Journal of Plant Physiology and Breeding
Volume:10 Issue: 2, Summer-Autumn 2020

Leaf area (LA) is one of valuable parameters in plant physiological studies. Therefore, the use of a non-destructive, accurate and simple model to estimate LA is very important. This research aimed to develop a non-destructive model to estimate LA accurately in Epilobium species. To estimate LA, leaf length (L) and leaf width (W) of five Epilobium species were determined. Moreover, the actual leaf area, using leaf area meter was measured. Regression analysis of LA versus L, W and LW revealed several models to predict LA in Epilobium species. Out of the models, the best fitted and validated model which is recommended to estimate LA accurately in each species, was quadratic model based on two dimensions (L and W), including the E. algidum (LA = 0.1264 + 0.6562 (L×W) + 0.0366 (L×W)2), E. parviflorum (LA = – 3.144 + 1.323 (L×W) – 0.030 (L×W)2(, E. sp. (LA = 0.4236 + 0.3033 (L×W) + 0.1368 (L×W)2), E. hirsutum (LA= 2.2417 + 0.2202 (L×W) + 0.0029 (L×W)2), and E. frigidum (LA = 0.2119 + 0.4162 (L×W) + 0.1191 (L×W)2), all with R2 ≥ 0.80.

Lead (Pb) stress adversely affects plant nutrient homeostasis and metabolism when present at an elevated concentrations in the surrounding media. In this research, the effects of 1mM Pb(NO3)2 on 14-day-old Carthamus tinctorius seedlings pretreated with arginine (Arg) as nitric oxide (NO) precursor, methylene blue (MB), a nitric oxide scavenger and Nω-nitro-L-Arg-methyl ester (LNAME) and a nitric oxide biosynthetic inhibitor, were investigated in the greenhouse of the Department of Biology, Shahid Bahonar University of Kerman, Iran. Pb exposure caused oxidative stress, reduced root and shoot growth and elevated malondialdehyde (MDA) content of the seedlings. Pb stress also increased the ascorbate peroxidase activity while decreasing the activity of the catalase (CAT) enzyme. Arg pretreatment decreased the harmful effects of Pb stress by increasing the root and shoot length and reducing the MDA content. Additionally, Pb-induced reduction of CAT enzyme activity in roots was reversed by the Arg pretreatment of the plants. In many characteristics which we measured, the effects of Arg pretreatment on alleviation of Pb-induced oxidative stress were reversed by LNAME and methylene blue pretreatments. Therefore, it seems that Arg induces a positive effect through NO production. Data showed that in the presence of Arg, the uptake and translocation of Pb declined and the application of Arg with LNAME or MB reversed these positive effects of Arg.  It seems that Arg can alleviate lead toxicity in plants through the prevention of Pb uptake and promoting the direct scavenging of reactive oxygen species or activating antioxidant enzymes. Also, results from the use of LNAME and MB indicated that the positive effect of Arg is probably related to its role in NO production.

We examined the combined effects of hydrogen peroxide (H2O2) and nitric oxide (NO) on the responses of oilseed rape(Brassica napus L.) plants to salt stress under acclimated and non-acclimated conditions. The results of the shoot and root dry weight traits together with the measurement of malondialdehyde (MDA) indicated that salt acclimation with a low concentration of NaCl (50 mM) could not alleviate the inhibitory effect of high salinity (200 mM NaCl). Under acclimated conditions, seed priming with H2O2 or NO resulted in effective protection against salt stress, however, maximum amelioration of salt stress was found by the combined treatments of H2O2 + NO. Interestingly, in the salt-exposed non-acclimated plants, only seed priming with H2O2 + NO was effective in improving salt tolerance. Pretreatment with H2O2 + NO tended to limit Na translocation into photosynthetic organs to prevent salt damages. Additionally, a large increase in salicylic acid contentwas correlated with phenylalanine ammonia lyase activation and flavonoid biosynthesis was observed when oilseed rape plants exposed to salinity in the presence of H2O2+NO. Interestingly, in this study, endogenous NO content of H2O2–primed plants exhibited a significant increase under non-saline conditions, indicating that H2O2 influences NO accumulation. In addition, oilseed rape plants primed with H2O2 + NO exhibited lower MDA and H2O2 content, contributing to the better induction of antioxidative enzyme activities. Higher levels of antioxidant enzyme activities maintained the integrity of cell membranes, resulting in better plant growth under salt stress. Taken together, our results revealed that oilseed rape plants pretreated with H2O2 + NO exhibited more effective tolerance to salt stress than plants that were pretreated with H2O2 or NO alone.

Biochemical and physiological responses of alfalfa under salinity stress were comparatively studied in a factorial experiment based on randomized complete block design by using Yazdi as the tolerant and Diabolourde as the sensitive ecotypes. Salt levels of 100, 150 and 200 mM were prepared by adding sodium chloride to the Hoagland half-strength culture medium. Total phenolics content, polyphenol oxidase (PPO), β-glucosidase and antiradical activities of leave′s extract, stomata properties and chlorophyll fluorescence parameters of the leaves including Fv/Fm and Fv/Fo were measured in response to salinity stress. Stomata characters were reduced in both ecotypes but chlorophyll fluorescence parameters only declined in Diabolourde but not in the Yazdi ecotype.  The PPO and β-glucosidase activities increased in both ecotypes. The phenolics content and antiradical activities increased in the Yazdi ecotype at all salt levels but those of Diabolurde increased only at the higher salinity levels. Our observations indicated that the Yazdi ecotype manipulated biochemical and physiological responses more efficiently to alleviate the reduction of growth parameters under salinity.

Analysis of the structure of genotype by environment (GE) interaction is essential in crop stability programs. To study the effects of GE interaction on the seed yield and identify stable genotypes of barley for warm and humid regions, 16 barley genotypes with two check cultivars were assayed in a randomized complete block design with four replications in Gachsaran, Moghan, Khorramabad and Gonbad regions for three years (2017-2019). Combined analysis of variance for yield data of 12 environments (year/location combined) showed significant differences among environments and genotypes and significant GE interaction. The GE interaction was examined using principal coordinates analysis (PCoA). Based on the deviation from the grand mean, 12 environments were divided into two main groups: five environments with higher mean yield and seven environments with lower mean yield. The most stable genotypes based on the minimum spanning tree and distance from the center of plots were G13 (2.43 kg/ha), G2 (2.38 kg/ha), G14 (2.29 kg/ha), which could be recommended for environments with a yield lower than the average mean of all studied environments. The results of the PCoA showed that the genotype G18 (2.32 kg/ha) was also located five times in the vertex positions of high cycles and so it can be recommended for favorable or high yielding environments.

The existence of genotype × environment interaction complicates the evaluation of cultivar performance and reduces gain to selection. One of the multivariate methods for interpreting genotype by environment interaction is GGE-Biplot, in which the main effect of genotype and genotype by environment interaction are investigated simultaneously. In this study, 13 mutant genotypes of rice along with three check cultivars Tarrom-Mahalli, Tarrom-Jelodar and Neda were evaluated for grain yield stability in the two locations of Sari and Tonekabon during the years 2016 and 2017 using randomized complete block design with three replications within each environment. The results of GGE-biplot analysis showed that the two first components explained 92.52% of the total yield variation. According to the polygon view, all four environments of the experiment were located in the place that the Neda cultivar was at the top. Genotypes 33, 30, 26, 31 were highly stable genotypes and genotypes 18, 16 and 25 were highly unstable. In this study, we found only one mega-environment. Also following Neda and Jelodar cultivars, genotype 31 was closest to the ideal genotype. Ton 95 was the most desirable environment.

To study the effect of 17β-estradiol on seedling growth, antioxidant enzyme activity and also, on callus induction from leaf explants of German Chamomile (Matricaria chamomilla L.), an experiment was conducted as a completely randomized design with three replications using MS medium containing different concentrations of 17β-estradiol (0, 0.01, 0.1, 1 and 10 mg/l) alone or in combination with 3 mg/l Benzylaminopurine (BAP) + 0 or 1.5 mg/l 1-naphthalene acetic acid (NAA). The results showed that 17β-estradiol at 0.01 and 0.1 mg/l increased root and shoot length and weight, respectively and at high concentration (10 mg/l) increased peroxidase, polyphenol oxidase and catalase activity of German chamomile seedlings. Also, the callus induction was observed after one to two weeks in all media, but the growth varied depending on the presence or absence of plant growth regulators and different concentrations of 17β-estradiol. Maximum callus weight was obtained in 0.01 mg/l of 17β-estradiol with about three-fold increase in comparison with the control (MS without17β-estradiol). This indicates that the 17-beta-estradiol at lower concentrations (0.01 mg/l) can significantly improve callus growth in the presence of plant growth regulators such as NAA and BAP. The results of this study indicate that using steroidal hormone 17β-estradiol can be used to optimize German chamomile cell growth under in vitro conditions.

Simple sequence repeat (SSR) markers are simple PCR-based co-dominant markers, which are highly polymorphic and informative due to the number and frequency of alleles, and thus they are most utilized among the molecular markers. However, the development of SSR markers is costly and time-consuming. Cross-species transferability of SSRs allows the SSRs isolated from one species to apply on a closely related species, which increases the utility of previously isolated SSRs. This study demonstrated the cross-species transferability of 196 SSR primer pairs of wheat in genetic diversity analysis of 40 varieties of barley (Hordeum vulgare L.). Of the 196 SSR primer pairs assayed, 59 (30.1%) showed transferability. Of the 59 primer pairs, 21 pairs were polymorphic with the polymorphism information content ranging from 0.19 to 0.70. The number of alleles detected at each locus ranged from one to seven with an average of 3.57. Cluster analysis using the Minimum Evolution algorithm and the coefficient of Number of Differences assigned the genotypes into five groups.

Increasing the efficiency of the hybrid-based maize breeding program has highly contributed to the heterotic group classification. The present study was aimed to compare the breeding efficiency of the three heterotic-group (TriHG) classification [Lancaster Sure Crop (LSC), Reid Yellow Dent (RYD), CIMMYT] system and usual two heterotic-group (DiHG) classification (RYD, LSC) system. To accomplish this, specific breeding efficiency (SBE) and general breeding efficiency (GBE) were estimated for the grain yield. The mating design was a line × tester scheme in which seven adapted tropical and subtropical lines were crossed to four testers. GBE increased by 128% in the TriHG classification system as compared to the DiHG system while no significant loss was observed in SBE. It seems that the TriHG system was advantageous over the DiHG system by improving the maize breeding efficiency. Therefore, using one tester from each of the three heterotic groups (RYD, LSC, CIMMYT) could be more efficient in hybrid-based maize breeding programs in temperate regions, including Iran.

The identification of the most favorable cultivar(s) with high yield and stable performance is usually done based on the analysis of the genotype × environment (GE) interaction. The yield stability of 16 barley lines with two check varieties was studied in a randomized complete block design with four replications across three years at five locations in a multi-environment trial layout. The dataset was analyzed with a GGE (genotype main effect (G) + GE interaction) biplot method. Results indicated that the first two principal components (PCs) explained 81, 78 and 71% of the GGE sum of squares for 2017, 2018 and 2019 growing seasons, respectively. According to the average environment coordinate abscissa, G2, G13 and G18 were the best genotypes in terms of grain yield in years 2017 and 2018 while genotypes G2, G7 and G14 were the highest yielding genotypes in 2019. When both yield performance and stability were considered simultaneously, the G2 and G13 genotypes in 2017 and G2, G8 and G13 in 2018, were closer to the ideal genotype. In 2019, G2, G7 and G14 were the best in terms of grain yield and stability. In the "which-won-where pattern", the five locations in 2017 fell into four sectors with different winning genotypes as G2, G5, G14 and G13. In 2018, the five locations fell into three sectors in which G2, G4 and G17 were the highest yielding genotypes while in 2019, locations were positioned in four sectors and G2, G7, G10 and G13 were chosen as the winning genotypes. However, for practical use of the “which-won-where” pattern, the mean performance of genotypes over three years in the five test locations was taken into account. Although the results revealed six mega-environments, by neglecting small differences, we can assume only one mega-environment in which G2 (the check variety Khorram) was the best performing genotype.

Drought is one of the most prevalent and critical environmental stresses affecting a variety of plants, particularly ornamental plants. One of the useful methods to alleviate the effect of drought stress is to screen for and develop drought-tolerant varieties. In this study, a factorial experiment based on the completely randomized design was conducted to investigate the responses of 11 genotypes from different Juniperus species at two irrigation regimes (normal, drought: not irrigated for a four-week period) in terms of growth and biochemical characters.Drought stress had a significant negative impact on the assessed growth characters. The G3 and G8 genotypes had the highest root fresh weight and root dry weight at both normal and water-deficit stress conditions. G3 showed the highest root volume at normal conditions but at the drought stress, the highest root volume belonged to G1 and G8. At drought stress conditions, the leaf fresh weight and dry weight of G9, G8, G6, G4, G3 and G11 were higher than other genotypes. The stem fresh weight of G3 and G11 and the stem dry weight of G11 and G8 manifested higher values than other genotypes when water deficit stress was imposed. Stem diameter decreased in the seedlings at the drought stress, however, G2, G3, G4, G8, G9 and G11 had higher values than others at stress conditions. The relative water content decreased in the plants under stress, however, the reduction in G3, G5 and G6 were smaller than the rest of the genotypes. Among the genotypes, G5 and G3 showed the highest antioxidant activity under water-deficit stress. The genotypes G1, G6, G7 and G8 had also a notable increase in the antioxidant activity at drought stress conditions. Under drought stress, the highest increase in the proline content belonged to G3 followed by G5, G6 and G7 and the G5, G6, G10 and G8 genotypes had the highest amount of soluble sugars. In conclusion, G3 (Juniperus chinensis var. Sargentii) and G8 (Juniperus chinensis ‘Kallayʼs Compact’) showed mainly better performance under drought stress, which can be suggested as candidate drought-tolerant genotypes to be used in breeding programs for the sustainable development of urban landscape in arid and semi-arid areas. Although G5 (Juniperus procumbens ‘Nana’) had low biomass in this experiment, it showed high antioxidant activity, proline and soluble sugars at the drought stress conditions. Therefore, further investigation is needed, especially at more severe drought stress conditions, to elucidate its outstanding response to drought stress in terms of antioxidant activity and proline and soluble sugars content.