Structural-functional state of thylakoid membranes of wheat genotypes under water stress

Plants were grown in field conditions in the wide area under normal water supply and severe water deficit. Two wheat (Triticum aestivum L.) genotypes contrasting by architectonics and differing in drought-resistance were used: Giymatli-2/17, short stature, with broad and drooping leaves, drought-sensitive, and Azamatli-95, short stature, with vertically oriented small leaves, drought-tolerant). It was found out that Giymatli-2/17 was characterized by relatively low content of Chl a-protein of PS I (CP I) and β-subunit of ATP-synthase complex, the high content of proteins in the 33-30.5 kDa region and LHC polypeptides (28-24.5 kDa), the intensive fluorescence at 740 nm and more high photochemical activity of PS II under normal irrigation compared with Azamatli-95. However, the content of CP I (M_r 115 kDa) and apoprotein of P700 with M_r 63 kDa insignificantly increases in the drought-resistant genotype Azamatli-95 under extreme water supply condition while their content decreases in drought-sensitive cv Giymatli-2/17. Intensity of synthesis α- and β-subunits of CF₁ (55 and 53.5 kDa) also decreases in Giymatli-2/17. The levels of the core antenna polypeptides of FS II with M_r 46 and 44.5 kDa (CP47 and CP43) remains stable both in normal, and stressful conditions. At the same time the significant reduction is observed in the content of polypeptides in the 33-30.5 kDa region in the more sensitive genotype Giymatli-2/17. There is an increase in the LHC II polypeptides level in tolerant genotype Azamatli-95 in contrast to Giymatli-2/17 (where the content of these subunits is observed decreasing). The intensity of short wavelength peaks at 687 and 695 nm sharply increases in the fluorescence spectra (77 K) of chloroplasts from sensitive genotype Giymatli-2/17 under water deficiency and there is a stimulation of the ratio of fluorescence band intensity F687/F740. After exposure to drought, cv Giymatli-2/17 shows a larger reduction in the actual PS II photochemical efficiency of chloroplasts than cv Azamatli-95.     

Salt resistance of chickpea genotypes in solutions salinized with NaCl or Na2SO4

Summary To assess the potential for developing a salt resistant cultivar of chickpea (Cicer arietinum L.) 160 genotypes were screened for percent survival after 9 weeks in greenhouse solution cultures, with 50 mM NaCl or 25 mM Na₂SO₄. All plants grew well in the sulfate treatment but only cv. L-550 survived the chloride treatment. Salt damage appeared and developed slowly. To check these apparent effects of cultivar and kind of anion, three genotypes including cv. L-550 were then grown in solutions with isoosmotic NaCl or Na₂SO₄ at three levels (−0.044, −0.088, and −0.132 MPa), and in a separate experiment cv. L-550 was grown with NaCl and Na₂SO₄ at four levels: 10, 20, 30 and 50 mM Na. Salt composition affected shoot weight less than salt level or cultivar did. Shoot dry weight was only slightly less in chloride treatments than in isoosmotic sulfate, and for the least sensitive cultivar (L-550) this held only at the highest salt level, corresponding to that in the screening trial. Further, sensitivity to sulfate and to chloride was equal when sodium concentrations in shoots were equal, regardless of anion compositions of media. Shoot Na concentration was a useful negative indicator of growth under salt stress regardles of cultivar, and may be a useful tolerance indicator also for other species that neither accumulate nor efficiently exclude Na.     

Cultivar Differences in Photosynthetic Tolerance to Photooxidation and Shading in Rice (Oryza Sativa L.)

Forty-four genotypes from the rice germplasm were identified under photoinhibition/photooxidation and shade conditions and divided into four basic types: (1) cultivars tolerant to both photooxidation and shading, (2) cultivars tolerant to photooxidation but sensitive to shading, (3) cultivars tolerant to shading but sensitive to photooxidation, and (4) cultivars sensitive to both photooxidation and shading. Photosynthetic characteristics of a cultivar tolerant (cv. Wuyugeng 3) and a cultivar sensitive (cv. Xiangxian) to photooxidation and shading were compared. The photochemical efficiency (F_v/F_m) of photosystem 2 (PS2) and the content of PS2-D1 protein in the tolerant cultivar Wuyugeng 3 decreased less under photooxidative conditions as compared with Xiangxian. Under similar conditions, superoxide dismutase was induced rapidly to a higher activity and the active oxygen (O^–) built up to a lower level in Wuyugeng 3 than in Xiangxian. Net photosynthetic rate (P _N) decreased by 23 % in Wuyugeng 3 vs. 64 % in Xiangxian. Shading (80 %) during the booting stage caused only small decreases (7–13 %) in ribulose-1,5-bisphosphate carboxylase activity and P _N in Wuyugeng 3 but severe decreases (57–64 %) were observed in Xiangxian which corresponded to the decreases in grain yield of the two cultivars (38 and 73 %, respectively). We described a simple and effective screening method and physiological basis for breeding crops for enhanced tolerance to both high and low irradiance.     

Differences in the Induction of Defence Responses in Resistant and Susceptible Muskmelon Plants Infected with Colletotrichum lagenarium

Defence reactions occurring in resistant (cv. Gankezaomi) and susceptible (cv. Ganmibao) muskmelon leaves were investigated after inoculating with Colletotrichum lagenarium. Lesion restriction in resistant cultivars was associated with the accumulation of hydrogen peroxide (H₂O₂). The activity of antioxidants catalase (CAT) and peroxidase (POD) significantly increased in both cultivars after inoculation, while levels of both CAT and POD activity were significantly higher in the resistant cultivar. Ascorbate peroxidase (APX) increased in both cultivars after inoculation, and level of APX activity was significantly higher in the resistant cultivar. Glutathione reductase (GR) activity significantly increased in both cultivars following inoculation, but was higher in the resistant cultivar, resulting in higher levels of ascorbic acid (AsA) and reduced glutathione (GSH). Phenylalanine ammonia lyase (PAL) significantly increased in inoculated leaves of both cultivars, resulting in higher levels of total phenolic compounds and flavonoids. The pathogenesis‐related proteins chitinase (CHT) and β‐1, 3‐glucanase (GLU) significantly increased following inoculation with higher activity in the resistant cultivar. These findings show that resistance of muskmelon plants against C. lagenarium is associated with the rapid accumulation of H₂O₂, resulting in altered cellular redox status, accumulation of pathogenesis‐related proteins, activation of phenylpropanoid pathway to accumulation of phenolic compounds and flavonoids.     

Increased risk of advanced prostate cancer associated with MnSOD Ala-9-Val gene polymorphism

We aimed to investigate the association between manganese superoxide dismutase (MnSOD) Ala-9-Val gene polymorphism and the initiation and/or progression of prostate cancer (PCa) as well as to evaluate its potential interactions with advanced age and smoking status. MnSOD Ala-9-Val gene polymorphism was carried out in 134 (mean age 64.1 ± 7.48) PCa patients and 159 (mean age 62.5 ± 7.53) healthy controls with serum prostate specific antigen (PSA) levels (<4 ng/ml) and normal digital rectal examination (DRE) findings in this prospectively designed study. PCa patients were classified as low stage disease (T₁ or T₂ and N₀M₀ stages) and high stage disease (T₃ or T₄ and N₀M₀ or N₁ or M₁ stages). Genotypes for MnSOD Ala-9-Val gene polymorphism were identified by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFPL). Despite lack of association between different genotypes of MnSOD Ala-9-Val gene polymorphism and the presence of PCa, patients with Ala/Ala genotype were at an increased risk of high stage disease compared with those with the Val/Val genotype [odds ratio (OR), 3.77; 95% CI, 1.30–10.94; P = 0.012]. However, no significant difference was observed in the distribution of each genotype among PCa patients, with respect to tumor grade. On the other hand, smoking status and aging did not seem to change the association between genotypes and PCa risk. Ala/Ala genotype of MnSOD polymorphism may have an effect on adverse features of PCa such as high stage disease.     

The Response of Lettuce Cultivars against Two Lettuce mosaic virus isolates,One Able to Systemically Infect the Resistant Cultivar Salinas 88

The response of seven lettuce cultivars to two geographically different Lettuce mosaic virus (LMV) isolates (LMV‐A, LMV‐T) was statistically evaluated based on infection rate, virus accumulation and symptom severity in different time trials. LMV‐A is characterized by the ability to systemically infect cv. Salinas 88 (mo1²‐carrying resistant cultivar), and inducing mild mosaic symptoms. Among lettuce cultivars, Varamin (a native cultivar) similar to cv. Salinas showed the most susceptibility to both LMV isolates, whereas another native cultivar, Varesh, was tolerant to the virus with minimal viral accumulation and symptom scores, significantly different from other cultivars at P < 0.05. LMV‐A systemically infects all susceptible lettuce cultivars more rapidly and at a higher rate than LMV‐T. This isolate accumulated in lettuce cultivars at a significantly higher level, determined by semiquantitative ELISA and induced more severe symptoms than LMV‐T isolate at 21 dpi. This is the first evidence for a LMV isolate with ability to systemically infect mo1²‐carrying resistant cultivar of lettuce from Iran. In this study, accumulation level of LMV showed statistically meaningful positive correlation with symptom severity on lettuce plants. Based on the results, three evaluated parameters differed considerably by lettuce cultivar and virus isolate.     

The decline in potassium concentration is associated with cadmium toxicity of rice seedlings

Cadmium (Cd) is one of the most dangerous environmental pollutants, among other things, affecting plant mineral composition. Thus, in this study, we investigated the changes in potassium (K) concentration in Cd-treated rice (Oryza sativa L.) seedlings of two cultivars. On treatment with 5 μM CdCl₂, the Cd concentration increased in the shoot and roots of Cd-sensitive cultivar (cv. Taichung Native 1, TN1) but not or slightly in the Cd-tolerant cultivar (cv. Tainung 67, TNG67). The decrease in K concentration in the shoot and roots of TN1 caused by Cd was more pronounced than that of TNG67. Exogenous addition of KCl decreased Cd concentration and reduced Cd toxicity of TN1 seedlings. Evidence presented in this study suggests that the improvement of K status is able to reduce toxicity of rice seedlings to CdCl₂.     

Genotypic differences in the responses of gas exchange,chlorophyll fluorescence,and antioxidant enzymes to aluminum stress in <Emphasis Type="Italic">Festuca arundinacea</Emphasis>

In this study, the gas exchange, chlorophyll fluorescence, and antioxidant activity in eight tall fescue cultivars were investigated under aluminum stress. The results showed that the net photosynthetic rate (P _N) and stomatal conductance (g _s) were decreased, while the intercellular CO₂ concentration (C_i) was stable or increased under Al stress conditions. The efficiency of excitation capture by open PSII reaction centers (F′_v/F′_m), the maximum quantum yield of PSII photochemistry (F _v/F _m), the quantum yield of PSII electron transport (Φ_PSII), and the photochemical quenching (qP) were also decreased after Al stress, while the non-photochemical quenching (NPQ) was increased. Moreover, Al stress increased the antioxidant activities and MDA contents in each tall fescue cultivars. However, there was a lot genotype differences between the Al-tolerant and Al-sensitive cultivars. Cv. Barrington was the most sensitive cultivar and cv. Crossfire 2 was the most tolerant cultivar. The excessive excitation energy could not be dissipated efficiently by antenna pigments, and reactive oxygen species could not be scavenged efficiently, thereby resulting in membrane lipid peroxidation in cv. Barrington under Al stress conditions.     

Comparison of Hexaploid and Tetraploid Wheat Cultivars in their Responses to Water Stress

We studied the effect of water stress imposed at anthesis and pre-anthesis stages on oxidative stress and antioxidant activity in four wheat cultivars, two hexaploid Triticum aestivum cultivars, drought resistant cv. C 306 and drought susceptible cv. Hira, and two tetraploid cultivars, T. durum cv. A 9-30-1 and T. dicoccum cv. HW 24. Water stress decreased relative water content (RWC), membrane stability index (MSI), and increased H₂O₂ and malondialdehyde (MDA) contents as well as activity of superoxide dismutase (SOD), catalase (Cat) and peroxidase (POX) in all the genotypes at all the stages. Both the tetraploid cultivars showed higher RWC, MSI and SOD activity, and lower H₂O₂ and MDA contents under water stress than hexaploid ones. Cat and POX activities were highest in C 306.     

Genetically manipulated Brassica genotypes affect demography and performance of Diadegma semiclausum parasitizing Plutella xylostella

The performance of Diadegma semiclausum (Hellen) (Hymenoptera: Ichneumonidae) on Plutella xylostella (L.) (Lepidoptera: Plutellidae) reared on canola's progenitor (Brassica rapa L.), two cultivated canola cultivars (Opera and RGS₀₀₃), one hybrid (Hyula₄₀₁), one gamma‐ray mutant‐RGS₀₀₃ and one transgenic (PF) genotype was compared using the age‐stage, two‐sex life table parameters. All experiments were carried out in a growth chamber at 25 ± 1°C, 65 ± 5% RH and a photoperiod of 16 : 8 (L : D) h. There were significant differences in duration of different life stages of D. semiclausum on its host larvae reared on different plant genotypes. The shortest (12.27 days) and longest (15.21 days) pre‐adult developmental times were observed on cultivar‐RGS₀₀₃ and hybrid‐Hyula₄₀₁, respectively. The intrinsic rate of increase (r) in D. semiclausum ranged between 0.189/day (cultivar‐Opera) and 0.141/day (transgenic‐PF). Moreover, the highest (20.078 offspring) and lowest (12.027 offspring) net reproductive rates (R₀) were observed on cultivar‐Opera and hybrid‐Hyula₄₀₁. The mean generation time (T) of D. semiclausum was the highest (18.34 days) and lowest (15.05 days) on mutant‐RGS₀₀₃ and cultivar‐RGS₀₀₃. The maximum and minimum parasitism values of this parasitoid were observed on canola's progenitor (44.28%) and hybrid‐Hyula₄₀₁ (37.09%). The heaviest pupae (3.82 mg) and females (3.22 mg) of the parasitoid were found on canola's progenitor and cultivar‐Opera, respectively. The results showed that performance of this parasitoid was better on canola's progenitor and cultivated plants known to have higher levels of glucosinolates concentration than others.     

The inheritance of resistance to Verticillium wilt caused by race 1 isolates of <Emphasis Type="Italic">Verticillium dahliae</Emphasis> in the lettuce cultivar La Brillante

Verticillium wilt of lettuce caused by Verticillium dahliae can cause severe economic damage to lettuce producers. Complete resistance to race 1 isolates is available in Lactuca sativa cultivar (cv.) La Brillante and understanding the genetic basis of this resistance will aid development of new resistant cultivars. F₁ and F₂ families from crosses between La Brillante and three iceberg cultivars as well as a recombinant inbred line population derived from L. sativa cv. Salinas 88 × La Brillante were evaluated for disease incidence and disease severity in replicated greenhouse and field experiments. One hundred and six molecular markers were used to generate a genetic map from Salinas 88 × La Brillante and for detection of quantitative trait loci. Segregation was consistent with a single dominant gene of major effect which we are naming Verticillium resistance 1 (Vr1). The gene described large portions of the phenotypic variance (R ² = 0.49–0.68) and was mapped to linkage group 9 coincident with an expressed sequence tag marker (QGD8I16.yg.ab1) that has sequence similarity with the Ve gene that confers resistance to V. dahliae race 1 in tomato. The simple inheritance of resistance indicates that breeding procedures designed for single genes will be applicable for developing resistant cultivars. QGD8I16.yg.ab1 is a good candidate for functional analysis and development of markers suitable for marker-assisted selection.     

Efficient production of androgenic doubled-haploid mutants in barley by the application of sodium azide to anther and microspore cultures

 The aim of this study was to establish a protocol for an efficient production of agronomical and/or physiological mutants from model (cvs. Igri and Cobra) and low-androgenic-responding (cv. Volga) cultivars of barley through the application of a mutagenic agent, sodium azide, to anthers and isolated microspores cultured in vitro. This technology offers the possibilities of screening for recessive mutants in the first generation, selecting for novel genotypes from very large haploid populations, avoiding chimerism and rapidly fixing selected genotypes as fertile true breeding lines. The mutagenic treatment, 10^–3–10^–5 M sodium azide, was applied during the anther induction pre-treatment or immediately after the microspore isolation procedure. Out of 616 M₂ doubled-haploid lines characterised under field conditions, a total of 63 morphological and developmental independent mutant lines were identified. The percentage of M₂ doubled-haploid lines carrying mutations per line analysed was 3.8% when 10^–4 M sodium azide was applied to anthers from the low-responding cv. Volga; this increased to 8.6% and 15.6% when 10^–5 and 10^–4 M sodium azide were applied to freshly isolated microspores from model cultivars. Received: 18 April 2000 / Revision received: 28 September 2000 / Accepted: 28 September 2000     

Biochemical and Physiological Responses of Cucumis sativus Cultivars to Different Combinations of Low-Temperature and High Humidity

Low-temperature and high humidity are typical environmental factors in the plastic tunnel and solar greenhouse during the cold season that restricts plant growth and development. Herein, we investigated the impact of different combinations of low-temperature and high humidity (day/night: T1 15/10 °C?+?95%, T2 12/8 °C?+?95%, and T3 9/5 °C?+?95%) along with a control (CK 25/18 °C?+?80%) on cucumber cultivars viz: Zhongnong37 (ZN37: resistant) and Shuyanbailv (SYB: sensitive). The low-temperature and high humidity stresses increased electrolyte leakage (EL), malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and intercellular concentration of carbon dioxide (Ci), and reduced morphological indices, relative water content (RWC), net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (E) and leaf pigments in both cultivars as compared to control (CK). Superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were decreased in cv. SYB under stress conditions as compared to cv. ZN37. Low-temperature and high humidity treatments showed an increase in proline and soluble protein content in cv. ZN37 as compared to cv. SYB. Abscisic acid (ABA) and jasmonic acid (JA) were augmented while indole-3-acetic acid (IAA), zeatin (ZT), zeatin riboside (ZR), and gibberellic acid (GA) were decreased in both cultivars. Under T3 (9/5 °C?+?95%), Pn, protoporphyrin, and ZT were extremely decreased by 71.3%, 74.3%, and 82.4%, respectively, in cv. SYB compared to control. Moreover, principal component analysis (PCA) based on physiochemical traits confirmed that cv. ZN37 had the strongest correlation with antioxidant enzymes, proline, and soluble protein content than cv. SYB under low-temperature and high humidity treatments. Our results suggest that a stress-tolerant cultivar mitigates stress damage in cucumber transplants by regulating photosynthetic efficiency, antioxidant capacity and hormonal profile when compared to a stress-sensitive cultivar.

     

Identification of Kunitz trypsin inhibitor mutations using SNAP markers in soybean mutant lines

The Kunitz trypsin inhibitor (KTi) in soybean has several polymorphic types that are controlled by multiple alleles, which behave in a co-dominant fashion. Of these, Tia and Tib, which differ by nine amino acids, are the predominant types. In order to develop a single nucleotide amplified polymorphism (SNAP) marker for the classification of the predominant KTi types, Tia and Tib, and evaluate KTi activities by differing KTi type total 451 soybean mutant lines (M₁₂–M₁₆ generation) were incorporated in this study. Among 451 soybean mutants, 144 and 13 mutant lines showed decreased and increased trypsin inhibitor activity when compared with the original cultivars, respectively. To identify the KTi type, we designed a SNAP marker. Among 451 mutant lines from 12 soybean cultivars and landraces, 8 mutant lines derived from cvs. Baekwoon, Paldal and Suwon115 showed a change in KTi type when compared with the original cultivars using the SNAP marker. Five mutant lines in Suwon115 changed from Tib to Tia, while two mutant lines derived from cv. Baekwoon and one mutant line derived from cv. Paldal were changed from Tia to Tib. These changes of KTi types were confirmed by sequencing of the KTi genes and non-denaturing polyacrylamide gel electrophoresis of the KTi proteins. To identify the effect of KTi activity based on the change in KTi type, we measured the KTi activity using the three cultivars and eight mutant lines that showed changes in KTi type. Two mutant lines (BW-1 and 7-2) derived from cv. Baekwoon and one mutant line (PD-5-10) from cv. Paldal that changed from Tia to Tib showed lower activity than the original cultivar. In cv. Suwon115, five mutant lines that changed from Tib to Tia showed higher activity than the original cultivar. These results indicate that the designed SNAP marker was capable of identifying the KTi type and that Tia activity was higher than Tib activity in soybean.     

New data on the distribution of hybrid necrosis genes in winter bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) cultivars

Hybrid necrosis genotypes have been identified in 125 Russian cultivars of winter bread wheat. More than half of them (56%) carry the Ne2 gene (genotype ne1ne1Ne2Ne2); others are free of necrosis genes (genotype ne1ne1ne2ne2). The possible causes of the increase in the Ne2 allele frequency and the loss of the Ne1Ne1ne2ne2 genotype in modern Russian cultivars of winter wheat are discussed. The principal component method has been used to compare the structures of the genetic diversity of cultivars differing in the hybrid necrosis genotype. It has been found that the Ne2 allele in winter wheat cultivars from northern Russia has originated from the cultivar Mironovskaya 808, whereas the cultivar Bezostaya 1 is not a source of this gene. In cultivars from southern Russia, the presence of the Ne2 allele is also mainly accounted for by the use of Mironovskaya 808 wheat in their breeding. The recessive genotype is explained by the presence of descendants of the cultivar Odesskaya 16 in the pedigrees of southern Russian winter wheats. The genetic relationship of cultivars with identical and different necrosis genotypes has been analyzed in nine regions of the Russian Federation.     

Impact of fusaproliferin on primary roots of maize cultivars differing in their susceptibility to <Emphasis Type="Italic">Fusarium</Emphasis>

Effects of fusaproliferin (FUS) on membrane potential (E _M), electrolyte leakage, enzymes activity and respiration of roots, were studied in two maize cultivars (Zea mays L.), differing in their susceptibility to this toxin. In short-term experiments (≤ 6 h), E _M has been rapidly and significantly depolarized by FUS. The rapidity of E _M depolarization in tolerant cv. Lucia was more expressive in comparison with susceptible cv. Pavla, but the extent of E _M depolarization was higher in cv. Pavla. In both maize cultivars, higher depolarization of E _M was registered in cells of root zone I. In long-term experiments after the first E _M depolarization, which occurred during the first 6 h of FUS treatment, gradual depolarization continued up to 24 h and was represented not only by the active component (E _P) but also by the passive component (E _D) of E _M. The decrease in E _M and E _D was followed by a loss of K⁺ ions from FUS treated roots of both cultivars. The leak of K⁺ ions from the root cells of both root zones as well as both maize cultivars increased with the time of FUS treatment and was significantly higher in susceptible cv. Pavla than in tolerant cv. Lucia. FUS treatment of maize roots resulted in a significant decrease of root respiration which was higher in susceptible cv. Pavla than in tolerant cv. Lucia.     

Relationship between osmotic stress-induced abscisic acid accumulation,biomass production and plant growth in drought-tolerant and -sensitive wheat cultivars

The effects of increasing osmotic stress induced by 100–400 mOsm (−0.976 MPa) polyethylene glycol (PEG 6000) were investigated in a drought-tolerant (Triticum aestivum L. cv. Mv Emese) and drought-sensitive (cv. GK élet) wheat cultivar at the three-leaf stage. During osmotic stress, the decline of the water potential (ψ _w) was more significant in the leaves, while the abscisic acid (ABA) levels of the roots increased earlier and remained higher in the sensitive than in the tolerant variety. There was an increasing gradient of ABA content toward the youngest leaves in the drought-sensitive GK élet, while more ABA accumulated in the fully developed, older leaves of the tolerant cultivar Mv Emese. In accordance with the rapid and significant accumulation of ABA, the stomatal conductance decreased earlier in the tolerant cultivar. The effect of water stress on the PSII photochemistry was pronounced only 1 week after the exposure to PEG, as indicated by the earlier decrease of the net CO₂ fixation, the effective quantum yield (Φ_PSII) and the photochemical quenching (q _P) in light-adapted samples of the tolerant variety in 400 mOsm PEG 6000. The stress treatment caused more significant reductions in these parameters toward the end of the experiment in the sensitive cultivar. In spite of small differences in the photosynthetic characteristics, the net biomass production was not significantly altered by this osmotic stress. The accumulation of ABA controlled the distribution of the biomass between the shoot and root systems under osmotic stress, and contributed to the development of stronger and deeper roots in the drought-sensitive cultivar GK élet. However, the root elongation did not correlate with the drought sensitivity of these cultivars on the basis of crop yield.     

Performance of some elite potato cultivars under abiotic stress at North Sinai

The current experiment was adopted during the summer 2018, fall 2018/2019 and summer 2019 respectively at the Experimental Farm of Baloza station, Desert Research Center. North Sinai Governorate, Egypt to study the effect of different doses of irradiation (0, 20, 30 and 40 Gy), three irrigation levels (100, 80 and 60% field capacity on growth, yield and its quality of some potato cultivars (Spunta, Cara, Caruso and Hermes). Treated Spunta cultivar pre planting with 20 (Gy) and irrigated with 80% field capacity was the best treatment for increasing number of aerial stem/plants, leaf area, total chlorophyll in leaves, average tuber weight, and total yield/fed. Hermes cultivar with 20 (Gy) and irrigation level of 80% was the best for increasing dry matter content in tuber in both mutagenic generations.     

β-1,3-glucanase and chitinase as pathogenesis-related proteins in the defense reaction of twoCapsicum annuum cultivars infected with cucumber mosaic virus

Pathogenesis-related (PR) proteins from pepper (Capsicum annuum L.) cv. Americano (tolerant) and cv. Smith-5 (sensitive), both elicited by infection with cucumber mosaic virus (CMV), were assayed for chitinase and glucanase activities. Two basic PR-proteins, M_r 49.0 and 28.0 kD, were elicicited from the intracellular fraction (INTRA-F) of both cvs. by CMV infection, while four acidic M_r 15, 19, 36 and 40 kD and two basic M_r 21.2 and 24 kD PR-proteins were elicited from the intercellular fluid (IF) of cv. Americano leaves. Five acidic M_r 21.5, 23.2, 24.4, 25.2 and 36 kD and five basic M_r 23.3, 26, 28.8, 30 and 32.3 kD PR proteins were elicited from the IF of cv. Smith-5. Isoelectric focusing (IEF) of the IF and the INTRA-F proteins revealed the occurrence, in both pepper cultivars, of one acidic M_r 36 kD and one basic M_r 25 kD PR-protein with glucanase activity. After native-PAGE for acidic proteins, the acidic PR-protein of Rf 0.7 and M_r 36 kD present in the IF of both pepper cvs. showed glucanase activity. Native-PAGE for basic proteins of the INTRA-F showed the presence of one band (Rf 0.61, M_r 25 kD) common to both cvs. and two additional bands (Rf 0.49, M_r 26 kD and Rf 0.79, M_r 33 kD) in the cv. Americano with glucanase activity. The specificity shown by the basic PR-proteins suggests glucanase activity is involved in the mechanisms of resistance to CMV in the cv. Americano. There was no difference in chitinase isoform patterns between the two pepper cultivars analyzed. After IEF of the IF proteins, one acidic chitinase isoform was detected. Native-PAGE separation of the IF showed one band (M_r 30 kD) with chitinase activity. Chitinase activity was not detected in the INTRA-F of either cultivar.