Cell Wall-Bound Phenolic Acid and Lignin Contents in Date Palm as Related to its Resistance to Fusarium Oxysporum

The root cell walls of the resistant cultivars of the date palm were more resistant to the action of the cell wall-degrading enzymes (CWDE) of Fusarium oxysporum f. sp. albedinis than those of the susceptible cultivars. Date palm roots contain four cell wall-bound phenolics identified as p-hydroxybenzoic acid, p-coumaric acid, ferulic acid and sinapic acid. The contents of p-coumaric acid and ferulic acid in the resistant cultivars (IKL, SLY, BSTN) were about 2 times higher than those in the susceptible cultivars (BFG, JHL, BSK). The contents of p-hydroxybenzoic acid and sinapic acid in the resistant cultivars were 8.4 and 4.5 times, respectively, higher than those in the susceptible cultivars. The lignin contents in roots of the resistant cultivars were 1.8 times higher than those of the susceptible cultivars. The cell wall-bound phenols accumulated particularly in resistant cultivars reduced strongly the mycelial growth and the CWDE production in vitro.     

Constituents of soybean cultivars differing in insect resistance

Leaf samples of two insect-resistant plant introductions (PI 227687 and PI 229358) and two susceptible (Ransom and Coker Hampton 266A) cultivars of soybeans, Glycine max, were analyzed at different growth stages for their contents of total nitrogen, carbohydrates, organic acids, and sterols. The two susceptible cultivars accumulated more total nitrogen and at a faster rate than did the two resistant plant introductions. At pod-filling, the two resistant cultivars had equivalent soluble carbohydrates and 33% more than the susceptible cultivars. The quantity of organic acids was essentially the same for the two susceptible cultivars. The resistant cultivars had distinctly different quantities from each other as well as from the susceptible cultivars. The quantity of total sterol of these soybean cultivars varied during the growth of the plant. The resistant cultivars accumulated sterol faster and by pod-filling contained from 20 to 50% more sterol than did the susceptible cultivars.     

Changes in Cell Wall-bound Phenolic Compounds and Lignin in Roots of Date Palm Cultivars Differing in Susceptibility to Fusarium oxysporum f. sp. albedinis

The roots of date palm contain four cell wall‐bound phenolic acids identified as p‐hydroxybenzoic, p‐coumaric, ferulic and sinapic acids. The ferulic acid represents the major phenolic compound since it constitutes 48.2–55.8% of cell wall‐bound phenolic acids. All these phenolic acids were present in the resistant cultivar (BSTN) and the susceptible cultivar (JHL). However, the pre‐infection contents of p‐coumaric, ferulic and sinapic acids were greater in the resistant cultivar than in the susceptible one. For the contents of p‐hydroxybenzoic acid, there was no significant difference between the resistant cultivar and the susceptible cultivar. Similarly, the pre‐infection contents of lignin were approximately equal for both cultivars. Inoculation of the date palm roots by Fusarium oxysporum f. sp. albedinis induced important modifications to the contents of the cell wall‐bound phenolic compounds and lignin, which made it possible to distinguish between resistant and susceptible cultivars. The post‐infection contents of cell wall‐bound phenolic compounds underwent a rapid and intense increase with a maximum accumulation on the tenth day for p‐hydroxybenzoic acid (1.54 μmol/g), p‐coumaric acid (2.77 μmol/g) and ferulic acid (2.64 μmol/g) and on the fifteenth day for sinapic acid (1.85 μmol/g). The maximum contents accumulated in the resistant cultivar were greater than those in the susceptible cultivar, namely, 11 times for p‐hydroxybenzoic acid, 2.6 times for p‐coumaric acid, 1.8 times for ferulic acid and 12.3 times for sinapic acid. In the susceptible cultivar, p‐coumaric acid and ferulic acid contents also increased after inoculation although they did not reach the pre‐infection contents of the resistant cultivar. The contents of p‐hydroxybenzoic acid in the susceptible cultivar roots did not present post‐infection modification and those of sinapic acid decreased instead. The lignin contents increased in both cultivars with a maximum accumulation on the fifteenth day. However, the maximum contents accumulated in the resistant cultivar roots were 1.5 times greater than those of the susceptible cultivar. These results showed clear differences between the resistant BSTN and the susceptible JHL cultivars. The implication of cell wall‐bound phenolic compounds and lignin in the resistance of date palm to F. oxysporum f. sp. albedinis appears to be dependent on the speed and intensity of their accumulation with greater contents in the first stage of infection.     

Wyerone Acid Phytoalexin Synthesis and Peroxidase Activity as Markers for Resistance of Broad Beans to Chocolate Spot Disease

Infection of broad bean (Vicia faba L.) leaves with Botrytis fabae (Sard.) resulted in wyerone acid phytoalexin accumulation and increase in peroxidase activities in resistant and susceptible broad bean cultivars. Rapid wyerone acid accumulation was observed in leaves of resistant cultivars that reached levels greater than twofold of the susceptible cultivars. Following infection of broad bean cultivars, either resistant or susceptible to B. fabae, wyerone acid synthesis in resistant cultivars peaked at 5 days then declined, whereas in susceptible cultivars synthesis gradually decreased. While the ethanol‐extract of wyerone acid significantly reduced B. fabae spore germination with increased concentrations, the phytoalexin had no effect on in vitro B. fabae germ‐tube growth. Peroxidase activity in infected leaves of resistant was 10 times higher than the susceptible cultivars and eight times higher in uninfected leaves of the resistant than the susceptible cultivars. Peroxidase activity in infected leaves was greater than twofold in resistant cultivars and less than twofold in susceptible cultivars, when compared with uninfected leaves. The ratio of peroxidase activity in infected to uninfected leaves increased over time in susceptible cultivars but remained unchanged in resistant cultivars. Peroxidase activity in uninfected and infected leaves and wyerone acid biosynthesis in infected broad bean plants were successfully used to ascertain the resistance and susceptibility of four broad bean cultivars to B. fabae. Using wyerone acid synthesis and peroxidase activity as preliminary markers for resistance of broad bean to chocolate spot disease, caused by B. fabae, is suggested in this study.     

Assimilatverteilung in Sommergerstensorten mit unterschiedlicher Resistenz gegenüber dem Echten Mehltau (Erysiphe graminis f. sp. hordei)

Distribution of assimilates in cultivars of spring barley with different resistance against powdery mildew (Erysiphe graminis f. sp. hordei) Transport and distribution of radioactive labelled assimilates in spring barley cultivars with different degrees of resistance to powdery mildew were studied after ¹⁴CO₂-treatment of single leaves. Plants of the cultivars ‘Amsel’ (susceptible), ‘Asse’ (adult plant resistant), and ‘Rupee’ (resistant) were analyzed at the vegetative growth stage (5. leaf unfolded) and the generative growth stage (anthesis). At the vegetative growth stage the assimilate export from the mildew inoculated 5. leaf of ‘Amsel’ and ‘Rupee’ is decreased; in ‘Asse’, there is no considerable change of assimilate distribution due to infection. At the generative growth stage the assimilate export from the infected flag leaf of ‘Amsel’ is reduced when the fungus, is sporulating. In the cultivar ‘Asse’ the assimilates are bound at the infection site until the seventh day after inoculation, then the transport of assimilates to the ear is increased. In ‘Rupee’ mildew inoculation causes an enhanced assimilate transport to the ear. The changes in assimilate distribution due to mildew inoculation are discussed with respect to the different types of host-parasite-interactions and the source-sink-activities in the different cultivars.     

Contrasting acclimation mechanisms of berry color variant grapevine cultivars (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L. cv. Furmint) to natural sunlight conditions

The acclimation mechanisms of two berry color variant grapevine leaves, Furmint White (FW) and Furmint Red (FR), to natural sunlight conditions were investigated comparing leaves from two distinct locations: at canopy surface (sun-exposed leaves) and in the inner layers (shaded leaves). We found that in contrast to FR leaves, sun-exposed FW leaves were thicker than shaded leaves due to thicker palisade tissues. Confocal laser scanning microscopy of Naturstoff-treated leaf segments revealed that flavonoids were accumulated in nuclei, cell walls, cytoplasm, and chloroplasts of the adaxial epidermal and palisade layers of sun-exposed leaves in both cultivars. High-performance liquid chromatography analysis showed that the main phenolic components in both cultivars were caftaric acid and various glycosylated flavonols. Among the latter, the dominant component was quercetin glucuronide in both cultivars, unaffected by light conditions. However, caftaric acid and quercetin glucoside were present in significantly higher amounts in sun-exposed than in shaded leaves of both cultivars, but the effect of light conditions on caftaric acid contents was more pronounced in FR than in FW. Accordingly, the total polyphenol content of leaf extracts characterized by Folin-reagent reactivity was more enhanced in sun-exposed leaves of FR, than in FW. Our data suggest two different sunlight acclimation strategies to protect photosynthetic mesophyll tissues from potential photo-oxidative damage. One is realized in FW leaves as stronger shading by thicker palisade layer accompanied by enhanced chemical defense. The other is achieved in FR leaves via a more pronounced increase in caftaric acid and total polyphenol content but without morphological adjustments.     

Zur Rolle des Pektins bei der Ausprägung sorten- und jahresbedingter Unterschiede der Naßfäuleanfälligkeit von Kartoffelknollen

The influence of soil moisture and mean day temperature of July to September on pectin structure and soft rot resistance of potato tubers was investigated. Tuber samples of middle early and middle late potato cultivars respectively were tested from 1976 to 1979. Cultivar characteristics as well as growth conditions effect the pectin structure. The tuber tissue of soft rot resistant cultivars contains relative high amounts of esterified pectin. The pectin esterification was promoted by drought during vegetation periods (1976, 1978). A late rise of metabolic activity caused by rainfall at the end of the vegetation period (1978) increased the amount of soluble pectin in the cell wall. This lack of pectin stabilization facilitates tissue maceration by soft rot bacteria. Increased pectin solubility was also caused by unfavorable storing conditions of potato tubers. A low degree of esterification and high solubility of the cell wall pectin affect the relative resistance of potato tubers against soft rot caused by Erwinia carotovora var. atro-septica (van Hall) Dye adversely.     

Differences in drought tolerance between cultivars of field bean and field pea. A comparison of drought-resistant and drought-sensitive cultivars

Relatively little research has been conducted to determine different responses to drought among cultivars of the legume species. The objective of this study was to identify differences in seedlings growth, water relations and leaf conductances resulting from drought imposed on two field bean and two field pea cultivars that had been observed to differ in their drought tolerances, and special emphasis was placed on the root system development. Distinct differences between resistant and sensitive cultivars of field bean and field pea became evident in measurements of the characteristics of the lateral root. The drought treatment induced statistically significant decrease in the number of the developed laterals, their total length and dry matter. In the drought resistant cultivars (field bean Gobo and field pea Solara) this reduction was smaller in comparison with sensitive ones (field bean Victor and field pea Bareness). The effect of drought on growth of tap root in the drought resistant and drought sensitive cultivars was smaller and statistically not significant. The results showed that drought resistant cultivars when compared with drought sensitive one would demonstrate less abundance in the above-ground part and greater dimensions of the root system. The measurements of leaf water potential and stomata diffusive resistance measurements indicate that the physiological reasons for the different reactions to drought between the resistant and the sensitive field bean and field pea cultivars may be due to a more effective protection of the level of tissue hydration and due to increase stomata diffusive resistance in the resistant cultivars. During recovery period it has been also demonstrated that in the drought resistant cultivars a tendency exists for a more complete return to the level of the control plants.     

Function of Host and Fungal Metabolites in Resistance Response of Banana and Plantain in the Black Sigatoka Disease Pathosystem (Musa spp. –Mycosphaerella fijiensis)

The host–pathogen interactions of Musa spp. and Mycosphaerella fijiensis were investigated in order to determine the function of secondary metabolites within the pathosystem of the Black Sigatoka disease. The pentaketide metabolites flaviolin, 2-hydroxyjuglone, juglone and 2,4,8-trihydroxytetralone (2,4,8-THT) of the pathogen were identified. The concentration of 2,4,8-THT was significantly increased by application of the synthetic compound tricyclazole and by natural activators extracted from the intercellular space of leaf tissue of resistant Musa cultivars. When inoculated host plants were treated with tricyclazole, extensive necrosis of both susceptible and resistant Musa cultivar leaves were observed. Plant defence mechanisms of resistant Musa cultivars were first detected as an activation of phenylalanine–ammonia lyase and the subsequent accumulation of post-infectional substances which blocked fungal growth. These results indicated the bivalent importance of 2,4,8-THT for host-specific reactions, depending on its concentration at different stages of pathogenesis. Early activation of fungal 2,4,8-THT metabolism by resistant Musa cultivars caused necrotic micro-lesions and elicitation of post-infectional defence reactions leading to incompatibility between pathogen and host plant; growth of the fungus on susceptible cultivars caused necrotizing doses of 2,4,8-THT only after the establishment of a compatible interaction and development of typical symptoms at late stages of pathogenesis.     

A Comparison of Soybean Agglutinin in Cultivars Resistant and Susceptible to Phytophthora megasperma var. sojae (Race 1)

The amount of soybean agglutinin (SBA) detectable by radioimmunoassay in seeds of resistant cultivars to Phytophthora megasperma var. sojae was approximately twice that of susceptible cultivars. SBA was preferentially released at earlier times (6-9 hours) and in higher amounts in the imbibate from resistant cultivars as compared to susceptible cultivars. The lectin in the imbibate was immunologically identical to the seed lectin, indicating little or no proteolysis had occurred, and was active in hemagglutination. Binding of fluorescein isothiocyanate-labeled SBA to mycelial cell walls could be abolished by adding N-acetyl galactosamine or galactose. Purified SBA at concentrations of 150 to 300 micrograms inhibited mycelial growth by 50%, and the imbibate from Govan (resistant) cultivar was more inhibitory than the imbibate from Shore (susceptible) cultivar. Removal of SBA from the imbibate by affinity chromatography abolished the inhibition of mycelial growth, but the inhibition could be recovered from the eluant containing lectin.     

Die Reaktion anfälliger und resistenter Gerstensorten auf pilzliche Krankheitserreger

Response to fungus pathogen in susceptible and resistant barley cultivars IV. Water- and dry matter content
The changes in dry matter- and water content dynamics in the root and shoots of barley infected with the fungus Erysiphe graminis f. sp. hordei Marchal were studied in variously receptive cultivars. Cultivation of plants in solid (perlite) or liquid medium was compared.
The response of susceptible barley to mildew infection is characterized at First by an increase in water content and slightly in dry matter of shoots accompanied with an unsignificant decrease in root growth. However, as the fructification progressed, barley growth is reduced in all investigated parameters. The infected resistant barley indicates unsignificantly increased values in water content of shoots, only.
In the susceptible host the growth of roots in relation to shoots is markedly reduced after infection.
The percentage of water content of shoots is slightly increased in both cultivars during the first phases of infection. Then, in susceptible barley it declines, compared with the control, from the stage of full developed fructification. In the resistant barley it doesn't change more expressively. In roots of infected plants the increased hydratation is found during the whole observation period (in the resistant barley only with plants growing in liquid medium).     

Activity and Differential Induction of Chitinase Isozymes in Soybean Cultivars Resistant or Susceptible to Root-knot Nematodes

Host physiological events in relation to infestation by parasitic nematodes are not well documented. Soybean plant responses to Meloidogyne incognita infestation were compared to resistant (Bryan) and susceptible (Brim) cultivars at 0, 1, 3, 10, 20, and 34 days after infestation (DAI). The resistant cultivar had higher chitinase activity than the susceptible cultivar at every sample time beginning at 3 DAI. Results from isoelectric focusing gel electrophoresis analyses indicated that three acidic chitinase isozymes with isoelectric points (pIs) of 4.8, 4.4, and 4.2 accumulated to a greater extent in the resistant compared to the susceptible cultivar following challenge. SDS-PAGE analysis of root proteins revealed that two proteins with molecular weights of approximately 31 and 46 kD accumulated more rapidly and to a higher level in the resistant than in the susceptible cultivar. Additionally, three major protein bands (33, 22, and 20 kD) with chitinase activity were detected with a modified SDS-PAGE analysis in which glycolchitin was added into the gel matrix. These results indicate that higher chitinase activity and early induction of specific chitinase isozymes may be associated with resistance to root-knot nematode in soybean.     

Rice callus physiology – Identification of volatile emissions and their effects on culture growth

Rice ( Oryza sativa L.) callus cultures modified the atmosphere of the headspace of the vessel used for culture maintenance by producing carbon dioxide, ethanol and ethylene, while utilizing oxygen. Small quantities of acetaldehyde and ethane were also measured in one cultivar. Under these conditions of culture maintenance, callus from some cultivars were much more difficult to keep alive than callus from others. The largest proportion of necrotic callus was produced from cultures growing under conditions of high ethylene production and low oxygen utilization. When callus was exposed to a controlled flowing gas mixture similar to that accumulated above necrotic callus, growth of 2 necrosis-susceptible cultivars was more strongly inhibited than growth of 2 necrosis-tolerant cultivars. The poor callus growth was associated with higher ethylene production and a lower rate of oxygen utilization.     

DNA marker analysis for pyramided of Fusarium head blight (FHB) resistance QTLs from different germplasm

A pyramided FHB resistance line of wheat (WSY) was previously developed from three FHB resistant cultivars (Sumai 3, Wangshuibai, and Nobeokabouzu) in the Jiangsu Academy of Agricultural Sciences, China. In the present study, we analyzed the genetic relationship between WSY and the three parental cultivars using DNA markers in order to clarify how many and which resistance genes had accumulated in WSY. We analyzed 282 DNA markers from the 21 wheat chromosomes. WSY was found to include different chromosome regions that harbored putative FHB QTLs of the three parental germplasm. Haplotypes of DNA markers on these QTL regions revealed that the 1BL, 2BL, 5AS, and 7AL QTL regions were from Sumai 3, the 2AS, 2DS, 3AS, and 6BS QTL regions were from Wangshuibai, and the 3BS QTL region was from Nobeokabouzu. This study showed that different resistance genes from the different resistant germplasm had indeed accumulated in WSY. WSY is a potential resistant resource for FHB resistance in wheat breeding programs.     

Amelioration of salinity tolerance in <Emphasis Type="Italic">Solanum tuberosum</Emphasis> L. by exogenous application of ascorbic acid

The present investigation envisaged revealing the role of exogenous application of ascorbic acid in increasing resistance against NaCl stress. Shoot apices from 60-d-old, in vitro-grown plants of two commercially important cultivars of Solanum tuberosum L., cvs. Desiree and Cardinal, were inoculated on Murashige and Skoog (MS) medium supplemented with 0.5 mM ascorbic acid for 72 h as a pretreatment. Pretreated and non-pretreated shoot apices were transferred to MS medium containing different concentrations of NaCl (0–140 mM; eight treatments). Results were recorded for morphological (shoot length, shoot number, root length, root number, and number of nodes) and biochemical features (protein, peroxidase, catalase, and superoxide dismutase activities) after 60 d of salt treatment. Similarly, 60-d-old, well-proliferated callus cultures were also pretreated with ascorbic acid for 24 h and transferred to an optimized callus proliferation medium containing different concentrations of salt. Results were recorded after 60 d of salt treatment for percentage relative fresh weight growth and biochemical parameters. Salinity severely inhibited all the growth parameters in both the cultivars. Pretreatment with ascorbic acid to both salt-treated plants and callus cultures showed significant differences with respect to almost all of the growth and biochemical parameters studied. Protein content as well as catalase and superoxide dismutase activities increased significantly in both the cultivars, although peroxidase activity showed a decreasing trend in ascorbic acid-pretreated plants as well as callus cultures.     

Detection of RAPD polymorphisms inGladiolus cultivars with differing sensitivities toFusarium oxysporum f. sp.gladioli

Fusarium oxysporum Schlecht. Fr. F. sp.gladioli (FOG) is the most important gladiolus pathogen. One of the most environmentally friendly methods to control its spread is to use cultivars that are minimally sensitive to the pathogen. Infected corm tissues in more resistant varieties have been shown to produce suberin layers that inhibit fungal iphae growth. RAPD analysis of genomes from 9 selected gladiolus cvs, chosen to be the most resistant and sensitive to FOG, were performed to verify DNA polymorphism levels. Total nucleic acid extraction was carried out with a chloroform-phenol method from tissues of plants in 3 growth stages. RAPD experiments were performed using 14 primers with varyingTaq polymerases and primer concentrations. Five of the primers tested gave no polymorphic profiles. Five primers produced polymorphic bands, allowing us to obtain RAPD profiles typical for one or more of the more resistant cvs. All the tested growth stages provided repeatable results, indicating the reliability of detected polymorphisms. Cloning the more interesting polymorphic DNA fragments in the future will verify the presence of specific genes related to FOG resistance mechanisms in gladiolus.     

Influence of Soil Temperature on Meloidogyne incognita Resistant and Susceptible Cotton,Gossypium hirsutum

The degree of resistance by a cotton plant to Meloidogyne incognita is affected by soil temperature, particularly in moderately resistant cultivars, The total number of nematodes in the resistant and moderately resistant rools at 35 C was equal to, or greater than, the number in susceptible roots at 20, 25, or 30 C. A shift in numbers to developing and egg-bearing forms of nematodes in the susceptible cultivar as tentperature increased indicates development was affected by temperature rather than by genetic resistance mechanisms. However, the nematode resistant cultivar did not support maturation of nematodes until a soil tempurature of 35 C was attained. This indicated that resistance mechanisms are partially repressed at 35 C and differences in nematode development cannot be explained in terms of accumulated heat units. The moderately resistant cultivar was significantly more sensitive to the effects of high temperature than was the resistant cultivar.     

Root Growth of Susceptible and Resistant Potato Cultivars and Population Dynamics of Globodera rostochiensis in the Field

Globodera rostochiensis population densities and potato root growth were measured in field plots of one susceptible and two resistant potato cultivars. Root growth and nematode densities were estimated from soil samples taken at three depths between plants within the rows, three depths 22.5 cm from the rows, and at two depths midway between rows (furrows). Four weeks after plant emergence (AE), nematode densities in the rows had declined 68% in plots of the susceptible cultivar and up to 75% in plots of both resistant cultivars. Significant decline in nematode densities in the furrows 4 weeks AE occurred only in plots of the susceptible cultivar. Total decline in nematode density in fallow soil was 50%, whereas in plots of the resistant cultivars, decline was more than 70% in the rows and more than 50% in the furrows. Nematode densities increased in the rows of the susceptible cultivar but declined in the furrows. We conclude that G. rostochiensis decline or increase is correlated with host resistance and the amount of roots present at any particular site.     

Comparative proteomic analysis of bacterial wilt susceptible and resistant tomato cultivars

To investigate the molecular mechanisms of bacterial resistance in susceptible and resistant cultivars of tomato, a proteomic approach was adopted. Four cultivars of tomato were selected on the basis of their response to bacterial (Pseudomonas solanacearum) inoculation wherein cultivar Roma and Riogarande, and cultivar Pusa Ruby and Pant Bahr were considered as resistant and susceptible cultivars, respectively. Proteins were extracted from leaves of 3-week-old seedlings of the four cultivars and separated by 2-DE. A total of nine proteins were found to be differentially expressed between the susceptible and resistant cultivars. Amino acid sequences of these proteins were determined with a protein sequencer. The identified proteins belongs to the categories of energy, protein destination and storage, and defense. Of these proteins, a 60 kDa chaperonin and an apical membrane antigen were significantly upregulated in resistant cultivars compared with susceptible cultivars. Application of jasmonic acid and salicylic acid resulted in significant changes in levels of apical membrane antigen and protein disulfide-isomerase. Taken together, these results suggest that apical membrane antigen might be involved in bacterial resistance process through salicylic acid induced defense mechanism signaling in tomato plants.