Journal of Plant Physiology and Breeding
Volume:3 Issue: 2, Summer-Autumn 2013

In this study ameliorative effects of ascorbic acid (0.5 mM) on onion (Allium cepa L. cv. Red Azarshahr) under copper stress (Cu: 6.5 μM) were studied. Fresh weights of leaves and roots were reduced in seven week old plants under excess copper condition. Cu stress also reduced membrane stability index in leaves. There was a considerable increase in H2O2 content and lipid peroxidation in both roots and leaves of plants under excess Cu. Leaves anthocyanin contents, leaves and roots phenolic compounds, soluble proteins and proline contents were increased in response to Cu toxicity. The fresh weights of leaves and roots were improved during addition of ascorbic acid to root medium in stressed and non-stressed plants. Exogenous ascorbic acid significantly increased membrane stability index in Cu stressed plants. We find considerable reduction in anthocyanins, phenolic compounds and proline with ascorbic acid treatments in all plants. Ascorbic acid application also reduced H2O2 content and prevented lipid peroxidation in leaves and roots during presence or absence of excess Cu. Treatment of plants with ascorbic acid increased soluble proteins content only in non-stressed plants. The results demonstrate that root applied ascorbic acid ameliorated the copper induced oxidative adverse effects on onion growth.

The crop water stress index (CWSI) is a valuable tool for monitoring and quantifying water stress as well as for irrigation scheduling. A field experiment was conducted during spring and summer 2012 at Research Station of College of Agriculture and Natural Resources of Darab, Shiraz University, Iran, to determine CWSI of turfgrass for irrigation scheduling. Four levels of water regimes including well watered [Irrigation according to 100% field capacity (FC)], mild drought stress (75% FC), severe drought (50% FC), and most severe drought (25% FC) stress were arranged in a randomized complete block design with four replicateions. The highest monthly average value of CWSI for all treatments was reached in August and decreased in September slightly. In all treatments the CWSI values showed an increasing trend from June (0.097 in well watered treatment) to August (0.684 under most severe drought) as a result of higher vapor pressure deficit values and negatively increase in Tc-Ta differential. Also, significant differences were observed between mean CWSI values of well watered and mild drought, with severe drought and most severe drought treatments. The color grading number for mild drought treatment in turfgrass decreased sharply from 8 to 4 at the start of the experiment in July, and remained constant (3) for August and September. The amounts of irrigation water more than 75% FC did not affect visual quality of turfgrass, which appeared to be sufficient to fulfill an acceptable turfgrass quality. A negative relationship was found between CWSI with water applied and color quality under different irrigation regimes. It appeared that under arid and semi-arid conditions, such as southern Iran, where the amount of water is a major limiting factor, the amount of applied water could be lowered to 75% FC without any loss in visual quality of turfgrass with the seasonal CWSI being kept about 0.15.

Seasonal drought is the most important factor to limit the production of maize in the world. Using a split plot design, a two year field experiment was conducted to determine the effect of limited irrigation regime on yield, yield components and water use efficiency of sweet corn (Zea mays var. saccharata). Responses of three sweet corn varieties KSC403, Merit and Obsession to three different water regimes were studied under two planting methods (raised bed and furrow planting). The three water levels (I1: 100%, I2: 80%, I3: 60%) of the estimated crop evapotranspiration (ETc)) were arranged as main plots. Combination of the two planting methods and three sweet corn varieties were arranged in subplots. The evaluated traits were significantly affected by varieties (p<0.01). The highest ear length and diameter and biomass belonged to Merit. Fresh ear weight was significantly affected by the interaction of variety and irrigation level. The highest (19.7 ton/ha) and lowest (7.4 ton/ha) yields (fresh ear weight) belonged to Merit at 100% and KSC403 and obsession at 60% irrigation level, respectively. There was no difference between planting methods with respect to the measured traits. Results showed that limited irrigation significantly decreased kernel number per row by increasing the anthesis-silking interval, which decreased grain yield. Biomass decreased by decrement of water amount. The reduction in fresh ear yield and biomass decreased water use efficiency (WUE), but there was no significant difference between I1 and I2 irrigation levels for WUE.

This study was conducted to evaluate the role of oxidative stress in roots of eight wheat genotypes with different drought tolerance, subjected to drought stress. For analyzing the changes of antioxidant enzymes, native PAGE analyses of protein extract were performed. The roots of wheat seedlings showed one unambiguous isoform of superoxide dismutase (SOD) and catalase (CAT). Eight isoforms of peroxidase (POX) were identified in the roots of wheat. The activities of SOD and POX isoforms decreased and the total activities of POX and CAT remained unchanged under the stress condition. The response of enzyme isoforms to drought were not the same for all isoforms of the antioxidant enzymes in the wheat genotypes, as POX isoforms showed the significant changes in the different drought tolerant genotypes. Significant interaction was observed between wheat group and stress treatments for total POX activity. POX total activity in the sensitive group of wheat genotypes was significantly higher than the tolerant group in the stress condition.

Determination of genetic diversity level is important in clarifying genetic relationships, characterizing germplasm and the registration of new cultivars. In this study, genetic variation among 56 accessions (G1~G56) of Citrus including several undefined local or native genotypes and some known varieties in Jiroft, Kerman province, Iran was investigated using SSR markers. In total, 12 SSR primers produced 54 alleles. The lowest number of alleles was observed on cAGG9 locus with 2 alleles and the highest number of alleles was observed in TAA41 locus with 8 alleles. Polymorphic Information Content (PIC) varied from 0.19 to 0.37 with mean of 0.28. The percentage of heterozygosity per marker detected in our samples ranged from 25% to 96% with an average of 67%. Grouping of the accessions using Jaccard similarity coefficient and based on the Neighbor-Joining method assigned the 56 accessions into four major clusters. The SSR data indicated a high relationship between G2 and G41 (unknown natural types) with grapefruits (Citrus paradisi) (G50 and G51), G17 (unknown natural type) with orange (C. sinensis) (G56) and G40 (unknown natural type) with pummelo (C. grandis) (G49). Unidentified genotype G43 in a single-accession cluster didn’t show any close molecular similarity to control samples [mandarin (C. reticulata), pummelo, sweet orange, sour orange (C. aurantium), etc.]. Mandarin, pummelo and citron (C. medica) were clustered into three particular groups as major species of Citrus. Also, our results demonstrated that SSR markers can be useful in evaluating citrus genetic diversity and in classifying accessions to phylogenetic groups based on their genetic similarity values.

The evaluation of the yield stability of genotypes and environment is of prime concern to plant breeders. Therefore, a comprehensive analysis of the structure of the GE interaction is needed. The objective of this investigation was to evaluate the use of sites regression (SREG) GGE methodology to stratify the pe × environment (GE) interaction in lentil. Yield data of 10 genotypes of lentil tested across 10 rain-fed environments during 2007 and 2008 growing seasons, using randomized complete block design with four replications, were analyzed. The location (L) explained 56 and 77% of the total (G + L + GL) variation for the first and second year, respectively. According to polygon view of biplot, Gonbad, Shirvan and Gachsaran with wining genotype G9, Ilam with wining genotype G5 and Kermanshah with wining genotype G8 were detected in the first year; and Gonbad and Ilam with wining genotype G5; Gachsaran with wining genotype G9; Kermanshah with wining genotype G2 and Shirvan with wining genotype G3 were detected in the second year. In the first year, genotypes G1 and G9 and in the second year genotypes G8 and G9 were the most favorable genotypes based on average tester coordinate biplot. Gachsaran location was more representative of the overall locations and more powerful to discriminate genotypes than the unfavorable ones. In conclusion, G9 (ILL6199) was found to be the most stable and higher yielding genotype which may be recommended for commercial release in semi-arid areas of Iran.

In order to evaluate morpho-physiological traits of confectionery sunflower under different irrigation regimes, an experiment was carried out under field conditions in Agricultural Research Center of West-Azerbaijan province, Urmia, Iran in 2012. Fifty six confectionery sunflower landraces were arranged in 7 × 8 rectangular lattice design with two replications in each one of well-watered, moderate and severe stress conditions with 50%, 70% and 90% depletion of available water, respectively. Combined analyses of variance revealed significant effect of genotype, irrigation regime and their interaction on studied traits including grain yield, chlorophyll content, grain and kernel weight, grain length and width and kernel/grain ratio. ''Urmia-Anghane 4'', '' Urmia-Gharagoz 1'' and ''Salmas-Sadaghian'' produced the highest grain yield (6310.31), (3778.83) and (2217.95 kg/h), under well-watered, moderate and sever stresses, respectively. In contrast ''Mashhad'', ''Piranshahr-Andizeh'' and ‘‘Mashhad’’ presented the lowest values. Severe drought stress caused 49% reduction in grain yield compared to well-watered condition. ''Shabestar-Kouzeh Kanan 2'' (46.05) and ''Urmia-Heydarlou 1'' (19.47) showed the highest and lowest chlorophyll content under well-watered and severe drought stress conditions, respectively. The high grain length was seen in ''Marand-Dizaj-Ghalami'' landrace (29.59 mm). Under the well-watered, moderate and severe stress conditions, grain yield had significantly positive correlations with kernel and grain weight and grain width and length. Based on cluster analysis, the studied landraces were grouped in three clusters both in well-watered and severe stress conditions. But under moderate stress conditions, the studied landraces were grouped in five clusters. Considering all studied traits, the landraces 1, 2, 3, 4, 5, 11, 12, 13, 49, 55, 56 were superior genotypes under well-watered conditions. In moderate and severe stress conditions, the best landraces were (12, 35, 26, 31, 32, 56) and (2, 3, 5, 7, 9, 11, 12, 14, 15, 18, 22, 25, 27, 30, 31, 42, 43 46, 47, 55), respectively.