فصلنامه تحقیقات غلات
سال هشتم شماره 4 (زمستان 1397)

To study the grain yield, nitrogen use efficiency, remobilization and grain filling components of grain rice (Oryza sativa L.) in response to application of nitrogen and biofertilizers, a factorial experiment based on randomized complete block design with three replications was conducted under field conditionin Siahkal, Guilan province, Iran, in 2014. The experimental factors were nitrogen rates in four levels (0, 60, 90 and 120 kg.ha-1N) from urea fertilizer and biofertilizers in four levels (without biofertilizer, application of Mycorrhiza, application of Azotobacter + Azospirillum andapplication ofMycorrhiza +Azotobacter + Azospirillum). The highest grain yield and grain filling components (rate, grain filling period and effective grain filling period) were obtained from the highest level of nitrogen and application of Mycorrhiza + Azotobacter+Azospirillum. Dry matter remobilization from whole plant and stem decreased with increasing nitrogenlevels.Application of Mycorrhiza+ Azotobacter+ Azospirillum together with 120 kg.ha-1 nitrogen reduced the contribution of dry mater remobilization for grain yield and stem reserves. The highest nitrogen use efficiency was obtained from the 60 and 120 kg.ha-1nitrogen, respevtively. The results of this research showed that the application of 120 kg.ha-1net N and the application of Mycorrhiza with Azotobacter+ Azospirillum can be used as a suitable tool to increase rice grain yield.

To detect main and epistatic QTLs and their environmental interactions for rice important agronomic traits, 242 recombinant inbred lines (RIL) from two F6 rice populations derived from crosses between Alikazemi / IR67017-180-2-1-2 (IRA population) and Ali Kakami / Saleh (SA) cultivars were evaluated in two locations. Results of the present experiment showed that the linkage map of the two populations using 87 polymorph microsatellite markers (SSR) covered 1356.0 cM of rice genome with an average distance of 15.58 cM between two markers. A total of 20 main QTLs (M-QTLs) and 33 epistatic QTLs (E-QTLs) were identified with positive and negative effects. Five M-QTLs and five E-QTLs had a significant interaction with the environment. Eight M-QTLs and ten E-QTLs with significant effect on agronomic traits were stable and did not have any significant interaction with the environment. These QTLs include two M-QTLs and two E-QTLs for reducing plant height, three M-QTLs and three E-QTLs for decreasing heading date, an M-QTL and an E-QTL for increasing panicle length and two M-QTLs and four E-QTLs to increase grain yield. These main QTLs explained 11.12% (qHD6) and 24.5% (qGY1) phenotypic variation, respectively. Therefore, such useful QTLs can be used for gene pyramiding programs to improve rice agronomical traits. Furthermore, six linked SSR markers (RM421, RM178, RM3441, RM5101, RM7551 and RM5302) were identified with less than 5 cM distance from important QTLs, suggesting that such SSR markers can be used in marker-assisted selection to select rice lines with desirable traits in segregation generations.

Increasing the grain yield is the most important goal for breeders. Since grain yield has a polygenic heritability, it's difficult to study and so often breeders use the yield components to improve it. In order to investigating the genetic analysis of yield and it’s related traits in wheat, a 7×7 one-way diallel design was carried out in drought stress condition at research field of the University of Birjand, Iran, in 2015-2016. The genotypes included seven parents (Alvand, Anfaram9, Chamran2, Back Cross-Roshan, Ghods, Ofogh and local variety Sorkh-Dane) and 21 hybrids. Analysis of variance showed that there was a significant difference between genotypes in all studied traits. Griffing;s diallel analysis showed that general combining ability (GCA) and specific combining ability(SCA) of the parents for all studied traits except for harvest index were significant. The analysis of variance by Hayman’s method showed that the component a (additive variance), component b (dominance variance), component b2 (unequal frequency of dominant and recessive alleles) and component b3 (specific combining ability) were significant for most of the traits. Also,the component b1 (heterosis) was significant in all traits, except for harvest index, peduncle length, biological yield, stem weight and spike weight. The results of this research showed thatthe local varieties Sorkh-Dane and Alvand were the best and Anfrarm9 and Ofogh were the worst varietiesfor general combing ability. Also,the hybrids Ghods×Sorkh-Daneand Anfarm9× Alvandwere the best and Ofogh ×Sorkh-Daneand Chamran2 ×Sorkh-Danewere the worst hybrids for specific combining ability in Birjand weather conditions.

The use of stress tolerance indexes is one of the most promising methods for selection of stress tolerant genotypes among researchers. In this research, 11 bread wheat cultivars were evaluated in a randomized complete block design with three replications under two non-stress and drought stress conditions at research field of Faculty of Agriculture, Lorestan University, Khorramabad, Iran, with warm and dry climate,in2016-2017 crop season, and different stress tolerance indices were used to evaluate drought tolerance of the studied cultivars. Also, coefficient of determination (R2, square of the correlation coefficient)between the indices and grain yield under two non-stress and drought stress conditions was usedto determine the best indices andR-square confidence intervals of the tolerance indices related to grain yield under non-stress and drought stress conditions were estimatedusing bootstrap method. The results showed that the modified stress tolerance index under non-stress conditions (K1STI), geometric mean productivity (GMP) and mean productivity(MP)were the specific indices for non-stress conditions andthe modified stress tolerance index under drought stress conditions(K2STI) and drought index (DI) were the specific indices for drought stress conditions. Harmonic mean(HM) index had also a relatively stable correlation with grain yield under both non-stress(Yp) and drought stress(Ys)conditions. Finally, according to all specific and general indices, Aftabwas the best cultivar under non-stress conditions and Pougari was identified as the most tolerant cultivar for drought stress conditions.

Corn susceptibility to cold stress during early autotrophic growth is an important limitation for its cultivation in the cold areas. To identify the physiological basis of cold tolerance heterosis in maize seedlings, the changes of some physiological traits were studied in maize cold tolerant and susceptible inbred lines and hybrids at seedling stage in University of Zanjan, Iran, in 2017. The results showed that the effect of cold treatment onchlorophyll fluorescence, relative water content, electrolyte leakage,chlorophyll acontent, chlorophyll bcontent, carotenoids, root volume, root area androot dry weight were significant. The better-parent heterosis was detected in chlorophyll b content, root area, root volume and electrolyte leakage in most hybrids. Performance of MO17×EP80 hybrid was better than other hybrids for all physiological traits under stress conditions. EP42×MO17 and A661×MO17 hybrids also had better root growth and extension under cold stress conditions.The significant correlation was only observed between heterosis values of some traits that had a common genetic, physiological and developmental basis, such as root dry weight and relative water content or chlorophyll b content and electrolyte leakage. However, the correlation between heterosis values of the other traits was generally poor, indicatingthat the genetic basis of heterosis is trait dependent and probably not controlled by a single mechanism. The significant differences among genotypes in all traits, provide a new opportunitto improve cold stress tolerance in a tropical plant using plant breeding.

The drought and its effect are the most important and common environmental stress that has limited agricultural production in the world. One of the useful strategies of crop breeding for drought resistance is maintaining and exploiting the diversity of their germplasms. To identify drought tolerant sources, 125 Aegilops tauschii genotypes in an augmented designwith three replications under twocontrol (supplementary irrigation in three stages of jointing, flowering and seed filling) and drought stress (without supplementary irrigation) conditions were cultivated and evaluated based on tolerance indices. Correlation coefficients between yield and tolerance indices showed that the indices ofmean productivity (MP), geometric mean productivity(GMP), stress tolerance index(STI) and tolerance index (TOL) were suitable for identifying high yielding genotypes under both stress and non-stress conditions. Based on these indices, genotypes 50, 55, 58 and 65 were identified as the most tolerant genotypes and genotypes 45, 34, 3 and 9 as the most sensitive genotypes. Cluster analysis based on tolerance indices using between-group average method (UPGMA) classified the studied genotypes into seven different groups. Genotypes number 50, 55, 58, and 65, with the highest values for above mentioned indices, were placed in two groups three and five. Finally, according to the results of different analyzes, genotypes number 50 and 55 were identified as the most tolerant genotypes, which could be considered as suitable genetic sources in wheat breeding programs for drought tolerance.