Electroantennogram responses of the Mediterranean fruit fly, Ceratitis capitata to identified volatile constituents from calling males

Fifty-six compounds from the odor of calling, sexually mature, laboratory reared males of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) were isolated by headspace trapping on Tenax columns and identified using GC/MS techniques (69 total compounds were detected). Electroantennogram responses (EAGs) to 54 of the 56 identified compounds as well as 5 analogs were tested on both sexes. Significant differences between the sexes in their responsiveness were found in 9 of the 54 identified compounds tested. There was no correlation between the amplitude of the EAG response and the relative abundance of compound identified from headspace analysis. Of the five major identified components, three elicited relatively small EAG responses, while two elicited large EAGs compared to the hexan-1-ol standard. The relative ranking of EAG responses were: methyl and ethyl hexenoates and hexanoates > C₄–C₆ esters and/or acetates > ethyl and methyl octenoates > monoterpenes > sesquiterpenes > C₂–C₅ acetates, alcohols and ketones. Behavioral bioassays on each of the five major identified components as well as a blend of six of the compounds showed some degree of attractancy to virgin females which in some cases approached the response to a pheromonal standard (male odors absorbed onto filter paper). These results are discussed in relationship to the insect's antennal sensitivity to putative pheromone components and/or allomonal components and to other reported C. capitata pheromone studies.

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Résumé Cinquante-six composés de l'odeur de mâles de C. capitata Weidemann, élevés en laboratoire, sexuellement mûrs et en appel, ont été isolés par piégeage sur colonnes tenax et identifiés par la technique GC/MS (69 composés avaient été détectés en tout). Les électroantennogrammes (EAGs) ont été examinés chez les deux sexes pour 54 des 56 composés identifiés et 5 de leurs analogues. Des différences significatives entre les sexes ont été observées pour 9 des 54 composés identifiés. Il n'y avait pas de corrélation entre l'ampleur de l'EAG et l'abondance relative du composé lors de son isolement. Pour les 5 principaux composés identifiés, 3 ont induit des EAGs relativement faibles, tandis que 2 étaient importants, par comparaison avec l'Hexane-1-ol utilisé comme témoin. Le classement relatif des EAG a été: hexénoates et hexanoates d'éthyl et de méthyl C₄–C₆ esters et/ou acétates octénoates d'éthyl ou de méthyl monoterpènes sesquiterpènes C₂–C₅ acétates, alcools et kétones. Les expériences de comportement avec chacun des 5 composés principaux identifiés, comme avec des mélanges de 6 composés ont mis en évidence une attraction des femelles vierges qui dans quelques cas avoisine la réponse à la phéromone témoin (odeur du mâle absorbée sur papier filtre). Ces résultats sont discutés en fonction de la sensibilité de l'antenne d'insexte aux composés supposés de la phéromone et aux composés allomonaux, et en fonction des autres études connues sur les phéromones de C. capitata.

     

Auxins,ABA and gibberellin-like activity in abscising and non-abscising flowers and pods of Vicia faba L.

Abscission probability varies among floral positions within inflorescences of Vicia faba L. Flowers from proximal positions have a greater chance to develop into mature pods than flowers from more distal positions which normally abscise either as older flowers or as young pods. In three field experiments with the indeterminate single stem variety Herz-Freya, changes in the contents of extractable auxins, abscisic acid (ABA) and gibberellins in flowers and pods during their development, and their possible influence on abscission were investigated.Inflorescences at different positions along the stem were divided into the two proximal and the remaining fruits. The content of all three hormones was at a low level during flower development, increased greatly in parallel with dry matter accumulation in the young pods, and then decreased to maturity. The first hormone to increase in the fruits was auxin and this took place when abscission from the distal positions began. ABA and gibberellins at this time were still at a low level. This ontogenic course of hormone production was very similar in fruits of both positions within an inflorescence, but in flowers and young pods from proximal positions, auxin content in most inflorescences was greater than in those from the abscising distal positions. No such positional differences were observed with ABA and gibberellins. Decapitation of the plants reduced flower and pod drop from the remaining reproductive nodes. Although decapitation resulted in less abscission among distal flowers and young pods from these nodes, it did not affect the ontogenic course of auxin and ABA production in these fruits.     

Amino acid increases in fruit infested by fruit flies of the family Tephritidae

Solanum mauritianum Scop, (wild tobacco) fruit is the major host of the fruit fly Dacus cacuminatus (Hering), and is a major source of food for the brown pigeon Macropygia phasianella (Temminck) in eastern Queensland. Amino acid analyses were undertaken on fruit fly infested and uninfested S. mauritianum fruits. Infested fruits contained approximately twice the level of protein and essential amino acids compared to uninfested fruit. This increase is probably due to the plant adding additional amino acids to infested tissue and the accompanying growth of bacteria established in the fruit during oviposition. The infested fruit would provide a valuable source of protein during the pigeon breeding season.     

The source of gibberellins in the parthenocarpic development of ovaries on topped pea plants

The role and source of gibberellins (GAs) involved in the development of parthenocarpic fruits of Pisum sativum L. has been investigated. Gibberellins applied to the leaf adjacent to an emasculated ovary induced parthenocarpic fruit development on intact plants. The application of gibberellic acid (GA₃) had to be done within 1 d of anthesis to be fully effective and the response was concentration-dependent. Gibberellin A₁ and GA₃ worked equally well and GA₂₀ was less efficient. [³H]Gibberellin A₁ applied to the leaf accumulated in the ovary and the accumulation was related to the growth response. These experiments show that GA applied to the leaf in high enough concentration is translocated to the ovary. Emasculated ovaries on decapitated pea plants develop without application of growth hormones. When [³H] GA₁ was applied to the leaf adjacent to the ovary a substantial amount of radioactivity accumulated in the growing shoot of intact plants. In decapitated plants, however, this radioactivity was mainly found in the ovary. There it caused growth proportional to the accumulation of CA₁. Application of LAB 150978, an inhibitor of GA biosynthesis, to decapitated plants inhibited parthenocarpic fruit development and this inhibition was counteracted by the application of GA₃ (either to the fruit, or the leaf adjacent to the ovary, or through the lower cut end of the stem). All evidence taken together supports the view that parthenocarpic pea fruit development on topped plants depends on the import of gibberellins or their precursors, probably from the vegetative aerial parts of the plant.Abbreviations FW flesh weight - GA_n gibberellin A_n - HPLC high-performance liquid chromatography     

Development of fertilized ovules and their role in the growth of the pea pod

The histological development of fertilized ovules during fruit-set and development in pea ( Pisum sativum L. cv. Alaska) has been investigated. Killing the ovules on day 0 (anthesis) or day 1 prevented fruit-set and resulted in ovary degeneration. When the ovules were destroyed at later stages the ovaries developed, though the rate of growth of the pod was reduced significantly. Pollination in pea occurs normally the day before anthesis, and fertilization of the egg cell 32 to 48 h later. The first divisions of the zygote and endosperm nuclei started simultaneously (ca 48 h after pollination) but the endosperm developed more rapidly than the embryo; the embryo sac cavity was lined with free endosperm nuclei at the time of beginning suspensor elongation. Extracts of endosperm and ovule coats from ovules at day 7 after anthesis showed fruit-set activity in pea, the latter material having about 3 times more activity than the former per ovule basis. These results indicate that fertilization of the ovule is necessary for fruit-set in pea, and that compounds which induce fruit-set are probably synthesized in the ovules following fertilization.     

Effect of incorporated green manure crops on subsequent oat production in an acid,infertile silt loam

A field-size experiment was initiated in 1982 on an acid, low fertility Springhill silt loam to determine the effect of five unfertilized green manure crops (alsike clover, sweet clover, single- and double-cut red clover, and buckwheat) on subsequent oat production and soil fertility. The field was limed in 1982 and green manures were seeded (without fertilizer) in spring, 1983 in 1400 m² strips randomly assigned within three treatment blocks. Plant tissue samples were taken from different locations in each plot in the fall of 1983 and all crops were incorporated. In 1984 the field was separated into an upper and lower section and each section received three rates of NPK fertilizer (0; 30-36-36; 60-72-72 kg ha^-1) spread across the previous strips. Gary oats were seeded and at harvest were divided into grain and straw. The results indicated significant effects of field sample location, green manure type and fertilizer level on oat yields. Buckwheat significantly reduced oat production compared to the four clovers, while the highest fertilizer rate improved oat yields compared with the other levels of fertilizers. Elemental analysis of the green manure crops and soil fertility was compared with data of the same crops grown in more fertile, neutral soils.     

Culture of soybean fruit explants: growth conditions and efficiency of nitrogen sources for reserve protein synthesis

A system was devised for the in vitro culture of soybean fruits. The culture system consisted of a single fruit attached to a short piece of stem through which the nutrients were supplied. The fruit explants were taken when pods were fully expanded and the seeds at initial stages of growth. During a 7-day culture period, the seeds accumulated dry matter and protein in quantities comparable to those in situ. Omission of the C source (sucrose) from the medium resulted in no dry matter accumulation in the seeds, but omission of the N source (glutamine) still led to some protein accumulation, indicating mobilization of N from other parts of the fruit explant. Optimum protein accumulation occurred when glutamine was supplied at 1.2 mg N ml^-1. Protein accumulation in the seeds was highly dependent on the nature of the N source. Glutamine, asparagine and the ureide, allantoin, were equally the most efficient sources, whereas several other amino acids tested showed lower degrees of efficiency. The data indicate a high metabolic capacity of the fruit tissues for principal N transport compounds of soybean, namely allantoin, asparagine and glutamine. The culture system described should prove useful for developmental and metabolic studies where the complex influence of the rest of the plant is to be avoided.Abbreviations ALN allantoin - ALC allantoic acid Preliminary report presented at the IV World Soybean Research Conference, Buenos Aires, Arggentina, March 1989.     

越冬期间香蕉果穗套袋的防寒效果及其对产量的影响

冬季香蕉果穗用兰色聚乙烯薄膜套袋之后,可提高袋内温度1～5℃,果实低温伤害卑只有1％左右,而未经套袋的达23％～35％,果指长度和径围增加率分别达12％和9％左右,果实产量比对照增加8％～16％。试验结果表明,兰色聚乙烯薄膜套袋是越冬期间香蕉防寒保果和增产的一项有效措施。