جستجوی مقالات مرتبط با کلیدواژه « accession » در نشریات گروه « زراعت »

Soil salinity, as one of the most important environmental stresses, is a serious threat to agricultural production. Currently, more than 20% of the agricultural lands, which includes 954 million hectares of the world's lands, is affected by soil salinity. Salinity is expanding daily and it is predicted that by 2050, more than 50% of the world's arable lands will be saline. The decrease in yield due to salinity stress in wheat is considerable and worrying, so that a 50% decrease in yield of durum wheat due to salinity of rainfed lands, and an 88% decrease in yield of bread wheat under irrigation with high salinity and and a 70% decrease in yield of bread wheat in sodic soils has been reported. The high levels of salt in soils and irrigation waters are worrying factors for agriculture, therefore it is necessary to develop the effective strategies to improve yield through salinity stress tolerance. The present study was carried out due to the importance of genetic accessions as sources of tolerance to biotic and abiotic stresses including salinity, and the existence of considerable genetic diversity in wheat germplasm to salinity stress tolerance. The objective of this experiment is to investigate the diversity of genetic accessions of bread wheat collection of Iran's National Plant Gene Bank, to compare the accessions with the tolerant control varieties, and to identify the new genetic resources for salinity tolerance.

To identify the genetic resources of salinity tolerance in wheat germplasm, 512 accessions from the bread wheat collection of the National Plant Gene Bank of Iran along with salinity tolerant varieties, Kavir, Roshan and Mahoti as controls, were investigated in two different augmented designs under normal and salinity stress conditions. The normal experiment was carried out at the research field of Yazd Research Center and the salt experiment was done at saline lands of Ardekan Research Station. The studied traits included spike length, spike density, 100-grain weight, number of tillers, plant height, number of spikelets per spike, number of florets per spikelet, number of grains per spike, days to heading, days to maturity, grain filling period and grain weight of five spikes,  which were recorded according to the international description. To perform data statistical analyses, descriptive statistical indices were first calculated and then the studied accessions were grouped using K-means cluster analysis. Discriminant function analysis based on principal components was used to investigate the differentiation between the groups resulting from cluster analysis. Statistical analyzes were performed by SPSS and R softwares.
 
 
Research

The results showed that grain weight of five spikes (with a minimum of 4.15 and a maximum of 12.26 g in normal conditions and a minimum of 2.19 and a maximum of 9.78 g in stress conditions) and the number of spikes (with a minimum of 3 and a maximum of 8 in normal conditions and a minimum of 3 and a maximum of 7 in stress conditions) had the highest coefficients of variation, while days to heading (with a minimum-maximum of 130-163 days and 126-168 days in normal and salinity stress conditions, respectively) and days to maturity (with a minimum-maximum of 173-189 days and 168-196 days in normal and salinity stress conditions, respectively) had the lowest coefficient of variation under both normal and salinity stress conditions. A large number of superior accessions were identified for various traits compared to the control cultivars under both normal and salinity stress conditions. The results of stepwise regression indicated the importance of three characteristics, 100-grain weight, number of grains per spike and number of florets per spikelet, in describing the variation of grain weight of five spikes. The investigated accessions were divided into five groups using K-means cluster analysis and the control cultivars were separated into different groups so that Roshan and Mahooti along with 70 accessions were grouped in the first cluster and Kavir along with 53 accessions in the fifth cluster.

The results of this experiment showed the presence of significant and valuable genetic diversity in traits related to salt stress tolerance in the studied bread wheat germplasm. The effect of salinity stress on different traits of the studied accessions was different. Among the studied traits, 100-grain weight, number of grains per spike and number of florets per spike were more important, so they can be used in breeding programs. A large number of accessions were also superior to control cultivars for various traits. Cluster analysis grouped the control cultivars into distinct clusters, which indicates different aspects of salt stress tolerance in these cultivars. The superior accessions identified in this research can be used to improve salt stress tolerance in bread wheat breeding programs.

Summer savory (Satureja hortensis L.) is a valuable medicinal plant with useful properties and applications, has been recently used in the pharmaceutical industry due to its high level of carvacrol, thymol and rosmarinic acid. In this research, different accessions of this plant were collected from other countries and different regions of Iran. An experiment was conducted in 2019 year based on randomized complete block design to evaluate the morphological, phytochemical and essential oil traits of these accessions in Ardabil climatic condition. Analysis of variance showed that there were significant differences for the most studied traits among 20 accessions. The important traits such as plant diameter (19.78-45.29 cm2), shoot dry weight (0.08-2.05 g/p), 100-seed weight (0.021 to 0.126 g/p), and essential oil yields (0.23 to 2.21 g/h) were varied among accessions. The Ahvaz and Greece accession were the best in term of vegetative and phytochemical traits respectively. Maximum correlation was shown between bract number and seed length per plant (0.96). Cluster analysis, classified the accessions into five major groups. Factor analysis indicated that the five factors explained 77.78 of the variation among the accessions. The results of path analysis showed that the leaf area, leaf length/width, number of flowers in inflorescence, phenolic content and shoot dry weight had effect in essential oil yield of accessions and phenolic content had the highest direct and positive effect (0.8). The results suggested that there was a considerable genetic variation among S. hortensis accessions.

One of approaches to reach sustainable agriculture is to exploit crop diversity, especially in legume species. Since Melilotus spp. (sweet clover) is a forage crop with a suitable yield especially in the marginal lands; therefore collection and characterization of this germplasm is the first effective step for its conservation and utilization in the country. Few accessions of Melilotus genetic resources had been collected in the National Plant Gene Bank of Iran, before this study.

Sweet clover genetic resources were collected all over the country using standard descriptors during two years. Twenty-six characteristics of collection sites were recorded and their descriptive statistics were estimated. The collected materials were planted in an experimental field to identify their life cycle. The seeds of collected germplasms were conserved in mid (2-4 °C)- and long (-20 °C)-terms conditions for further using.

A total of 258 accessions were collected. The geographical altitude of plant origin differed from -11 m in Babolsar to 3090 m in Noor Abad in Lorestan. The materials were mostly collected from non-saline habitats. However, eight accessions were collected from mid to high salinity locations. Taxonomically, M. albus, M. officinalis, and M. indicus were identified with a number of 21, 201 and 36 accessions, respectively. M. dentatus and M. sulcatus, which have been mentioned in the former researches in Iran, were not collected in the recent study.

The collected germplasms from marginal lands (saline, low drainage and low fertility lands) may be tolerant to such marginal lands, therefore they can be exploited for the future research. All M. indicus species were annual; whereas there were annual as well as facultative and obligate biennial accessions in the two other species. Lack of access to M. dentatus and M. sulcatus may be an alarm that they may be threatened species in the country. Collected materials in this study along with the former collection in the Iranian National Plant Gene Bank (80 accessions) have provided high potentials of Melilotus genetic resources for exploitation in the further. Highlights: 1- The three-fold increase in the Melilotus germplasms in the ex-situ conservation system. 2- Alarm for M. dentatus and M. sulcatus which may be threatened with extinction in the country.

Safflower is the most suitable crop plant for oil production in dry areas and regarding the fact of climate change, it has been come in consideration in recent years. A broad genetic base and rich germplasm is necessary for breeding of this crop. This research was performed in 2011 to investigate variability of safflower germplasm. A total of 345 accessions of safflower collection of National Plant Gene Bank of Iran were planted and evaluated in research field of Seed and Plant Improvement Institute in Karaj. Preliminary evaluation showed that many accessions consisted of several diverse morphotypes, hence, by isolating and morphotype determination, the number of accessions reached to 534, which were investigated in an observational design. The results indicated that corolla color and spine intensity of outer involucral bracts had considerable amount of Shannon index. The highest (85.62) and the lowest (7.24) coefficient of variation belonged to seed weight of single plant and days to flowering, respectively. The first three principal components justified 56.13% of variation, the first one emphasized on yield components and the second on vegetative traits. The accessions were located in five groups by K means clustering method. Distribution of country origin of the accessions was consistent with their geographical situation in some cases. Totally, results showed that the studied accessions have a considerable variation which could be exploited in breeding programs.

Landraces are a valuable source of genetic diversity for varietal improvement. Despite, Iran is the fifth squash and pumpkin producer, but no available information exists about the diversity of summer squash landraces. In order to evaluation of floral and fruit production characteristics among four Iranian summer squash and a check cultivar of F1 hybrid ‘Asma’, an experiment was conducted in a randomized complete block design (RCBD) with three replications. Each plot had four tagged sample plants of one accession. The results were demonstrated significantly substantial differences for number of node, node position to first female, number of female flower, female/male flower, number of harvested fruit from main stem, number of lateral branch/plant, number of harvested fruit from branches/plant and total harvested fruit/plant traits in studied accessions. Number of female flower ranged from a minimum of 8 to a maximum of 18. It was resulting to a broad variability in number of harvested fruit from main stem (5.2-12). There was a significant difference between Iranian landraces and check cultivar for floral and fruit production characteristics. Growth habit and number of female flower were two main factors that influenced fruit production/plant variability.

In order to compare the reaction of 13 millet accessions from gen bank collection to late season drought stress and with the aim of completion of gen bank information، specific assessments and determination of the best indices for drought tolerance، two separate experiments based on randomized complete block design with three replications were conducted at the Agricultural Research Center of Southern Khorasan during 2005 and 2006. The first experiment was conducted under normal irrigation and the second experiment was taken place under drought stress conditions (irrigation up to the 10% of panicle emergence). Experiment treatments included 13 millet accessions. Results showed that accessions number 15-143 (Southern Khorasan) and 15-24 (Yazd) had the highest two years average for grain and dry forage yields and number 15-132 (Hamadan) had the lowest grain yield among all accessions. Evaluation of accessions in terms of drought tolerance was made using MP، TOL، SSI، GMP، STI and HARM indices. HARM، GMP and STI were recognized as the best indices for severance of drought tolerant accessions according to the high correlation of these indices with grain and dry forage yields under stressed and non-stressed conditions. Based on using three dimensional graphics and accessions positioning on it، numbers 15-143 (Southern Khorasan)، 15-131 (Southern Khorasan) and 15-24 (Yazd) were identified as the most yielding and tolerant accessions to drought stress.

In order to screen sorghum germplasm in National Plant Gene Bank of Iran for salinity tolerance, 142 sorghum accessions from five different types were planted in two different field growing conditions. Electronic conductivity (EC) of irrigation water was 2.12 and 14.8 ds/m in non-stress and salinity stress conditions, respectively. Experimental design was Balanced Group Blocks with two replications. The grouping in each block was based on sorghum types (wild, grass, grain, forage, and broom sorghums). This experimental design allowed us to compare sorghum types in order to differentiate and identify the most tolerant and susceptible germplasm. Stress susceptibility index (SSI) and stress tolerant index (STI) based on single plant biological yield and plant height traits were used in the analysis. Based on these indices the tolerant accessions were identified within and between sorghum types. The distribution of tolerant and susceptible accessions in each type was determined by using biplot for SSI and STI. These analyses facilitated the identification of the tolerant germplasm in both local or introduced accessions. These germplasm can be used in sorghum breeding programs for tolerance to salinity. Passport data showed that there was no correlation between the tolerance to salinity and the origin of germplasm. However, the correlation coefficients of STI, SSI, yield and plant height showed a high relationship between STI and the first cutting yield (r = 0.695**), implying that STI is the most suitable index for screening sorghum germplasm for tolerance to salinity stress.