International Journal of Agronomy

Cultivated Legume Species

Antonio M. De Ron, José I. Cubero, Shree P. Singh, and O. Mario Aguilar — Mon, 20 May 2013 11:14:32 +0000

Quantitative Trait Loci Analysis of Folate Content in Dry Beans, Phaseolus vulgaris L.

S. Khanal, J. Xue, R. Khanal, W. Xie, J. Shi, K. P. Pauls, and A. Navabi — Wed, 06 Mar 2013 13:47:43 +0000

Dry beans (Phaseolus vulgaris L.) contain high levels of folates, yet the level of folate may vary among different genotypes. Folates are essential vitamins and folate deficiencies may lead to a number of health problems. Among the different forms of folates, 5-methyltetrahydrofolate (5MTHF) comprises more than 80% of the total folate in dry beans. The objectives of this paper were to compare selected genotypes of dry beans for the folate content of the dry seeds and to identify quantitative trait loci (QTL) associated with the folate content in a population derived from an inter-gene-pool cross of dry beans. The folate content was examined in three large-seeded (AC Elk, Redhawk, and Taylor) and one medium-seeded (Othello) dry bean genotypes, their six F1 (i.e., one-way diallel crosses), and the F2 of Othello/Redhawk that were evaluated in the field in 2009. Total folate and 5MTHF contents were measured twice with one-hour time interval. The significant variation () in the folate content was observed among the parental genotypes, their F1 progeny, and members of the F2 population, ranging from 147 to 345 μg/100 g. There was a reduction in the 5MTHF and total folate contents in the second compared to the first measurement. Dark red kidney variety Redhawk consistently had the highest and pinto Othello had the lowest total folate and 5MTHF contents in both measurements. A single marker QTL analysis identified three QTL for total folate and 5MTHF contents in the first measurement and one marker for the total folate in the second measurement in the F2. These QTL had significant dominance effects and individually accounted for 7.7% to 10.5% of the total phenotypic variance. The total phenotypic variance explained by the four QTL was 18% for 5MTHF and 19% for total folate in the first measurement, but only 8% for total folate in the second measurement.

Response of Herbicide-Resistant Palmer Amaranth (Amaranthus palmeri) Accessions to Drought Stress

Mon, 25 Feb 2013 17:32:03 +0000

Palmer amaranth is a very problematic weed in several crops in the southern USA due to its competitive ability and resistance to herbicides representing different mechanisms of action. Variation in growth and subsequent interference of North Carolina Palmer amaranth accessions has not been examined. A greenhouse experiment determined response of 15 North Carolina Palmer amaranth accessions to drought stress beginning 15 days after seedling emergence (DAE) for a duration of 3, 5, 7, and 9 days. Following exposure to drought, plants were grown under optimal moisture conditions until harvest at 30 DAE. Five accessions each of glyphosate-resistant (GR), acetolactate synthase inhibitor-resistant (ALSR), and acetolactate synthase inhibitor-susceptible and glyphosate-susceptible (ALSS/GS) were compared. Variation in response to drought stress, based on height and dry weight reduction relative to nonstressed controls, was noted among accessions. Stress for 3 or more days affected height and dry weight. Height and dry weight of GR and ALSR accession groups were reduced less by drought than the ALSS/GS accession group. Results suggest a possible relationship between herbicide resistance and ability of Palmer amaranth to withstand drought stress and thus a possible competitive advantage for resistant accessions under limited moisture availability.

Comparing Relationships among Yield and Its Related Traits in Mycorrhizal and Nonmycorrhizal Inoculated Wheat Cultivars under Different Water Regimes Using Multivariate Statistics

Armin Saed-Moucheshi, Mohammad Pessarakli, and Bahram Heidari — Sun, 03 Feb 2013 13:15:07 +0000

Multivariate statistical techniques were used to compare the relationship between yield and its related traits under noninoculated and inoculated cultivars with mycorrhizal fungus (Glomus intraradices); each one consisted of three wheat cultivars and four water regimes. Results showed that, under inoculation conditions, spike weight per plant and total chlorophyll content of the flag leaf were the most important variables contributing to wheat grain yield variation, while, under noninoculated condition, in addition to two mentioned traits, grain weight per spike and leaf area were also important variables accounting for wheat grain yield variation. Therefore, spike weight per plant and chlorophyll content of flag leaf can be used as selection criteria in breeding programs for both inoculated and noninoculated wheat cultivars under different water regimes, and also grain weight per spike and leaf area can be considered for noninoculated condition. Furthermore, inoculation of wheat cultivars showed higher value in the most measured traits, and the results indicated that inoculation treatment could change the relationship among morphological traits of wheat cultivars under drought stress. Also, it seems that the results of stepwise regression as a selecting method together with principal component and factor analysis are stronger methods to be applied in breeding programs for screening important traits.

Grain Sorghum Response to Row Spacing and Plant Populations in the Texas Coastal Bend Region

Carlos J. Fernandez, Dan D. Fromme, and W. James Grichar — Tue, 18 Dec 2012 14:42:05 +0000

Two grain sorghum (Sorghum bicolor L. Moench) studies were conducted in the Coastal Bend Region of Texas over a two-year period. In one study, sorghum growth and yield were compared when planted in a single row on beds or planted in twin rows on beds with different plant populations under dryland or irrigation. Above average rainfall occurred in May 2000 which resulted in twin rows at any plant population producing higher yields than the single row at lower plant population. In 2001, single-row plantings with either plant population (124,000–160,000 or 161,000–198,000 plants/ha) produced higher yield than twin rows planted at 161,000–198,000 plants/ha. Under irrigation, twin rows planted at 161,000–198,000 plants/ha produced higher yields than single row at the same population; however, no other yield differences were noted when row systems or plant populations were compared. In another study, 38 cm row spacings were compared with 76 cm row spacings under two plant populations. In 2000, when rains fell at an opportune time, no yield differences were noted; however, in 2001 with below average rainfall, the 76 cm plantings at 170,000–200,000 and 210,000–240,000 plants/ha produced higher yield than the 38 cm plantings at those same plant populations.

Changes in Protein, Nonnutritional Factors, and Antioxidant Capacity during Germination of L. campestris Seeds

Tue, 18 Dec 2012 11:50:42 +0000

The changes in SDS-PAGE proteins patterns, oligosaccharides and phenolic compounds of L. campestris seeds, were evaluated during nine germination days. SDS-PAGE pattern showed 12 bands in the original protein seeds, while in the samples after 1–9 germination days, the proteins located in the range of 28–49 and 49–80 kDa indicated an important reduction, and there was an increase in bands about 27 kDa. On the other hand, oligosaccharides showed more than 50% of decrease in its total concentration after 4 germination days; nevertheless after the fifth day, the oligosaccharides concentration increases and rises more than 30% of the original concentration. Phenolic compounds increased their concentration since the first germination day reaching until 450% more than the original seed level. The obtained results are related with liberation or increase of phenolic compounds with antioxidant properties, allowing us to suggest that the germination would be used to produce legume foods for human consumption with better nutraceutical properties.

Effect of the Soil pH on the Alkaloid Content of Lupinus angustifolius

Gisela Jansen, Hans-Ulrich Jürgens, Edgar Schliephake, and Frank Ordon — Wed, 28 Nov 2012 08:37:09 +0000

Field studies were conducted in growing seasons 2004, 2005, and 2010 to investigate the effect of different soil pH values on the alkaloid content in seeds of Lupinus angustifolius. Two-year experiments with eleven cultivars were carried out in acid soils with an average of (Mecklenburg-Western Pomerania) and on calcareous soils with an average pH of 7.1 (Bavaria), respectively. In addition, in 2010, eight cultivars were grown in field experiments in soils with pH values varying between and . In all experiments conducted on soils with a higher pH ( and ), a significantly lower alkaloid content was detected in all Lupinus angustifolius cultivars than on soils with a lower pH ( and ). Results clearly show that the alkaloid content is significantly influenced by the soil pH but genotypic differences regarding the reaction to different pH values in the soil were observed.

Foliar Potassium Fertilizer Additives Affect Soybean Response and Weed Control with Glyphosate

Mon, 26 Nov 2012 12:02:35 +0000

Research in 2004 and 2005 determined the effects of foliar-applied K-fertilizer sources (0-0-62-0 (%N-%P2O5-%K2O-%S), 0-0-25-17, 3-18-18-0, and 5-0-20-13) and additive rates (2.2, 8.8, and 17.6 kg K ha−1) on glyphosate-resistant soybean response and weed control. Field experiments were conducted at Novelty and Portageville with high soil test K and weed populations and at Malden with low soil test K and weed populations. At Novelty, grain yield increased with fertilizer additives at 8.8 kg K ha−1 in a high-yield, weed-free environment in 2004, but fertilizer additives reduced yield up to 470 kg ha−1 in a low-yield year (2005) depending on the K source and rate. At Portageville, K-fertilizer additives increased grain yield from 700 to 1160 kg ha−1 compared to diammonium sulfate, depending on the K source and rate. At Malden, there was no yield response to K sources. Differences in leaf tissue K , S , B , and Cu concentrations among treatments were detected 14 d after treatment at Novelty and Malden. Tank mixtures of K-fertilizer additives with glyphosate may provide an option for foliar K applications.

Weed Control and Grain Sorghum (Sorghum bicolor) Tolerance to Pyrasulfotole plus Bromoxynil

Dan D. Fromme, Peter A. Dotray, W. James Grichar, and Carlos J. Fernandez — Thu, 22 Nov 2012 15:18:32 +0000

Field studies were conducted during the 2008 and 2009 growing seasons at five locations in the Texas grain sorghum producing regions to evaluate pyrasulfotole plus bromoxynil combinations for weed control and grain sorghum response. All pyrasulfotole plus bromoxynil combinations controlled Amaranthus palmeri, Cucumis melo, and Proboscidea louisianica at least 94% while control of Urochloa texana was never better than 69%. Pyrasulfotole plus bromoxynil combinations did result in early season chlorosis and stunting; however, by the end of the growing season no visual injury or stunting differences were noted when compared to the untreated check. Early season grain sorghum chlorosis and stunting with pyrasulfotole plus bromoxynil combinations did not affect grain sorghum yields with the exception of pyrasulfotole at 0.03 kg ai/ha plus bromoxynil at 0.26 kg ai/ha plus atrazine at 0.58 kg ai/ha applied early postemergence followed by pyrasulfotole plus bromoxynil applied mid-postemergence which reduced yield at one of two locations in 2008. Grain sorghum yield increased following all pyrasulfotole plus bromoxynil treatments compared to the untreated check in 2009.

Resistance of Echinochloa crus-galli Populations to Acetolactate Synthase-Inhibiting Herbicides

Thu, 01 Nov 2012 15:42:29 +0000

Three Echinochloa crus-galli (barnyardgrass) populations from rice fields in Arkansas (AR1 and AR2) and Mississippi (MS1), USA, were recently confirmed to be resistant to imazethapyr. Experiments were conducted to characterize cross-resistance to acetolactate synthase- (ALS-) inhibiting herbicides and determine if malathion, a known cytochrome P450 monooxygenase (CYP) inhibitor, would overcome resistance. The AR1 and MS1 populations were cross-resistant to bispyribac-sodium; however, AR2 was sensitive to bispyribac-sodium. The AR1, AR2, and MS1 populations were >94, >94, and 3.3 times, respectively, more resistant to imazamox; >94, 30, and 9.4 times, respectively, more resistant to penoxsulam; and 15, 0.9, and 7.2 times, respectively, more resistant to bispyribac-sodium compared to a susceptible population. Addition of malathion to penoxsulam reduced dry weight of all populations and increased mortality of AR2 and MS1 populations compared to penoxsulam alone. Addition of malathion to imazethapyr and bispyribac-sodium increased the mortality of MS1 population in mixture with imazethapyr and AR1 population in mixture with bispyribac-sodium compared to treatments with imazethapyr and bispyribac-sodium applied alone. Synergism of ALS-inhibiting herbicides with malathion indicates increased herbicide degradation by CYP as partial mechanism of resistance to penoxsulam in all resistant populations and probably to imazethapyr in MS1 and bispyribac-sodium in AR1 populations.

Management of Wheat Diseases

María Rosa Simón, Juan G. Annone, and Paul C. Struik — Thu, 01 Nov 2012 13:51:09 +0000

Influence of Corn (Zea mays L.) Cultivar Development on Grain Nutrient Concentration

Wed, 26 Sep 2012 11:26:43 +0000

While corn productivity has been increased by the adoption of high-yield hybrids, there are concerns that increased grain potential may be associated with diminished grain nutrient concentration. Ten corn (Zea mays L.) cultivars representing five technological levels (landrace variety, commercial variety, and double, triple, and single cross-hybrids) were cropped on a Rhodic Ferralsol Eutric soil with high fertility in 2006 (dry year) and 2007 (normal year) in Rolândia County, Brazil. At maturity, grain was evaluated for concentrations of P, K, Ca, Mg, Fe, Mn, Zn, and Cu. In general, differences among cultivars were noted for all nutrients in both years. Concentrations of P, K, Fe, and Mn were lower in the dry year, while Ca, Mg, Cu, and Zn were higher. Soil water availability appeared to exert more influence on grain nutrient concentration than did cultivar development; nutrient removal due to grain harvest was also greatly influenced by rainfall patterns and their impact on corn productivity. Even though genetic differences were noted, which may be useful to breeding programs, long-term testing in subtropical environments will be required to clarify the interaction between genetics and climate events on grain nutrient quality and exportation.

Growth and Physiological Responses of Phaseolus Species to Salinity Stress

J. S. Bayuelo-Jiménez, N. Jasso-Plata, and I. Ochoa — Thu, 20 Sep 2012 10:35:49 +0000

This paper reports the changes on growth, photosynthesis, water relations, soluble carbohydrate, and ion accumulation, for two salt-tolerant and two salt-sensitive Phaseolus species grown under increasing salinity (0, 60 and 90 mM NaCl). After 20 days exposure to salt, biomass was reduced in all species to a similar extent (about 56%), with the effect of salinity on relative growth rate (RGR) confined largely to the first week. RGR of salt-tolerant species was reduced by salinity due to leaf area ratio (LAR) reduction rather than a decline in photosynthetic capacity, whereas unit leaf rate and LAR were the key factors in determining RGR on salt-sensitive species. Photosynthetic rate and stomatal conductance decreased gradually with salinity, showing significant reductions only in salt-sensitive species at the highest salt level. There was little difference between species in the effect of salinity on water relations, as indicated by their positive turgor. Osmotic adjustment occurred in all species and depended on higher K+, Na+, and Cl− accumulation. Despite some changes in soluble carbohydrate accumulation induced by salt stress, no consistent contributions in osmotic adjustment could be found in this study. Therefore, we suggest that tolerance to salt stress is largely unrelated to carbohydrate accumulation in Phaseolus species.

Genetic Transformation of Common Bean (Phaseolus vulgaris L.) with the Gus Color Marker, the Bar Herbicide Resistance, and the Barley (Hordeum vulgare) HVA1 Drought Tolerance Genes

Kingdom Kwapata, Thang Nguyen, and Mariam Sticklen — Thu, 20 Sep 2012 10:06:26 +0000

Five common bean (Phaseolus vulgaris L.) varieties including “Condor,” “Matterhorn,” “Sedona,” “Olathe,” and “Montcalm” were genetically transformed via the Biolistic bombardment of the apical shoot meristem primordium. Transgenes included gus color marker which visually confirmed transgenic events, the bar herbicide resistance selectable marker used for in vitro selection of transgenic cultures and which confirmed Liberty herbicide resistant plants, and the barley (Hordeum vulgare) late embryogenesis abundant protein (HVA1) which conferred drought tolerance with a corresponding increase in root length of transgenic plants. Research presented here might assist in production of better P. vulgaris germplasm.

Oilseeds Crops: Agronomy, Science, and Technology

Thu, 13 Sep 2012 13:27:49 +0000

Inheritance of Evolved Glyphosate Resistance in a North Carolina Palmer Amaranth (Amaranthus palmeri) Biotype

Thu, 06 Sep 2012 19:21:54 +0000

Inheritance of glyphosate resistance in a Palmer amaranth biotype from North Carolina was studied. Glyphosate rates for 50% survival of glyphosate-resistant (GR) and glyphosate-susceptible (GS) biotypes were 1288 and 58 g ha−1, respectively. These values for F1 progenies obtained from reciprocal crosses (GR×GS and GS×GR were 794 and 501 g ha−1, respectively. Dose response of F1 progenies indicated that resistance was not fully dominant over susceptibility. Lack of significant differences between dose responses for reciprocal F1 families suggested that genetic control of glyphosate resistance was governed by nuclear genome. Analysis of F1 backcross (BC1F1) families showed that 10 and 8 BC1F1 families out of 15 fitted monogenic inheritance at 2000 and 3000 g ha−1 glyphosate, respectively. These results indicate that inheritance of glyphosate resistance in this biotype is incompletely dominant, nuclear inherited, and might not be consistent with a single gene mechanism of inheritance. Relative 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) copy number varied from 22 to 63 across 10 individuals from resistant biotype. This suggested that variable EPSPS copy number in the parents might be influential in determining if inheritance of glyphosate resistance is monogenic or polygenic in this biotype.

Role of Pigeonpea Cultivation on Soil Fertility and Farming System Sustainability in Ghana

S. Adjei-Nsiah — Tue, 28 Aug 2012 12:05:51 +0000

The productivity of the smallholder farming system in Ghana is under threat due to soil fertility decline. Mineral fertilizer is sparingly being used by smallholder farmers because of prohibitive cost. Grain legumes such as pigeonpea can play a complementary or alternative role as a source of organic fertilizer due to its ability to enhance soil fertility. Despite its importance, the potential of pigeonpea as a soil fertility improvement crop has not been exploited to any appreciable extent and the amount of land cultivated to pigeonpea in Ghana is vey negligible. This paper synthesizes recent studies that have been carried out on pigeonpea in Ghana and discusses the role of pigeonpea cultivation in soil fertility management and its implication for farming system sustainability. The paper shows that recent field studies conducted in both the semi-deciduous forest and the forest/savanna transitional agro-ecological zones of Ghana indicate that pigeonpea/maize rotations can increase maize yield by 75–200%. Barrier to widespread adoption of pigeonpea include land tenure, market, and accessibility to early maturing and high yielding varieties. The paper concludes among other things that in order to promote the cultivation of pigeonpea in Ghana, there is the need to introduce varieties that combine early maturity with high yields and other desirable traits based on farmers preferences.

Management Options and Factors Affecting Control of a Common Waterhemp (Amaranthus rudis) Biotype Resistant to Protoporphyrinogen Oxidase-Inhibiting Herbicides

Dana B. Harder, Kelly A. Nelson, and Reid J. Smeda — Sun, 26 Aug 2012 18:09:21 +0000

Repeated use of protox-inhibiting herbicides has resulted in a common waterhemp (Amaranthus rudis Sauer) biotype that survived lactofen applied up to 10 times the labeled rate. Field and greenhouse research evaluated control options for this biotype of common waterhemp. In the field, PRE applications of flumioxazin at 72 g ai ha−1, sulfentrazone at 240 g ai ha−1, and isoxaflutole at 70 g ai ha−1 controlled common waterhemp >90% up to 6 weeks after treatment. POST applications of fomesafen at 330 g ai ha−1, lactofen at 220 g ai ha−1, and acifluorfen at 420 g ai ha−1 resulted in <60% visual control of common waterhemp, but differences were detected among herbicides. In the greenhouse, glyphosate was the only herbicide that controlled protox resistant waterhemp. The majority of herbicide activity from POST flumioxazin, fomesafen, acifluorfen, and lactofen was from foliar placement, but control was less than 40% regardless of placement. Control of common waterhemp seeded at weekly intervals after herbicide treatment with flumioxazin, fomesafen, sulfentrazone, atrazine, and isoxaflutole exceeded 85% at 0 weeks after herbicide application (WAHA), while control with isoxaflutole was greater than 60% 6 WAHA. PRE and POST options for protox-resistant common waterhemp are available to manage herbicide resistance.

Interference of Selected Palmer Amaranth (Amaranthus palmeri) Biotypes in Soybean (Glycine max)

Sun, 26 Aug 2012 13:31:53 +0000

Palmer amaranth (Amaranthus palmeri S. Wats.) has become difficult to control in row crops due to selection for biotypes that are no longer controlled by acetolactate synthase inhibiting herbicides and/or glyphosate. Early season interference in soybean [Glycine max (L.) Merr.] for 40 days after emergence by three glyphosate-resistant (GR) and three glyphosate-susceptible (GS) Palmer amaranth biotypes from Georgia and North Carolina was compared in the greenhouse. A field experiment over 2 years compared season-long interference of these biotypes in soybean. The six Palmer amaranth biotypes reduced soybean height similarly in the greenhouse but did not affect soybean height in the field. Reduction in soybean fresh weight and dry weight in the greenhouse; and soybean yield in the field varied by Palmer amaranth biotypes. Soybean yield was reduced 21% by Palmer amaranth at the established field density of 0.37 plant m−2. When Palmer amaranth biotypes were grouped by response to glyphosate, the GS group reduced fresh weight, dry weight, and yield of soybean more than the GR group. The results indicate a possible small competitive disadvantage associated with glyphosate resistance, but observed differences among biotypes might also be associated with characteristics within and among biotypes other than glyphosate resistance.

N Mineralization in Production Agriculture

H. Allen Torbert and Dexter B. Watts — Tue, 21 Aug 2012 12:06:26 +0000

Effects of Cropping System and Cowpea Variety on Symbiotic Potential and Yields of Cowpea (Vigna unguiculata L. Walp) and Pearl Millet (Pennisetum glaucum L.) in the Sudano-Sahelian Zone of Mali

Zoumana Kouyaté, Tatiana Krasova-Wade, Inamoud Ibny Yattara, and Marc Neyra — Thu, 16 Aug 2012 08:23:44 +0000

Many cowpea varieties (Vigna unguiculata L. Walp) have been proposed by research in Mali. None of these varieties were investigated for their symbiotic potential in terms of root nodulation and mycorrhizal infection. An experiment was conducted at Cinzana Research Station, from 2007 to 2009 with an objective to identify a cowpea variety with high symbiotic potential which may improve millet/cowpea cropping global production. Randomized complete block (RCBD) design with a factorial combination of 3 cowpea varieties (IT89KD-374, CZ1-94-23-1, and CZ11-94-5C) and 2 cropping systems (millet/cowpea intercropping and cowpea-millet rotation) was used. On farm test was conducted to evaluate CZ11-94-5C and IT89KD-374 nodulation performance. Cowpea variety CZ11-94-5-C had the highest nodule number and nodule weight. Millet/cowpea alternate rows intercropping (1/1), only, had a significant influence on cowpea root infection rates by mycorrhizae, on the 45th day after emergence. IT89KD-374 gave the best cowpea grain yield (1540 kg ha−1) in sole crop. The highest millet grain yield (1650 kg ha−1) was obtained under CZ11-94-5C-millet rotation. Farmers' fields assessments results confirmed CZ11-94-5C performance on research station. The CZ11-94-5C cowpea variety needs to be more characterized.

Responses of Metabolites in Soybean Shoot Apices to Changing Atmospheric Carbon Dioxide Concentrations

Richard Sicher — Thu, 09 Aug 2012 09:50:59 +0000

Soybean seedlings were grown in controlled environment chambers with CO2 partial pressures of 38 (ambient) and 72 (elevated) Pa. Five or six shoot apices were harvested from individual 21- to 24-day-old plants. Metabolites were analyzed by gas chromatography and, out of 21 compounds, only sucrose and fructose increased in response to CO2 enrichment. One unidentified metabolite, Unk-21.03 decreased up to 80% in soybean apices in response to elevated CO2. Levels of Unk-21.03 decreased progressively when atmospheric CO2 partial pressures were increased from 26 to 100 Pa. Reciprocal transfer experiments showed that Unk-21.03, and sucrose in soybean apices were altered slowly over several days to changes in atmospheric CO2 partial pressures. The mass spectrum of Unk-21.03 indicated that this compound likely contained both an amino and carboxyl group and was structurally related to serine and aspartate. Our findings suggested that CO2 enrichment altered a small number of specific metabolites in soybean apices. This could be an important step in understanding how plant growth and development are affected by carbon dioxide enrichment.

Corn-Soybean Rotation Systems in the Mississippi Delta: Implications on Mycotoxin Contamination and Soil Populations of Aspergillus flavus

Sun, 29 Jul 2012 11:38:32 +0000

The effect of corn-soybean rotation on mycotoxin contamination in corn (Zea mays L.) and soybean (Glycine max L. Merrill.) grains has not been fully evaluated. Therefore, this research investigated the effect of corn-soybean rotation on aflatoxin and fumonisin contamination in respective grains. The results showed that aflatoxin levels in soybean averaged 2.3, <0.5, 0.6, and 6.8 ng/g in 2005, 2006, 2007, and 2008, while corn aflatoxin levels were 16.7, 37.1, 2.4, and 54.8 ng/g, respectively. Aspergillus flavus colonization was significantly greater (𝑃≤0.05) in corn (log 1.9, 2.9, and 4.0 cfu/g) compared to soybean (<1.3, 2.6, and 2.7 cfu/g) in 2005, 2007, and 2008, respectively. Aflatoxigenic A. flavus isolates were more frequent in corn than in soybean in all four years. Higher fumonisin levels were found in corn (0.2 to 3.6 μg/g) than in soybean (<0.2 μg/g). Rotating soybean with corn reduces the potential for aflatoxin contamination in corn by reducing A. flavus propagules in soil and grain and reducing aflatoxigenic A. flavus colonization. These results demonstrated that soybean grain is less susceptible to aflatoxin contamination compared to corn due to a lower level of colonization by A. flavus with a greater occurrence of non-aflatoxigenic isolates.

Grain Sorghum Response to Hybrid, Row Spacing, and Plant Populations along the Upper Texas Gulf Coast

Dan D. Fromme, Carlos J. Fernandez, W. James Grichar, and Rick L. Jahn — Thu, 26 Jul 2012 14:22:34 +0000

Grain sorghum (Sorghum bicolor L. Moench) along the upper Texas Gulf Coast is planted at different row spacings, plant populations, and hybrids according to grower preference and location. This study was conducted over a 3-year period (2001 to 2003) to determine the combination of hybrid, row spacing, and plant population on yield and net return per hectare. Below average rainfall for May and June occurred in 2002 and 2003 which resulted in lower yields than 2001. In 2001 and 2003, Dekalb (DK) 54 generally produced higher yields than Asgrow (A) 571 on the 51 cm row spacing. In 2002, no differences in grain sorghum yield were found when comparing both hybrids, plant populations, or row spacing with the exception of A 571 planted at 148,000 plants/ha on 102 cm centers which resulted in a yield reduction of at least 25%. When net returns were compared regardless of year or rainfall received, net dollar value per hectare tended to be higher for the 51 cm row spacing, especially with A 571.

Genotype × Environment Interaction of Mosaic Disease, Root Yields and Total Carotene Concentration of Yellow-Fleshed Cassava in Nigeria

Norbert G. Maroya, Peter Kulakow, Alfred G. O. Dixon, and Busie B. Maziya-Dixon — Thu, 26 Jul 2012 11:16:16 +0000

Twenty-one yellow-fleshed cassava genotypes were evaluated over two years in five major cassava growing agroecological zones in Nigeria. The trials were established in a randomized complete block design with four replications to assess genotype performance and Genotype × Environment interaction for cassava mosaic disease (CMD), fresh and dry root yield (FYLD; DYLD), root dry matter content (DMC), and total carotene concentration (TCC). Combined analysis of variance showed significant differences (𝑃<0.001) among genotypes (G), environment (E), and Genotype × Environment interaction (GE) for all the traits tested. For reaction to CMD, the best genotypes showing stable resistance were TMS 07/0539 and TMS 07/0628. For root yield, the best genotypes were TMS 01/1368 and TMS 07/0553. Genotype TMS 07/0593 was the best for DMC and TCC across the 10 environments. Variation among genotypes accounted for most of the Total Sum of Squares for CMD (72.1%) and TCC (34.4%). Environmental variation accounted for most of the Total Sum of Squares for FYLD (42.8%), DYLD (39.6%), and DMC (29.2%). This study revealed that TMS 07/0593 has the highest and most stable TCC, DMC with the lowest CMD severity score and appeared to be the best genotype.

Determining Critical Soil pH for Grain Sorghum Production

Thu, 19 Jul 2012 09:14:21 +0000

Grain sorghum (Sorghum bicolor L.) has become a popular rotation crop in the Great Plains. The transition from conventional tillage to no-tillage production systems has led to an increase in the need for crop rotations. Some of the soils of the Great Plains are acidic, and there is concern that grain sorghum production may be limited when grown on acidic soils. The objective of this study was to evaluate the effect of soil pH for grain sorghum production. Potassium chloride-exchangeable aluminum was also analyzed to determine grain sorghum’s sensitivity to soil aluminum (Al) concentration. The relationship between relative yield and soil pH was investigated at Lahoma, Perkins, and Haskell, Oklahoma, USA with soil pH treatments ranging from 4.0–7.0. Soil pH was altered using aluminum sulfate or hydrated lime. Soil acidity reduced grain sorghum yield, resulting in a 10% reduction in yield at soil pH 5.42. Potassium chloride-exchangeable aluminum levels above 18 mg kg−1 resulted in yield reductions of 10% or greater. Liming should be considered to increase soil pH if it is below these critical levels where grain sorghum will be produced.

Responses of Jatropha curcas to Salt and Drought Stresses

Genhua Niu, Denise Rodriguez, Mike Mendoza, John Jifon, and Girisha Ganjegunte — Thu, 12 Jul 2012 10:29:23 +0000

Two greenhouse experiments were conducted to quantify growth responses of Jatropha curcas to a range of salt and drought stresses. Typical symptoms of salinity stress such as leaf edge yellowing were observed in all elevated salinity treatments and the degree of the foliar salt damage increased with the salinity of irrigation water. Total dry weight (DW) of Jatropha plants was reduced by 30%, 30%, and 50%, respectively, when irrigated with saline solutions at electrical conductivity of 3.0, 6.0, and 9.0 dS m−1 compared to that in the control. Leaf Na+ concentration was much higher than that observed in most glycophytes. Leaf Cl− concentrations were also high. In the drought stress experiment, plants were irrigated daily with nutrient solution at 100%, 70%, 50%, or 30% daily water use (DWU). Deficit irrigation reduced plant growth and leaf development. The DW of leaves, roots, and total were reduced in the 70%, 50%, and 30% DWU compared to the 100% DWU control treatment. In summary, salinity stress and deficit irrigation significantly reduced the growth and leaf development of greenhouse-grown Jatropha plants.

Rhizome Yield of Sweet Flag (Acorus calamus L.) as Influenced by Planting Season, Harvest Time, and Spacing

R. K. S. Tiwari, K. Das, D. Pandey, R. B. Tiwari, and Jola Dubey — Sun, 01 Jul 2012 14:38:37 +0000

A study was undertaken for two consecutive years to assess the possibility of optimizing rhizome yield of Acorus calamus L. (sweet flag) by shifting the time of planting (i.e., growing in rainy and autumn seasons), maintaining different spacings, and harvesting in different months. Significantly higher yields of A. calamus were recorded when seeded in autumn (13150 kg ha−1) than rainy (6570 kg ha−1) season. Harvesting of crop after 12 months gave maximum rhizome yields of 16470 kg ha−1 and 9370 kg ha−1 respectively during autumn and rainy seasons. A similar trend was also noticed in various yield components (i.e., length, width and weight of rhizome). Closer planting (20×20 cm, 30×20 cm) gave significantly higher rhizome yield (8620 kg ha−1, 8120 kg ha−1) than wider spacing 40×40 cm (7030 kg ha−1). This study illustrated the possibility of optimizing rhizome yield of A. calamus by manipulation in the time of planting and harvesting as well as maintaining proper plant spacing.

Nitrogen Fertilizer and Growth Regulator Impacts on Tuber Deformity, Rot, and Yield for Russet Potatoes

Mark S. Reiter, Steven L. Rideout, and Joshua H. Freeman — Sun, 01 Jul 2012 11:30:19 +0000

Potatoes (Solanum tuberosum) are an important high-value commodity for producers in the Mid-Atlantic Region. Current production recommendations were based on white potatoes, and practices for Russet potatoes have not been researched in this region. The objective of this study was to test impacts of N rate (0, 67, 134, 201, and 268 kg N ha−1), N application timing (100% applied with planter, 2-way split (30% with planter and 70% band applied approximately 30 days after planting at dragoff), and three-way split (30% with planter, 50% band applied prior to drag-off, and 20% band applied at first sight of bloom)), and additions of the growth regulator maleic hydrazide (MH-30). We tested “Goldrush” and “Norkotah” Russet potato varieties on marketability, total yield, tuber deformity, and tuber soft rot incidence for sandy loam soils in the Mid-Atlantic. Overall, year variations were significant with substantial rots (up to 86.5%) occurring in year 3. Maleic hydrazide and N application timing had little consistent effect on any tested parameter. Nitrogen rate and variety factors had the greatest impacts on deformity, tuber rots, and yields for Russet potatoes in the Mid-Atlantic Region with 134 kg N ha−1 producing the highest total yields in 2009 and 2010. If tuber rots can be controlled, both “Goldrush” and “Norkotah” are acceptable varieties under the Mid-Atlantic production practices.

Influence of Verticillium dahliae Infested Peanut Residue on Wilt Development in Subsequent Cotton

Shilpi Chawla, Jason E. Woodward, and Terry A. Wheeler — Wed, 20 Jun 2012 09:51:32 +0000

Texas ranks first in cotton production in the United States and accounts for approximately 40% of the total production. Most of the cotton production is concentrated in the Texas High Plains where cotton and peanut are commonly grown in rotation. With peanut being a legume crop, farmers routinely leave residue on the soil surface to improve soil fertility; however, V. dahliae can survive in the crop residue contributing inoculum to the soil. A microplot study was conducted to investigate the impact of peanut residue infested with V. dahliae on subsequent microsclerotia density in soil and Verticillium wilt development in cotton. The effects of infested peanut residue rate on percent germination of cotton seeds and on wilt incidence were monitored in 2008 and 2009. In both years microplots were planted with a susceptible cotton cultivar, Stoneville (ST) 4554B2RF. Increasing infested peanut residue rate was positively correlated with wilt incidence in cotton and negatively correlated with germination of cotton seeds. Density of microsclerotia in the soil increased significantly with increasing rates of infested peanut residue over time. Results indicate infested peanut residue serve as a source of V. dahliae inoculum, and removing infested residue can reduce disease development in subsequent cotton crops.