Glandular trichome exudate is the critical factor in geranium resistance to foxglove aphid

Resistance to the foxglove-aphid (Acyrthosiphon solani Kaltenbach) has been demonstrated in some inbred geranium lines (Pelargonium Xhortorum Bailey). To establish more definitively the cause/effect relationship between tall glandular trichome exudate and resistance, an intact plant bioassay was performed comparing a resistant plant line, a resistant plant line from which the tall glandular trichome exudate had been removed using a basic buffer solution, a susceptible line and a susceptible line treated with the buffer wash. After 5 days of isolation on the respective surfaces, the number of surviving adult aphids as well as the number of nymphs produced and remaining alive were determined. Aphids on the buffer washed, resistant line exhibited mortality and fecundity which was not significantly different from that produced by the susceptible line. In contrast, the untreated resistance line was clearly resistant with lower adult survival and fewer living nymphs. The tall glandular trichome exudate must therefore be a critical factor in geranium resistance to the foxglove aphid.

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Zusammenfassung Widerstandsfähigkeit dem Fingerhut-Blattlaus (Acyrthosiphon solani Kaltenbach) gegenüber wurde in einigen durch Inzucht erzeugten Pelargonie-Linien (Pelargonium Xhortorum Bailey) gezeigt. Um das Verhältnis von Ursache und Wirkung zwischen dem hochgewachsenen glandulären Trichom-Exudat und Widerstandsfähigkeit genauer zu bestimmen, wurde eine Bio-Untersuchung an intakten Pflanzen unternommen. Dabei wurden eine widerstandsfähige Pflanzenlinie, eine widerstandsfähige Pflanzenlinie, von der das hochgewachsene glanduläre Trichom-Exudat durch eine basische Pufferlösung entfernt worden war, eine anfällige Linie und eine mit Pufferlösung behandelte Linie verglichen. Zwei erwachsene weibliche Blattläuse wurden fünf Tage durch ein engmaschiges Netz auf den zu untersuchenden dritten und vierten Knotenblättern eingesperrt. Bei jeder Pflanze wurde die Untersuchung an einem nichtbehandelten Blatt und an einem Blat, von dem das Exudat durch Waschen mit der Pufferlösung entfernt worden war, durchgeführt. Für jede Linie wurden fünf Pflanzen gebraucht, und der ganze Versuch wurde sechsmal wiederholt. Nach einer fünftägigen Isolierung auf den jeweiligen Oberflächen wurden die Blätter von der Pflanze entfernt, und sowohl die Zahl der überlebenden erwachsenen Blattläuse wie auch die der produzierten und noch am Leben gebliebenen Nymphen festgestellt. Mit einer niedrigeren Überlebensrate der Erwachsenen und weniger noch lebenden Nymphen war die nichtbehandelte widerstandsfähige Linie deutlich widerstandsfähig. Im Gegensatz dazu zeigten die Blattläuse auf der mit Puffer gewaschenen widerstandsfähigen Linie eine Sterblichkeit und Fruchtbarkeit, die nicht erheblich höher waren, als die auf der anfälligen Linie, was beweist, daß das Waschen mit der Pufferlösung den Widerstandsfaktor entfernt hatte. Das hochgewachsene glanduläre Trichom-Exudat muß deshalb ein kritischer Faktor in der Widerstandsfähigkeit gegen Pelargonie-Schädlinge sein.

     

Regulation of seed number and female incitation of mate competition by a pH-dependent proteinaceous inhibitor of pollen grain germination in Leucaena leucocephala

Summary Leucaena leucocephala generally produces pods with more than 7–9 seeds. This is regulated by the stigmatic inhibition of pollen grain germination when the pollen grains are less than a critical number in the stigma. This number-dependent inhibition of pollen grain germination is effected by a pH-dependent proteinaceous inhibitor active at the stigmatic pH. Only when the pollen grains in the stigma exceed the critical number, they inactivate the inhibitor by collectively raising the stigmatic pH and thus overcoming the inhibition. The adaptive significance of such pre-fertilization mechanism for the female in inciting mate competition among the pollen grains is discussed. The evolution of en masse pollen grain dispersal units is explained as a sexual selection strategy by males in response to such stigmatic inhibition by females.     

Test of circular dichroism (CD) methods for crambin and CD-assisted secondary structure prediction of its homologous toxins

Methods that analyze protein circular dichroism (CD) spectra for fractions of secondary structure are evaluated for the plant protein crambin, which has a known high-resolution crystal structure. In addition, a two-step secondary structure prediction scheme is presented and used for the toxins homologous to crambin, shown by others to have secondary structures similar to crambin. The test of CD spectral analysis methods with the protein crambin employed two computer programs and several CD basis sets. Crambin's crystal structure, known to 0.945A resolution (Hendrickson, W.A., Teeter, M.M. Nature 290:107-113, 1981), allows accurate evaluation of results. Analysis with the protein spectra basis sets (Provencher, S.W., Gl?ckner, J. Biochemistry 20:33-37, 1981) as modified (Manavalan, P., Johnson, W.C., Jr. Anal. Biochem. 167:76-85, 1987) agreed most closely with crambin's crystal structure. This method was then applied to the CD spectra of the membrane-active toxins homologous to crambin (alpha 1- and beta-purothionin, phoratoxin A and B, and viscotoxin A3 and B). The new program SEQ (pronounced "seek") was developed to assign the secondary structure along the protein chain in a hierarchical fashion and applied to the plant toxins. The method constrained the secondary structure fractions to those from CD analysis and combined standard statistical methods with amphipathic helix location. Both CD-arrived secondary structure percentages and sequence assignment indicate that the viscotoxins are structurally most similar to crambin. Purothionin's secondary structure was predicted to be fundamentally similar to crambin's with a difference at the start of the first helix. This assignment agreed with Raman and NMR analyses of purothionin and lends validity to the method presented here. Differences from the NMR in the CD secondary structure fraction analysis for phoratoxin suggest interference in the CD from tryptophan residues.     

Survey of allergic respiratory symptoms in grain terminal workers in the Port of Genoa

Summary Fifty workers from two grain elevator terminals were examined to evaluate the prevalence of respiratory symptoms and their relationship with grain dust exposure.Fifty per cent of subjects complained of respiratory symptoms (rhinitis, asthma, chronic cough and dyspnea on exertion). In 34% of the workers the ventilatory function revealed some abnormalities (slight or moderate obstruction).Twenty-two (44%) showed a positive cutaneous reaction to one or more of the allergens tested, mostly towardsDermatophagoides and storage mites. The self-measurement of PEF over 14 days in 27 workers, showed significant differences between symptomatic and asymptomatic subjects. In particular, the results obtained from the cutaneous reactions could suggest a bronchial hypereactivity, worsened by the working exposure to dusts. The monitoring of PEF appears to be a simple and useful method for investigating the relationship between respiratory symptoms and the working environment.     

Leaf photosynthetic rate is correlated with biomass and grain production in grain sorghum lines

Significant genetic variation in leaf photosynthetic rate has been reported in grain sorghum [Sorghum biocolor (L.) Moench]. The relationships between leaf photosynthetic rates and total biomass production and grain yield remain to be established and formed the purpose of this experiment. Twenty two grain sorghum parent lines were tested in the field during the 1988 growing season under well-watered and water-limited conditions. Net carbon assimilation rates were measured at mid-day during the 30 day period from panicle initiation to head exertion on upper-most fully expanded leaves using a portable photosynthesis system (LI-6200). Total biomass and grain production were determined at physiological maturity. The lines exhibited significant genetic variation in leaf photosynthetic rate, total biomass production and grain yield. Significant positive correlations existed between leaf photosynthesis and total biomass and grain production under both well-watered and water-limited conditions. The results suggest that leaf photosynthetic rate measured prior to flowering is a good indicator of productivity in grain sorghum.     

Penicillium verrucosum in feed of ochratoxin A positive swine herds

Ochratoxin A contamination of cereal feed grain was monitored during October 1989–September 1990 by analysis of blood samples from slaughter swine in Sweden. The detection of ochratoxin A in swine blood was used as a method to identify swine herds fed ochratoxin A contaminated feed. The contamination level of ochratoxin A in the blood of the positive herds was in the range 2–45 ng/ml with the mean concentration 5.2 ng/ml. Feed samples for mycological analysis were collected from both ochratoxin A positive herds (2 ng/ml blood) and ochratoxin A negative herds (<2 ng/ml blood). From the ochratoxin A positive herds and the ochratoxin A negative herds 22 and 21 feed samples were collected, respectively. No quantitative differences in mould content, as determined by colony forming units, were observed between the two groups. However, there were differences in the mycoflora. The incidence of storage fungi (Penicillium and Aspergillus spp.) was significantly higher (p < 0.05) in feed from ochratoxin A positive herds. Particularly, Penicillium verrucosum was found to be significantly more common (p < 0.001). Altogether 274 isolates were screened for their ability to produce ochratoxin A. Ochratoxin A producers were found only within P. verrucosum; 38% of the 63 isolates produced detectable amounts of ochratoxin A. Ochratoxin A producing isolates of P. verrucosum were found in 60% of the feed samples collected from ochratoxin A positive swine herds and in one sample (5% ) of the feed samples collected from the ochratoxin A negative herds.     

Management of Root-knot Nematodes by Phenamiphos Applied through an Irrigation Simulator with Various Amounts of Water

Phenamiphos (6.7 kg a.i./ha) was applied via an irrigation simulator to squash at planting (AP) and 2 weeks after planting (PP), and to corn AP and 1 week PP to manage root-knot nematodes (Meloidogyne incognita). The nematicide was applied with 0.25, 0.64, 1.27, and 1.91 cm surface water/ ha to a Lakeland sand in which the soil moisture was at or near field capacity. Based on efficacy and crop response, no additional benefits resulted when phenamiphos was applied in volumes of water greater than 0.25 crn/ha. The cost of applying each 0.25 cm of water over a hectare is approximately $1.08, or a 92% reduction in nematicide application cost over conventional methods ($13.50/ha). Low root-gall indices and high yields from squash and corn indicate more effective nematode management when phenamiphos was applied AP rather than PP. Results from this method of applying phenamiphos suggest that certain nematicides could be used as salvage alternatives when nematodes are detected in crops soon after planting. For multiple-pest management, nematicides, other compatible biocides, and fertilizers could be applied simultaneously with sprinkler irrigation.     

Critical nuclear DNA size and distribution associated with S phase initiation

Using HeLa S-3 cells synchronized by selective detachment, in this paper we report a parallel study of nuclear morphology and autoradiography grain patterns between middle G₁ and middle S phases: Our results show two distinct [³H]-thymidine labeling patterns. The first “peripheral” labeling pattern has a characteristic nuclear size distribution, in contrast to the heterogeneous and varying size distributions of Feulgen-stained nuclei, and apparently is characteristic of very early S phase. The sizes of the second labeling pattern—homogeneous or inhomogeneous grain distribution throughout the nucleus—are equal or larger than the first and vary with S phase progression. Together, the corresponding nuclear sizes of the labeled nuclei represent the larger extreme of nuclear areas, and the labeling index closely parallels the fraction of nuclei with areas larger than the minimum size of the labeled nuclei. These results suggest a characteristic nuclear size (reflecting unique intranuclear DNA distribution) as a necessary, if not sufficient, requirement for S phase initiation. Parallel experimentation with rat liver cells—synchronized in vivo by partial hepatectomy and analyzed by thin section autoradiography—confirms the existence of a peripheral labeling pattern in both the very early part and the very late part of S phase, which reconciles our data with previous results and points to the fact that both initiation and termination sites for DNA replication are near the nuclear periphery.     

Mottling phenomena and quality of grains of different genotypes of Durum wheat grown under limited irrigation conditions

Summary Field experiment was conducted to show the effect of one irrigation of 10 cm water applied to durum wheat (Triticum durum) at crown root initiation stage, active tillering stage, anthesis stage and compared them with non irrigated plot using A-206, A-28, A-1-8-8-42-1, G.W.-1 and A-23-10 genotypes under the conditions of salt affected areas having shallow saline aquifer, on quality, yield and mottling phenomena in wheat grain. Application of irrigation significantly increased the yield and decreased the per cent mottled grain and the maximum achievement was obtained when water was applied during the stage of anthesis. Non mottled grain contained higher protein than mottled grain and there were no considerable differences in other biochemical constituents. Genotype G.W.-1 stands first in its yield performance and low mottled grain.     

Death of Cydia pomonella larvae and damage to apple fruit, after field application of codling moth granulosis virus

In field experiments, larvae of codling moth Cydia pomonella (L.) rarely acquired granulosis virus on hatching from the egg, but picked up most later, on the tree surface. Deposits of virus sprayed in 1.0% w/v skimmed milk did not affect neonate larval behaviour. Larvae died, usually in the first instar, after entering treated fruit, but they frequently entered via the calyx or near the base of the stalk or through cracks in the skin, where little feeding damage by first-and sometimes second-instar larvae was seen.

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Résumé En verger, la pulvérisation d'oeufs de carpocapse avec du virus de la granulose en suspension dans l'eau (additionnée de lait écrémé dilué à 1%) n'a pas modifié la survie des chenilles avant pénétration dans le fruit; par contre la pulvérisation des arbres a provoqué une forte mortalité. Bien que des chenilles consommant des poils et la surface des feuilles aient été observées avant leur pénétration dans le fruit, ce qui aurait pu provoquer leur contamination par le virus, il semble que la contamination létale provienne des fruits seuls.La présence de produit n'a modifié ni le comportement larvaire, ni le taux de pénétration dans les fruits; la mortalité y a lieu ensuite, généralement au premier stade. Dans 74 à 78% des cas, les chenilles ont pénétré dans le fruit par le calice ou près de la base du pédoncule — aucun dégât provenant de larves du premier stade n'y était visible, de même que dans le calice pour les larves du deuxième stade. Par contre, toute pénétration par la surface du fruit était repérable dès le premier stade. Il est possible que la répartition des lieux de pénétration dans le fruit influe sur la létalité due au virus et explique les variations d'efficacité observées en verger. Un système de classification des dégâts, provoqués lors de la pénétration dans le fruit, de chenilles du premier au troisième stade est proposé pour évaluer l'efficacité des essais en verger.