فصلنامه علوم زراعی ایران
سال دوازدهم شماره 2 (پیاپی 46، تابستان 1389)

To evaluate the effect of terminal heat stress on grain yield and its components in 20 spring bread wheat cultivars, a field experiment was conducted in Mollathani (35 Km Norh-east of Ahwaz) in 2007-2008 and 2008-2009 cropping seasons-using stripe block design with three replications. Four sowing dates (06 Nov., 06 Dec., 05 Jan. and 04 Feb.) were assigned to horizontal plots and 20 spring bread wheat cultivars (Shoeleh, Arvand 1, Chenab 70, Chamran, Vee/Nac, Atrak, S-80-18, Star, Inia 66, Bolani, Bayat, Darab, Dez, Kavir, Maroon, Hamoon, Hirman, Pishtaz and Roshan) were randomized in vertical plots. Results showed that year, sowing date, genotypes and sowing date × genotype had significant effect on all measured traits. Mean comparisons revealed that grain yield in 2008-2009 was greater than 2007-2008. Of the highest average grain yield (6049 kg.ha-1) was produced in 06 Nov. and lowest average grain yield (1755 kg.ha-1) was produced in 04 Feb. sowing dates. Cv. Chamran produced the highest average grain yield (5020 kg.ha-1) and the lowest average grain yield belonged to Inia 66 (3663 kg.ha-1). Using stress tolerance index (STI) classified Arvand (0.394), Vee/Nac (0.393), Chamran (0.378) and Bayat (0.356) as tolerant cultivars and Roshan (0.199), Hamoon (0.223), Falat (0.227), Star (0.233), Inia 66 (0.237) and Darab 2 (0.244) as susceptible cultivars to terminal heat stress. Generally, in Ahawaz conditions, adapted wheat cultivars with suitable maturity (early, mid and late maturity) and appropriate agronomic packages would result in stable high grain yield and sustainable production.

To study the effects of water stress and type of fertilizer on osmotic properties, essential oil content in chamomile (Marticaia chamomilla) a field experiment was conducted- using a split plots design with three replications in Research Field Station, Zabol University, Zabol, Iran in 2008. Water stress treatments included control as 90% of field capacity (W1), 70 % field capacity (W2) and 50 % field capacity (W3) assigned to the main plots and different types of fertilizers, including control or without any fertilizer (F1), chemical fertilizer (F2), manure: 25 t.ha-1 (F3) and urban waste compost (F4) randomized in sub plots. Results showed that in water stress of 50% field capacity, flower yield of chamomile decreased by 18.1% in comparison with control. However, the highest flower yield and flower yield components (biomass, plant height, number of main stem and number of flower.plant-1) were obtained from W1 and application of chemical fertilizer, but in W3 and F3 had the best effect on flower yield and its components in chamomile. The highest essential oil content and oil yield were obtained in W2. With increasing stress severity, carbohydrates and proline contents, in green leaf tissues of chamomile, increased. Chemical fertilizer was the most effective type of fertilizer. It is concluded that under sever water stress, manure fertilizer was the suitable type of fertilizer in chamomile production.

To evaluate terminal drought stress tolerance in rapeseed cultivars, field experiments was carried out using split plot arrangements in randomized complete block design with four replications in Karaj Research Field Station, Seed and Plant Improvement Institute, Karaj, Iran in two successive growing seasons (2004-2005 and 2005-2006). Irrigation in two levels; optimum irrigation and no-irrigation from silique formation till end of life-cycle were assigned to main plots. Rapeseed genotypes including; Licord, Okapi, SLM 046, RGS 003, Hyola420, Option500, Zarfam, Orient, Opera, Talaye, Sarigol and Hyola401 were randomized in sub-plots. Results showed that drought stress decreased plant height, number of branch.plant-1, number of silique.plant-1, number of grain.silique-1, 1000 grain weight, grain yield, and oil yield, but increased harvest index. However, it had not significant effect on grain oil content. There were significant differences among cultivars for all measured traits. SLM046 and Zarfam in optimum irrigation had the highest grain yield (3771 kg.ha-1 and 3727 kg.ha-1, respectively) as well as in drought stress conditions (2705 and 2663 kg.ha-1, respectively). These cultivars had the highest oil yield. Therefore, Zarfam and SLM046 can be considred as stable cultivars in optimum irrigation as well as in terminal drought stress conditions.

‏To study the effects of agronomic practices on incidence and development of damping-off and verticillium wilt diseases, yield and yield components of cotton, two field experiments were conducted in Karkandeh Cotton Disease Research Station, 35 Km west of Gorgan, Iran-using split plot arrangements in randomized complete block design with three replications. Autumn agronomic practices: 1- without agronomic practices as control, 2- chopper, 3- chopper + disk, 4- chopper + moldboard plow, 5- chopper + disk plow, 6- moldboard plow,7- disk plow were assigned to main plots. Spring agronomic practices: 1- moldboard plow + disk and 2- disk were randomized in sub-plots. Combined analysis of variances showed that damping-off and verticillium wilt incidences were severely affected by interactions of agronomic  tillage practices (autumn and spring tillages). Hence, moldboard plow × spring disk and (chopper + autumn moldboard plow) × spring disk had the least effect of incidence of pre-emergence damping-off and verticillium wilt diseases, respectively. The highest rate of incidence of damping-off disease due to Rhizoctonia solani was observed in chopper × spring disk package (62.5%). The highest and lowest seed cotton yield were obtained from (chopper + autumn moldboard plow) × (spring moldboard plow + disk), and (chopper + autumn disk) × (spring moldboard plow+disk), respectively. It is concluded that field establishment and reduce losses of damping-off and verticillium wilt diseases were significantly improved by implementation of the suitable agronomic practices for seedbed preparation in cotton production.

Development and release of high quality rice cultivars is one of the major objectives in rice breeding programs in Iran. Amylose content (AC), gelatinization temperature (GT) and gel consistency (GC) are very important characteristics determining end-use and cooking quality in rice. However, there are rice cultivars with similar AC, GT and GC, but are different in cooking quality. It seems that starch viscosity properties are also effective in rice cooking quality. Six local rice cultivars including: Hashemi, Binam, Salari, Domsiah, Gharib and Hassansaraei, and six improved cultivars including: Khazar, Sepidroud, Bahar-1 hybrid rice, Dorfak, Saleh and Kadous were considered for study of grain starch viscosity characteristics. All cultivars had similar AC, GT, GC and protein content (PC), but were different in cooking quality. 30 samples were taken from each cultivar and evaluated for viscosity parameters using rapid visco analyzer in completely randomized design with three repetitions. Analysis of variance showed that differences between local and improved cultivars were significant for viscosity characteristics, however, viscosity characteristics were inter-mediate in the local cultivars. 95% confidence intervals for viscosity characteristic of local cultivar including peak viscosity (PV), minimum viscosity (MV), breakdown (BD), final viscosity (FV), setback (SB) and pasting temperature (PT) were 258.07-297.61, 170.72-214.98, 78.06-105.28, 278.15-333.57, 106.20-138.84 and 94.61-99.07, respectively. However, minimum and maximum values of most viscosity characteristics were extended in the improved cultivars as compared to local cultivars. Therefore, starch viscosity characteristics are suggested as efficient criteria for assessment of cooking quality in rice cultivars..

Genetic components controlling some of cooking quality related traits in rice (Oryza sativa L.) were studied using a 7×7 complete diallel cross design in Rresearch Field Station, Rice Research Institute of Iran (RRII) in 2006 and 2007 growing seasons. Analysis of variance showed significant differences among genotypes for traits of inetest including; amylose content (AC), gel consistency (GC), gelatinization temperature (GT) and grain elongation (GE). Based on Hayman’s diallel method, both additive (D) and dominance components (H1 and H2) were significant for AC and GC. However, for the other traits, only additive variance was significant. The average degree of dominance showed partial dominance effects of genes in controlling all the studied traits. The H2/4H1 ratio indicated nearly symmetrical distribution of the genes for AC and GE. Results also indicated that increase in AC and GT and decrease in GC were controlled by genes with dominance effects while decrease of GEL was governed by recessive genes. The broad sense heritability estimates were high (0.97% and 90% and 83%, for AC, GT and GC, respectively) to moderate (0.66 for GE). The magnitude of additive gene effects and heritabilities for traits of interest demonstrated high response to selection, particularly for AC and GT. Consequently, appropriate breeding schemes based on hybridization and selection for these traits may bring about an improvement of cooking quality in rice. Some crosses such as Sepidrood × IRFAON-215, Neda × IRFAON-215 and Saleh × IRFAON-215 can be employed for improving AC, GT and GC traits, respectively.

To evaluate terminal drought tolerance in barley genotypes and to study the relationship between morpho-physiological traits and grain yield in terminal drought stress conditions, 214 barley genotypes as well as two checks were examined at three locations; Varamin, Birjand and Esfahan Research Field Stations in 2002 -2003 growing season. Morpho-physiological traits including: days to anthesis, days to maturity, plant height, peduncle length, spike length, number of fertile tillers, grain.spike-1 and 1000-grain weight were measure and recorded in three locations. Results indicated significant differences between Six row and two row genotypes for grain yield components (number of fertile tillers, grain.spike-1 and 1000 grain weight), days to heading and spike length. Correlation, stepwise regression and path analyses studies indicated that days to anthesis, peduncle length and 1000 grain weight not only had the highest correlation with grain yield, but also had the highest direct effects on grain yield in both six row and two row barley genotypes. However, these correlations and effects were more pronounced in two row barley genotypes.

To identify and isolate resistance gene analogues (RGAs) in potato, 46 genotypes from F1 diploid mapping population of SH × RH with highest recombination were assessed by NBS profiling technique in the genomics laboratory of Wageningern University, The Netherlands. Using five degenerate primers, that were designed based on conserved motifs NBS domain, in total, 187 polymorphic markers were produced and mapped in relation to AFLP map of the population comprising 10,000 markers. Following sequencing and alignment of several markers, 68 of them revealed homology between known resistance genes or TIR-NBS-LRR type disease resistance proteins. Seven of these RGAs showed similar genetic position and sequence with resistance genes identified in potato or tomato. Thirty seven of the sequenced RGAs were mapped in the chromosomal regions similar to resistance genes or RGAs identified in tomato or potato without having sequence homology with these resistance genes or RGAs, and the rest of RGAs were mapped in positions where no RGA was reported, before. The majority of the RGAs were positioned in new or existing clusters or sub-clusters in the map. Phylogenetic analysis revealed the grouping of RGA sequences based on degenerate primers that were used for amplification. The result of this research could be used in mapping of single resistance genes and quantitative resistance loci.

To determine the inheritance of germination related traits in bread wheat, a 8×8 diallel cross design was carried out in 2007 at the Ardebil Branch, Islamic Azad University, Iran. The F1 and F2 seeds were germinated under osmotic stress and also subjected to atmospheric drought stress. Different germination rate indices, seedling characteristics and germination recovery after desiccation were measured and recorded. For evaluating the relationship between germination characteristics and drought tolerance, 18 wheat varieties including the parents of diallel cross were grown under irrigated and rainfed conditions in the field. Results of these experiments indicated that germination rate indices had high narrow sense heritability and close relationship with drought tolerance. Among seedling characteristics, coleoptile length under normal condition showed high narrow sense heritability and a close relationship with drought tolerance. Root number under stress conditions was considered as a moderately heritable character with significant relationship with drought tolerance indices. Despite of the close relationship of root: shoot length ratio with drought tolerance, it had low narrow sense heritability. Germination recovery showed negative relationship with drought tolerance and had low narrow sense heritability.

To study the genetic variation in baking quality related characteristics bread wheat commercial cultivars and advanced breeding lines, an experiment was conducted with 85 cultivars/lines- using an α-lattice design with three replications. Thirteen characteristics including; 1000 grain weight, hectoliter weight, grain protein content, Zeleny sedimentation volume, bread volume, grain moisture (%), grain hardness, falling number, wet gluten (%), dry gluten (%), gluten index, SDS-sedimentation volume, as well as four farinograph components: dough development time, dough stability, degree of softening (after 10 and 12 minutes), were measured. Analysis of variance showed significant differences among genotypes for all traits. This shows high genetic variation among the cultivars and advance lines. Multivariate factor analysis performed for 12 traits, and found that three common factors defined 97% of observed variation. The first factor defined 78.55% of variation including farinogram triats. The second factor explained 16.78% of variation included; protein content, bread volume and Zeleny sedimentation volume, and the third factor explained only 1.75% of variation included; gluten index and SDS-sedimentation volume. Cluster analysis based on variances of inta-groups recognized four different clusters. The cluster with high bread making quality consisted of 23 cultivars and advanced lines. This findings would be employed in bread wheat breeding program to improve the baking quality characteristics in breeding materials.