DURUM-WHEAT LANDRACES FROM SYRIA .3. AGRONOMIC PERFORMANCE IN RELATION TO COLLECTION REGIONS AND LANDRACE GROUPS

Syrian durum wheat landraces from diverse collection sites were evalua ted for agronomic performance under arid conditions over two seasons a t four locations, at two levels of nutrient availability. Grain yield differed considerably among locations. Within locations, significant p opulation and fertilizer effects were demonstrated. In most cases, max imum yield was achieved by landraces, which demonstrates the breeding value of local germplasm. In a particular environment, the population effect was nonsignificant for total dry matter production, but signifi cant for straw and grain yield. Nitrogen application was ineffective i f moisture availability was the dominant growth limiting factor. Corre lations between plant characteristics at evaluation and collection sit e characteristics were limited, and therefore, their utilization in ge rmplasm evaluation appear limited. The negative relation between grain yield and soil nitrogen content at the collection site may be caused by the comparative disadvantage that germplasm from regions with favou rable growing conditions has under low-yielding conditions. Particular environmental conditions at the collection site were no indicator for the response to changed growing conditions. Relatively high grain yie lds under good and adverse growing conditions excluded each other in a ll but two cases. Also, it was difficult to relate grain yield to regi ons of collection, as the response of individual landraces from a cert ain region to changing growing conditions differed strongly. Different iation on the basis of landrace groups appears more promising. The Hau ran landrace group provided the largest number of populations with rel atively high grain yields over diverse environments.