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Previous research results of Blue Panic (Panicum antidotale Retz) in arid conditions under different irrigation methods proved an increase in forage yield and water productivity (WP) under full and water stress conditions. However, a thorough search in the literature revealed that its water requirement has not yet been determined. Therefore the objective of this research was to measure evapotranspiration (ETc) and crop coefficient (Kc) for a Blue Panic crop under arid conditions. Four draining lysimeters constructed in Jeddah (21° 480 300 N, 39° 430 2500 E) were used to measure its ETc and Kc under a plentiful water supply. Results revealed that ETc varied from 141 mm in the first harvest to 292 mm in the sixth, with an average of 225 mm per harvest. The Kc value was different from one harvest to another. The average Kc over all harvests was 0.7, 1.2, 1.3 and 1.0 for the initial, development, midseason and late stages, respectively. Average fresh and dry forage yields per harvest were 30.5 and 12.6 t ha1, respectively. AverageWP was 55 kg ha1 mm1. The predicted ETc based on the measured crop coefficient value and ET0 show a good fit between measured and calculated ETc. Copyright © 2018 John Wiley & Sons, Ltd.

Field experiment was carried-out during 2015/16 and 2016/17 seasons at the Agriculture Experimental Station of King Abdulaziz University to investigate the effect of stress and fully irrigations with different plant densities on yield and yield attributes of sunflower and to determine water productivity under the investigated treatments. The design of the experiment was a split block with four replications. Main blokes contained fully and stress irrigation water regimes while the sub mains comprised six plant densities of sunflower cultivar (Helianthus annuus L). Results revealed that decreasing irrigation water regime to 65% of field capacity (FC) reduced daily and seasonal water supplies, yield, yield attributes and oil content of sunflower crop but increased water productivity. Increasing plant density reduced head diameter, seeds yield/plant and seed index. Combination of 50 cm row spacing with 15 cm inter row spacing under 100% FC and 60 cm row spacing with 15 cm inter row spacing under 65% FC produced the highest significant seeds yield and water productivity. In these combinations using full irrigation requirement increased seeds yield by about 10% compared with the stressed one. However, the stress combination increased water productivity by about 38% compared with fully irrigation combination.

This study was conducted during 2015–2017 seasons in the Agricultural Research Station, King Abdulaziz University at Hada Al-Sham region, Saudi Arabia. The aim was to investigate the effects of planting Al- Hassawi clover between sugar beet rows in two intercropping systems: 1 sugar beet row: 2 clover rows (1:2) and 1 sugar beet row: 3 clover rows (1:3) besides sugar beet monocrop and Al-Hassawi clover monocrop. Also, number of harvested cuts from clover during the sugar beet growing season (1, 2 and 3 cuts) on sugar beet yield, sucrose yield, clover yield, leaf area index and land equivalent ratio (LER) were investigated. No significant differences were found between sugar beet fresh root or sucrose yield/ha under the intercropping systems 1:2, 1:3 or sugar beet sole crop with one or two cuts from clover. Fresh forage yield/ha from clover significantly increased as number of cuts increased using the two intercropping systems. The highest clover forage yield/ha was produced from the clover sole with three cuts. The highest LER was produced under the 1:3 intercropping system with two cuts or one cut of clover.

Charcoal rot disease, a root and stem disease caused by the soil-borne fungus Macrophomina phaseolina (Tassi) Goid., is a major biotic stress that limits sorghum productivity worldwide. Charcoal rot resistance-related parameters, e.g., pre-emergence damping-off%, post-emergence damping-off%, charcoal rot disease severity, and plant survival rates, were measured in a structured sorghum population consisting of 107 landraces. Analysis of variance of charcoal rot resistance-related parameters revealed significant variations in the response to M. phaseolina infection within evaluated accessions. Continuous phenotypic variations for resistance-related parameters were observed indicating a quantitative inheritance of resistance. The population was genotyped using 181 simple sequence repeat (SSR) markers. Association analysis identified 13 markers significantly associated with quantitative trait genes (QTLs) conferring resistance to charcoal rot disease with an R2 value ranging between 9.47 to 18.87%, nine of which are environment-specific loci. Several QTL-linked markers are significantly associated with more than one resistance-related parameter, suggesting that those QTLs might contain genes involved in the plant defense response. In silico analysis of four novel major QTLs identified 11 putative gene homologs that could be considered as candidate genes for resistance against charcoal rot disease. Cluster analysis using the genotypic data of 181 SSR markers from 107 sorghum accessions identified 12 main clusters. The results provide a basis for further functional characterization of charcoal rot disease resistance or defense genes in sorghum and for further dissection of their molecular mechanisms.

Charcoal rot disease, a root and stem disease caused by the soil-borne fungus Macrophomina phaseolina (Tassi) Goid., is a major biotic stress that limits sorghum productivity worldwide. Charcoal rot resistance-related parameters, e.g., pre-emergence damping-off%, post-emergence damping-off%, charcoal rot disease severity, and plant survival rates, were measured in a structured sorghum population consisting of 107 landraces. Analysis of variance of charcoal rot resistance-related parameters revealed significant variations in the response to M. phaseolina infection within evaluated accessions. Continuous phenotypic variations for resistance-related parameters were observed indicating a quantitative inheritance of resistance. The population was genotyped using 181 simple sequence repeat (SSR) markers. Association analysis identified 13 markers significantly associated with quantitative trait genes (QTLs) conferring resistance to charcoal rot disease with an R2 value ranging between 9.47 to 18.87%, nine of which are environment-specific loci. Several QTL-linked markers are significantly associated with more than one resistance-related parameter, suggesting that those QTLs might contain genes involved in the plant defense response. In silico analysis of four novel major QTLs identified 11 putative gene homologs that could be considered as candidate genes for resistance against charcoal rot disease. Cluster analysis using the genotypic data of 181 SSR markers from 107 sorghum accessions identified 12 main clusters. The results provide a basis for further functional characterization of charcoal rot disease resistance or defense genes in sorghum and for further dissection of their molecular mechanisms.

Mapping of quantitative trait genes (QTGs) associated with drought related traits is essential for improving drought tolerance in crop species. In silico identification of candidate genes relies on annotation of critical QTGs to a variety of web resource-based datasets. The barley reference sequence was employed to map QTGs significantly associated with the proline accumulation and osmotic potential. Annotation of the critical QTGs contigs to the NCBI protein database identified 72 gene orthologs located on chromosomes 1H, 2H, and 7H, from which seven genes were identified as candidates. Expression analysis of all seven candidate genes revealed differential expression pattern between plants grown under well-watered conditions and drought-stress. The results represent a successful and highly powerful implementation of genome-wide scanning approach based on in silico mapping of QTGs to identify gene clusters having a common transcript pattern with similar function.

Drought is the most important yield limiting abiotic stress worldwide and could have negative effects on food security. This study was conducted to map yield and yield-contributing trait QTLs under drought stress by association mapping, and to in silico identify drought responsive genes and assay their expression profile. Association analysis was conducted using 181 SSR markers and nine phenotypic traits collected from a structured sorghum population consisting of 96 accessions evaluated under optimum and drought stressed conditions at Assiut University Experimental Farm, Assiut, Egypt. Genomic regions associated with major drought tolerance QTLs were annotated with NCBI and sorghum databases to identify drought responsive genes, which were further transcriptionally analyzed. Significant differences between optimum irrigation and drought-stressed conditions were observed in all measured phenotypic traits. Association analysis revealed 93 marker-trait associations between 71 SSR markers and the nine phenotypic traits with an R2 value ranging from 6.56 to 42.64%. A high degree of linkage disequilibrium (>52%) was identified among markers on different chromosomes, suggesting epistatic interaction. BLASTP annotation of QTL genomic sequences identified 86 gene homologs, from which fifteen genes are drought responsive. All fifteen genes were differentially expressed in drought tolerant and susceptible accessions and their expression levels were highly induced in response to drought stress. The results provide a powerful approach coupling association and in silico analyses to identify gene clusters having a common expression profile with similar function, pointing to an evolutionary mechanism to initiate a quantitative drought stress tolerance mechanism.