Intraguild predation among the predatory mites Amblyseius eharai,Amblyseius cucumeris and Amblyseius barkeri

Predator species with the same prey interact not only by competition for food and space but also by intraguild predation (IGP). The impact of IGP on introduced phytoseiid mites and native species in the context of biological control is a matter of considerable debate. Amblyseius eharai is the dominant native citrus species in central China, while Amblyseius cucumeris and Amblyseius barkeri are candidates for importation. All three species can feed on the spider mite Panonychus citri, which is the main pest in citrus. This study investigated, in the laboratory, possible IGP among these species in the absence and presence of P. citri, respectively. IGP in different densities of shared prey and intraguild (IG) prey was also studied. All three species consumed heterospecific larvae and eggs but not adults, and the IGP rate of larvae was significantly higher than that of eggs in the absence of shared prey. Additionally, the IGP rate of each group was reduced dramatically in the presence of both shared and IG prey when compared to the absence of shared prey. This occurs most likely because the three species prefer to feed on their natural prey P. citri, rather than on IG prey. Our results showed that A. eharai seems to be a more voracious IG predator than A. cucumeris. A. eharai was much more prone to IGP than A. barkeri.     

Life history of Amblyseius herbicolus (Chant) (Acari: Phytoseiidae) on coffee plants

The predaceous mite Amblyseius herbicolus (Chant) is the second most abundant phytoseiid on coffee plants (Coffea arabica L), after Euseius alatus DeLeon, in Lavras, MG, Brazil, associated to the vector of the coffee ring spot virus, Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae). Its life history was studied taking into account biological aspects, life table, predatory activity and functional and numerical responses in relation to the density of the prey. The adult female has longevity of 38 days when supplied with B. phoenicis. The intrinsic rate of population increase (r m) was 0.150 and the mean generation time (T) 25.3 days. The population doubles every 4.6 days. Thirty mites B. phoenicis /3-cm diameter coffee leaf arenas were separately offered to one specimen of each predator phase. Adult females were more efficient in killing all developmental phases of B. phoenicis, followed by the nymph stages. For the functional and numerical responses studies, from 0.14 to 42.3 immature specimens of the prey /cm(2) of arena were submitted to the predator, the preferred phase for predation. Predation and the oviposition of A. herbicolus increased with increasing prey density, with a positive and highly significant correlation. Regression analysis suggests a functional type II response, with a maximum daily predation near 35 B. phoenicis /cm(2) /one adult female.     

Diversity among Bradyrhizobium isolates nodulating yardlong bean and sunnhemp in Guam

AIMS: To isolate and characterize bradyrhizobia that nodulate yardlong bean and sunnhemp in Guam. METHODS AND RESULTS: Bradyrhizobia populations that nodulate yardlong bean and sunnhemp in Guam were examined for genetic diversity and their relatedness to Bradyrhizobium japonicum and B. elkanii reference strains. Genomic DNA of 58 isolates of Bradyrhizobium spp. was hybridized with B. japonicum nodY and B. elkanii nodK genes. Based on the hybridization patterns, the isolates were classified into three nodY-nodK hybridizing groups. Group I comprised the majority of the isolates and hybridized with nodY whereas group II isolates hybridized with nodK. The group III isolates, that did not hybridize with either nodY or nodK, formed nitrogen-fixing nodules on cowpea but did not nodulate soybean. DNA sequence analysis of a 280-bp fragment of the variable region of the 16S rRNA gene of a few group III isolates showed that these isolates were more similar to Bradyrhizobium spp. than to B. japonicum or B. elkanii. CONCLUSIONS: The majority of the isolates nodulating yardlong bean and sunnhemp in Guam are similar to B. japonicum, although some isolates are similar to Bradyrhizobium spp. that nodulate a miscellaneous group of legumes including cowpea. SIGNIFICANCE AND IMPACT OF THE STUDY: Since both yardlong bean and sunnhemp are nodulated by a range of bradyrhizobia, selection of superior strains may be based on nodulation effectiveness on both legumes.     

Evidence that the castor bean allergens are the albumin storage proteins in the protein bodies of castor bean

The well characterized castor bean (Ricinus communis L.) allergens were identified as the low molecular weight albumin storage proteins in the matrix of the protein bodies in the endosperm. The methods of identification involved molecular weight estimation, amino acid composition, stability at 100° C, solubility in various solvents, gel electrophoresis, and immunological techniques. The finding explains the wide distribution of allergens in various seeds.     

The development of domestic castor bean production

Shatter resistance, earliness, high yield and plant form best adapted to mechanical harvesting have been the principal and already partly achieved objectives in breeding castor beans, which, along with improvements in harvesting and hulling machinery, increase the prospects for greater domestic production of this crop.     

Characterization of glyoxysomes from castor bean endosperm

Electron micrographs are presented which establish the identity of the components of the 3 major bands observed after sucrose density centrifugation of the crude particulate fraction from the endosperm of germinating castor bean seedlings. These are: mitochondria (density 1.19 g/cc), proplastids (density 1.23 g/cc) and glyoxysomes (density 1.25 g/cc). Further evidence is provided on the enzymatic composition of the glyoxysomes. Essentially all of the particulate malate synthetase, isocitrate lyase, catalase, and glycolic oxidase is present in these organelles. The distribution of glyoxysomal enzymes on sucrose density gradients is contrasted with that of the strictly mitochondrial enzymes fumarase, NADH oxidase, and succinoxidase. Malate dehydrogenase and citrate synthetase are present in both organelles. The functional role of glyoxysomes and their relationship to cytosomes from other tissues is discussed.     

Studies on NADP-isocitrate dehydrogenase from maturing castor bean seeds

NADP-specific isocitrate dehydrogenase from the soluble fractionof maturing castor bean endosperm was partially purified (approximately180-fold) and some of its enzymatic properties were studied.Mg⁺⁺, Mn⁺⁺, Cd⁺⁺, Ba⁺⁺, Co⁺⁺, Zn⁺⁺, and Sr⁺⁺ were activatorsof the enzyme reaction at a concentration of 6.7x10 M. The optimumpH of this enzyme was about 8.5. The enzyme was stable in thenarrow range from pH 7.0 to pH 8.0. Km values for isocitrateand NADP at pH 8.5 were 3.5x10^–6 M and 3.6x10^–6M, respectively. Enzyme stability was not affected by NaCl concentrationand enzyme reaction was inhibited at 5x10^–6 M PCMB (80%inhibition). It is suggested that the condensation product ofglyoxylate and oxalacetate also inhibits the reaction. NADP-IDHin the crude extract from maturing castor bean endosperm washeat-stable but the dialyzed enzyme preparation and the partiallypurified enzyme were labile against heat treatment at 57°C.When Mg⁺⁺ was added to the partially purified enzyme in thepresence of isocitrate or NADP, the enzyme was stabilized againstheat treatment. Mn⁺⁺, Ca⁺⁺, Co⁺⁺, Sr⁺⁺ or Ba⁺⁺ could be substitutedfor Mg⁺⁺. Addition of only one of the factors, Mg⁺⁺, isocitrateor NADP, had no effect on the heat stability. Moreover, a combinationof isocitrate and NADP did not establish stabilization. A divalentcation plays a central role, while adenine nucleotide, especiallyATP, may have an important part in stabilization. (Received August 14, 1972; )     

Purification and properties of glyoxysomal lipase from castor bean

The alkaline lipase in the glyoxysomes from the endosperm of young castor bean seedlings, an integral membrane component, was solubilized in deoxycholate:KCl and purified to apparent homogeneity. The molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was 62,000 daltons. The enzyme reaction was markedly stimulated by salts and inhibited by detergents. Triricinolein, the endogenous storage lipid, was hydrolyzed by the purified enzyme which is therefore a true lipase. Treatment of intact glyoxysomes with trypsin strongly diminished the lipase activity but did not affect matrix enzymes. An antibody preparation raised in a rabbit against the purified enzyme inhibited the purified enzyme and that in glyoxysomal membranes.     

Precursors of ricinine in the castor bean plant

Isotopic tracer experiments confirmed that glycerol and succinic acid are good precursors of the pyridine ring of ricinine in castor bean plants. Tritium from C-2 was lost from tritiated glycerol while tritium from C-1 was retained. Thus a derivative of dihydroxyacetone is likely to be intermediate. By simultaneous feeding of glycerol-1-(3)-[³H] and succinic acid-2(3)-[¹⁴C], it was hoped to find precursors of ricinine containing both labels, but none could be found. There was no evidence for the appearance of labeled quinolinic acid, which is presumed to be a precursor of ricinine.     

迎春花花粉对伪钝绥螨生长发育和繁殖的影响

伪钝绥螨Amblyseius fallacis Garman是控制害螨的有效天敌,研究迎春花花粉和二斑叶螨Tetranychus urticaeKoch对伪钝绥螨生长发育和繁殖的影响,比较伪钝绥螨取食2种食料时各种参数的异同。结果表明,迎春花花粉可使伪钝绥螨正常生长发育并产卵,但发育时间较取食二斑叶螨的长,产卵量与取食二斑叶螨的相当。取食迎春花花粉时伪钝绥螨的内禀增长率、净增殖率和周限增长率均低于取食二斑叶螨时的值,世代平均周期较取食二斑叶螨略短,而种群倍增所需时间更长。由以上结果可知迎春花花粉可作为伪钝绥螨的替代或补充食料。     

Studies on the rhizosphere mycoflora of broad bean and cotton

Summary Seed and root exudates from three varieties of both broad bean and cotton grown aseptically were analyzed for amino acids and sugars. Broad bean varieties were found to excrete considerable amounts of amino compounds with 15 different amino acids, while cotton varieties excreted less consisting of 12 amino acids. Five sugars were identified in the seed and root exudates from broad bean varieties, while three were present in the seed and root exudates from cotton varieties. Seed and root exudates stimulated spore germination and growth of fungi isolated from the rhizosphere.     

Studies on the rhizosphere mycoflora of broad bean and cotton

Investigations were made on the effect of species of fungi isolated from therhizosphere of broad bean (Vicia faba Linn.) variety Giza I, and cotton (Gossypium barbadense Linn.) variety Giza 47, on plant growth. Broad bean rhizosphere fungi differently affected plant growth.Fusarium moniliforme, Penicillium martensii, Rhizopus stolonifer, andCladosporium sphaerospermum stimulated both root and shoot growth.Aspergillus niger andAlternaria tenuis have an inhibitory effect on plant growth. On the other hand, the rhizosphere fungi of cotton namely,Penicillium cyclopium, Aspergillus terreus, Cephalosporium sp.,Aspergillus niger, Cladosporium sphaerospermum, andFusarium oxysporum stimulated plant growth.     

Studies on the rhizosphere mycoflora of broad bean and cotton

Summary The fungal flora of the rhizosphere of three varieties of broad bean and cotton was studied by the dilution-plate technique. The numbers of fungi were higher in the rhizosphere than in the non-rhizosphere soil. Plant type and age, and soil type have a significant influence of the nature and numbers of fungal flora associated with plant roots.Cladosporium was relatively more abundant in the rhizosphere of broad bean varieties, whilePenicillium was found to constitute a high percentage of fungi found in the rhizosphere of cotton varieties. Plant variety has no influence on the nature of such fungal flora.     

Transport of dicarboxylic acids in castor bean mitochondria

Mitochondria from castor bean (Ricinus communis cv Hale) endosperm, purified on sucrose gradients, were used to investigate transport of dicarboxylic acids. The isolated mitochondria oxidized malate and succinate with respiratory control ratios greater than 2 and ADP/O ratios of 2.6 and 1.7, respectively. Net accumulation of ¹⁴C from [¹⁴C]malate or [¹⁴C]succinate into the mitochondrial matrix during substrate oxidation was examined by the silicone oil centrifugation technique. In the presence of ATP, there was an appreciable increase in the accumulation of ¹⁴C from [¹⁴C]malate or [¹⁴C]succinate accompanied by an increased oxidation rate of the respective dicarboxylate. The net accumulation of dicarboxylate in the presence of ATP was saturable with apparent K_m values of 2 to 2.5 millimolar. The ATP-stimulated accumulation of dicarboxylate was unaffected by oligomycin but inhibited by uncouplers (2,4-dinitrophenol and carbonyl cyanide m-chlorophenylhydrazone) and inhibitors of the electron transport chain (antimycin A, KCN). Dicarboxylate accumulation was also inhibited by butylmalonate, benzylmalonate, phenylsuccinate, mersalyl and N-ethylmaleimide. The optimal ATP concentration for stimulation of dicarboxylate accumulation was 1 millimolar. CTP was as effective as ATP in stimulating dicarboxylate accumulation, and other nucleotide triphosphates showed intermediate or no effect on dicarboxylate accumulation. Dicarboxylate accumulation was phosphate dependent but, inasmuch as ATP did not increase phosphate uptake, the ATP stimulation of dicarboxylate accumulation was apparently not due to increased availability of exchangeable phosphate.

The maximum rate of succinate accumulation (14.5 nanomoles per minute per milligram protein) was only a fraction of the measured rate of oxidation (100-200 nanomoles per minute per milligram protein). Efflux of malate from the mitochondria was shown to occur at high rates (150 nanomoles per minute per milligram protein) when succinate was provided, suggesting dicarboxylate exchange. The uptake of [¹⁴C]succinate into malate or malonate preloaded mitochondria was therefore determined. In the absence of phosphate, uptake of [¹⁴C]succinate into mitochondria preloaded with malate was rapid (27 nanomoles per 15 seconds per milligram protein at 4°C) and inhibited by butylmalonate, benzylmalonate, and phenylsuccinate. Uptake of [¹⁴C]succinate into mitochondria preloaded with malonate showed saturation kinetics with an apparent K_m of 2.5 millimolar and V_max of 250 nanomoles per minute per milligram protein at 4°C. The measured rates of dicarboxylate-dicarboxylate exchange in castor bean mitochondria are sufficient to account for the observed rates of substrate oxidation.

     

Sugar uptake and translocation in the castor bean seedling

Summary Radioactive sucrose entering the cotyledons of germinating castor bean seedlings has been partly localised with the aid of microautoradiography. Complete penetration of these organs was achieved in twenty minutes from 0.1M aqueous sucrose. Radioactive material was found to occur predominantly in the vicinity of cell walls and in intercellular spaces. It is suggested that this region offers a diffusion pathway by which solutes can gain access to the vascular system from an external source.     

Composition of phosphoglycerides and glycosyl glycerides in castor bean mitochondria

Phosphoglycerides and glycosyl glycerides in mitochondria fromcastor bean endosperms were determined by silicic acid columnchromatography using C-A and C-M as eluting solvents and bysupplemental use of TLC. The small amount of glycosyl glyceridedetected in the mitochondrial fraction may be due to contaminationby other organelle(s). ¹Present address: Ocean Research Institute, University of Tokyo,Nakano, Tokyo 164, Japan. (Received June 13, 1974; )