Ecological Aspects of the Heritability of Body Size in Drosophila Buzzatii

The heritability of thorax length in the cactophilic Drosophila buzzatii was determined for flies from each of 10 rotting cactus cladodes. For each rot, emerging flies were used as parents of progeny reared in the laboratory. The methods used were full sib analysis with the parents mated assortatively and also offspring-parent regression. From this, heritabilities were measured for the laboratory environment and for the natural environment of the rotting cladode. For the laboratory environment, h2 = 0.3770 +/- 0.0203 and for the natural environment h2 = 0.0936 +/- 0.0087 within rots and h2 = 0.0595 +/- 0.0123 for a population drawn randomly from different rots. Because of the possibility of genotype-environment interaction between the laboratory and rot environments, the methods of B. Riska, T. Prout and M. Turelli were used to show it is possible that there is no such interaction, but if there is, the above natural heritabilities are approximate lower bounds. These results are related to the general problem of determining heritabilities in nature where it is impractical to measure both parents and progeny in nature. Determining heritability not only in nature but in relation to subdivision into ephemeral patches (cladodes in this case) has an important bearing on natural selection response and to general theories of stabilizing selection proposed to explain the existence of genetic variation. Attempts were made to detect selection by using the size of emerging adults as an indicator of various levels of larval stress. No selection was detected, but the power to do so was very weak. Differences between progeny means from different rots indicated some genetic differences between rots which can be adequately explained by small numbers of founders. This suggests a random fine scale subdivision amounting to FST = 0.1483 +/- 0.0462.     

Comparative toxicity of purified human eosinophil granule proteins for newborn larvae of Trichinella spiralis

Eosinophils have been implicated in both in vivo and in vitro destruction of helminths. One approach toward elucidating the role of the eosinophil in parasite killing has been to test the toxicity of purified eosinophil granule proteins for parasites in vitro. Previously, major basic protein (MBP) and eosinophil cationic protein (ECP) were shown to be toxic for schistosomules of Schistosoma mansoni, while eosinophil-derived neurotoxin (EDN) was only marginally so. We tested the toxicity of MBP, ECP, and EDN over a range of concentrations (0.006-5 X 10(-4) M) for newborn larvae of Trichinella spiralis. Our observations confirm previous reports of toxicity of mildly reduced and alkylated (R & A) MBP. At concentrations of 5 X 10(-5) M and above, R & A MBP killed 75% or more of the larvae within the first hour of culture. ECP was an effective toxin for these larvae after 3 hr of culture, and by 12 hr, dose-related toxicity was evident. After 24 hr, 100% of the larvae were killed at 5 X 10(-5) M ECP. EDN was much less toxic; after 12 hr, 90% of the larvae survived at concentrations of 1 X 10(4) M, while 5 X 10(-4) M EDN killed all the larvae. At the optimal toxic concentrations of 5 X 10(-5) M ECP and 5 X 10(-4) M EDN, kinetics of killing by these 2 proteins were essentially the same. Thus, on a molecular basis, both MBP and ECP appear to be potent helminthotoxins whereas EDN is much less so.     

Effects of Temperature,Plant Age,Soil Texture,and Meloidogyne incognita on Early Growth of Soybean

A digitizer-microcomputer combination was utilized to determine soybean seedling response to population densities of M. incognita (Mi) under varied environmental conditions. Plant age, temperature, soil texture, and initial Mi inoculum (Pi) influenced the pattern of shoot and root growth. Effects of Mi on plant top growth were evident on plants inoculated 2 days after seeding, but generally were not noticeable on those receiving Mi after 4, 6, or 8 days (observations limited to 6 days after inoculation). The greatest Pi of Mi (16,700 juveniles/plant) suppressed root growth on plants inoculated at 2 or 4 days after seeding. Mi had no impact on root growth at 22 C on plants inoculated 6 or 8 days after seeding at any temperature used (22, 26, 30 C). New root initiation was inhibited on soybeans inoculated 2 days after seeding at the highest Pi at all three temperatures, but only at 30 C for a Pi of 1,670 juveniles/plant. Growth of first order lateral roots and general root length were suppressed by Mi on the youngest (2-day) plants. However, a low Pi (167 juveniles/ plant) resulted in root proliferation on 4-day-old plants at 26 C. Mi was most damaging in a low clay-content soil mixture.     

Allozyme genotypes of Drosophila buzzatii: feeding and oviposition preferences for microbial species, and habitat selection

Mature, mated female D. buzzatii were given a choice of nine microbial communities actively growing on cactus homogenate in laboratory population cages, and tests were made to determine if flies of different genotypes (for seven allozyme loci) chose different microorganism species for either feeding or oviposition. Variation in feeding preferences was determined from assays of electrophoretic genotypes and the ingested microorganism species of individual flies. Oviposition preference variation was analyzed indirectly by assaying the genotypes of individuals raised from eggs laid on different microorganisms. No significant evidence was found for differences in feeding preferences among adults of different genotypes. For oviposition preferences, there were significant microorganism-genotype associations for each of seven polymorphic loci. Analyses of the total electrophoretic genotype, rather than of individual loci, showed that the genotypes of eggs laid on the same microorganism species were more similar than those laid on different species. That is, females of different genotypes show habitat selection for oviposition sites, which would facilitate the maintenance of genetic polymorphisms.     

General methods for enriching aldoses with oxygen isotopes

Synthetic methods are described for enriching 4-, 5-, and 6-carbon aldoses with oxygen isotopes. The general approach includes exchange between H2(1)8O and the aldehyde group of an aldose, exchange of O-1 onto C-2 of both of the 2-epimeric aldoses formed by molybdate-resin epimerization, and chain extension using cyanide addition. These methods make possible the production of all 16 aldohexoses enriched at 5 of the 6 oxygen atoms, all 8 aldopentoses enriched at 4 of the 5 oxygen atoms, and the four aldotetroses enriched at 2 of the 4 oxygen atoms. The general applicability of these methods is illustrated by the synthesis of a group of 22 different, 18O-enriched, biologically important D-aldoses having 4, 5, and 6 carbon atoms. The group includes D-[1-, 2-, 3-, 4-, O]glucose, D-[1-, 2-, 3-, 4-, and 6-18O]mannose, D-[1-, 2-, 3-, and 5-18O]arabinose, D-[1- abd 2- 18O] erythorose, and D-[1- and 2-18O]threose. The g.l.c.-m.s. characterization of these sugars with respect to the position and degree of 18O-enrichment is reported. The potential of the methods for producing aldoses having oxygen labels at multiple positions, or aldoses labeled simultaneously with oxygen, hydrogen, and carbon isotopes is discussed.     

Winter Survival of Meloidogyne incognita in Six Soil Types

Winter survival of Meloidogyne incognita in six soil types (Fuquay sand, Norfolk loamy sand, Portsmouth loamy sand, muck, Cecil sandy clay loam, and Cecil sandy clay) was determined in microplots at one location from November 1981 to May 1982 and from November 1982 to March 1983. Survival, based on second-stage juveniles (J2) of M. incognita, from November 1981 until May 1982 ranged from 1% in the muck soil to 6% in a Cecil sandy clay loam, but survival rates were much higher the next year following a winter with higher average temperatures. Survival rates of J2 from November to March ranged from 20 to 40% the first winter and from 38 to 87% the second. Soil type did not have a striking effect on the overwintering capabilities ofM. incognita. There were no differences between clay and sand soils, whereas survival of J2 in the muck tended to be lower than in the mineral soils.     

Histology of the Interactions of Paecilomyces lilacinus with Meloidogyne incognita on Tomato

Excised tomato roots were examined histologically for interactions of the fungus Paecilomyces lilacinus and Meloidogyne incognita race 1. Root galling and giant-cell formation were absent in tomato roots inoculated with nematode eggs infected with P. lilacinus. Few to no galls and no giant-cell formation were found in roots dipped in a spore suspension of P. lilacinus and inoculated with M. incognita. Numerous large galls and giant cells were present in roots inoculated only with M. incognita. P. lilacinus colonized the surface of epidermal cells as well as the internal cells of epidermis and cortex. The possibility of biological protection of plant surfaces with P. lilacinus against root-knot nematodes is discussed.     

Influence of Aldicarb on the Growth and Yield of Tobacco

Microplot and field experiments were used to examine the plant-growth stimulation frequently associated with the use of aldicarb on tobacco in the absence of major pests. Aldicarb rates of 1.5-4.5 kg a.i./ha enhanced tobacco growth and yield in most experiments, but higher rates (≥ 4.5 kg) usually resulted in a neutral to negative effect. Tobacco cultivars NC 82 and Speight G-28 were more responsive than McNair 944 to the pesticide in microplots. Supplemental irrigation enhanced the responsiveness of Speight G-70 tobacco and McNair 944 to aldicarb, but excessive moisture (ca. 7-8 cm/week) limited cured-leaf yields. Aldicarb also resulted in the greatest mean tobacco yields in 35 field experiments involving Meloidogyne spp. over 3 years, relative to ethoprop, 1,3-dichloropropene (1,3-D), 1,3-D + chloropicrin, and nontreated controls. Thus, aldicarb generally enhanced tobacco growth and yield in the presence or absence of nematodes, but its impact is dependent on other variables, including cultivar, soil moisture, and soil type.