Pod Density Research Articles

Insecticidal Efficacy <i>Mitrocarpus villosus</i> and <i>Momordica charantia</i> Extracts for the Control of Flea Beetles Podagrica spp. Jacq. (Coleoptera: Chysomelidae) on Okra <i>Abelmoschus esculentus</i> (L.) Moench

Okra is one of the most important vegetables in terms of consumption and production in Nigeria. However, a number of insects are known to attack both the leaves and fruits. In light of recent increased interest in developing plant based secondary chemistry into products suitable for integrated pest management, the objective of the present study was to investigate the efficacy of Momordica charantia and Mitrocarpus villosus crude extracts against the flea beetles on V 35 okra variety under field conditions. The field experiment was laid out in Randomized Complete Block Design (RCBD) replicated three times. The plant extracts were obtained by pounding 1 kg of plant materials using mortar and pestle and soaked overnight in 3 lts of cold water. Synthetic insecticide (Lambda cyhalothrin) was used as check to monitor the effectiveness of the plant extracts. All treatment was applied from crop establishment till harvest. Result obtained showed that at 50 days after planting (DAP) all the treatments significantly (P<0.05) suppressed flea beetle infestation. Fresh fruit (pods) weights obtained from plot sprayed with plant extract were not significantly different from synthetic insecticide treated plots. While pod density per plant in the plots treated with M. villosus and M. charantia leaves extract in the study was significantly (P<0.05) different from the insecticide (Lambda cyhalothrin) treated plots, the control treatment produced highest pod density (23.50 pods/plant) followed by M. villosus (20.33 pods/plant) and M. charantia (19.20 pods/plant). It is evident from the study that crude extracts of M. villosus and M. charantia could be used as plant based biopesticides as alternatives to synthetic insecticides to manage flea beetle on okra. They have proven to be effective and could be exploited and used by small to medium scale okra farmers.

Study on Plant Morphological Traits and Production Characteristics of Super High-Yielding Soybean

Super high-yielding soybean cultivar Liaodou 14, soybean cultivars from Ohio in the United States, and the common soybean cultivars from Liaoning Province, China, with similar geographic latitudes and identical pod-bearing habits were used as the study materials for a comparison of morphological traits and production characteristics to provide a theoretical basis for the breeding of improved super high-yielding soybean cultivars. Using a randomized block design, different soybean cultivars from the same latitude were compared under conventional and unconventional treatments for their production characteristics, including morphological traits, leaf area index (LAI), net photosynthesis rate, and dry matter accumulation. The specific characteristics of the super high-yielding soybean cultivar Liaodou 14 were analyzed. The results showed that the plant height of Liaodou 14 was significantly lower than that of the common cultivars from Liaoning, whereas the number of its main-stem nodes was higher than that of the cultivars from Ohio or Liaoning. A high pod density was observed in Liaodou 14 under conventional treatments. Under both conventional and unconventional treatments, the branch number of Liaodou 14 was markedly higher than that of the common cultivars from Liaoning, and its branch length and leaf inclination angle were significantly higher than those of common cultivars from Liaoning or Ohio. Only small changes in the leaf inclination angle were observed in Liaodou 14 treated with conventional or unconventional methods. Under each treatment, Liaodou 14 exhibited the lowest amplitude of reduction in SPAD values and net photosynthesis rates from the grain-filling to ripening stages; the cultivars from Ohio and the common cultivars from Liaoning exhibited more significant reductions. Liaodou 14 reached its peak LAI later than the other cultivars but maintained its LAI at a higher level for a longer duration. Under both conventional and unconventional treatments, Liaodou 14 produced a higher yield than the other two cultivars, with significant differences from the Ohio cultivars. In summary, super high-yielding soybean cultivars have several main features: suitable plant height, high pod density, good leaf structure with strong functionality, and slow leaf senescence at the late reproductive stage, which is conducive to the accumulation of dry matter and improved yield.

Yield performance of late-maturing winter canola (Brassica napus L.) types in the High Rainfall Zone of southern Australia

Area and production of canola (Brassica napus L.) in the High Rainfall Zone (HRZ) of southern Australia has increased significantly over the past decade. Varieties available to growers have not been bred specifically for the HRZ and are generally adapted to the drier regions of the cropping belt. Field experiments were conducted at Hamilton in south-west Victoria in 2005, 2006 and 2008 to identify canola traits and management suited to the HRZ of southern Australia. Nine varieties with different reported maturities (winter and spring types) were sown at either two times of sowing and/or under different nitrogen (N) fertiliser regimes. Dates of key phenological development were recorded, dry matter was determined at bud, flowering and maturity and grain yield and yield components were determined at harvest. Plant traits and climate data were assessed in relation to grain yield. Yields of the winter types were either significantly (P &lt; 0.05) greater or not significantly less than the spring types in all 3 years and similar to those reported under experimental conditions in Europe. This was despite the winter types flowering up to 35 days later than the spring types and spring rainfall being approximately half that of the long-term average. In general, the winter types had greater early vigour, greater dry matter production at the bud, flowering and maturity stages and were taller than the spring types. Regression analysis showed positive relationships between grain yield and pod density and plant size (dry matter and plant height). Plant size was influenced by variety, time of sowing and N fertiliser application rates. Crops in the HRZ were able to sustain more seeds per pod at larger canopy sizes and pod densities than those achieved in the northern hemisphere. Despite the number of pods per g of dry matter at flowering being nearly double that reported in the UK, there was little apparent reduction in the number of seeds per pod. It is possible that higher solar radiation and warmer minimum temperatures in the HRZ of Australia provide conditions more favourable for growth before, and during grainfill. This indicates that different dry matter production and yield component targets may be appropriate for canola in this environment especially in more typical seasons. It is likely that growers will need to sow new, later maturing varieties earlier and with higher rates of N fertiliser than is current practice in Australia. This study indicates that winter types may have the potential to provide improvements to the yield of canola in the HRZ either through the direct importation of varieties from overseas or through the identification and incorporation of desired traits into existing material. It is recommended that a wider range of germplasm be assessed over a greater geographical area to identify traits and management practices to optimise phenology and canopy structure. This information can be used to help inform breeders on crop improvement priorities as well providing tailored management practices to maximise grain yields for this environment.

Invasive Plants and Enemy Release: Evolution of Trait Means and Trait Correlations in Ulex europaeus

Several hypotheses that attempt to explain invasive processes are based on the fact that plants have been introduced without their natural enemies. Among them, the EICA (Evolution of Increased Competitive Ability) hypothesis is the most influential. It states that, due to enemy release, exotic plants evolve a shift in resource allocation from defence to reproduction or growth. In the native range of the invasive species Ulex europaeus, traits involved in reproduction and growth have been shown to be highly variable and genetically correlated. Thus, in order to explore the joint evolution of life history traits and susceptibility to seed predation in this species, we investigated changes in both trait means and trait correlations. To do so, we compared plants from native and invaded regions grown in a common garden. According to the expectations of the EICA hypothesis, we observed an increase in seedling height. However, there was little change in other trait means. By contrast, correlations exhibited a clear pattern: the correlations between life history traits and infestation rate by seed predators were always weaker in the invaded range than in the native range. In U. europaeus, the role of enemy release in shaping life history traits thus appeared to imply trait correlations rather than trait means. In the invaded regions studied, the correlations involving infestation rates and key life history traits such as flowering phenology, growth and pod density were reduced, enabling more independent evolution of these key traits and potentially facilitating local adaptation to a wide range of environments. These results led us to hypothesise that a relaxation of genetic correlations may be implied in the expansion of invasive species.

Soybeans Compensate at Low Seeding Rates but not at High Thinning Rates

Soybean [Glycine max (L.) Merr.] seed costs have more than tripled, so high seeding rates are expensive insurance against poor emergence associated with planting conditions or pest damage to established plant stands. Drilled soybeans (0.19 m spacing) were evaluated in New York (NY) in 2006 and 2007 at three seeding (358,000; 469,000; and 580,000 seeds ha−1) and four thinning rates (0, 10, 25, and 50% at the sixth node stage) to determine if yields can be maintained at lower seeding rates. Soybean plants responded linearly to seeding rates with 20% more grams of biomass, 0.9 more side branches, 21% more pods, and 21% more seeds plant−1 at 358,000 seeds ha−1 vs. the recommended 469,000 seeds ha−1 (21.1 g, 1.4 side branches, 30.6 pods, and 70.1 seeds plant−1), resulting in similar biomass accumulation (∼555 g m−2) during seed development (∼R5 stage), pod density (817 vs. 805 m−2), and seed density (1883 vs. 1816 m−2, respectively). Seeds pod−1 (∼2.30) and seed mass (∼170 mg) did not vary and all seeding rates yielded similarly (∼3.1 Mg ha−1). Thinning rates resulted in linear reductions in biomass accumulation and pod density with no effect on seeds pod−1 or seed mass. Thinning reduced yields linearly (3.3 Mg ha−1 for no‐thinning and 2.8 Mg ha−1 for 50% thinning). Seeding by thinning rate interactions were not observed so plant density reductions after stand establishment posed no greater risk at lower seeding rates. Growers who drill soybeans in the northeastern United States should consider lower seeding rates.

Planting Date and Seed Treatment Effects on Soybean in the Northeastern United States

Soybean [Glycine max (L.) Merr.] production is limited in the northeastern United States so research on optimum planting date is scarce. Soybean production in this region may increase because of biodiesel demand so we initiated a 2‐yr study in New York that compared soybean planting dates with and without seed‐applied fungicide/insecticide treatments. Soybean planted in mid‐ compared with late May had a longer emergence time (15 and 6 d) and lower plant densities (35.6 and 39.5 plants m−2), but produced more pods side branch−1 (7.4 and 5.5), which contributed to more pods plant−1 (30.9 and 25.7) and pods m−2 (1079 and 958, respectively). The late compared with mid‐May planting date, however, had more seeds pod−1 (2.28 and 2.19), which contributed to similar seeds m−2 (2180 and 2357) and seed yield (3.8 and 3.9 Mg ha−1, respectively). Soybean planted in mid‐June compared with mid‐May had more plants m−2 (38.0) but fewer pods side branch−1 (3.4), pods plant−1 (22.5), pods m−2 (879), seeds m−2 (1 910), and lower seed yield (3.5 Mg ha−1). Seed treatments did not affect plant density, pod density, and seed yield, but had inconsistent effects on seeds pod−1, seeds m−2, and seed mass. The results of this study indicate that there is a fairly broad optimum planting date range and that insecticide/fungicide seed treatment is not required for soybean production in the northeastern United States, but more research is necessary to corroborate these findings.

The potential for controlling Megalurothrips sjostedti (Thysanoptera: Thripidae) on cowpea, Vigna unguiculata (L.) Walp flowers using extracts of cashew (Anacardium occidentale L.) products

The efficacy of aqueous extracts of cashew, Anacardium occidentale L. products was tested on Legume flower bud thrips on field cowpea in the 1999 and 2000 seasons using nutseed and nutshell at 10% w/v, bark and leaf at 20% w/v. Aqueous extract of cashew nutshell was superior to other cashew products in reducing thrip populations in cowpea flowers and compared favourably with cypermethrin + dimethoate. Pod density per plant was significantly enhanced on cowpea plants sprayed with aqueous extract of cashew nutshell compared to other extracts. Cashew extract contains cardole (a caustic substance) and anacardic acid, which may have been responsible for its insecticidal effect on thrips. This result indicates the potential of cashew products especially the nutshell for integrated management of thrips in legume crops.

Botanical Pesticide Mixtures for Insect Pest Management on Cowpea, Vigna unguiculata (L.) Walp Plants–The Legume Flower Bud Thrips, Megalurothrips sjostedti Trybom

ABSTRACT The efficacy of aqueous neem and Eucalyptus leaf extracts in mixtures containing extracts of other plant species was investigated for the management of the legume flower bud thrips, a major post-flowering insect pest of cowpea in the Research Farm of the Institute for Agricultural Research, Ahmadu Bello University, Zaria, Nigeria. The extracts mixtures were applied at 10:10% w/v in equal ratio and sprayed four times at weekly intervals. The results showed that thrips pressure on cowpea flowers was significantly (P < 0.05) less (< 1.0/flower) on plants sprayed with leaf extract mixtures of Neem + Eucalyptus, Neem + lemon grass, Neem + bitter leaf, Neem + tomato, and Eucalyptus + African curry (in that order) than on unsprayed plants. These extract mixtures also increased pod density per plant compared with the unsprayed plants in the two years of investigation. The synergistic attributes of some plant extracts in mixtures with those of other plant species could form the basis of biopesticides formulations for resource-limited farmers in low input agriculture in the developing countries.

Field Activity of Three Mixture Levels of Plant Extract Formulations for the Management of Post-Flowering Insect Pests of Cowpea, Vigna unguiculata (L.) Walp–The Flower Thrips, Megalurothrips sjostedti (Trybom)

ABSTRACT Insecticidal attributes of aqueous extracts of West African black pepper (Piper guineense Schum and Thonn) seeds mixed at three proportional levels (10:10, 10:20, and 20:10% w/v) with neem (Azadirachta indica A. Juss) seeds, African pepper (Xylopia aethiopica (Dunal) A. Rich.) pods, garlic (Allium sativum L.) bulbs and clove (Syzigium aromaticum (L.) Merr. & Perr.) inflorescence, were evaluated against the flower thrips, Megalurothrips sjostedti Tryb. in two-year field trials. Compared with the other mixture treatments, the mixtures of West African black pepper with garlic bulb at 10:10% and 20:10% w/v were superior (P < 0.05) in reducing the numbers of M. sjostedti in cowpea flowers during the periods. Pod density was significantly (P < 0.05) higher at these mixture proportions compared with the other P. guineense mixtures and was comparable to cypermethrin + dimethoate used as synthetic check. All the plant extracts at different mixture proportions were superior to the untreated control in all the parameters considered. This result indicates the potential of incorporating P. guineense extract in mixtures with other plant species in the management of M. sjostedti on cowpea flowers to ensure optimum pod load of cowpea.

The sensitivity of flower bud thrips, Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae), on cowpea to three concentrations and spraying schedules of Piper guineense Schum. &amp; Thonn. extracts

The extracts of pods of West African black pepper, &lt;i&gt;Piper guineense&lt;/i&gt;, at 5, 10 and 20% (w/v), were applied at two, four and six weekly schedules to control the legume flower bud thrips, &lt;i&gt;Megalurothrips sjostedti&lt;/i&gt; on flowers of cowpea, &lt;i&gt;Vigna unguiculata&lt;/i&gt;. The trials were conducted for 2 years under rain fed conditions in the northern Guinea savanna region of Nigeria. The results showed that the &lt;i&gt;M. sjostedti&lt;/i&gt; population was significantly controlled on treated plots compared with the untreated check in both years. The extracts at the 20 and 10% rates and with six or four weekly applications significantly (&lt;i&gt;P&lt;/i&gt; &lt; 0.05) reduced thrips pressure on cowpea flowers, were better than the 5% extract at all spraying schedules, and had the same efficacy as the synthetic insecticide treatment. Pod density per plant was significantly higher (&lt;i&gt;P&lt;/i&gt; &lt; 0.05) on plots treated with the 20% extract at six or four weekly applications compared to other extract rates and was similar to that of the synthetic insecticide treatment. Thus, the extracts could be a good alternative to the synthetic insecticides on organically managed farms as well as on farms of limited resource farmers in the tropics and subtropics.

Field screening of nine plant extracts for the control of post-flowering insect pests of cowpea, Vigna unguiculata (L.) Walp

Crude water extracts of leaves from nine plant species were tested for efficacy against three major post flowering insect pests of cowpea in Samaru, Zaria, located in the northern Guinea savanna of Nigeria. These extracts were evaluated based on the number of pests (thrips, legume pod-borers and pod-sucking bugs complex dominated by Clavigralla tomentosicollis Stals) observed after weekly spraying intervals, pod density per plant, pod damage per plant, and grain yield (Kg/ha). All the leaf extracts gave some level of protection to cowpea crops relative to the untreated control. Pod density per plant was increased on plots sprayed with extracts of African marigold (Tagetes sp.), African Goat weed (Chromolaena odorata) and African curry (Ocimum gratissimum L.) in that order. Extracts of African curry, African bush tea (Hyptis suaveolens Poit), African marigold significantly (p < 0.05) reduced pod damage and ensured relatively higher grain yield compared with other extracts and the untreated control. However, none of the extracts were comparable to the synthetic insecticide (Cypermethrin + Dimethoate) used in the two years of study.

Studies on insecticidal potential of extracts of Gmelina arborea L. products for insect pests control on cowpea. 1. The legume flower bud thrips, Megalurothrips sjostedti Trybom

The effects of weekly foliar application of extracts of Gmelina arborea (L.) fruits, bark and leaves on flower bud thrips, Megalurothrips sjostedti Trybom and the pod carrying capacity of cowpea variety SAMPEA 7, were investigated in field studies in the 1998 and 1999 cropping seasons. All the Gmelina extracts and the synthetic insecticide (Uppercott) caused significant a reduction of thrips on treated plots compared to the untreated check. However, no significant differences were observed on the number of thrips after the first two weeks of spraying and insect sampling between the fruits, bark extracts on one hand and Uppercott on the other in both seasons. This period corresponds to the period of high thrips number on this variety of cowpea planted in the northern Guinea savanna ecological zone of Nigeria. Pod density (a measure of the ability of insecticides to control the population of thrips on field cowpea) observed in untreated plots was inferior to those in treated plots. Uppercott treated plots had superior pod density compared to plots sprayed with Gmelina extracts while the fruit extract produced superior number of pods among the other extracts treated plots.

Genetic analyses of agronomic and seed quality traits of doubled haploid population in Brassica napus through microspore culture

The results showed that the F1 genotype from the cross (Brassica napus cv. Zheshuang 758 × cv. Z-4115) had good response to embryogenesis, and their embryo yield and rate of plant regeneration reached 69.8 embryo/bud and 46.9%, respectively. Characters from the doubled haploid (DH) populations in B. napus were analyzed and it was showed that the means of each agronomic trait were between their parents, but they were nearer to the paternal in 6 agronomic traits (plant height, branch position, number of pods in the main raceme, length of pod, number of pods/plant and number of seeds/pod). The number of genes controlling each agronomic trait was analyzed based on the DH populations. The results showed that the number of genes controlling number of pods in the main raceme was the highest (15.6), and the least number of genes was involved for stem width (only 7.9). According to estimated coefficients of skewness and kurtosis of the traits tested, gene interaction was found to be absent for stem width, plant height, length of main raceme, number of primary and secondary branches, pod density in the main raceme and seed weight/plant. Complementary interaction was also observed in five agronomic traits (number of pods in the main raceme, length of pod, number of pods/plant, number of seeds/pod and 1000-seed weight). A significantly positive correlation was observed between seed yield/plant and four agronomic traits (length of main raceme, length of pod, number of pods/plant and 1000-seed weight). The experiment also showed that the erucic acid, glucosinolate, oil and protein contents of DH populations were 34.23%, 87.09 μmol/g, 44.09% and 42.67%, respectively. The numbers of genes controlling each quality trait were 7.8, 9.7, 9.4 and 8.7, respectively. Partial correlations between the seed quality traits and the agronomic characters of DH populations were analyzed. In this experiment, the partial correlations among seed quality traits were also analyzed and it was found that the oil content had a negative correlation with the other three seed quality traits.

PREDICTING YIELD LOSS IN INDETERMINATE SOYBEAN FROM POD DENSITY USING SIMULATED DAMAGE STUDIES

Developing relationships between seed yield and pod density can be useful for predicting yield loss in soybean [Glycine max (L.) Merr.] damaged by deer (Odocoileus virginianus). The objectives of this research were to (i) develop a modeling tool using differences between biomass removal treatments and controls for pod density and seed yield to quantify yield loss and (ii) assess the tool using double cross‐validation. Model development using linear and polynomial exponential (PE) equations was accomplished using 1998–2001 data from studies examining different biomass removal treatments, varieties, and row spacings. The PE model had a slightly higher coefficient of determination (R2 = 0.93) than the linear model (R2 = 0.92). Double cross‐validation of both models produced strong relationships with high coefficients of determination and predictive ability; however, the model performance statistics indicated that the PE model had higher coefficients of determination, lower mean bias error, and more robust slope estimates than the linear model. Depending on the end‐user, the simplicity of the linear model should be carefully considered in weighing the benefits of each tool. Nevertheless, these approaches provide robust tools that are not sensitive to moderate abiotic fluctuations, varying cultural practices, and a wide range of temporal biomass removal. Validating the relationship using additional data should be the next step before implementation.

Comparing Brassica oilseed crop productivity under contrasting N fertility regimes in the semiarid northern Great Plains

We compared the growth and yield of five Brassica spp. genotypes [two B.juncea (L.) Coss., two B. napus L. and one B. rapa L.] in 11 environments spanning two degrees of latitude and longitude in southern Saskatchewan in 1996–1998. All entries were managed with three levels of N fertility at each site. Plant height for the canola-quality B. juncea breeding line J904316 was 21% greater than the mean of the other genotypes, but shoot biomass did not differ for the same comparison. Cutlass Oriental mustard consistently yielded greatest across all environments while the yield of J904316 was highly variable among environments. The mean seed yield of Cutlass was 12% greater than the highest-yielding B. napus cultivar and 32% greater than the B. rapa cultivar, and had a greater harvest index. Earlier genotypes yielded greater than late-flowering and maturing genotypes within B. juncea and B. napus, but the earliest genotype, Maverick (B. rapa), yielded lower than all other genotypes. All Brassica spp. genotypes were responsive to N fertilization, and high total available N (average = 109, range = 91 to 131 kg N ha-1) was generally required to maximize seed yield, but not shoot biomass, under the conditions of this study. Pod density was the primary yield component influenced by N level. This study illustrates the potential adaptive advantage of B. juncea on the semiarid northern Great Plains. Key words: Brassica, canola, genotype, mustard, N fertility, semiarid, northern Great Plains

Comparison of an Organophosphate Insecticide with a Mycoinsecticide for the Control of Oedaleus senegalensis (Orthoptera: Acrididae) and Other Sahelian Grasshoppers at an Operational Scale

Operational scale field trials were conducted in 1996 and 1997, in the east of the Niger Republic, on 50 and 800 hectare plots, to compare the efficacy of an oil based formulation of the entomopathogenic fungus, Metarhizium anisopliae (flavoviride) var. acridum (Deuteromycotina: Hyphomycetes) with fenitrothion for the control of Sahelian grasshoppers. The Senegalese Grasshopper Oedaleus senegalensis Krauss was the most abundant species in the trials. M. anisopliae was applied at 5 x 1012 spores ha-1 at volume application rates of 2 and 0.5 l ha-1 in successive years. Fenitrothion was applied at 220 g/ha-1 at 1.25 and 0.22 l ha-1 volume application rates. Ultra low volume equipment mounted on a vehicle (1996) or a fixed wing aircraft (1997) was used for application. The M. anisopliae treatment reduced the grasshopper population significantly after 7 days and by 93% within 16 days. Fenitrothion caused a population reduction of more than 90% shortly after application, but due to immigration, the grasshopper population recovered to the initial level within 16 days. Grasshoppers treated with the fungus and given the opportunity to thermoregulate in the sun died more slowly than grasshoppers incubated in the shade. The survival of spores in the spray residue of the M. anisopliae plots assessed by exposing grasshoppers to the sprayed vegetation at intervals and monitoring disease levels during subsequent laboratory incubation, showed the spray residue to remain highly infective, for three weeks after spraying. At the end of the 1997 season, egg pod density and viability in the plot treated with the fungus was reduced compared with both untreated and the fenitrothion plots. Compared with the existing practice of large-scale treatment of grasshopper infestations with fenitrothion, use of M. anisopliae would not only be safer to mammals and less damaging to non-target organisms, but also be more effective in the long-term control of grasshoppers.

A Gregarizing Factor Present in the Egg Pod Foam of the Desert Locust Schistocerca gregaria

The behavioural phase state and coloration of hatchling Schistocerca gregaria were examined in a series of experiments to determine the means by which phase characteristics are passed between generations. Both crowding of solitary-reared females at the time of oviposition and high egg pod densities promoted behavioural gregarization, although the former appeared to be a rather more potent factor. In contrast, egg pod density alone appeared to promote the development of hatchlings with dark patterns characteristic of the gregarious phase. The phase characteristics of hatchlings were unaffected when sand previously used for oviposition was used to collect further egg pods. Early separation of presumptive gregarious eggs from egg pods laid by crowd reared females led to solitarization of the hatchlings, indicating that a factor, either in or around the eggs, removed by early separation promoted gregarization. Both the eggs and foam plugs of egg pods from crowd reared, gregarious females appeared to be a source of this gregarizing factor. In contrast, there was no evidence for a solitarization factor in egg pods from solitary-reared S. gregaria. Saline extracts of egg pod foam plugs produced an active factor which promoted gregarization both in eggs from solitary-reared females and in eggs from gregarious females which were separated and washed to remove the factor. Solitary eggs were influenced by the gregarizing factor in foam plug extracts for up to 1 day after oviposition. Saline extracts of foam plug retained their activity for up to 1 day. Initial studies on the properties of this factor were made. We conclude that the foam plugs of egg pods from crowd-reared, gregarious locusts contain a small (<3 kDa), hydrophilic gregarizing factor which is produced at the time of oviposition and which predisposes hatchlings to attain characteristics of the gregarious phase.

A gregarizing factor present in the egg pod foam of the desert locust Schistocerca gregaria.

The behavioural phase state and coloration of hatchling Schistocerca gregaria were examined in a series of experiments to determine the means by which phase characteristics are passed between generations. Both crowding of solitary-reared females at the time of oviposition and high egg pod densities promoted behavioural gregarization, although the former appeared to be a rather more potent factor. In contrast, egg pod density alone appeared to promote the development of hatchlings with dark patterns characteristic of the gregarious phase. The phase characteristics of hatchlings were unaffected when sand previously used for oviposition was used to collect further egg pods. Early separation of presumptive gregarious eggs from egg pods laid by crowd-reared females led to solitarization of the hatchlings, indicating that a factor, either in or around the eggs, removed by early separation promoted gregarization. Both the eggs and foam plugs of egg pods from crowd-reared, gregarious females appeared to be a source of this gregarizing factor. In contrast, there was no evidence for a solitarization factor in egg pods from solitary-reared S. gregaria. Saline extracts of egg pod foam plugs produced an active factor which promoted gregarization both in eggs from solitary-reared females and in eggs from gregarious females which were separated and washed to removed the factor. Solitary eggs were influenced by the gregarizing factor in foam plug extracts for up to 1 day after oviposition. Saline extracts of foam plug retained their activity for up to 1 day. Initial studies on the properties of this factor were made. We conclude that the foam plugs of egg pods from crowd-reared, gregarious locusts contain a small (<3 kDa), hydrophilic gregarizing factor which is produced at the time of oviposition and which predisposes hatchlings to attain characteristics of the gregarious phase.

Evaluation of seed yield determining factors of winter oilseed rape ( Brassica napus L.) by means of crop growth modelling

A simple crop growth model of winter oilseed rape ‘LINTUL-BRASNAP’, is briefly described and evaluated. The model simulates crop growth and development under optimum growth conditions and calculates 1) light reflection and absorption by the green canopy and flower layer, 2) total dry matter production based on light absorption and light-use efficiency by the green canopy 3) seed density (seeds m −2), 4) partitioning of dry matter to the seeds based on whether seed growth is limited by source or sink, 5) accumulation and mobilization of reserve carbohydrates and 6) crop phenological development. Two hypotheses on the duration of a critical period (CP) for seed set in a crop, (1) the duration of the flowering period and (2) a period of 350°Cd since onset of flowering, were tested by means of the model. Variation in seed density was better simulated with the second hypothesis. When the model was tested with data used for parameterization (cultivar Jet Neuf) and with other data (cultivar Victor), highly significant correlations were found between simulated and experimental data of various crop characteristics such as total dry matter production at various stages of crop development, seed density, pod density and seed yield. The differences between sowing dates were simulated better than the differences between years per sowing date. LINTUL-BRASNAP appears to be a useful tool for identifying the main crop characteristics responsible for variation in winter oilseed rape yield such as leaf area development, density of the flower layer and subsequent light absorption during the critical period of seed set. It can be used to explore options for improving the seed yield of winter oilseed rape.

Sorting Peanuts by Pod Density to Improve Quality and Kernel Maturity Distribution and to Reduce Aflatoxin1

Abstract Peanut maturity and several peanut quality factors are closely related. An examination of peanut physical properties revealed that by sorting farmer-stock peanuts into pod density classes before shelling, the maturity distributions within shelled-stock classes can be manipulated. An unsorted sample of farmer-stock peanut having an initial maturity distribution in No. 1 kernels of 66% immature, 23% mid-mature and 11% mature was sorted using a gravity separator into four pod-density fractions ranging from 98% immature and 2% mid-mature in the least dense fraction to 8% immature, 43% mid-mature and 49% mature in the most dense fraction. Along with improvements in maturity distributions, we also found that the higher test weight fractions (higher pod density) had less aflatoxin and a greater percentage of large kernels than did the low test weight fractions. Many density sorting devices were tested, including air columns, pod cleaners, and gravity tables. All of these devices were capable of sorting pods into maturity groups, but the gravity table was the most precise.