Distribution of Bemisia tabaci within soybean plants and on individual leaflets

To control whiteflies on soybean crops in an effective and economically viable way, it is necessary to quantify the occurrence and density of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) on the leaflets. Estimating the number of B. tabaci cm^‐2 on leaflets is difficult, because its distribution pattern on the various parts of the plant canopy and on the leaflet surface is unknown. The aim of this study was to evaluate the distribution of B. tabaci nymphs on soybean plants and leaflets, under greenhouse and field conditions. One hundred soybean plants infested with all nymph stages were randomly selected in a greenhouse, and 25 in a field. Of each plant, a trifoliate leaf of the middle third of the plant’s height was selected and its central leaflet was collected (greenhouse experiment), or a trifoliate leaf of each third layer (upper, middle, and lower), of which the left, central, and right leaflets were collected (field experiment). The collected leaflets were divided into 32 sections (1 cm² per section), arranged in an array of eight rows and four columns to count whitefly nymphs. The Morisita index (I_δ), the negative binomial parameter k, and the dispersion index (I) were calculated for each leaflet, using the number of nymphs as variable. The highest population densities of whitefly nymphs were found in the middle third of the soybean plants. In leaflets from the middle third, the nymphs concentrated in the middle and bottom parts of the leaflets, whereas in the upper and lower thirds of the plant, they were randomly distributed on the leaflets.     

Sampling strategies for assessing the overall density of the cassava green mite (Mononychellus tanajoa)

Six different sampling methods to estimate the density of the cassava green mite, Mononychellus tanajoa, are categorized according to whether leaves or leaflets are used as secondary sampling units and whether the number of leaves on the sampled plants are enumerated, estimated from an independent plant sample, or not censused at all. In the last case, sampling can provide information only on the average number of mites per leaf and its variance, while information on stratum sizes is necessary to estimate the mean number of mites per plant as well. It is shown that leaflet-sampling is as reliable as leaf-sampling for the same number of sampling units. When stratum sizes are estimated from a separate plant sample, sampling time may also be reduced, but the estimated mean density and its variance may be biased if mite density and plant size are correlated. Sampling data show that the within-plant variance contributes relatively little to the overall variance of the population density estimates. It points at a sampling strategy in which the number of primary units (plants) is as large as possible at the expense of secondary units (leaflets) per plant. Mean-variance relationships may be applied to estimate sample variances and can be used even when only one leaflet is taken per plant per stratum. An unequal allocation of primary units among strata can increase precision, but the gain is small compared with an equal allocation. Leaf area can be predicted from the length of the longest leaflet and the number of leaflets.     

Expression of the narrow leaflet gene for yield and agronomic traits in soybean

Genes that affect plant form and function may be used to enhance the yield of soybean [Glycine max (L.) Merr.]. Most soybean cultivars have broad (ovate) leaflets. A single gene, ln, controls inheritance for the narrow leaflet characteristic. Narrow leaflet cultivars (ln/ln) also tend to have a higher percentage of four-seeded pods than ovate (Ln/Ln) leaflet cultivars. Heterozygous (Ln/ln) plants have a leaflet shape intermediate between narrow and ovate. Determining the agronomic effects of the narrow leaflet allele (ln) in the heterozygous (Ln/ln) condition in soybean may have applications in practical plant breeding. We studied an ovate leaflet and a narrow leaflet cultivar, crosses between them in the F(1) and F(2), and backcrosses to both cultivars. The ratio of leaflet width to leaflet length accurately distinguished among narrow, ovate, and intermediate leaflet plants in the F(2) and backcross generations. In the F(2) generation, differences occurred among plants with different leaflet morphology. Narrow leaflet plants produced more seeds per pod and lower seed weight than ovate leaflet plants. Narrow and ovate leaflet plants produced comparable numbers of pods per plant and plant yield. Compared to ovate leaflet plants, intermediate leaflet plants produced similar numbers of seeds per pod and seed weight. Intermediate leaflet plants produced significantly more pods per plant and plant yield than plants with either ovate or narrow leaflets. The heterozygous condition at the locus for leaflet morphology resulted in heterosis for plant yield and may be of benefit in association with commercialization and development of hybrid soybean.     

Spatial distribution of Tenuipalpus heveae Baker (Acari: Tenuipalpidae) on rubber tree plantations

The objective of this work was to study the spatial distribution of Tenuipalpus heveae Baker in rubber tree plantations. The experimental area was located in Marinópolis, State of S?o Paulo, and corresponded to a total of 1,000 plants (clone RRIM 600) divided in 100 plots of ten plants each. A total of 16 samplings were conducted, approximately once every 10 days, between December 2007 and June 2008. On each date, samples were taken from two plants per plot, each sample corresponding to the top 30 cm of a branch randomly taken from the median region of the canopy of each plant. The number of T. heveae was evaluated on three leaflets randomly taken from each sample, using a 20x power pocket magnifying glass. The number of mites was evaluated in two areas of 1 cm2 delimited on the lower surface of each leaflet, being one along the midrib and the other along a lateral vein. The calculated dispersion indexes were: variance/mean relationship (I), index of Morisita (I′), coefficient of Green (Cx) and k exponent of negative binomial distribution. Tenuipalpus heveae showed aggregate distribution. The negative binomial distribution model was the most appropriate to represent the spatial distribution of the mite in the rubber tree plantation.     

Utilization of early soybeans for food and reproduction by the tarnished plant bug (Hemiptera: Miridae) in the delta of Mississippi

Commercially produced maturity group (MG) IV soybeans, Glycine max L., were sampled during bloom for tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), during May and June 1999 (3 fields) and 2001 (18 fields). The adults and nymphs were found primarily in single population peaks in both years, indicating a single new generation was produced during each year. The peak mean numbers of nymphs were 0.61 and 0.84 per drop cloth sample in 1999 and 2001, respectively. Adults peaked at 3.96 (1999) and 3.76 (2001) per sweep net sample (25 sweeps). Tests using laboratory-reared and field-collected tarnished plant bugs resulted in very poor survival of nymphs on 16 different soybean varieties (MG III, one; IV, four; V, nine; VI, two). A large cage (0.06 ha) field test found that the number of nymphs produced on eight soybean varieties after mated adults were released into the cages was lower than could be expected on a suitable host. These results indicated that soybean was a marginal host for tarnished plant bugs. However, the numbers of adults and nymphs found in the commercially produced fields sampled in the study may have been high enough to cause feeding damage to the flowering soybeans. The nature of the damage and its possible economic importance were not determined. Reproduction of tarnished plant bugs in the commercially produced early soybean fields showed that the early soybeans provided tarnished plant bugs with a very abundant host at a time when only wild hosts were previously available.     

Influence of trichomes on attractiveness and ovipositional preference of Bemisia tabaci (Genn.) B biotype (Hemiptera: Aleyrodidae) on tomato genotypes

Brazil is one of the world's largest tomato producer, but considerable part of the production is lost due to the attack of Bemisia tabaci (Genn.) B biotype. Resistant germoplasm plants can be an important method for B. tabaci control in integrated pest management approaches. The attractiveness and ovipositional preference of B. tabaci for 17 tomato genotypes were evaluated in a free-choice test. Trials were set up in a randomized block design with ten replicates. Each replicate (one tomato plant per pot) was placed in a cage (80 x 50 x 50 cm) and infested with 1,000 adults during four days. Linear correlation tests were applied between the number of insects and eggs and number of trichomes in each tomato genotype. LA716, LA444-1 and PI134418 genotypes were the least attractive, while the 'Santa Clara' was the most attractive; PI134417 trapped the largest number of adults. LA716 genotype (4.1 eggs/leaflet and 2.1 cm2/eggs per leaflet) was the least preferred for whitefly oviposition; NAV1062, 'Fanny', LA1335, 'Santa Clara' and IAC294 were the most preferred genotypes. The glandular trichomes density was negatively correlated with whitefly's attractiveness and oviposition per leaflet and per leaf, and positively with the number of trapped insects. The non-glandular trichomes density was negatively correlated with the number of trapped insects and positively with whitefly's oviposition per cm2/leaflet andper cm2/leaf. LA716 had high antixenosis level (ovipositional nonpreference) toward B. tabaci B biotype related with type IV glandular trichome.     

Eggs Distribution Behaviour of Dubas Bug (Ommatissus Lybicus: Homoptera: Tropiduchidae) in Relation to Seasons and Some Physico- Morphic Characters of Date Palm Leaves

Dubas bug, Ommatissus lybicus, is a major pest of date palm in Panjgur Balochistan. Both the nymphs and adults suck the sap from fruit stalk, leaves and may cause about 50 % of economic losses. Chlorophyll contents and leaf thickness was measured by using SPAD-502 chlorophyll meter and vernier caliper respectively. Eggs distribution density was highly significant in different frond rows and within frond during spring (1^st) and summer (2^nd) generations. In both generations number of eggs per leaflet decreased towards the apex fronds rows and within frond number of eggs decreased towards the terminal leaflets. Eggs distribution had negative correlation with leaf thickness; chlorophyll contents (SPAD value) and frond row (bottom to top). Apparently shade affect the eggs laying behaviour of dubas bug.     

Application of linear models for estimation of leaf area in soybean [<Emphasis Type="Italic">Glycine max</Emphasis> (L.) Merr]

Leaf area estimation is an important measurement for comparing plant growth in field and pot experiments. In this study, determination of the leaf area (LA, cm²) in soybean [Glycine max (L.) Merr] involves measurements of leaf parameters such as maximum terminal leaflet length (L, cm), width (W, cm), product of length and width (LW), green leaf dry matter (GLDM) and the total number of green leaflets per plant (TNLP) as independent variables. A two-year study was carried out during 2009 (three cultivars) and 2010 (four cultivars) under field conditions to build a model for estimation of LA across soybean cultivars. Regression analysis of LA vs. L and W revealed several functions that could be used to estimate the area of individual leaflet (LE), trifoliate (T) and total leaf area (TLA). Results showed that the LW-based models were better (highest R ² and smallest RMSE) than models based on L or W and models that used GLDM and TNLP as independent variables. The proposed linear models are: LE = 0.754 + 0.655 LW, (R ² = 0.98), T = −4.869 + 1.923 LW, (R ² = 0.97), and TLA = 6.876 + 1.813 ΣLW (summed product of L and W terminal leaflets per plant), (R ² = 0.99). The validation of the models based on LW and developed on cv. DPX showed that the correlation between calculated and measured LA was strong. Therefore, the proposed models can estimate accurately and massively the LA in soybeans without the use of expensive instrumentation.     

INTRAPOPULATIONAL VARIATION IN LEAFLET MORPHOLOGY OF ZAMIA PUMILA L. IN RELATION TO MICROENVIRONMENT AND SEX

The cycad Zamia pumila L. was examined for differences in leaflet morphology between sun and shade plants and between males and females within a single population in northern Puerto Rico. Sun leaflets are significantly smaller than shade leaflets in length, width, and surface area; and sun leaflets have a higher length: width ratio than shade leaflets. Also, average densitythickness is greater for sun leaflets than for shade leaflets. Males and females are similar in leaflet size; but the females had a larger number of leaflets per leaf than males.     

Genetic transfer of a twospotted spider mite (Acari: Tetranychidae) repellent in tomato hybrids

Lycopersicon hirsutum Dunal is very resistant to arthropod herbivory, and research on causes of resistance has often implicated trichomes and their secretions. To better understand relationships among resistance, repellency, and 2,3-dihydrofarnesoic acid, a trichome-borne sesquiterpenoid spider mite repellent, two tomato, Lycopersicon esculentum Miller, varieties were interbred with a highly resistant, spider mite repellent accession (LA1363) of L. hirsutum. Backcross and F2 generations were produced with each tomato variety. Whole leaves of 99 hybrids were bioassayed with twospotted spider mites, Tetranychus urticae Koch, allowing selection of six hybrids (two susceptible and four resistant) for each generation of each family. When these 24 hybrids were characterized for spider mite repellency with thumbtack bioassays, two hybrids had repellent leaflets, demonstrating that repellency was genetically transferred to interspecific tomato hybrids. Leaflet washes containing trichome secretions from each of three hybrids, including the two having repellent leaflets, were repellent in bridge bioassays. For the two hybrids having repellent leaflets and leaflet washes, removal of trichome secretions by dipping leaflets in methanol eliminated leaflet repellency. 2,3-Dihydrofarnesoic acid was present in trichome secretions of the hybrids having leaflet repellency, and it also was present in secretions of other hybrids, indicating that its presence is essential, but not sufficient for leaflet repellency. With regard to resistance, 16 of the hybrids tested had been identified as resistant in a whole leaf bioassay, but only two had repellent leaflets, indicating that other mechanisms of resistance are present in the resistant L. hirsutum parent.     

Mites (Acari) of rubber trees (Hevea brasiliensis Muell. Arg., Euphorbiaceae) in Piracicaba, state of São Paulo, Brazil

This study determined the main mite species on rubber trees (clone RRIM-600) in Piracicaba, southeast of S?o Paulo State, from June 2002 to May 2003 and evaluated the possible relation between them. It was conducted in a plantation of 5 ha on 11 year old trees, 15 m high, surrounded with crops as pearl millet, cotton, bean or corn. Samples were taken monthly and consisted of five leaflets, five petioles (only from October 2002 on) and five terminal sections of twigs (10 cm) from 15 rubber trees. All mites of one leaflet, one petiole and one twig section of each plant were mounted for identification to genera/species to estimate the proportional occurrence of each species. A total of 84,850 mites belonging to 38 species of 34 genera and 16 families were found. Tydeidae was the family with the highest number of species (11), followed by Phytoseiidae and Stigmaeidae (4 each). The most abundant families were Eriophyidae, Tenuipalpidae and Tydeidae (totals of 43,023, 26,390 and 13,644 individuals, respectively). The highest population levels of the pest mites Calacarus heveae Feres and Tenuipalpus heveae Baker occurred at the end of the rainy season. The most abundant predators were Metaseiulus camelliae (Chant & Yoshida-Shaul), Amblyseius compositus Denmark & Muma and Euseius citrifolius Denmark & Muma. The predators could not prevent the increase of C. heveae and T. heveae from March on. However, their presence might have prevented an earlier increase and even higher levels of those mites.     

Factors that affect the selection of tomato leaflets by two whiteflies,Trialeurodes vaporariorum and Bemisia tabaci (Homoptera: Aleyrodidae)

In Japan, although greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and sweet potato whitefly, Bemisia tabaci (Gennadius), co-occur on tomato plants under greenhouse conditions, the two whiteflies are distributed differently with regard to leaf position. To elucidate the factors that determine the leaf position of these whiteflies, we investigated traits for leaflets collected from three positions on tomato plants. Furthermore, we examined leaflet selection by and fertility of the two whiteflies under choice and non-choice conditions. In addition, the effect on whitefly behavior of volatile compounds released from leaflets was evaluated by use of a Y-tube olfactometer test. Nitrogen and carbon content were highest for upper leaflets. In choice tests, more T. vaporariorum and B. tabaci adults selected upper and middle leaflets, respectively. Similarly, they oviposited more eggs on upper and middle leaflets. In non-choice tests, T. vaporariorum oviposited more eggs on upper leaflets, but B. tabaci oviposited equally on each leaflet. In Y-tube olfactometer tests, more T. vaporariorum adults moved to upper leaflets whereas more B. tabaci adults moved to middle leaflets. These results suggest that different leaflet selection by adults of these two whiteflies is likely to be associated with the different volatile compounds emitted by tomato leaflets at each position.     

Sampling strategies for assessing the intra-plant density of the cassava green mite (Mononychellus tanajoa): A case-study

Sampling data from a single cassava plant were used for testing various sampling methods. It was found that the degree of leaf damage was poorly correlated with the number of cassava green mites (CGM) present on a leaf. Sampling of specific mite stages should take into consideration the effect of leaf damage on the age distribution of the mites. Simple random sampling resulted in a high between-leaf variation caused by a vertical gradient in spider-mite abundance. The between-leaf variation could be reduced by stratified sampling. The optimum number of strata was three. Subsampling of leaflets combined with stratification provided the most precise estimates for a given sampling effort.Various regression methods for estimating the area of a cassava leaf from some simple measurements were compared. Combining the length of the longest leaflet with the number of leaflets gave the best prediction, explaining 95.8% of the total variation in observed leaf areas.     

Fine genetic mapping of the genomic region controlling leaflet shape and number of seeds per pod in the soybean

Narrow leaflet cultivars tend to have more seeds per pod than broad leaflet cultivars in soybean [Glycine max (L.) Merr.], which suggests that the leaflet-shape trait locus is tightly linked to or cosegregates with the trait locus controlling the number of seeds per pod (NSPP). Here, we attempted to further elucidate the relationship between leaflet shape and NSPP. A BC₃F₂ population from a cross between the ‘Sowon’ (narrow leaflets and high NSPP) and ‘V94-5152’ (broad leaflets and low NSPP) variants was used. The results of the molecular genetic analyses indicated that, although the NSPP characteristic, in particular, the occurrence of 4-seeded pods, is governed by additional modifying genes that are likely present in Sowon, the two traits cosegregate in the BC₃F₂ population. The mapping results generated using public markers demonstrated that the narrow leaflet-determining gene in Sowon is an allele of the previously highly studied ln gene on chromosome 20. A high-resolution map delimited the genomic region controlling both the leaflet shape and NSPP traits to a sequence length of 66 kb, corresponding to 0.7 cM. Among the three genes annotated in this 66 kb region, Glyma20g25000.1 appeared to be a good candidate for the Ln-encoding gene, owing to its 47.8% homology with the protein encoding for the JAGGED gene that regulates lateral organ development in Arabidopsis. Taken together, our results suggested that phenotypic variations for narrow leaflet and NSPP are predominantly from the pleiotropic effects of the ln gene. Thus, our results should provide a molecular framework for soybean breeding programs with the objective of improving soybean yield.     

Effects of decreasing source/sink ratio in soybeans on photosynthesis, photorespiration, transpiration and yield

Abstract. Shading of all side leaflets of a determinate soybean cultivar during pod filling significantly increased rates of photosynthesis in the unshaded centre leaflets, compared to centre leaflets of controls. Higher rates were associated with both higher stomatal and mesophyll conductances, and were reversible within 2 days when shades were removed. These higher rates of photosynthesis were not associated with decreased percentage enhancement by low oxygen, indicating that treatment effects were probably not associated with changes in photorespiration relative to photosynthesis. Percentage enhancement did, however increase as the plants approached physiological maturity, chiefly because of a decrease in photosynthesis.
In spite of these increases in rates of photosynthesis seed weight per plant was decreased by 37% in plants with side leaflets shaded for the entire pod-filling period and by 28% in plants shaded for only the second half of the period. In plants where shades were removed during the second half of pod filling seed yield was reduced by only 19% because shade removal delayed leaf senescence. The four treatments reduced yield by different mechanisms. Plants shaded continuously during pod filling produced fewer seeds than controls, but the weight per seed was similar. When shading was applied during the second half of pod fillings seed number was unchanged but weight per seed was significantly reduced. In contrast when shades were removed for the second half of pod filling, seed number remained similar to that of continuously shaded plants, but seed weight increased.
Although all shading treatments reduced yield, the reduction was not proportional to the 63% reduction in leaf area available for photosynthesis. This was because (1) photosynthetic rates in the centre leaflet of shaded plants were higher than rates in controls, (2) stem and lower surface photosynthesis in shaded leaf-lets contributed to whole leaflet photosynthesis.     

Binomial sampling to estimate rust mite (Acari: Eriophyidae) densities on orange fruit

Binomial sampling based on the proportion of samples infested was investigated for estimating mean densities of citrus rust mite, Phyllocoptruta oleivora (Ashmead), and Aculops pelekassi (Keifer) (Acari: Eriophyidae), on oranges, Citrus sinensis (L.) Osbeck. Data for the investigation were obtained by counting the number of motile mites within 600 sample units (each unit a 1-cm2 surface area per fruit) across a 4-ha block of trees (32 blocks total): five areas per 4 ha, five trees per area, 12 fruit per tree, and two samples per fruit. A significant (r2 = 0.89), linear relationship was found between ln(-ln(1 -Po)) and ln(mean), where P0 is the proportion of samples with more than zero mites. The fitted binomial parameters adequately described a validation data set from a sampling plan consisting of 192 samples. Projections indicated the fitted parameters would apply to sampling plans with as few as 48 samples, but reducing sample size resulted in an increase of bootstrap estimates falling outside expected confidence limits. Although mite count data fit the binomial model, confidence limits for mean arithmetic predictions increased dramatically as proportion of samples infested increased. Binomial sampling using a tally threshold of 0 therefore has less value when proportions of samples infested are large. Increasing the tally threshold to two mites marginally improved estimates at larger densities. Overall, binomial sampling for a general estimate of mite densities seemed to be a viable alternative to absolute counts of mites per sample for a grower using a low management threshold such as two or three mites per sample.     

Changes in photosynthesis and other chloroplast traits in lanceolate leaflet isoline of soybean

Lanceolate leaflet soybean (Glycine max L. Merrill) has been known to photosynthesize more CO₂ per unit leaf area than normal leaflet soybean. The exact reason for this increase in photosynthetic rate is still unclear. The present study was undertaken to investigate the leaf photosynthetic rate and other physiological traits in relation to chloroplast of lanceolate leaflet soybean. Ontogenic changes in apparent photosynthesis (AP) were related primarily to variations in the amount of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) per unit leaf area, and only secondarily to difference in specific activity of the said enzyme. Moreover, lanceolate leaflet consistently maintained a higher leaf AP, higher Rubisco activity, and more chloroplasts per unit leaf area basis than did normal leaflet soybean throughout leaf ontogeny. However, lanceolate soybean tended to have lower AP and Rubisco activity on a chloroplast basis. The superiority of leaf AP and other leaf physiological traits, expressed on a leaf area basis, in lanceolate leaflet soybean is associated with a corresponding increase in chloroplast number.     

Effects of CO(2) Concentration on Rubisco Activity, Amount, and Photosynthesis in Soybean Leaves

Growth at an elevated CO₂ concentration resulted in an enhanced capacity for soybean (Glycine max L. Merr. cv Bragg) leaflet photosynthesis. Plants were grown from seed in outdoor controlled-environment chambers under natural solar irradiance. Photosynthetic rates, measured during the seed filling stage, were up to 150% greater with leaflets grown at 660 compared to 330 microliters of CO₂ per liter when measured across a range of intercellular CO₂ concentrations and irradiance. Soybean plants grown at elevated CO₂ concentrations had heavier pod weights per plant, 44% heavier with 660 compared to 330 microliters of CO₂ per liter grown plants, and also greater specific leaf weights. Ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) activity showed no response (mean activity of 96 micromoles of CO₂ per square meter per second expressed on a leaflet area basis) to short-term (~1 hour) exposures to a range of CO₂ concentrations (110-880 microliters per liter), nor was a response of activity (mean activity of 1.01 micromoles of CO₂ per minute per milligram of protein) to growth CO₂ concentration (160-990 microliters per liter) observed. The amount of rubisco protein was constant, as growth CO₂ concentration was varied, and averaged 55% of the total leaflet soluble protein. Although CO₂ is required for activation of rubisco, results indicated that within the range of CO₂ concentrations used (110-990 microliters per liter), rubisco activity in soybean leaflets, in the light, was not regulated by CO₂.     

Effects of reducing sample size on density estimates of citrus rust mite (Acari: Eriophyidae) on citrus fruit: simulated sampling

The consequence of reducing sample size on the accuracy and precision of estimates of citrus rust mite, Phyllocoptruta oleivora (Ashmead), densities on oranges was investigated. The sample unit was a 1-cm2 surface area on fruit. Sampling plans consisting of 360, 300, 200, 160, 80, 48, 36, or 20 samples per 4 ha were evaluated through computer simulations by using real count data from 32 data sets of 600 sample units per 4 ha. The original and reduced sampling plans were hierarchical with different numbers of sample areas per 4 ha, trees per area, fruit per tree, and samples per fruit. Individual estimates (n=100 simulations per data set) using each plan were sometimes considerably below or above target densities. In an original set of count data with a mean of six mites per cm2, simulations of 36 samples per 4 ha produced individual estimates ranging from one to 16 mites per cm2, whereas 80 samples per 4 ha produced estimates ranging from two to 10 mites per cm2. The plans consisting of 36 or more samples were projected to provide precision levels of 0.25 (SEM/mean) or better at densities of five or more mites per cm2 based on log-data, a projection that needs to be verified under real-grove situations. Each plan consistently provided mite detection in these sampling simulations except those consisting of 20 or 36 samples, which sometimes failed to detect mites when the target density was less than five mites per cm2. The study provided insight into the probable precision, accuracy and detection thresholds for eight candidate sampling plans varying from relatively low to high resource input.     

Characterization of X-ray induced increase of mitotic cross-overs in Glycine max

Summary Three types of spots can be identified on the leaves of heterozygous light green, Y/y, Glycine max (L.) Merrill: dark green (D) and aurea (A) single spots (resembling the phenotypes of the homozygotes) and double (Db) spots consisting of adjacent D and A tissue. X-irradiation increased the frequency of each type of spot on simple and first compound leaves. The Db spots, indicative of mitotic crossing-over (MCO), increase linearly with increasing dosage. Moisture content of the seeds was independent of the rate of spot increase. At high dosages morphological alterations were observed, including spots on homozygotes, leaf area reduction, smaller seedlings, and abnormal leaf shapes. The frequency of light green spots on normal dark green, Y/Y, seedlings was tabulated and, as with all other spot types, increased with increasing X-ray dosage. Dormant soybean seeds contain leaf primordia of both simple and first compound leaves. Mature simple leaves contained more spots, reflecting a larger primordial cell number, while first compound leaves had larger spots, since each affected cell underwent more mitoses prior to leaf maturation. Within first compound leaves, the terminal leaflets developed asynchronously in relation to the lateral leaflets. Terminal leaflets were shown to be initiated first, have a larger percentage of the leaflet area covered with spots, and have larger mature leaflet area. The spontaneous rate of MCO, 3.39×10^–5 MCO events per mitosis, was increased 282-fold by 1600 R. We also ascertained that Mitomycin C is more specific for Db spot induction than X-rays. These results are compared with our similar irradiation experiments on tobacco shoot apices.