Yes, it is possible to study drought tolerance, yield and some diseases observations in the same field trial (RCBD factorial) on wheat genotypes. However, there are some considerations and challenges that need to be addressed.

First, the experimental design should be appropriate for the objectives and hypotheses of the study. An RCBD factorial design can be used to test the effects of two or more factors (such as genotype and irrigation level) and their interactions on one or more response variables (such as yield and disease incidence). However, the number of factors and levels should be kept to a minimum to avoid excessive replication and complexity. The randomization and blocking should also ensure that the experimental units are homogeneous and independent within each block.

Second, the experimental conditions should be representative of the target environment and stress level. For example, if the study aims to evaluate drought tolerance, the irrigation treatments should simulate realistic drought scenarios that affect wheat production in the region. The timing, duration, and severity of drought stress should also be carefully controlled and monitored. Similarly, if the study aims to evaluate disease resistance, the disease inoculation or natural infection should be sufficient and uniform to cause significant disease pressure and variation among genotypes.

Third, the experimental measurements should be accurate and reliable. For example, if the study aims to measure yield, the harvest should be done at the optimal maturity stage and the grain weight and quality should be adjusted for moisture content. If the study aims to measure disease incidence or severity, the disease symptoms should be assessed using standardized scales or methods at appropriate growth stages. The measurements should also account for possible confounding factors such as plant density, lodging, or weed competition.

Fourth, the experimental analysis should be valid and robust. For example, if the study aims to compare genotypes for drought tolerance or disease resistance, the analysis should include appropriate statistical tests and models that account for the effects of genotype, irrigation level, disease level, block, and their interactions. The analysis should also check for assumptions such as normality, homogeneity of variance, and independence of errors. The results should be interpreted with caution and supported by biological explanations.

Therefore, studying drought tolerance, yield and some disease observations in the same field trial (RCBD factorial) on wheat genotypes is feasible but requires careful planning, execution, measurement, and analysis. It can provide valuable information on the performance and adaptation of wheat genotypes under different environmental conditions and stress factors.

Sayed Muhammad Baqer Hussaini Natural infection by most of wheat diseases is highly variable in filed. Moreover, if you intend to estimate potential yield of varieties, it is better to do under standart disease control scheme. As Fayaz Hussain wrote: "studying drought tolerance, yield and some disease observations in the same field trial (RCBD factorial) on wheat genotypes is feasible but requires careful planning, execution, measurement, and analysis." Usual scheme of varieties trial may be unsuitable for this purpose.

Thank you both of you dear Fayaz hussain and Alex ignatov for your technical answers and nice discussions. The trial is started under open field conditions as specified above. However we are facing severe drought in the last years in Afghanistan, needed focusing on drought tolerant crops.