Knowledge aboutbiomass partitioning of maize grown in arid and semi-arid climatesis scarceand yet essential to select a robust and effective deficit irrigation management (DIM) strategy for these regions.The objectives of this study were to: i)investigate the effects of different levels of water application under two DIM strategies on the root and aboveground characteristics, the response factor to water stress (K y) and irrigation water use efficiency (IWUE) of silage maize at different growth stages, andii) determine the best DIM strategythat 44 would maximize biomass productivity.Field pot experimentswere conducted in Isfahan, 45 Iran,during 2009 and 2010.The twoDIM strategies werefixed irrigation interval-variable 46 irrigation depth (M 1), and variable irrigation interval-fixed irrigation depth (M 2).Each DIM strategy was tested at four water-deficit levels, including: severe, moderate, mild,and a fullirrigation.In M 1 , irrigation intervals were consistent for all irrigation treatmentsbut were varied over the growing season. Treatment effects weremeasured at the10-leaf, 16-leaf, tasseling, milk,and silage harvestcrop growth stages.There was significant effect of irrigation and growth stage on total aboveground biomass (TB), leaf area (LA), root biomass (RB), and root:shoot ratio (RSR)for both DIM strategies during the two years.For M 2 , there was 53 significant difference in TB, LA, RB, and RSR between all irrigation levels at all growth 54 stages.TB production was on the average around 25% higher for M 1 compared to M 2 , even 55 though total applied irrigation water was only 6% higher for M 1 .Comparing the two DIMsshowed that RSR and K y wereboth higherforM 2 , indicating that the crop was more sensitive to this strategy.In conclusion, M 1 was selected as the best management practicesince it had more favorable effects on improving the IWUE and also on the development of maize rootsduring the growing season.

Powdery mildew (Oidium lini Skoric, [PM]), an obligate biotrophic ascomycete, is a common and widespread foliar disease of flax in most flax‐growing areas of the world. In this study, we constructed a linkage map using 143 simple sequence repeat (SSR) markers and an F2 population of 300 individuals generated from a cross between the susceptible cultivar NorMan and the resistant cultivar Linda. The F2–derived F3 families were phenotyped in the field and the F3–derived F4 families were phenotyped in a controlled environment growth chamber. The 15 linkage group map covered 1241 cM and was largely collinear with the previously published consensus map. Quantitative trait loci (QTL) analysis was performed and three PM resistance QTL located on LG1, 7, and 9 were identified consistently using phenotyping data from both field and growth chamber studies. These QTL explained 97% of the phenotypic variation exhibiting a mainly dominant gene action. This work represents a first step toward understanding the genetics of PM resistance in flax and map‐based cloning of candidate genes underlying the QTL.

Using plant genotypes adaptable to water-deficit stress is an optimal strategy in sustainable agriculture. This study was conducted to assess the selection criteria for identifying high yielding-drought tolerant F 2 -derived F 3 flax families from a cross between Iranian genotype KO37 and the Canadian genotype SP1066. One hundred and nineteen F 2:3 were evaluated under drought stress and non-stress conditions using an 11*11 lattice design with three replications. Sixteen drought tolerance indices adjusted based on grain yield under drought stress and non-stress conditions were calculated. The presence of high variability for grain yield and irrigation water use efficiency in parental lines and F 2:3 families under both conditions indicated that the F 2:3 population or its advanced generations can be used in selection programs to increase drought tolerance and also to identify quantitative trait loci / genes related to grain yield and drought tolerance in flax. The results of biplot based on the PC 1 and PC 2 and triplot analysis based on STI index and grain yield in both stress and non-stress conditions introduced thirteen families as the most promising families for drought tolerance and therefore, their advanced generations can be used in future breeding programs to improve drought tolerance in flax.