Durum wheat production in Tunisia according to variety and water regime

Experimentation was carried out to test the response of three durum wheat (Triticum durum L.) varieties (Karim, Khiar, Razzak) at four water regimes to identify distinguishing agronomic production characteristics for each variety at certain stages of growth as well as to draw up an estimate of their correlation to grain yield independently of the variety and the water regime. Plastic pots (6 liters) were filled with 5 kg of a silt-clay soil. Seeds were placed in the soil at 3 cm depth (5 seeds per pot) and were thinned upon emergence to two plants per pot (39 plants/m2). Nitrogen was applied between stages 3 and 8 (120 kg/ha of ammonium nitrate, 33 % N). Water was supplemented at stages 10.5 and 11. The pots were placed in the field in a randomized complete block design (RCBD). For significant main effects, means were separated using the LSD test at the level of 5 % of probability. Twelve agronomic production characteristics were measured for the three wheat varieties cultivated at four water regimes with natural as a control. Measurements were made at phenologic stages 3 (leaf and tiller development), 8 (stem elongation), 10.5 (head emergence and flowering) and 11 (grain development), according to the Feekes scale. Results showed that varieties expressed differential growth as early as stage 8 for the main root growth. At plant maturity, varieties could be differentiated by three characteristics: leaf dry matter, the number of grains per spike and grain yield per plant. When water regimes were applied, their effects were significantly different depending on the agronomic characteristics. Grain yield was associated with the partitioning of dry matter among plant parts (roots, stems, leaves). The relationship of nine characteristics to grain yield was studied using a matrix correlation analysis. Results showed that leaves participated more in grain yield (r = 0.629) than did stems (r = 0.596) or roots (r = 0.478)