Crop Breeding Journal
Volume:9 Issue: 2, Winter-Spring 2019

To provide information about genetic control of head inclination in sunflower, 12 selected hybrids developed by crossing four lines and three testers were evaluated as a line × tester mating design using randomized complete block design with three replications in Karaj, Iran. The results showed that the parental lines contributed, more than other sources, in variation of head weight (62.4%) of hybrids while contribution of the testers was more for head diameter (62.8%), plant height (48.6%), head height (70.5%), achene yield (41.7%) and head inclination (54.5%). We found that the two hybrids; RGK33 × AGK370 (23.7%) and RGK33 × AGK356 (24.0%) had the lowest head inclination, respectively, while among the parental lines only RGK33 and AGK356 were in suitable range (25-35%) indicating that crossing the parental lines with undesirable head inclination may lead to the production of hybrids with suitable head inclination. We also found that head weight and head inclination are controlled mainly by additive gene action that suggests the crucial role of parental lines in development of hybrids with desirable head inclination. Both additive and non-additive gene action were significant for head diameter, plant height, head height and achene yield. Over-dominant gene action observed for plant height, achene yield and inclined length, and partial dominance for head diameter, weight, height and inclination. Higher broad sense heritability for plant height (0.86), head weight (0.72), head height (0.73) and head diameter (0.71), and lower heritability for head inclination, indicated that heritability of head inclination is independent from these components. All hybrids developed by crossing of restorer lines RGK21 and RGK33 had suitable head inclination as compared with the progenies of RGK15. This information is valuable for improvement of head inclination and developing ideo-types in sunflower breeding programs.

Walnut (Juglans regia L.) is one of the most important horticultural crops grown in Iran. To characterize the phenology of walnut genotypes in different seasons and its relationship with climatic conditions, this study was carried out in temperate fruits research center of Horticultural Science Research Institute, Karaj, Iran. The phenological characteristics of 39 selected superior walnut genotypes were compared with Chandler, Jamal and Rond de Montignac cultivars during 2012-18. The results showed that the overall average leafing dates of genotypes varied from March 15-29 over seasons. ‘Z16’ had the earliest leafing date (March 13) together with ‘Kr95’and high variation (24 and 25 days, respectively). Latest leafing date (April 13) and least variation (four days over seasons) belonged to ‘Ronde de Montignac’. The average leafing dates in ‘Chandler’, ‘88-1, ‘88-2’ were in April 6-8. The average pollen shedding, in different seasons, started in genotypes from March 29 to April 12. While the average of pistillate flowers receptivity varied from April 2 to April 11. The effect of season was not significant on nut ripening. The overall average fruit ripening was on August 24-25 in different seasons. However, the ripening dates for walnut genotypes varied from August 15 in ‘Kr111’ to September 16 in ‘Chandler’. The temperature of March showed to have a crucial effect on bud break, catkin development, pollen shedding, and pistillate flowers development and receptivity period. Leafing date showed to be more affected by season in comparison to other phenological characteristics. The leafing dates varied 5.5 and 2.8 days, with 1 °C increase in average temperature, in early and late leafing genotypes, respectively.

Barley powdery mildew caused by the biotrophic obligate pathogen, Blumeria graminis f. sp. hordei, is one of the most important foliar diseases in major barley production areas in Iran. To determine the virulence spectrum of the powdery mildew pathogen in southwestern regions of the country and effectiveness of new sources of resistance, barley powdery mildew trap nurseries were established and evaluated under natural field conditions for disease development in three disease prone locations including Zarghan, Ahvaz, and Dezful during 2013-14 to 2017-18 cropping seasons. The trap nurseries consisted of a differential set including the barley cultivar Pallas and 18 near-isogenic ‘Pallas’ lines and a supplementary set including 34 barley cultivars carrying known or unknown resistance gene(s). Our results showed that there is virulence variation in the population of the pathogen in different locations. While the resistance genes Mla6, Mla14, Mla7, Ml(No3), Mla12, Ml(Em2), Mla13 and Ml(Ru3) were effective across the years and locations, the Mlk, Mlh, MlLa and Mlp genes were ineffective in most years and locations. New virulence factors matching Mla6, Mlp, Mlg+MlCP, Mla7 and Mla3 genes were detected. Ineffectiveness of all resistance genes except the recessive mlo allele in Dezful and Zarghan over years indicating that the pathogen population in Dezful and Zarghan are more aggressive than Ahvaz. We concluded that the European mlo carrying barley cultivars and other sources of resistance with a combination of genes, such as Meltan and Escort could be considered as effective sources of powdery mildew resistance to be incorporated in the national barley breeding programs for the southwestern regions of Iran.

Stress caused by abiotic factors, such as salinity, decreases production of bananas, because it is very sensitive to salinity. This study aimed to investigate the effect of gamma (γ) ray-induced in vitro mutagenesis as well as in vitro and ex vitro reaction to salt stress (NaCl) in banana (Musa AAA cv. ‘Dwarf Cavendish’). Shoot tips of banana were irradiated with gamma rays at doses of 25, 35 and 45 Gy, and subjected to MS medium containing additional NaCl (0, 100, 120, 140 and 160 mM) for two months (1st salinity stress) as factorial based on completely randomized design with five replications.The surviving shoots were transferred to a salt-free MS medium for one month, and then the salinity stress, as before, was re-applied (2nd salinity stress). Increasing NaCl concentrations resulted to a decrease in growth rate during 1st salinity stress. Also, irradiated explants had higher survival percentage, shoot number and shoot fresh weight than non-irradiated ones. In 2nd salinity stress, only the irradiated explants under 160 mM NaCl had decreased in shoot number compared to other salinity treatments. In vitro-regenerated plants were rooted and acclimatized in the greenhouse and evaluated under normal and saline conditions (3rd salinity stress). A sharp decrease in the survival percentage and leaf number observed with an increase of salinity, while irradiated plants had more survival rate and leaves number than non-irradiated plants. In addition, as the salt concentration increased, the leaf burn and yellowing rate increased and its intensity was higher in non-irradiated plants. Overall, banana shoot tips exposed to different doses of gamma irradiation had higher growth parameters under in vitro and greenhouse salt stress. However, further studies are required to evaluate agro-morphological characteristics of these mutants in the field conditions under salinity stress.

Drought is one of the most important environmental stresses affecting tea plantation productivity in tea growing areas. Nine field-grown tea [Camellia sinensis (L.) O. Kuntze] clones in the north of Iran were subjected to drought stress by withholding irrigation for 50 days. The effects of drought stress were measured by studying growth and morphological (shoot number, shoot length, shoot fresh weight, length of 5th leaf, width of 5th leaf, green leaf yield), physiological (relative water content), biochemical (proline and total sugar content), and chemical (polyphenol) attributes after 50 days from the time drought stress was imposed. Drought stress resulted in decrease in growth and morphological characteristics, polyphenol content, and an increase in proline and total sugar concentration, that was attributed to reduction of RWC of leaves. Grouping of clones showed that clones 276, 100, and 285 formed drought-tolerant group. These tea clones can be used in the national tea breeding programs for improvement of drought tolerance.

Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) is one of the most devastating wheat diseases worldwide. Identification of virulence factors of the pathogenas well as using resistant cultivars are effective approaches in controlling wheat strip rust. Knowledge of genetic basis of resistance to stripe rust in commercial wheat cultivars is an important objective to ensure that diverse resistance genes are deployed in breeding programs.Five bread wheat commercial cultivars were evaluated for stripe rust using 40 Pst races that were collected from different locations in Iran. Among them cultivar Aflak showed seedling resistance to all races and the other cultivars displayed field resistance at the adult plant stage. To study the heritability and genetic basis of resistance to stripe rust inbread wheat cv. Aflak, it was crossed with susceptible cultivar Avocet‘s’ and F1, F2, BC1 and BC2 generations were developed. The generations along with their parents were planted in Randomized Complete Block Design (RCBD) with three replications under greenhouse conditions. The seedlings were inoculated using the race 230E158A+, Yr27+ urediniospores. The resistance components including infection type, latent period, pustule size and pustule density were recordedon single plants of each generation. The results ofthe weighted analysis of variance showed that there were significant (p ≤ 0.01) differencesamong generations for each of the four traits. Generations mean analysis showed that in addition to additive and dominance effects, epistasis, particularly the additive × dominance epistasis also played a significant role in controlling resistance to stripe rust.For all traits, high broad-sense heritability was observed. Moderate to high narrow-sense heritability wasestimated for resistance components