Effect of water stress on above ground parts, roots and yield of durum wheat (Triticum durum Desf.) in mixed cropping of genotypes

 Durum wheat (Triticum durum) is predominantly grown in the Mediterranean area, the northern plains of the United States, Canada, Europe, and many parts of the Asia.(FAO, 2017).A large part of the wheat cultivated land in Iran is located in arid and semi-arid regions. Due to lack of water resources and consequently stress for plants, wheat yieldis significantly reduced. Unde rstanding the effect of drought stress on grain yield is an effective step in durum wheat production.(Garcia del moral et. al., 2003).

A factorial experiment with 2 factors in a completely randomized design with 3 replicates including durum wheat genotypes and water stress was conducted in the research greenhouse of College of Agriculture and Natural Resources of Darab in 2017-2018. Mixtures of 4 durum wheat genotypes (Behrang, Shabrang, Dw-92-4 and Dw-94-14) were planted in binary and quadruple combinations and pure culture. Plants were treated in two levels of water stress including normal irrigation and water stressed. Plants which went under water stress did not watereduntil the plants showed rolled leaves.
 

 The results of analysis of variance of yield and yield components are shown intable 1. Interactions ofwater stress and genotype mixtures on grain yield per plant, number ofseeds per spike, number of seeds per spikelet, one thousand seed weight were significant at the probability level of 0.01 (p≤0.01).This means that the response of the genotype mixtures to the same water stress was not the same and the amount of these losses due to water stress were higher for some of the genotype mixtures than others. (table 1). The results showed that the highest grain yield obtained in shabrang+behrang genotype mixture at normal irrigation level (8.75 g per plant) and the least grain yield was observed  in DW-92-4 pure crop under water stress conditions.(1.1 g per plant). The highest positive and significant correlation were observed between grain yield andplant height, 1000 grain weightand leaf length (r = 0.443 **) (r = 0.434 **) (r = 0.312 **) respectively.Some researchers revealed that grain yield in mixed crop combination with the same seeding rate is 15 to 23 percent superior to pure crop cultivation.(Nazeri et al., 2004).

 In general, the results indicated that the combination of genotypes under normal irrigation conditions, than pure culture as an agro-ecological method have some, positive effects on grain yield and other agronomical traits.The highest positive and significant correlation was observed between grain yield andplant height, 1000 grain weightand leaf length (r = 0.443 **) (r = 0.434 **) (r = 0.312 **). According to the results of this experiment, it seems that under irrigation conditions, the use of genotype mixtures can produce more yield than pure culture of a genotype in greenhouse conditions.