Crop Breeding Journal
Volume:3 Issue: 2, Summer-Autumn 2012

Salt tolerance in crops is multigenic in nature and quantitatively inherited, and therefore controlled by minor genes. To study the diversity of QTLs conferring salt tolerance in barley, four barley mapping populations including L94 × Vada (L × V, 103 RILs), Oregon Wolf Barley (OWB) (Dom × Rec, 94 DHs), SusPtrit × Vada (Su × V, 152 lines), and SusPtrit × Cebada Capa (Su × CC, 113 lines) were tested; L × V and OWB showed unexpected segregation for salt tolerance at an early growth stage and were selected for this study. Two morphological traits (shoot length and total root length) were quantified under different salinity levels (0, 200 and 300 mM of NaCl) at an early growth stage. In total, eight QTLs were mapped in OWB and eight QTLs were mapped in L × V under 200 and 300 mM NaCl; of these, only two QTLs were common to the two populations. In the OWB and L × V populations, two and one QTLs were shared between two traits, respectively. Comparing QTL positions on a consensus map of barley showed that the number and location of the identified salt tolerance QTLs varied depending on the different NaCl concentrations and barley genotypes. Hence, there is a high diversity of QTLs conferring salt tolerance at the early growth stage of barley. In each barley genotype, a set of specific QTLs was responsible for salt tolerance and very few QTLs were common to them.

The genetic diversity of 89 flue-cured tobacco varieties was examined using 12 ISSR primers. These cultivars were evaluated at the Guilan Tobacco Research Center, Rasht, Iran, using a 7×7 simple lattice design with two replications, and 12 morphological traits. The total number of PCR amplified products was 143 bands ranging from 450 to 3000 bp, of which 108 bands (74.28%) were polymorphic. Primers UBC 811 and UBC 814 with 16 bands and UBC 825 with 6 bands generated the highest and lowest number of bands, respectively. Of all the primers, UBC817, UBC824 and UBC873 showed the maximum amount (0.47) of polymorphism information content (PIC) and the greatest diversity. To determine the genetic relationship among tobacco cultivars, cluster analysis was performed based on either morphological traits or ISSR markers using the un-weighted pair-group method with arithmetic average (UPGMA). Tobacco genotypes were divided into five main groups. Principal coordinate analysis (PCoA) on a similarity matrix of genotypes showed that the first 12 coordinates explained 60.16% of the total variance, whereas the first two coordinates explained only 28.96% of total variance. Cluster analysis of morphological traits divided tobacco genotypes into five groups. Based on canonical discriminate function analysis using the Fisher linear method, the UPGMA method separated the genotypes with 78.5% accuracy. UBC817, UBC824 and UBC873 were the most informative primers and thus could be used to assess the diversity of tobacco cultivars. In addition, UBC813, UBC823 and UBC826 would be appropriate ISSR primers because of the reasonable amount of PIC, Nei and Shannon’s information index.

Knowledge of traits associated with drought tolerance would be useful for developing breeding materials for target environments. To study these traits, 119 spring durum wheat breeding lines (BLs) from the International Maize and Wheat Improvement Center (CIMMYT) were evaluated along with local checks (one modern cultivar and three landraces) in three experiments under terminal and non-terminal drought stress conditions in the 2009-10 and 2010-11 cropping seasons. Ten agro-physiological traits were measured and recorded. Best linear unbiased prediction (BLUP) data representing adjusted genotypic means were used to analyze trait relations and trait profiles of genotypes. Durum wheat BLs showed considerable variability for yield and agro-physiological traits that could be exploited in the national durum wheat breeding programs. Grain yield reduction due to terminal drought stress ranged from 29.1-64.8%. In contrast to the BLs, the landraces were characterized by minimal responsiveness to improved environmental conditions. Six BLs were identified as having high drought response index (DRI) and low grain yield reduction, and thus may be useful to national spring durum wheat breeding programs. Significant correlations between DRI and traits such as canopy temperature, SPAD reading, plant height, flag-leaf length and heading date suggest these traits could be useful for screening durum wheat BLs for drought tolerance. Results indicated that both grain yield and specific adaptation traits are useful criteria in breeding durum wheat for drought environments and should be incorporated into breeding materials to achieve optimum performance and adaptation to drought stress conditions in Iran

Olive cultivars with specific characteristics have been developed thanks to Iran’s particular climatic conditions and long-term olive cultivation. The genetic variation and relationships among 40 olive cultivars, as well as 17 unknown genotypes from the national olive collection orchard at Tarom Research Station, Zanjan, Iran, were evaluated using SSR markers. Using 10 microsatellite primer pairs, 43 polymorphic bands were obtained on 57 olive genotypes. In addition to molecular markers, 14 morphological traits were measured in all olive genotypes. Based on discriminant and cluster analysis, the group of Iranian genotypes showed the greatest genetic distance from Spanish, Greek, Syrian, Italian and French groups. Based on cluster analysis using molecular and morphological data, most of the unknown genotypes showed high genetic similarity with genotypes from Spain and Syria. Despite the high genetic variation among cultivars in each group, geographical origin had significant impact on observed variability using Shannon’s information index and polymorphism information of olive accessions. Climatic conditions in Iran, which are very different from conditions in Mediterranean countries, probably played a significant role, although this needs to be investigated further. The lowest mean of Shannon’s index (0.76) for Iranian accessions indicated limited gene exchange with other genetic resources worldwide. The different genetic background of Iranian olive cultivars may help breeders access new and valuable genetic resources for national olive breeding programs

Drought stress is the most important environmental constraint contributing to grain yield instability of maize (Zea mays L.). Evaluation of maize genotypes under different stresses would be useful for identifying genotypes that combine stability with high yield potential for stress-prone areas. This study was conducted to estimate grain yield stability of maize hybrids and to identify hybrids that combine stability with high yield potential across stress and non-stress environments. Seven maize hybrids were tested in three consecutive growing seasons under four irrigation regimes (E1 = well-watered; E2 = water deficit at the vegetative growth stage; E3 = water deficit at flowering; E4 = water deficit at grain-filling) at Ultan Agricultural Research Station, Moghan, Iran. Combined analysis of variance showed that environments, genotype and genotype  environment (GGE) interaction effects were highly significant. Genotype and genotype  environment analysis using GGE biplot explained 94.7% of the total grain yield variation. The GGE biplot analysis ranked maize hybrids with above-average yield across growing seasons (SC704 > SC724 > SC703 ≈ SC720 > SC647) and grain yield stability (SC700 > TWC600 > SC724). According to the variation in maize hybrids as well as G × E interaction sources, hybrids SC704 and SC724 in environments E1, E2 and E4 as well as hybrid SC647 in E3 were the superior hybrids and had better specific adaptation. The hypothetical ideal genotype''s biplot indicated that hybrid SC704 had higher grain yield and yield stability and was better adapted to all the test environments

This study was conducted to evaluate traits that have an effect on yield, and genetic variation for these traits, including dry matter accumulation, remobilization, and traits associated with them, in 10 grain sorghum genotypes obtained from the National Plant Gene Bank of Iran under moisture stress conditions. Field trials were carried out in the 2008 cropping season using split-plot arrangements in a randomized complete block design with three replications at Torogh Agricultural Research Station of the Agricultural and Natural Resource Research Center of Khorasan Razavi Province, Mashhad, Iran. Trials were conducted separately under three water regimes: normal conditions and two water deficit levels at the vegetative and reproductive stages. Genotypes were assigned to main plots and two levels of photosynthetic status, normal and disturbed current photosynthesis, by applying potassium iodide after anthesis, in sub-plots. Results revealed significant genetic variation for traits related to dry matter remobilization (amounts of remobilized dry matter [ARDM], remobilization efficiency [REE] and remobilization percentage [REP]) among sorghum genotypes under moisture stress and well-watered conditions. Cluster analysis using the Ward method grouped sorghum genotypes differently under different irrigation conditions. There were no differences between grouping of genotypes treated with potassium iodide (disturbed current photosynthesis) and grouping under normal current photosynthesis as well as in the drought stress environment at the vegetative stage. Results also showed that genotype 04-12 had the highest REE and REP under the three irrigation regimes. Therefore, these traits could be used to improve grain yield and yield stability in sorghum breeding programs

Despite the profusion of flowers that develop on olive trees, only a few set fruit during the growing season and only about 1-2% of the fruit remains on the trees at maturity. Therefore, to maximize fruit set and yield, it is important for growers to understand the cross-compatibility between cultivars when planning to establish an olive orchard. This study was carried out in Shiraz, Fars Province, in 2005 and 2006 to identify the best pollinizers for Zard, Roghani, Fishomi and Shiraz olive cultivars. Flowers were pollinated using pollen from cultivars Dezfoul, Roghani, Zard, Shengeh, Shiraz, Fishomi and Fishomi-Roudbar and/or the flowers were self-pollinated or open-pollinated. Initial and final fruit set, fruit yield and self-incompatibility were assessed. Results showed that cultivars Zard and Fishomi are self-compatible, whereas Roghani and Shiraz are relatively self-incompatible (self-incompatibility index = 0.47 and 0.34, respectively). Cultivars Fishomi-Roudbar and Dezfoul were identified as suitable pollinizers for Roghani and Shiraz, respectively