To study the genetic variation, heritability and genetic correlations of some agro-morphological traits in tall fescue, 25 parents from a genetically broadbase germplasm were polycrossed and their respective half-sib families were generated. Clonally propagated parents and their half-sib families were grown as spaced single plants using a randomized completeblock design with three replications, and observed for seven traits in 2006 and 2007. The estimates of broad-sense heritability h 2 n À Á were moderate to high h 2 b ¼ 0:43 À 0:80 À Á for the traits studied. Narrowsense heritability h 2 n À Á estimates from analyses of progenies and from regression of half-sib (HS) progenies on parents h 2 op suggested that genetic variation for these traits was largely controlled by additive gene action. Association of dry matter yield (DMY) with plant height, number of fertile shoot, curbs width and spring growth was positive and significant. With the exception of number of days to pollination, correlation coefficients of the traits between the parents and offspring were not significant. Based on parentoffspring regression, genetic gain from selection for DMY was high, demonstrating genetic potential for improving this trait. Overall, there was high genetic variation and moderate heritability for most traits in the tall fescue populations evaluated. In conclusion, to improve herbage yield, selection would be more effective based on forage yield components.

Seeds of 20 accessions of six Brassica species including cultivated and five wild relatives were analyzed for oil and fatty acid composition. The Results showed that oil content varied from 21 (B. nigra) to 46% (B. napus). Among wild species, B. rapa and B. oleracea had highest oil content (31 and 28 %, respectively). The main fatty acids of oleic, linoleic, linolenic, erucic,

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Research on crop response to deficit irrigation is important to reduce agricultural water use in areas where water is a limited resource. The objective of this study was to evaluate changes in physiological and root traits under mild and intense drought stress in tall fescue. It also sought to find associations between these changes and field drought tolerance. A total of 24 tall fescue genotypes were selected from a wide polycross population and assessed for field drought tolerance during 2011-2012 in the field. The genotypes were classified as tolerant, moderately tolerant, and susceptible based on drought stress tolerance index (STI), tolerance index (TOL), and yield reduction (YR). In 2013, 24 genotypes were clonally propagated and planted in polyvinylchloride (PVC) tubes under, three levels of moisture regimes. Root characteristics were investigated at 0-30 and 30-60 cm depths of soil. Also 11 physiological traits, dry forage yield, STI, TOL, and YR were recorded. At the 30-60 cm depths of soil, the root length increased by 5.95 and 7.30 % under mild and intense stress, respectively. Under mild stress, root area and root volume were positively correlated with STI. Consequences of drought stress, manifested as declined relative water content and chlorophyll, could be associated with a decrease in the activity of antioxidant enzymes. Some tall fescue genotypes had extensive root systems, high photosynthetic capacity, and less YR in the field. These genotypes may adapt to drought through drought avoidance and drought tolerance mechanisms. The application of principle component analysis for screening suitable genotypes was also discussed.

Development of a standard evaluation protocol has been a pressing problem for the selection of drought‐resistant genotypes of tall fescue (Festuca arundinacea). This study was conducted to evaluate the association of forage yield with specific phenological and morphological traits to find a proper model for indirect selection under irrigated (normal) and drought‐stress conditions in tall fescue. A random sample of seventy‐five genotypes were clonally propagated and evaluated in normal and drought‐stress environments in the field during 2009 and 2010. Results showed that water stress had a negative effect on forage yield and most of the morphological traits measured and reduced genotypic variation for most of them. Forage yield had the highest genotypic variation, whereas days to pollination had the lowest variation. Low broad‐sense heritability estimates were obtained for dry‐matter yield, but heritability for the traits of number of stems per plant, plant height and crown diameter was moderately high. These traits were identified as the main components of forage yield. The importance of these components and their direct and indirect effects on forage yield was different in normal and drought‐stress conditions. This suggests that indirect selection for developing high‐yielding, drought‐tolerant varieties should be performed under drought‐stress conditions with a specific model.

Tall fescue (Festuca arundinacea Schreb.) is an outcrossing allohexaploid grass species extensively used for forage and turf worldwide. Twenty‐five genotypes of tall fescue were chosen from a broad‐base population and the genetic diversity was evaluated based on expressed sequence tag‐simple sequence repeat molecular markers and agronomical and morphological traits. Their respective half‐sib polycross progenies were also evaluated for these same traits at six environments (two locations for 3 yr). The high genotypic variation observed for plant seed yield and some morphological traits in parental genotypes and their respective progenies indicated high potential for improving these traits through targeted selection in breeding programs. Family and family × location interactions were significant for most characteristics. Narrow‐sense heritability estimates were moderately high for plant seed weight (49%), number of fertile tillers (46%), panicle length (45%), and plant height (44%). These indicate that family selection methods should be more effective than individual selection. Stable families across environments were identified based on the regression coefficients, deviations from the regression, and yield potential indicating the usefulness of these parameters in the selection process for seed and forage yield improvement where additive × environment interactions are present.

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Although relationships among plant, biological N 2 fixation, and response to soil and environmental conditions have received considerable coverage in the scientific literature, a comprehensive summary and interpretation of these interactions with specific emphasis are lacking. Fluctuations in pH, nutrient availability, temperature, and water status, among other factors, greatly influence the growth, survival, and metabolic activity of nitrogen fixation bacteria. The subsequent inhibition of nitrogenase would result in O 2 accumulation in the infected zones, inducing the decrease in nodule permeability. Poor nodulation of legumes in arid soils is likely due to decreases in population levels of rhizobia during the dry season. Fixation, therefore, also tends to decrease with legume age, mainly because of the concomitant increase in soil N. Calcium deficiency, with or without the confounding influence of low pH also affects attachment of rhizobia to root hairs. Rhizobia may have different tolerances to soil acidity factors than the host plant. Relatively, high-root temperature has also been shown to influence infection, N 2-fixation ability, and legume growth. Also, root nodulation by the bacteria can be dependent on the formation of mycorrhiza.