Susceptible Cvs Research Articles

The maintenance of photosynthetic electron transport in relation to osmotic adjustment in durum wheat cultivars differing in drought resistance

The relationships between photosynthesis and osmotic adjustment (OA) under water stress are not yet well understood. Therefore, a possible association between the quantum yield of photosynthetic electron transport at the Photosystem II level ( Φ PSII) and OA was evaluated in drought-stressed durum wheat plants in this paper. Four cultivars (cvs) differing in the degree of drought resistance as estimated by the Φ PSII maintenance, were grown in a growth chamber under two different water stress cycles; in both cases two stress intensities (moderate and severe) were used. Leaf water potential ( Ψ W), osmotic potential at full turgor ( Ψ π100 ), Φ PSII and the efficiency of excitation capture by open Photosystem II reaction centres (EC PSII) were determined in the different experimental conditions, both in control and stressed plants. Φ PSII and EC PSII were evaluated by in vivo chlorophyll fluorescence analysis. Φ PSII showed a significant decrease only under severe water stress and for the drought susceptible cvs; on the other hand, EC PSII showed no change under the different water stress conditions. The percent decrease of Φ PSII under water deficit was confirmed to be a good indicator of drought resistance in durum wheat. OA was estimated as the difference in the Ψ π100 between leaves from water-stressed and well-watered plants. No relationship between the maintenance of the Φ PSII and OA under water deficit was observed in the adopted experimental conditions; this result is discussed in the light of the contrasting evidence in the literature.

Effects of cucumber genotype on the induction of resistance to powdery mildew, Sphaerotheca fuliginea, by 2, 6‐dichloroisonicotinic acid

Conspicuous differences in inducibility of resistance to powdery mildew between susceptible and partially resistant cucumber cultivars were found when 2, 6‐dichloroisonicotinic acid (INA) was used as a model substance. In the partially resistant cv. Flamingo, EC50 was approximately 0·25 mg/1. In the susceptible cvs Corona and Lange Groene Gigant it was approximately 6mg/1. In greenhouse experiments with cv. Flamingo, powdery mildew could be well controlled with fortnightly applications in doses as low as 0·5 mg/1. The effect was highly cumulative.

Relative susceptibilities of eleven potato cultivars and breeders' clones toGlobodera pallida pathotype Pa 3, with a discussion of the interpretation of data from pot experiments

Curves according to the equationPf=M′ (1-e −aPi/M′ ) fitted well to the relations according to Seinhorst's (1993) modelPf=y e y h M(1-e −aPi/M ) between initial egg densities of potato cyst nematodes (Globodera rostochiensis, G. pallida)Pi up to 5T h (T h =the tolerance limit of haulm weight) andPf at the end of the growing season (a=maximum rate of reproduction,M, M′=different theoretical maximum egg densities). Variation of estimates ofM′, due to variation of the parameters of the submodelsy e andy h for the effect of weight reduction of haulms (and, therefore, of roots) on cyst production and damage to root tissue on egg production, respectively, was small enough to be ignored relative to experimental error. Therefore, ratios of values ofM′, determined in simultaneous pot experiments with different potato cultivars, are reliable measures of the relative host status of these cultivars at initial egg densitiesPi of these nematodes up to about 5T h . Variation between potato cultivars of growth reduction and damage to root tissue by the nematodes reduces the reliability of ratios of rates of relative susceptibility of these cultivars. The ratios between the maximum rates of reproduction ofG. pallida, pathotype Pa 3, on 8 out of 9 cultivars and one breeder's clone of potatoes and this rate on the susceptible cvs Bintje and Irene (relative susceptibilitiesrs a ) could be considered to be equal to the ratios of maximum population densitiesM′ on these cultivars (relative susceptibilitiesrs M′ ) (relative susceptibilities independent of initial egg density). The latter ratios were 0.59 times the first (relative susceptibilities negatively correlated with initial egg density) in one cultivar and one breeder's clone. Relative susceptibilitiesrs a andrs M′ of the tested cultivars and breeders clones suggest the existence of continuous ranges of both relative susceptibilities between 0.50 and 0.15 with, in a great majority of cases,rs a =rs M′ .

647 PB 413 REACTION OF POTATO CV. BELRUS TO INFECTION WITH POTATO LEAFROLL VIRUS

Potato leafroll virus (PLRV) is a serious aphid transmitted virus disease of potato (Solanum tuberosum L.). Field observations suggest that the cv. BelRus is tolerant to PLRV. Greenhouse grown BelRus and PLRV susceptible potato cvs. Green Mountain and Katahdin were tested for PLRV with enzyme linked immunosorbant assay (ELISA) and subsequently infested with PLRV infected green peach aphids (Myzus persicae). ELISA was used to test leaves from the top, middle and bottom portion of the plants at 7 day intervals beginning 7 days after aphid infestation. PLRV was detected in all tested locations of the Green Mountain and Katahdin plants 21 days after inoculation. In BelRus, throughout the 11 week test, PLRV was detected predominantly in the top portion of the plants and at low titres. These results suggest that tolerance to PLRV infection in the cv. BelRus may be due to suppression of virus replication.

Susceptibility of Cut Rose Flower Cultivars to Infections by Different Isolates of Botrytis cinerea

AbstractA method was developed for the inoculation of flowers of cut roses with conidia of Botrytis cinerea. Flower buds were inoculated by spraying of conidial supensions that were ultrasonicated for 10 s. The differences in susceptibility between 8 rose cvs to infections of isolate Bc‐33 and the differences in pathogenicity between 14 5. cinerea isolates to cv. ‘Sonia’ were evaluated. Isolates obtained from rose flowers caused higher infection rates than those obtamed from various other hosts. The CVS ‘Madelon’, ‘Melody’ and ‘Sonia’ were found to be highly susceptible, whereas the cvs ‘Caramboie’, ‘Gabriella’, ‘Pasadena’ and ‘Rubinette’ were only slightly susceptible. The lower disease severity in the less susceptible cvs was based on a retardation of the growth of mfection hyphae in the petals, which may have been due to partial resistance. The formation of symptoms is effectuated already by the initial stages in the infection process. Thus, the apparent existing partial resistance to infections of B. cinerea cannot prevent the loss of ornamental value.

Identification of a constitutive 45 kDa soluble protein associated with resistance to downy mildew in muskmelon ( Cucumis melo L.), line PI 124111 F

Analysis by sodium dodecylsulphate-polyacrylamide gel electrophoresis of the soluble proteins extracted from muskmelon ( Cucumis melo L.), inbred line PI 124111F (PI) with resistance to Pseudoperonospora cubensis (Berk, et Curt.) Rost, and two susceptible cvs, Hemed and AnanasYokneam revealed the presence of a unique 45 kDa protein (P45) in the resistant but not in the susceptible plants. Subcellular fractionation indicated that P45 is a cytoplasmic soluble protein. It was detected in leaves and cotyledons but not in stems or roots. F 1 hybrid plants (Hemed × PI) that displayed only a partial resistance against P. cubensis expressed P45 at an intermediate level, whereas plants of the inbred generations F 5, F 7 and F 10 that displayed a high degree of resistance, expressed P45 at a level similar to the parental PI. Back-cross progeny plants [(Hemed × PI) × Hemed] segregate 1:2:1 partially resistant: susceptible: highly susceptible to the disease. The partially resistant plants showed an intermediate level of P45 (similar to F 1) whereas the highly susceptible plants had no P45, thus indicating cosegregation of P45 with resistance. The resistance of PI to P. cubensis was found to decrease at a colonization temperature of 12 °C. 35S-methionine in vivo protein labelling revealed a reduction in the intensity of the P45 band in plants incubated for 11 h at 12 °C. The application of P45 in breeding programs of muskmelon for downy mildew resistance and its possible involvement in resistance to P. cubensis are discussed.

Cellulase production in varied crucifer seedlings having susceptible and resistant response towards Xanthomonas campestris pv. campestris (Pammel) Dowson.

Summary The bacterium, Xanthomonas campestris pv. campestris through its presence and activity effects a different cellulase (Cx) production during 15- to 19-days of host-pathogen interplay in the leaf tissues of the seedlings of susceptible cauliflower cvs. ‘Dania’, ‘Pusi’ and ‘Pusa Deepali’. In the leaves of mustard variety ‘Baruna’ and Kohlrabi variety ‘Early Vienna’ lesser amount of cellulase was secreted than in the cauliflower cvs. In the leaves of inoculated seedlings of restistant mustard cv. ‘Yellow’ and Kohlrabi cv. ‘Earliest White’ a very low amount of this enzyme was produced, being much less than that found in suscepts. Similarly in inoculated seedling leaf tissues of resistant cauliflower cv. ‘Snowball’ insignificant amount of cellulase elaboration was discernible. Thus cellulase activity has some significance in pathogenicity and disease development in crucifers invaded by X. campestris pv. campestris .

Organic nitrogen metabolism of crucifer seedlings in relation to their responses towards Xanthomonas campestris pv. campestris

Summary Diminution or increase in the amount of protein in the tissue extracts of bacterium-inoculated crucifer seedlings was parallel to the enhanced or diminished protease activities. The invariable loss or occasional accretion of amino acid constituents in such tissues were irrespective of the utilization or build up of protein. Breakdown of protein, enhanced protease activity and concurrent accumulation of amino acids in excess of that nutritionally utilized by the bacteria were detected in root, stem and leaf tissue extracts of susceptible cauliflower cvs. “Dania”, “Pusi”, “Pusa Deepali”, Kohlrabi cv. “Early Vienna” and mustard cv. “Baruna” after 7, 9, 11, 13 and 15 days of infection of Xanthomonas campestris pv. campestris. Exclusive amino acids present during susceptible response alone, were leucine/isoleucine (cauliflower cv. “Pusa Deepali”), serine (cauliflower cv. “Pusi”; mustard cv. “Baruna”) and proline (Kohlrabi cv. “Early Vienna”). Protein accumulation invariably occurred in the root, stem and leaf tissue extracts of the seedlings of resistant cauliflower cv. “Snowball”, Kohlrabi cv. “Earliest White” and mustard cv. “Yellow” at different stages (7, 9, 11, 13 and 15 days) of host-bacterium interaction. There was a concomitant accretion of certain exclusive amino acids as well. These were valine, tyrosine, tryptophan, β-phenyl-alanine and asparagine. However, there were some amino acids namely γ-aminobutyric acid, β-alanine, dl-alanine, glycine and threonine, which accumulated in the tissues of the crucifer seedlings having either susceptible or resistant response.

The complementary effects of plant resistance and reduced pesticide dosage in field experiments to control the turnip root fly, Delia floralis, in swedes

SummaryThe integration of different doses of chlorfenvinphos with plant resistance to different levels of Delia floralis attack in swedes was investigated at Saerheim Research Station in field experiments during 1987, 1988 and 1989. The indices of damage and grade 1 yields indicated different levels of resistance ranging from the partially resistant cvs Melfort, Angus and Vige down to the susceptible cvs Gry and Ruta. The relative resistance of the cvs changed with increasing levels of damage. Cvs Melfort and Angus were consistently the most resistant, while the resistance of Vige seemed to break down at high levels of attack. At these levels and in the absence of chemical treatment Gry was as resistant as Melfort and Angus. At the lowest level of attack, the resistance alone gave satisfactory control with Melfort, Angus and Vige. A half dose of chlorfenvinphos was sufficient to protect Melfort and Angus at higher levels of attack. Damage levels recorded in October showed that the different cultivars expressed widely different levels of resistance to D. radicum than to D. floralis.

Effect of rust infection on levels of uricase, allantoinase and ureides in susceptible and hypersensitive bean leaves

The enzymatic activities involved in two sequential steps of purine catabolism and ureide biosynthesis, i.e. uricase, catalase and allantoinase, were determined in susceptible and hypersensitive bean leaf tissue after infection with Uromyces phaseoli. Uricase increased to approx. two times more than the control value 20–22 h after inoculation of the hypersensitive cv. K.W. 765 (reaction grade 2 ++) close to pathogen penetration and first haustoria formation and, 1 day later, in the susceptible cvs Golden Gate Wax, Pinto 111 (reaction grade 6) and in the hypersensitive cv. K.W. 814 (reaction grade 1). Afterwards, the highest increases in uricase activity (up to 10 times the control), mainly localized in fractions of leaf homogenate sedimenting at 2000 g and 15000 g , were detected in c.v. K.W. 765 during lesion development, indicating that a peroxisome-associated enzyme was involved. Lower increases (up to two to three times the control) were observed in the susceptible cultivars during stroma differentiation (flecks) and uredospore formation. Catalase linked to the particulate fractions increased in susceptible cultivars to the same extent as uricase from 2 to 6 days after inoculation. Also in cv. K.W. 765 it increased during lesion development, but very much less than uricase, with the consequence that a possible toxic action, due to unscavenged H 2O 2 production, could arise during hypersensitivity expression. An enhancement of allantoinase two or three times the control values during stroma differentiation was detected in susceptible cultivars. By contrast, allantoinase activity was unchanged during local lesion formation in cv. K.W. 765, indicating that the activation of this enzyme is specifically involved during the establishment of a biotrophic relationship between Phaseolus vulgaris and Uromyces phaseoli. In the susceptible cultivar, an increase in allantoic acid during the late stages of infection (uredospores differentiation) was observed. Both allantoin and allantoic acid were enhanced during lesion development in the hypersensitive cultivar. The results are consistent with the interpretation that the enhanced purine catabolism in rust-infected bean leaves is connected both to a nutritional benefit for the parasite in the compatible relationship, and to a toxic effect for the host in the incompatible one.

The Effect of Different Planting Dates on the Infestation of Soybean by Heterodera glycines Race 5

The effects of different planting dates on infestation of susceptible soybean cvs. Essex and Lee by Heterodera glycines were investigated during three growing seasons. Early planting dates of susceptible soybean cvs. at lower temperatures resulted in smaller nodules, lower nematode populations and field infestations, lower soybean cyst nematode (SCN) disease ratings, taller plants, and higher yields. SCN induced more nodules on soybean roots at 14 May plantings date. The development of SCN race 5 in the field was associated closely with soil temperature. The infestation of susceptible soybean cvs. at early planting dates by H. glycines greatly affected the agronomic performance of these cvs. in the field. Susceptible soybean cvs grown in infested soil with SCN race 5 planted earlier than the recommended planting dates escaped severe infestation of SCN in the field.

Effect of light duration and growth season on verticillium wilt in potato

The tolerance response to Verticillium in potato is affected by external abiotic and biotic factors. Short-day photoperiod enhanced disease level in the susceptible cvs. ‘Nicola’ and ‘Maris Bard’, as well as in the tolerant cvs. ‘Cara’ and ‘Desiree‘. This was observed under field conditions, where plant reaction in the spring was compared with that in autumn. In some cases the disease was more pronounced in autumn, with its shorter days, than in spring, when the days are longer. The effect was measured by disease symptom severity, fungus colonization in the plants, plant height and final yield. This disease enhancement was more pronounced under controlled growth room conditions, where the only different parameter was illumination. A short photoperiod of 8 h increased the disease level relative to 16 h of light.

Reactions to a verticillium dahliae phytotoxin in tissue cultures derived from susceptible and tolerant potato

Tissue cultures of potat ( Solanum tuberosum L.) have been used successfully to determine host-specific properties of a Verticillium dahliae phytotoxin (Vd toxin) which was partially purified from culture fluids of a fungal isolate pathogenic for potato. The Vd toxin, at concentrations of 5 μg/ml and above, significantly reduced ( P = 0.05) the viability of suspension cells from the disease susceptible cvs. Blanka and Russet-Burbank but not those obtained from the tolerant cv. Alpha. The lethal effect was concentration dependent ( P = 0.01) and increased with time, but cells of cv. Alpha were not killed by any concentration tested. The differential effect on root cultures was similar. The fresh weight of sterile plantlets from cv. Russet-Burbank was markedly reduced ( P = 0.001), compared to that of cv. Alpha, after 30 days in the presence of Vd toxin. A bioassay test was developed, based on the inhibition of growth of cultured potato roots, to assess the relationship between the Vd toxin and the stunting effect in V. dahliae-infected plants. The toxin killed 95% of susceptible root tips (cv. Blanka), while roots from the tolerant cvs. (Desiree and Alpha) were unaffected ( P = 0.01). However, when the toxin was incubated with protoplasts or calli of the susceptible cv. Blanka or diseass tolerant cvs. Alpha and Spunta, no difference was observed among the cultivars. The results indicate that bioassays using suspension cells, sterile plantlets or root cultures are comparable and reliable for the detection of Verticillium with tolerance.

Influence of NaCl Salinity on Growth and Metabolic Status of Protein and Amino Acids in Rice Seedlings

AbstractSeeds of four rice cultivars differing in salt tolerance when grown under increasing level of NaCl salinity and seedling vigour as well as metabolic status of total and soluble proteins, amino acids were evaluated in seedlings at increasing days of growth it was observed that increasing level of salinity caused loss in dry wt. of seedlings as well as reduction in lengths of root and shoot. In both sets of cultivars salt stressed seedlings showed higher levels of total as well as soluble proteins, total amino acids compared to non salinized seedlings. In roots of salt susceptible cvs. Ratna and Jaya increased salinity up to 14 mmhos/cm remarkably increased total as well as soluble protein level whereas in shoots moderate level of salinity increased protein level compared to controls and higher salinity level caused suppression in such increase. Tolerant cultivars always maintained higher levels of total as well as soluble proteins and total amino acids in salt stressed seedlings compared to susceptibles. Amino acids which accumulated greatly in salinized seedlings were arginine, phenylalanine, alanine, leucine, proline, valine and glutamine. Results suggest possible role of proteins and amino acids in confering salt tolerance in rice.

Field screening for resistance to barley net blotch

SUMMARYInoculation with barley net blotch from infested straw debris was compared with that from diseased plants after sowing infected grains. The straw debris had a high, uniform inoculation potential which gave an early, continuing infection and easily reproducible results that were effective for screening barley cultivars in the field for resistance against a natural population of the pathogen. Further, it minimises an eventual influence from other leaf pathogens coming from the surroundings.Irrigation was decisive for the success of the method ‐ especially in the initial phase. Ten m separation with an immune crop was insufficient to completely prevent infection in the uninoculated plots.The tested 25 cvs were differentiated in six categories of resistant and susceptible on the basis of disease development and final level of attack. None of them was free of symptoms. The most resistant cvs kept a constant, low level of attack during the whole growing season, whereas the most susceptible cvs showed an early and rapidly increasing attack. Intermediate cvs were characterised with more or less slow increase of the attack. The size and proportion of the brown necrotic spots and the surrounding yellow halo varied greatly from one cultivar to the other.The grain yield reduction was due solely to an effect on the thousand grain weight which decreased linearly with the squared point score for net blotch. Further, the disease affected the quality of the grains as less nitrogen was transported from straw to grain in the severely diseased plants.

Tolerance of white bean ( Phaseolus vulgaris) to white mold ( Sclerotinia sclerotiorum) associated with tolerance to oxalic acid

The growth of Sclerotinia sclerotiorum in white beans ( Phaseolus vulgaris) was much slower in the tolerant cv. Ex Rico-23 than in the susceptible cvs. Kentwood and Seafarer. The difference was paralleled by the rate of diffusion in leaf tissue of oxalic acid, a phytotoxin of the white mold fungus ( Sclerotinia sclerotiorum). Uptake of oxalic acid into excised leaves through the petiole resulted in more severe brown-rot-like symptoms in the leaves of cv. Kentwood than in those of Ex Rico-23. When [ 14C] oxalic acid was fed through petioles, radioactivity in the interveinal tissue of Kentwood was about three times higher than that in Ex Rico-23. Autoradiographs of leaves showed that radioactivity in Ex Rico-23 was confined to major veins and that activity in the interveinal tissue was low, whereas in Seafarer and Kentwood radioactivity did not accumulate in the veins but was distributed uniformly throughout the leaf tissue, with a slight accumulation along leaf margins.

Studies on host-specific AF-toxins produced by Alternaria alternata strawberry pathotype causing alternaria black spot of strawberry. 1. Production of host-specific toxins and their biological activities.

The causal pathogen of Alternaria black spot of strawberry was identified as a distinct pathotype of Alternaria alternata (Fries) Keissler. Only one strawberry cultivar Morioka-16 was susceptible to the pathogen. Several cultivars of Japanese pear including Nijisseiki which were susceptible to A. alternata Japanese pear pathotype were also diseased by this pathogen. This fungus produced at least three species of host-specific toxins (named AF-toxin I, II and III, respectively). AF-toxin I and II were considered the major toxins. AF-toxin I induced necrosis and potassium leakage on the susceptible cvs. Morioka-16 and Nijisseiki. AF-toxin II induced only potassium leakage from cv. Morioka-16 but did not induce necrosis. AF-toxin II as well as AF-toxin I caused necrosis and potassium leakege from the cv. Nijisseiki.

Effect of Soybean Mosaic Virus on Root Volume and Dry Weight of Soybean Plants1

The effect of soybean mosaic virus (SMV) on root volume and dry weight of soybean [Glycine max (L.) Merr.] seedlings was determined in two environments (greenhouse and controlled environment chamber). Root volume of susceptible cvs. ‘Bragg’ and ‘Tracy’ was reduced up to 61% 30 days after 10‐day‐old seedlings were inoculated. The reduction in dry weight of roots and top portion of Bragg and Tracy seedlings ranged from 38 to 59%. Root volume of D73‐7725 (resistant) was reduced 18% by SMV when the plants were grown in a controlled environment chamber but was not reduced in the greenhouse environment.

Cercospora oryzae . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Cercospora oryzae . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Oryza saliva . DISEASE: Narrow brown leaf spot of rice. The fungus has been reported on Panicum repens ( Plant Disease Reporter 54: 272, 1970). The linear leaf lesions are 2-10 mm long, usually up to 1-1.5 mm wide, the long axis parallel to that of the leaf; centre dark brown with the border fading as the outer margin is reached. Lesions on the sheath are similar to those on the leaf, whilst those on the glumes are shorter and tend to lateral spread. On susceptible cvs. the leaf lesions are wider and lighter brown whereas on resistant ones they are narrow and a more uniform dark brown. Symptoms are usually extensive during the later stages of growth and should not be confused with those caused by Ramularia oryzae Deighton & Shaw (white leaf streak; 40, 104). GEOGRAPHICAL DISTRIBUTION: Widespread in the tropics and S. and S.E. USA (CMI Map 71, ed. 3, 1967). TRANSMISSION: No studies reported.

Inheritance and linkage relations of reaction to Xanthomonas phaseoli (E. F. Smith) Dowson (common blight), stage of plant development and plant habit in Phaseolus vulgaris L.

The inheritance of the reaction to Xanthomonas phaseoli (E. F. Smith) Dowson Nebraska isolate Xp-816, cause of common blight disease of beans Phaseolus vulgaris L. was studied in crosses between the late flowering, indeterminate, blight tolerant dry bean PI 207262 (Colombia) and susceptible cvs. GN 1140, an early flowering and indeterminate dry bean; Dark Red Kidney, a late flowering and determinate dry bean; and Gallatin 50, an early and determinate green bean. The tolerant disease reaction was dominant in the F1. A continuous distribution of disease reaction ratings, skewed in the direction of dominance, occurred in the F2 derived from the first 2 crosses while a slight bimodal distribution was observed in the F2 of the last cross. A low narrow sense heritability estimate of 14% was calculated by the regression of F3 progeny means on individual F2 plants, in the cross GN 1140×PI 207262. The occurrence of a small number of nonsegregating families in a low number of F3 families indicates that a small number of major genes were involved in controlling the disease reaction. Linkage did not appear to be involved between genes controlling early flowering (early maturity) and common blight tolerance. Coupling linkage occurred between genes controlling determinate plant habit and early flowering. A crossover value of 8.4% was estimated. Recombinants for early maturity, determinate habit, and blight tolerance were obtained. Transgressive segregation for early flowering and common blight susceptibility occurred in progeny derived from the cross of the two late-flowering blight tolerant lines, PI 207262 and GN Nebraska 1, sel. 27, indicating that the parents possessed different genes controlling these traits.