Agro-morphological and physiological traits affecting grain yield of durum wheat advanced generations under rainfed conditions

Durum wheat production in the Mediterranean climate is limited when water shortages occur during anthesis. Breeding programs try to increase crop yield under challenging weather conditions such as water shortage. The improvement in phenotyping with the purpose of selecting key plant traits is important for increasing the efficiency of the breeding program. In this study, 125 and 119 durum recombinant inbred lines (RILs) from F7 and F8 generations, respectively, derived from the cross between the Iranian landrace “Iran_249” and the Iranian variety “Zardak” were compared in the field over two successive years (2015 and 2016) in the temperate rainfed conditions with the Mediterranean climate. The results showed that the performance of RILs was influenced by the year. Harvest index, biomass, number of spikes per plant, number of tillers per plant, straw yield, spike weight, spike density, and weight of grains per spike were positively associated with the grain yield in two years. According to path analysis in the first year, the number of spikes per plant and awn length had a positive and significant direct effect on the grain yield whilst, in the second year, the positive and significant direct effects on the grain yield belonged to the number of tillers per plant, grain filling rate, and plant height. In conclusion, based on the two-year data, the RILs with higher spike weight, the weight of grains per spike, number of tillers per plant, biomass, grain filling rate, higher plant height with longer peduncle length, and longer spikes with longer awn length may have higher yield under rainfed conditions. These traits are promising traits for the indirect selection of grain yield. RILs No. 2, 16, 29, 43, 66, 80, 100, and 118 had the highest rank in both years and were superior to their parents.