فصلنامه علوم زراعی ایران
سال چهاردهم شماره 2 (پیاپی 54، تابستان 1391)

To estimate the crop sensitivity factor (Ky) and to assess water stress effect in different growthstages of sugar beet، an experiment was conducted as split plot arrangement in randomized complete block design with four replications. The experiment was carried out in 2004 and 2005 growing seasons in the Agricultural and Natural Resources Research Center of Hamadan Province، Hamedan، Iran. Main plots consisted of four different growth stages including; 1: germination to establishment، 2: establishment to 70-80% canopy development، 3: full canopy development and 4: beginning of canopy senescence to crop maturity (maximum extraction coefficient). Sub-plots consisted of different water consumption levels; 100، 85، 70 and 55% of full irrigation requirements. Combined analysis of variance showed that there was significant difference between growth stages for sugar yield and white sugar yield. Quality properties including sugar content and white sugar content also differed significantly. There was significant difference between irrigation levels for quantitative traits as well as alkalinity coefficient. Interaction effect of growth stage × irrigation level was significant for different quantitative traits. In conclusion sugar beet sensitivity to water stress is alike in all of the growth stages. The most sensitive growth stage of sugar beet to water stress was the first stage for root yield and sugar yield. The crop sensitivity factor for different growth stages of sugar beet was 1. 23، 1. 02، 1. 06 and 0. 84، respectively. It is suggested that the available irrigation water is applied during the growth stages of sugar beet with crop sensitivity factor less than one. Therefore، water consumption can be reduced by 45% at the second and fourth growth stages and 15% at third growth stage، relative to full irrigation، without significant decrease in white sugar yield.

To evaluate the effect of short and long term cold acclimation on biochemical characteristics of spring and winter wheat (Triricum aestivum L.) cultivars، an experiment was conducted in completely randomized design with three replications in greenhouses of the University of Tehran in 2009. The quantity of some antioxidant enzymes، reducing sugars، chlorophyll and carotenoids contents in two wheat winter (Norstar) and spring (Koohdasht) cultivars were measured and recorded، when seedling were acclimated at 3°C for 0، 3، 6، 12، 24 hours and two weeks. Results of LT50 showed that only Norstar winter cultivar was able to tolerate 12°C after two weeks of cold acclimation. In most cases the activities of enzymes were increased during the short term and then decreased after long term of cold acclimation. The increase of enzymes in the initial phases of cold acclimation represented that reactive oxygen species were rapidly detoxified during the short term cold acclimation. Since chlorophylls are the source of production of reactive oxygen species، the decrease in chlorophyll content in Norstar showed that this attribute، during cold acclimation، can be involved in freezing tolerance. In conclusion، results of this experiment indicated that both short-and long-term cold acclimation are important، however some metabolites are effective during the short term while others are effective during long term.

To study the effect of salt stress on morphological and physiological traits of different Brassica species a greenhouse experiment was conducted in Tarbiat Modares University. Eighteen rapeseed cultivars (fifteen cultivars of B. napus and three cultivars of B. rapa)، and two levels of soil salinity (2 and 12 dS. m-1) were experimented as factorial arrangement in randomized complete block design with three replications. The total experiment duration was 50 days (time from planting to the end of rosette stage). Results showed that salt stress reduced number of leaf، leaf area، weight of petiole، blade and biomass. However salt increased the water content and relative water content of leaf، but the ratios of blade to petiole weight and phloem to xylem weight. The lowest variation was observed in the relative water content of leaf، whereas the highest variation was in biomass and leaf water content. There was no significant correlation between biomass and number of leaf. Biomass was significantly correlated with the blade area and weight. Salinity decreased the total and chlorophylla and chlorophyllb contents، potassium (K+)، ratio of potassium to sodium (K: Na+) in blade and membrane integrity. Salinity increased the concentration of Na+ in blade. Increase in the concentration of Na+ was higher than decrease in the concentration of K+ in blade. Salt stress had no effect on a/b chlorophyll and other plant pigments such as carotenoid، antocyanine and flavonoids. The concentration of proline increased in B. napus and decreased in B. rapa with increasing salinity. No significant correlation was found between proline and biomass in both species. Results of this study demonstrated that B. napus coped better with salt stress than B. rapa in early stages of growth which can be attributed to the amphidiploidy of B. napus.

Heritability and gene actions of some important quantitative agronomic traits were studied in the progenies of a cross between a drought tolerant and a susceptible barley lines in normal irrigation and terminal drought stress conditions. A cross was made between two genotypes EC 84-12 and 1-BC-80455 susceptible and tolerant to drought، respectively. Parents as well as F1، F2، BC1 and BC2 generations were evaluated under field conditions in two separate experiments using randomized complete block design (RCBD) with three replications. These experiments were carried out in the research field station، Seed and Plant Improvement Institute، Karaj، Iran in 2005-2006 and 2006-2007 cropping cycles. In normal irrigation and terminal drought stress conditions، irrigation was applied until physiological maturity and anthesis stages، respectively. Plant height، spike length، awn length، grain yield plant-1، 1000 grain weight (TGW)، harvest index (HI)، number of days to heading، number of days to physiological maturity were measured and recorded. Analysis of variances in both environments indicated that significant differences were found between generations for all traits; therefore، generation mean analysis could be performed. Results revealed that under both normal irrigation and terminal drought stress conditions، all traits، except harvest index، were controlled by additive، dominance and epistatic gene effects. For traits as grain yield plant-1، TGW، HI، the contribution of dominance gene effects under terminal drought stress conditions was higher، considering the dominance/additive ratio، as compared to normal irrigation conditions. Comparison of gene actions in both normal irrigation and terminal drought stress conditions indicated that the contribution of dominance genes effects has been increased as compared to the additive gene effect for grain yield plant-1، and harvest index، number of days to physiological maturity، and decreased for plant height، spike length، awn length. In general، for traits showed high ratio of additive to dominance gene effect، selection could be effective in early generation، however for traits with high dominance to additive gene effects selection should be made in later generations till desirable genes are fixed. The broad and narrow sense of heritabilities for the traits under normal irrigation ranged between 0. 43 to 0. 69 and 0. 31 to 0. 43، respectively. In terminal drought stress conditions، heritabities ranged between 0. 41 to 0. 81 and 0. 36 to 0. 45، respectively. The maximum number of genes for the traits under normal irrigation and terminal drought stress conditions was estimated 1. 51 and 4. 32 genes، respectively.

Study of grain yield stability in different environmental conditions is very important in plant breeding programs. To study grain yield stability of 18 barley promising lines with two check cultivars (Bahman and MAKOUEE//ZARJOW/80-5151) in six - field stations (Hamedan، Miandoab، Karaj، Arak، Jolgheh Rokh and Mashhad) in cold agro-climatic zone of Iran for two cropping cycle (2007-2009). However، in Tabriz and Ardabil field stations the genotypes were only evaluated in 2007-2008 cropping cycle. The experimental design used in all locations and cropping cycles was randomized complete block design with three replications. Combined analysis of variance performed assuming environment (years and locations) as random and genotypes as fixed factors. Results showed that there was no significant difference among the genotypes. However، the effect of environments and genotype × environment interaction were significant (P < 0. 01). The genotype No. 16 with regression coefficient near to 1 and the lowest standard deviation from regression line determined as high yielding with high yield stability. Genotypes No. 18 and 11 with the lowest standard deviation from regression line and minimum regression coefficients using Eberhart and Russell method was determined as stable genotypes for unfavorable environment. Using Tai method، regression coefficients of barley genotypes No. 16، 18 and 11 showed that these genotypes were of high grain stability in comparison with other genotypes. In conclusion، comparison of the three regression methods showed that Tai method is the complementary method for other regression methods considering the biometrical aspects. Using three regression methods، the genotype No. 16 was determined as high yielding with high yield stability among all of the genotypes in all environments. The genotype No. 19 is recommended for high yielding environments and the genotypes No. 18 and 11 can be suggested for unfavorable conditions.

To assess genetic diversity of pod and seed characteristics in native lentil germplasm of Iran، 302 accessions from the lentil collection of the National Plant Gene Bank of Iran were evaluated. Lentil germplasm studied، were collected from 13 provinces in the country and characterized for variation in: number of pods plant-1، number of seeds pod-1، pod dehiscence، cotyledon color، color pattern on seed testa، pattern of testa، background color of testa، pod pigmentation and epicotyl color in 2008-2009 cropping cycle in Alarouq field station، Ardabil، Iran. The statistics calculated for analysis the variation included: mean standard deviation and coefficient of variation for quantitative traits، and mode and Shanoon-Weaver diversity index for qualitative traits. A high level of diversity was observed in Iranian lentil accessions examined in this experiment. The highest level of variance in qualitative traits was observed for pod pigmentation and cotyledon color. Pod dehiscence and number of pods plant-1 showed the highest diversity among the quantitative traits. The cluster analysis using all nine characteristics grouped the lentil accessions in five distinct clusters. Number of pods plant-1 appeared to be the major differentiating trait among the main clusters. The comparison among clusters for pod and seed characteristics revealed that lentil accessions in cluster 5 had the highest pod. plant-1 and are of high potential for utilization in lentil breeding programs.

This experiment was conducted with 13 grain sorghum genotypes in three different moisture conditions including: non-stress and two water deficit conditions (in vegetative and reproductive stages) using randomized complete block design with three replications. In the non-stress experiment، irrigation applied according to the plant requirement، and for two experiments: (1) drought stress imposed in vegetative stage (since four leaves up to flowering stage) and (2) drought stress imposed in reproductive stage (since flowering up to maturity). Analysis of variance showed significant differences among genotypes in all traits in three conditions. Positive and significant correlations of grain yield with harvest index and grain. panicle-1 were obtained in non stress conditions. There were positive and significant correlation of grain yield with flag leaf height، plant height، harvest index and biological yield in drought stress in the vegetative stage as well as with harvest index and days to flowering in drought stress in the reproductive stage. Results of multiple linear regression analysis (MLRA) revealed that in non-stress conditions grain. panicle-1، flag leaf area، 1000 kernel weight، stem dry weight، plantheight، leaf dry weight and days to maturity، in drought stress in vegetative stage conditions، grain. panicle-1 and flag leaf height، and in drought stress in reproductive stage conditions، flag leaf area and panicle height were determined as independent variables that explained variations in grain yield as dependent variable in the models. Plant characteristics in non-stress conditions، vegetative and reproductive drought stress conditions explained grain yield variation with r= 0. 86، r= 0. 75 and r= 0. 56 coefficient of determination، respectively. Also path analysis for grain yield indicted that grain weight. panicle-1، grain. panicle-1 and stem dry weight hadthe highest direct effect in non-stress conditions، vegetative and reproductive drought stress conditions، respectively. These characteristics had the highest indirect effect through grain. panicle-1، grain weight. panicle-1، stem diameter، flag leaf area and plant height on increasing yield.