal range in exploited or abandoned old natural grasslands, natural pastures or in the wild, and the varieties Perseo and Divin were evaluated for 2-year forage yield, for plant survival and for some morphophysiological traits. Evaluations were made at two sites, one with a subcontinental climate (Lodi) and the other with a Mediterranean climate (Viterbo). Specific adaptation was particularly large in natural populations, whose interaction with location implied a widespread inversion of population ranks across sites for forage yield depending on their geographical origin. Forage yield and persistence of the populations were not correlated, owing to the trend of landrace and variety germplasm towards high yield but poor persistence. At Lodi, forage yield was associated with winter hardiness and was maximized by landrace germplasm, whereas persistence depended on various factors and was high only in a set of natural populations collected from pastures. At Viterbo, natural populations that evolved under severe summer drought stress tended towards high yield and persistence, showing no yield disadvantage relative to the best-performing landrace or variety germplasm.