THE ROLE OF INTRA-SPECIFIC BIODIVERSITY TO COPE WITH CLIMATE CHANGE: A CASE STUDY ON DURUM WHEAT CULTIVARS

The perspective of climate change requires an analysis of adaptation options for species currently cultivated. The relevant intra-specific biodiversity of crops may be a powerful tool for adaptation. Therefore the knowledge, for different crop cultivars, of the responses to different environmental conditions (e.g. cultivar-specific yield response functions to water regime) can allow identifying adaptation options to future climate and responsivity to supplemental irrigation. Models of crop response to environmental forcing might be used for this purpose, but their use is severely constrained by the very scarce knowledge on cultivar-specific values of model parameters, thus limiting the potential exploitation of intra-specific biodiversity towards adaptation. We have developed an approach to identify adaptation options that relies on three complementary elements: o a database on climatic requirements of durum wheat cultivars: the yield response functions to water availability were determined both from scientific literature and field experiments. Cultivar-specific climatic requirements were thus determined with respect to soil water availability; o simulations performed with the agro-hydrological model SWAP to determine the soil water regime, accounting for soils hydrological properties and climate forcing. The hydrological indicator Relative EvapoTranspiration Deficit was calculated for a reference and a future climate case and for each soil type within the study area; o comparison of hydrological indicators with cultivar-specific requirements for all combinations of climate, cultivar and soil types to identify options for adaptation. The selected study area is a hilly region of about 40,000 ha in Southern Italy (Fortore Beneventano, Campania Region). In this area three soils types were identified and deemed representative of the whole area. Two climate cases were studied: "reference" (1961-1990) and "future" (2021-2050), produced within the Italian National Project AGROSCENARI. The reference climate case was generated from climatic statistics on observed variables while the future climate case was obtained from statistical downscaling of general circulation models (AOGCM). Climatic data consist of daily time series of maximum and minimum temperature and daily rainfall on a regular grid with a spatial resolution of 35 x 35 km. The downscaled climate case includes 50 realizations of daily data. By means of the SWAP model the soil water regime was described in the three soil types using the Relative EvapoTranspiration Deficit (RETD). Cultivars hydrologic requirements were compared with the simulated values of RETD and the comparison was performed for each soil type, cultivar and climate realization to assess adaptability. In the future climate case, during the cropping season (December-June), a significant reduction (about 80 mm) of rainfall is foreseen, in particular during Spring. According to the soils hydrological indicators values and to the cultivar-specific requirements, the adaptability of several durum wheat cultivars (Waha, Haurani, Cham 5, Cham 1, Balcali 85, Cappelli, Creso, Simeto and Claudio) was assessed. The results indicate different adaptability among cultivars, soil types and climate cases. The different physical properties of the three soil types and the difference in the rainfall regime, occurring between the two climate cases, strongly affected the adaptability of the cultivars. The case study shows how, in the future climate scenario, the intra-specific biodiversity would allow maintaining current crop production system. Moreover, in the future climate, the reduction of precipitation could require supplemental irrigation as another tool to cope with climate change.