نشریه نهال و بذر
سال سی و چهارم شماره 1 (بهار 1397)

To identify resistance sources to wheat yellow rust (Puccinia striiformis. f. sp. tritici) in bread wheat collection of the National Plant Gene Bank of Iran, 41 genotypes of bread wheat were evaluated against four races of yellow rust. The isolates collected from Gorgan, Karaj, Mashhad and Sari, propagated as single pustules and inoculated on differential sets to determine the races. Genotypes were evaluated in three replications in a green house at seedling stage, separately for each race. By investigating on the reaction of the differential sets to the isolates, four isolates of Gorgan, Karaj, Mashhad and Sari were designated as 6E6A+, 134E134A+, 134E142A+ and 6E4A+, respectively. All four races were virulent on Yr2, Yr6, Yr7, Yr9, Yr25, Yr24 and YrA. None of the races were virulent on Yr1, Yr3, Yr4, Yr5, Yr8, Yr10, YrSD, YrCV and YrSP. Twenty-nine genotypes (46.7%) were resistant to all four races. These genotypes were from different origin (East-Azarbayjan, Khorasan, Kordestan, Kermanshah, Lorestan, Markazi, Hamedan, Portugal, China). Comparison of reaction genotypes against the studied races in comparison with differential varieties indicated that some genotypes may have a different resistance gene than the differential varieties do or they may contain a combination of two or more resistance genes. In conclusion, the results of this research indicated the potential of genetic resources for resistance to yellow rust in bread wheat collection of the National Plant Gene Bank of Iran.

To estimate combining ability and genetic parameters for some agronomic and physiologic characteristics, a reciprocal diallel experiment was conducted with nine rapeseed (Brassica napus L.) varieties. Parents and their F1's were sown in drought stress (S) and non-stress (NS) environments using 9 × 9 lattice design with two replications at the Dryland Agricultural Research Institute, Sararood, Kermanshah, in 2015-2016 cropping season. Results showed that effect of general and specific combining ability (GCA and SCA), and reciprocal crosses (REC) were significant (P < 0.01) for most traits in both environments. Parents Shiralee for seed oil content (SOC), Comet and Dalgan for seed yield (SY) were the best general combiners while cross RGS003 × Licord was the best specific combination for thousand seed weight (TSW), relative water content (RWC), SOC, and SY in both environments. Additive genetic variance was more important component for days to flowering, plant height, silique length, TSW and SOC in both environments, while dominance gene effect was greater than the additive component for SY (both environments), number of siliques/plant (NSP), RWC and leaf temperature (S) and electrolyte leakage (NS). According to the results of the graphical analysis, the gene action for most traits was partial dominance, while it was over-dominance for NSP (S), RWC and SY (NS). Maximum and minimum of narrow-sense heritability were obtained for TSW (0.92, in S) and RWC (0.21, in NS), respectively. This study showed that it is possible to improve SY, SOC and other agronomic and physiologic traits through crossing between different varieties of rapeseed for both conditions.

To determine the type of genes action and estimate genetic parameters under moisture stress condition, two inbred lines of S0200237 (P1) and ILYH0231 (P2), sensitive and resistant to moisture stress, respectively, were crossed in 2013. Six generations P1, P2, F1, F2, BC1 and BC2 were planted in a randomized complete block design in 2015 and generation mean analysis was performed. Significant and positive heterosis was observed for ear biomass/ plant and ear-grain yield/plant. The joint scale test and the average of gene dominance confirmed the inadequacy of the additive-dominance model for most traits, indicating the importance of epistatic and over-dominant effect in genetic control of the traits. The results showed that row number/ear, ear diameter, cob diameter and grain depth were controlled by additive effect. The broad and narrow sense heritability of the ranged varied from 68.9 to 88.6 and 13 to 50.40, respectively. The average of genes number controlling the traits varied from 1-7 genes for grain yield. The maximum positive heterosis was observed for ear biomass and grain yield per plant. Generally, selection in early generations for grain yield-related traits with high narrow sense heritability, including the number of rows per ear, will improve grain yield in advanced generations. In addition, selection in early generations to reduce cob percent, to some extent, does not result in a significant reduction in total ear weight, and will result in an increase in harvest index, thus improves grain yield under moisture stress conditions.

Milk Thistle (Silybum marianum L.) is a plant from the Asteraceae family that has high therapeutic properties due to its secondary metabolites, such as silymarin. Considering the significant therapeutic effects of this plant and the necessity of its cultivation in Iran, evaluation of its genetic diversity is important for breeding purposes. In the present study, the genetic relationship of eight milk thistle accessions was studied using CDDP and SCoT markers. Based on the results of the molecular evaluation, a total of 62 detectable bands were obtained from seven selective SCoT primers, of which 53 polymorphic band (85.48%) were found, while from the seven CDDP primers, a total of 58 detectable bands were obtained, of which 50 bands were polymorphic (86.2%). The mean polymorphic information content index (PIC) obtained from CDDP and SCoT markers were 0.39 and 0.23, respectively. Both the CDDP and SCoT markers showed more variation between accessions than within accessions. The high level of genetic diversity observed in the studied accessions can be used in milk thistle breeding programs.

Genetic diversity and germplasm introduction provide the potential for plant improvement in breeding programs. So far, few studies have been carried out on the evaluation of hazelnut (Corylus avellana L.) varieties and genotypes in Iran. This study was conducted to investigate morphological, phenological and pomological characteristics of 10 selected hazelnut genotypes and varieties including Gerche, Paeizeh, Christiana, Cote Kashen, Futocramy, Koban, Ata Baba, Yaghly Fandaog, Sochi 1 and Pioneer, and Gerduoei 89 and Pashmineh 89 cultivars as control in 2015 and 2016 in Kamalshahr horticultural research station, Karaj, Iran. The traits included tree phenology, fruit and kernel characteristics, yield per tree, oil and protein contents, which were evaluated in randomized complete block design with three replications. The results showed that there was significant difference between varieties/genotypes for all studied traits. Paeizeh, Christiana, Sochi 1 and Gerdouei 89 varieties showed the highest amount of oil content (69.2%), protein content (16.3%), nut weight (2.8 g) and kernel weight (1.2 g), respectively. The results suggest that Gerdouei 89, Paeizeh, Cote Kashen, Gerche and Pashmineh 89 had the highest yield and desirable fruits characteristics and are suitable for being grown in climate conditions of Karaj in Iran.

To understand the genetic control of resistance against yellowing variant of fusarium wilt of melon (FOM 1.2y) in Iranian melon landraces, seven commercial landraces were studied in a half diallel model ( including F1s and parents) using Gardner- Eberhart Analysis II. Parents included: Magasi, Jalali, Sooski, Khaghani, Chapalizi, Semsori and Shadegani. Eighteen seedling of each genotype (totally 36 plants in the experiment) were evaluated using randomized complet block design with three replications. Indices including: area under disease progress curve (AUDCP), disease severity index (DSI) and latent period (LP) were calculated to evaluate the reaction of genotypes. Magasi had the lowest positive difference with resistant check in AUDPC and DSI, and had the lowest negative difference with the resistant check, therefore, identified as the highly resistant parent in this experiment. All genetic variances and their components including additive and dominance (non- additive) were estimated as significant at least at P < 0.05 followed by corresponding significant additive and dominant coefficients of variation. The highest GCA/SCA ratio (0.86) was calculated for DSI which showed the highest significant broad sense and narrow sense heritability ( 0.82 and 0.71, respectively). The results showed the higher importance of additive variance comparing with non-additive (dominance) variance for DSI. Magasi and Chapalizi were identified as the best resistance parents according to estimated GCA. Considering significant broad sense and narrow sense heritability for LP (h2b=0.66, h2n=0.47) followed by significant additive and non-additive variances, it is concluded that LP can be used as a reliable index in breeding programs for improving resistance against FOM 1.2y.