Temporal Growth Inhibition of Rice Plant and Growth Recovery Observed under Application of Anaerobically-DigestedCattle Manure

Abstract

A field experiment assessing the effect of the annual application of anaerobically-digested cattle manure (ADM), produced at a biogas plant, on paddy rice was conducted. In plots with ADM (MF), the early growth of rice plants, from transplanting to the active tillering stage, was inhibited compared to the plots with chemical fertilizers (CF). This phenomenon was observed over many growing seasons and was especially obvious in nitrogen uptake and leaf area index (LAI). However, after panicle initiation, the growth of MF-treated plants was equal to or superior to CF-treated plants. The grain yield in all the MF plots was 96 – 105% of that in the CF plots. The inorganic nitrogen content of the soil in the MF plots was higher than that in the CF plots, which was contradictory to the growth inhibition observed in the initial growth of plants in the MF plots. In contrast, the oxidation/reduction potential and pH of the surface soil in MF plots were within the normal range, indicating that these soil factors were not associated with growth inhibition observed in MF plots. Our results implied that rice cultivars with a long growing period that are able to recover from the initial growth inhibition, such as medium or late maturing cultivars, are suitable for paddy rice production fertilized with ADM.     

An evaluation on intensity of infection of Pseudocercospora leaf spot disease of cowpea cultivars (Vigna unguiculata L. Walp), with respect to infector rows, dates of inoculation and cultivars, grown under field conditions in Northeast Thailand

This investigation was carried out at the Experimental Farm, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand to evaluate intensity of infection of Pseudocercospora Leaf Spot disease of cowpea cultivars, grown under field conditions with the use of Yasothon soil series (Oxic Paleustults). The experimental design used was a strip split plot design with four replications. The experiment consisted of three factors, i.e., with and without infector rows (Factor A), with and without inoculation and inoculated dates, i.e. none inoculation, inoculated at days 15 and 30 after sowing of seeds in main plots (Factor B) and three cowpea cultivars of KVC7, KKU25 and IT81D-1228-14-1 (Factor C). The results showed that the use of infector rows of cowpea plants (KKU25) being sown at 15 days before sowing seeds of cowpea cultivars in main plots gave a similar intensity of disease as those infector rows being sown at 30 days before sowing seeds of cowpea cultivars in main plots but significantly higher than without infector rows. Pathogenic disease being inoculated to the cowpea plants at 15 days after the sowing of seeds in main plots gave significantly higher intensity of disease than none inoculation. The establishment of infector rows at 15 days ahead of the sowing of seeds in main plots together with an inoculation of the disease at 15 days after the sowing of seeds in main plots gave the best results in evaluating amount of the infected disease. Thus infector rows surrounded the main plots are required whenever trials on disease evaluation are taken place.     

Effect of defoliation on flower initiation in white clover in summer

Flowering behaviour of plants of six cultivars of Trifolium repens (Kent Wild White, Grasslands Huia, S100, Blanca, Olwen and Milkanova) growing in field plots at the Grassland Research Institute, Hurley, was recorded in mid-July. Half of each plot had been defoliated in early May, the other half in mid-June. In all cultivars defoliated in May, inflorescence initiation had stopped even though the natural photoperiod at that time was well above the critical daylength for initiation Defoliation in mid-June had led to a renewal of inflorescence initiation in all cultivars.
The results confirm that the stimulatory effect of defoliation on inflorescence initiation in plants that have stopped initiation in long days, which has previously been observed in Grasslands Huia in controlled environments, also occurs in the field and in other cultivars.     

Effects of new field resistant cultivars and in-furrow applications of phorate insecticide on tomato spotted wilt of peanut

Field experiments were conducted at Tifton, Georgia from 2008 to 2014 to determine the effects of new peanut (Arachis hypogaea) cultivars and in-furrow applications of phorate insecticide on severity of tomato spotted wilt (TSW) caused by Tomato spotted wilt virus. Several cultivars, including Florida-07, Georgia-06G, Georgia-07W, Georgia Greener, and Tifguard, had final incidence of TSW that were less than that of Georgia Green. In-furrow applications of phorate insecticide reduced incidence of TSW in Georgia Green in three experiments in which that cultivar was included. In-furrow application of phorate insecticide reduced incidence of TSW in most cases where incidence in nontreated plots was 10% or higher. Cultivars Georganic, and Georgia-10T, had final incidence of TSW that was lower than that of Georgia-06G, or Florida-07 within nontreated plots across 2011–2012. Georgia-10T and Georgia-12Y had final incidence that was lower than that of Georgia-06G, Georgia-07W, Georgia-09B and Georgia Greener across insecticide treatments in 2013. In-furrow application of phorate increased yields across cultivars in 2008–2009, and increased yield of Georgia-09B in 2010. In most other cases, phorate had no significant effect on yield. With higher levels of field resistance in most of these cultivars, especially those such as Georgia-12Y, benefits from use of phorate insecticide for TSW suppression were small, and typically did not result in yield increase. Based on these results, several of these cultivars should allow greater flexibility for insecticide choice for thrips management without increasing the risk of losses to TSW.     

种植密度对青贮玉米品种产量及相关性状的影响

以6个青贮玉米品种为试验材料,研究了3种种植密度对青贮玉米生物产量、干物质产量及相关性状的影响。结果表明,不同品种之间生物产量和干物质产量差异极显著;不同密度下品种的生物产量和干物质产量差异极显著;品种与密度互作之间生物产量和干物质产量差异分别为显著和极显著。龙育1号、高油169和高油115作为优质青贮高油玉米在黑龙江省适宜种植密度分别为7.0～8.0万株/hm2、7.0万株/hm2和6.0万株/hm2;黑饲1号在6万株/hm2时产量较高;龙辐208在7万株/hm2种植条件下,其生物产量和干物质产量均较高,尤其干物质产量最高;青贮玉米品种的青贮生育日数、株高、穗位、茎粗、收获期绿叶片数差异不大,品种之间差异主要由品种自身特性决定。中原单32可作为粒用玉米种植推广。     

Effects of infestation with Globodera rostochiensis (Wollenweber) Behrens Rol on the growth of four potato cultivars

Four potato cultivars were grown in plots which, following previous treatments, contained few or many Globodera rostochiensis (Wollenweber) Behrens Rol. Soil moisture content, leaf water potential and percentage ground cover were measured each week, and whole-plant samples (including roots) were taken $\text{6}\text{1}\text{2}$ and 9 weeks for planting. Leaf areas, fresh and dry weights and inorganic nutrient contents were measured on these samples. Stomatal resistance was measured on one occasion, 13 weeks after planting, and soil samples were taken midway between plants on the same date and roots extracted from them. Yields were measured 30 weeks after planting. In terms of yield Cara, which contains the resistance gene H₁, tolerated nematode attack better than the other cultivars. Of the non-resistant cultivars, Pentland Crown was the most tolerant and Pentland Dell the least; the fact that Maris Peer yielded less than Pentland Dell in heavily infested plots is probably attributable to its early maturity date and lower yield potential. The shoot:root ratio measured 9 weeks after planting was similar for all cultivars following the same previous treatment, but was decreased from 11·9 when the previous crop was Maris Piper to 5·6 when the previous crop was Pentland Crown. Good yields in the presence of nematodes were produced by Cara (and to a lesser extent Pentland Crown) because it produced extra roots in the heavily infested plots; Pentland Dell and Maris Peer produced fewer roots in heavily infested plots. Measuring leaf water potentials and soil water contents was of little value for estimating tolerance but the least tolerant cultivar, Pentland Dell, showed the largest increase in stomatal resistance in heavily infested plots, with Cara showing the smallest. Percentage ground-cover measurements through the growing season gave the best overall picture of the reactions of the four cultivars to nematode infestation, but were time-consuming. Concentrations of potassium in haulm dry matter were decreased and those of calcium increased by nematodes, with the magnitudes of the effects least in Cara and greatest in Pentland Dell. The prospect of developing an assay for tolerance sufficiently convenient for use by plant breeders must depend upon adapting a simple test of this type to a pot scale.     

Response of two sweet potato cultivars to weed interference

Field experiments were conducted at the U.S. Vegetable Laboratory, Charleston, SC, U.S.A in 2000, 2001, and 2004 to assess the effect of different durations of weed interference on two sweet potato cultivars with different shoot growth habits. The cultivars were Beauregard, which has a spreading growth habit that is typical of U.S. sweet potato cultivars and Carolina Bunch, with an erect growth habit. Weed interference treatments included control plots that were maintained weed free throughout the growing season and plots that were maintained weed free for 0, 10, 20, and 30 days after transplanting. In general, Carolina Bunch was more tolerant of weed interference than was Beauregard. In two of three years Carolina Bunch storage root yields were higher than Beauregard yields in plots that received no weeding; whereas, yields of the two cultivars in weed free plots were not different. Weed interference affected shoot growth to a greater extent than it affected storage root production. At the end of the growing season, Carolina Bunch shoot biomass was greater than Beauregard shoot biomass in plots receiving no weeding and in plots that were maintained weed free for 10 days in all three years. Shoot biomasses of the two cultivars were not different in weed-free plots. Weed shoot biomasses were greater in Beauregard plots than in Carolina Bunch plots in several instances. These results demonstrate that sweet potato cultivars with a vigorous, erect shoot growth habit (with shorter stems, greater branching, and a denser and taller canopy early in the growing season) may be less susceptible to weed interference than cultivars with spreading shoot growth. This study also confirmed previous observations that sweet potato productivity is not greatly affected by moderate weed interference; thus, it may not require intense weed management to produce high yields.     

Effects of pasture age on the genotype and phenotype of perennial ryegrass

Limited persistence of perennial ryegrass (Lolium perenne L.) in dairy pastures is a significant issue in parts of New Zealand. The contribution of plant genetic background to this problem is not well understood. Temporal changes were investigated in genotypic and phenotypic composition of two perennial ryegrass cultivars (Nui SE and Alto AR37, older and newer cultivars respectively) sown as fields plots at three locations. Samples from survivor populations collected annually over 6 years from each location were established in a field nursery, analysed by simple sequence repeat (SSR) markers and assessed for vigour, leaf morphology and tiller number. SSR-based estimates of the statistic G′_ST indicated no significant (p > .05) genetic differentiation between survivor populations and plants grown from remnant seed (ex-seed) after 5 years, and no significant change (p > .05) in within-population genetic diversity for either cultivar at any location. SSR analysis of endophytic fungus (Epichloë festucae var. lolii) type revealed only limited ingress of off-type ryegrass volunteers into plots at two locations. Vigour scores of survivor plants were not significantly (p > .05) different among plants collected from different locations and ex-seed plants. Leaves on ex-seed plants were longer (p < .001) than those on the survivor plants after four but not 6 years and may reflect a short-term response to climatic conditions experienced in the field nursery. Our results suggest that the reported poor ryegrass persistence is not driven by changes in population genetic structure and that the sown cultivars survived and remained true to type.     

Chloris gayana cultivars: RAPD polymorphism and field performance under salinity

Variability in the response to salinity within Chloris gayana (Rhodes grass) germplasm was evaluated under field conditions, and random amplified polymorphic DNA (RAPD) markers were used to assess genetic relatedness among cultivars/accessions. RAPD analysis showed a clustering of cultivars of known relatedness: cv. Pioneer and accessions Local and Trancas (derived from an old Pioneer pasture established in saline soil) belonged to the same cluster, Katambora to another and tetraploid Boma and Callide could be further separated, Boma belonging to a fourth, distant cluster. Field experiments were laid out in two types of plots: control [with electrical conductivity of the saturation extract (EC) = 3·64 dS m⁻¹] and saline (EC=13·10 dS m⁻¹) and two experiments were carried out: one to evaluate the effects of salinity on emergence and establishment, and the other, with a uniform number of plants per plot, to evaluate yield under saline conditions. All cultivars/accessions had salinity-associated decreases in dry-matter (DM) production during the establishment phase. After this stage, 1-year DM yield was similar in all cultivars within each salinity level and production in the saline plots was significantly lower than in controls only in cv. Callide and accession Trancas. Second-year production in the non-saline plots increased by 30% on average over the previous year, whereas an average 40% reduction was observed in the saline plots. Thus, salinity had a negative effect on Rhodes grass establishment and persistence. The cultivars could not be ranked unequivocally by production under saline conditions, but tetraploids Boma and Callide may be said to be less tolerant than the rest on the basis of an increased proportion of dead leaves and decreased number of stolons observed in the saline plot.     

Yield losses due to missing plants in potato crops

Missing plants in potato crops can be caused by diseases and other factors, and can result from non-emergence or from plants incapacitated at any time during the growing season. Field experiments were conducted to simulate missing plants and to estimate the resulting yield losses by removing different percentages of plants at random from plots at emergence and/or later stages. The recorded yield losses were not proportional to the percentage of missing plants. Two surveys of fields of table stock and seed stock of the cultivar Netted Gem in New Brunswick in 1972 showed that approximately 25% of the plants were missing at emergence, probably causing around8% loss in total tuber yield. Assuming all cultivars have similar levels of misses, the yield loss clue to missing plants at emergence in New Brunswick in 1972 was equivalent to a financial loss of approximately $1 1/2 million.     

Dependence of Grain Weight of Spring Barley Genotypes on Traits of Individual Stems

Abstract

The aim of the paper is to evaluate relationships between some plant traits and grain weight per spike of spring barley (Hordeum vulagre L.). Field trials were conducted in 1999, 2001, and 2002 in central Poland. Data were collected on morphological traits of individual plants of two cultivars, Rasbet and Rastik. The data were analyzed using path analysis. Causal relationships studied were similar for both cultivars: grain weight per spike was determined mainly by number of grains per spike (path coefficient was 0.723 for Rasbet and 0.700 for Rastik), whereas the effect of mean kernel weight was weaker (0.487 for Rasbet and 0.510 for Rastik). The only noticeable indirect effect was that of spike length on grain weight per spike via number of grains per spike (0.490 for Rasbet and 0.468 for Rastik); all the indirect effects of shoot length on grain weight per spike were negligible. We concluded that to develop new semi-dwarf and dwarf genotypes, emphasis should be placed on increased number of grains, kernel weight, and spike length.     

Performance of a High-Yielding Modern Rice Cultivar Takanari and Several Old and New Cultivars Grown with and without Chemical Fertilizer in a Submerged Paddy Field

Abstract

A high nitrogen-uptake capacity and effective use of absorbed nitrogen for dry matter and grain production are required to improve the production cost and environmental pollution. We characterized grain yield, dry matter production and nitrogen accumulation in six rice cultivars: Sekitori (released in 1848) and Aikoku (1882), referred to as SA cultivars hereafter; Koshihikari (1956); Nipponbare (1963) and Asanohikari (1987), referred to as NA cultivars hereafter; and Takanari (in 1990) as a high-yielding modern cultivar. The plants were grown with and without chemical fertilizer in a submerged paddy field. When plants were supplied with manure and chemical fertilizer, Takanari consistently produced the heaviest grain and dry matter, followed by the NA cultivars, and the SA cultivars the lightest. Dry matter production before heading was greater in Takanari and the NA cultivars due to the longer duration of vegetative growth. Dry matter production after heading was greatest in Takanari, with a larger crop growth rate (CGR), and smallest in the SA cultivars with a shorter ripening time. Greater dry matter production during ripening was accompanied by the greater accumulation of nitrogen by Takanari and NA cultivars. These plants developed a larger amount of roots. The smaller light extinction coefficient of the canopy was also attributed to the higher CGR in Takanari. When plants were grown without chemical fertilizer, Takanari also produced heavier grain and dry matter, followed by the NA cultivars. The heavier grain in these cultivars resulted from the greater dry matter production before heading, which was due to the longer period of vegetative growth. The greater dry matter production and nitrogen accumulation by Takanari and NA cultivars were evident when plants were grown with chemical fertilizer. Koshihikari was characterized by a higher CGR and greater nitrogen accumulation during ripening in the absence of chemical fertilizer which should be noted in efforts to decrease rates of nitrogen application.     

Water-soluble carbohydrates in perennial ryegrass breeding

Water-soluble carbohydrate (WSC) contents of the early heading perennial ryegrass cultivar Aurora and five late heading cultivars were assessed in samples from spaced plants cut five times in 1982. Aurora had the highest overall WSC content. Majestic and Aberystwyth S23 had the lowest while Perma, Melle and Ba 9795 were intermediate. Samples from F₁ and F₂ spaced plants derived from crosses between Aurora and the five late heading cultivars were also analysed for WSC contents and heading dates were recorded. As expected, heading date behaved as a polygenic character controlled mainly by additive gene effects. However, WSC contents behaved in a more complex way with evidence of non-additive gene effects comprising dominance, overdominance (heterosis) and epistasis. It was concluded that by crossing contrasting cultivars, significant improvements in WSC content could be achieved, which may be more stable than those obtained by within-cultivar selection.     

超高产冬小麦四种微量元素的积累及其与产量性状的关系

为了明确超高产冬小麦锰、锌、铜、硼的吸收积累特点及与产量相关性状的关系,于2005-2006年冬小麦成熟期测定了不同小麦品种产量相关性状及植株和籽粒中锰、锌、铜、硼的含量与积累量。结果表明,成熟期不同冬小麦品种植株和籽粒中4种元素的含量和积累量存在不同程度的差异,但都表现为锰>锌>铜>硼。植株锰积累量与穗粒数呈显著正相关,植株锰含量和积累量与单株成穗数呈显著负相关。植株和籽粒锌含量和积累量与每穗小穗数、结实小穗数和穗粒数呈正相关,与不孕小穗数呈负相关,但相关均未达到显著水平。植株铜含量与每穗小穂数、结实小穗数、穗粒数和产量均为正相关,且相关达到显著或极显著水平。植株铜积累量与总小穗数、结实小穗数呈显著正相关,与不孕小穗数呈显著负相关。植株硼积累量与产量达到显著正相关水平。综合分析可知,4种微量元素在增加产量和优化产量构成因素中起着不同的作用,在小麦生产中应针对具体的限制因素确定不同微量元素肥料的施用技术。     

The Use of Mineral Oil in Potato Protection: Dynamics in the Plant and Effect on Potato Virus Y Spread

The focus of this study was to evaluate two mineral oils (Superior 70 and Vazyl-Y) in reducing the seasonal spread of Potato Virus Y (PVY). Three concentrations of oil (0, 5, and 10 L ha^?1 of Superior 70; 0, 7.5, and 15 L ha^?1 of Vazyl-Y) and three spray regimes for both oils (every 3–4, 7, and 10–11 days) were tested. Two weeks after top-kill, two tubers from each of 49 plants free of virus at emergence were harvested from treatment plots, sprouted, and tested for PVY with enzyme-linked immunosorbent assay (ELISA). Results revealed that in the case of Superior 70, PVY spread in mineral oil treated plots ranged from 2.1 to 12.2 %, while in the control plots it ranged from 20.4 to 37.7 % across three cultivars. In the case of Vazyl-Y, PVY spread in mineral oil treated plots ranged from 2.1 to 26.5 %, while in the control plots it ranged from 49.9 to 85.7 % across three cultivars. These data show that there was a significant reduction in PVY due to spray of mineral oils. In addition, mineral oil was quantified in plants from the Superior 70 treated and the control plots to understand the dynamics of mineral oil during the season. While there was little to no oil measured in the leaves at the early stages of plant growth, a considerable amount of mineral oil was detected close to plant maturity. A basic model of the concentration of oil in the treated foliage was formulated to confirm our understanding of the factors at play. The model could explain from 50 to 90 % of the variation in oil content observed in the field. Plant growth and size are important factors affecting oil content in mineral oil treated foliage.     

Tree thinning as an option to increase herbaceous yield of an encroached semi-arid savanna in South Africa

Background  

The investigation was conducted in a savanna area covered by what was considered an undesirably dense stand of Colophospermum mopane trees, mainly because such a dense stand of trees often results in the suppression of herbaceous plants. The objectives of this study were to determine the influence of intensity of tree thinning on the dry matter yield of herbaceous plants (notably grasses) and to investigate differences in herbaceous species composition between defined subhabitats (under tree canopies, between tree canopies and where trees have been removed). Seven plots (65 × 180 m) were subjected to different intensities of tree thinning, ranging from a totally cleared plot (0 %) to plots thinned to the equivalent of 10 %, 20%, 35 %, 50% and 75 % of the leaf biomass of a control plot (100 %) with a tree density of 2711 plants ha^-1. The establishment of herbaceous plants (grasses and forbs) in response to reduced competition from the woody plants was measured during three full growing seasons following the thinning treatments.     

Scale and spatial structure effects on the outcome of barley cultivar mixture trials for disease control

The effects of field-trial scale, including plot size, and its interaction with fertiliser level and barley germplasm on mixture efficacy in controlling powdery mildew were investigated. Two groups of cultivars, one from cultivars grown in the UK and the other from cultivars grown in Poland, along with all their respective three-component mixtures, were grown in three field trials, one with 13.5 m² plots, one with 0.4 m² plots, and the third in intermediate size plots, which included a mixture of all the cultivars in both groups in equal size treatments of structured spatial arrangements. Another trial utilised similar structured spatial arrangements to trial 3 was carried out using a combination of cultivars with appropriate matching virulence levels (trial 4). Mixtures showed either a reduction in powdery mildew infection compared with the component monoculture mean, or no significant effect. There was a trend towards greater reductions at the low fertiliser level and smaller plot size. The most structured spatial arrangement was most effective for reducing infection in trials 3 and 4, but the complex-homogeneous arrangement in the fourth trial was also effective. Rhynchosporium was reduced by a similar and substantial amount by both spatial treatments in trial 3. The plot size and structuring effects may be explained by the interaction between host heterogeneity structure and pathogen dispersal scale effects, but resource exploitation for yield was best in the complex-homogeneous arrangement in trial 3 where all components were present to respond directly. These findings have implications for methods of trialling mixtures for large-scale field use and for testing component combining ability.     

不同小麦品种对干旱锻炼响应的综合评价

为明确不同小麦品种对干旱锻炼响应的差异,采用PEG6000模拟干旱胁迫,选取江苏、山东、河南、河北等地大面积种植的110个小麦品种进行水培试验,分析了不同小麦品种叶片相对含水量、叶面积、地上部干鲜重、根干鲜重、植株干物质积累量、根系形态、脯氨酸含量、可溶性总糖含量和蔗糖含量等14个指标的锻炼系数,通过主成分分析、聚类分析方法对这些品种的锻炼响应进行综合评价。结果表明,干旱胁迫下经锻炼处理的植株各指标总体均值大于未经锻炼处理的植株。小麦不同指标的锻炼系数存在差异,其中,可溶性糖、脯氨酸等渗透物质含量的锻炼系数较大。采用主成分分析将14个形态及生理指标综合成4个相互独立的综合指标,其累计贡献率为77.178%;根据主成分综合得分评价值进行系统聚类,可将110个小麦品种分为锻炼敏感型和锻炼不敏感型两大类,前者包括扬麦158、晋麦33、济麦22、豫麦47、洛旱11等81个品种;后者包括淮麦20、淮麦28、泗水38、苏麦188等29个品种。     

Effect of cultivar maturity period on the growth and yield of potato plants grown from microtubers and conventional seed tubers

Potato plants of early cultivars grown from microtubers have been reported to have a much lower growth vigor and produce lower yields than microtubers of late cultivars. This study intended to clarify the field performance of plants grown from directly planted microtubers of cultivars with different maturity periods, with a special attention to early cultivars. The experiments were conducted at Hokkaido University, Japan, over four years. Microtubers and conventional seed tubers of the early cultivar Kitaakari, late cultivars Konafubuki and Norin 1, and very late breeding line IWA-1 were planted, and the plant growth and tuber yields were analyzed. The microtuber plants of Kitaakari had a lower initial increase in leaf area index than conventional seed tuber plants, but at the maximum shoot growth had the same leaf area index. This pattern was also observed in the other cultivars. Tuber initiation and tuber bulking occurred on average five days later in microtuber plants than in conventional seed tuber plants of cultivar Kitaakari. At maximum shoot growth, microtuber plants had on average 65% of tuber dry weight of conventional seed tuber plants, with small variation among cultivars. Irrespective of maturity period, microtuber plants showed a higher tuber increase after maximum shoot growth, achieving around 86% of tuber dry weight of conventional seed tuber plants at harvest. From the results of this study we conclude that microtuber plants of early and late cultivars have a similar yield potential relative to conventional seed tuber plants, and microtubers of both early and late cultivars might be used as an alternative seed tuber source for potato production, if necessary.     

Yield losses in soybeans from frogeye leaf spot caused by Cercospora sojina

Three soybean [Glycine max (L.) Merr.]cultivars (Samsoy 1, TGx 1025-12E and TGx 996-26E) were evaluated for yield losses resulting from frogeye leaf spot caused by Cercospora sojina Hara. Replicated field plots were established at two locations in Nigeria that have a high natural infestation of C. sojina. The cultivars were either not sprayed, sprayed once or sprayed twice during the growing season with the fungicide benomyl. Disease spread early in the season was from border rows of a susceptible soybean cultivar into the plots. Mean disease severity (DS) for unsprayed cultivars ranged from 0.6 to 4.5 on a scale of 0–5. Plots receiving two sprays had lower DS values, ranging from 0.5 to 2.4. Differences between unsprayed and double-sprayed plots for yield and 300-seed weight ranged from 2.5 to 58.8 and 0.6 to 28.6%, respectively. Seed weight was negatively correlated with DS.