Evaluation of alfalfa cultivars under rainfed Mediterranean conditions

Twenty alfalfa cultivars were tested, under rainfed conditions in central Greece, for forage yield, agronomic and nutritive value in order to identify adaptive responses contributing to high resilience and productivity. From 2014 to 2017, five harvests (H-1 to H-5) per season were conducted. Two cultivars were also grown as irrigated checks. Annual and total dry matter (DMA and DMT) and harvest ratios (R-H) were estimated. DMT was reduced by 42.9-48.1% under ambient rainfall compared to irrigated checks, which received 50.2% more water. The seasonal yield distribution demonstrated two contrasting strategies, however, equally effective for high resilience under rainfed conditions. The winter-active imported cultivars were the most resilient in the driest year, potentially due to their ability to exploit autumn rains, whereas the locally adapted genotypes were more productive in summer. The spring harvest ratio (R-H1) was more indicative (r = 0.94, P < 0.01) of cultivar productivity, compared to plant survival (r = 0.65, P < 0.01), whereas the autumn harvest ratio (R-H5) was representative of productivity under extreme drought (r = 0.53, P < 0.05). R-H1 and R-H5 were increased by 11.8 and 12.3%, respectively, whereas the summer ratios (R-H3, R-H4) were reduced by 47.3%, under rainfed v. irrigated conditions. Two Australian cultivars ('Blue Ace', 'Icon') achieved the highest R-H5 suggesting an adaptive response by being more productive in autumn. However, the development of specifically adapted cultivars in terms of higher summer yield and plant survival may be necessary to cope with future climatic changes in the Mediterranean region.