Agronomic evaluation of testcrosses of drought-tolerant maize (Zea mays L.) inbred lines using different selection index methods

The present study aims at identifying potentially high-yielding testcross maize hybrids using different selection indices that consider agronomic traits other than grain yield alone. Forty-one (41) testcross hybrids developed from 20 elite drought-tolerant maize inbred lines and two inbred testers plus three hybrid checks were evaluated in the rainy seasons of 2013 and 2014 in Ogbomoso in the derived savanna agroecological zone of Nigeria. Hybrids were planted in each year in 11 × 4 lattices with two replications. Testcross hybrids and checks exhibited significant differences for all measured traits except ear height, husk cover and number of ears per plant. Grain yield of hybrids and checks averaged over the 2 years varied from 3117 to 8393 kg ha^?1 with a mean of 5935 kg ha^?1. Top 11 hybrids produced vigorous plants, each yielding >7000 kg ha^?1. Base index and multivariate index methods identified EXL11 × 9071 whereas base index and Smith–Hazel selection index methods identified EXL18 × 9071 as superior hybrids at 5% selection intensity. These hybrids will be considered for advanced breeding program and release to farmers as high-yielding drought-tolerant hybrid maize varieties in the increasingly drought-prone derived savanna agroecology of Nigeria.     

Evaluation of an acid phosphatase assay for detection of phosphorus deficiency in leaves of maize (Zea mays L.)

Assays based on acid phosphatase activity in plant tissue show promise for rapid diagnosis of phosphorus deficiency. This study was undertaken to evaluate a simple leaf disc assay for the detection of the phosphorus deficiency in maize leaves. Leaf discs were excised from 36 to 48 day old greenhouse‐grown maize plants which had been supplied with phosphate in solution culture at levels of 5, 25 or 75 yM and which had total P concentrations in the leaves ranging from 26 to 309 mmol kg^‐1 dry wt. For acid phosphatase activity determinations, discs were incubated 15 min. at 30°C with 5 mM paranitrophenol phosphate in a pH 5.8 acetate buffer. In plants which showed visual symptoms of P‐deficiency, acid phosphatase activity was 2 to 3 times as great as in P‐suf‐ficient plants. Results were inconsistent in plants which were only moderately P‐deficient. This study indicates that the leaf disc acid phosphatase assay should be useful in confirming visual diagnosis of acute phosphorus deficiency in maize, but may not be adequately sensitive to detect moderate P deficiency.     

Foliar nutrition of baby corn (Zea mays L.)

Abstract

Field experiments were conducted during late Rabi (January to March) and Kharif (June to September) seasons of 2002, to study the influence of foliar spraying of nutrients on growth and yield of baby corn (Zea mays L.). The experiment was laid out in randomized complete block design with three nutrients (phosphorous [P], potassium [K] and boron [B]) each at three concentrations along with control (water spray) and absolute control (no spray). Di-ammonium phosphate, Muriate of Potash and Borax are the sources of P, K and B nutrients respectively. Results showed that spraying of P favorably influenced the growth parameters, yield attributes and green cob and fodder yields of baby corn. Application of P at 0.75% concentration at 25 and 45 days after sowing (DAS) gave significantly higher growth parameters with thicker cobs and corns, increasing the individual cob weight, which in turn increased the green cob yield of baby corn. Increased growth parameters resulted in increased green fodder yield. Application of B and K with different concentrations and P (0.25 and 0.50%) failed to influence the growth and yield of baby corn.     

Nutrient concentration and yield of maize (Zea mays L.) after vetch (Vicia sativa L.) in conventional and reduced tillage systems

The effects of tillage on plant availability nutrients are critical to develop nutrient management strategies to optimize yield. The objective of this study was to evaluate differences in the concentration of 19-nutrient and yield after 4-year of conventional [moldboard plough (MT)] and two reduced [rototiller (ST) and chisel (CT)] tillage systems in maize (Zea mays L.) after winter vetch (Vicia sativa L.) in double crop one year. Three tillage systems were compared from 2005 to 2008 in area located in the western region of Turkey under semi-arid Mediterranean clay-loam soils. Nutrients were determined in maize leaves, stems, roots and soils. Results show that the concentration of macronutrients were found to be higher in leaves and stems of maize than roots in three tillage systems of all years, while the opposite was true for micronutrients. Among the macro and micro-nutrients, there was no effect of tillage on nutrient concentration in all maize tissues for sulfur, magnesium, sodium and copper (S, Mg, Na and Cu). However, the nitrogen, potassium, calcium, boron, zinc, manganese, iron, aluminum, barium, cadmium, cobalt, chromium, nickel, lead and selenium (N, K, Ca, B, Zn, Mn, Fe, Al, Ba, Cd, Co, Cr, Ni, Pb and Se) were affected by tillage. ST increased N in stems of 2006 compared with other systems. K in roots of 2006 was 52 and 30% greater in CT than in ST and MT, respectively, while ST and MT of 2007 resulted in 38 and 41% greater than CT. In two of four years, ST contributed to higher grain yield compared with other systems. In general, ST can effectively contribute to increase maize yield following winter vetch compared with MT under this region. Results suggested the need for different management systems associated with reduced tillage including rotation, particularly for basic nutrients. Further, results showed similarities and differences with other studies under tillage with maize following winter vetch.     

Brassinolide effects on maize (Zea mays L.) growth and yield under waterlogged conditions

Our aim was to assess if Brassinolide (BR) could ameliorate stress caused by waterlogging on maize. Two BR levels (with and without), two maize varieties [Ikom White (IKW) and Obatanpa-98 (Oba-98)] and three growth stages [control (WL_o), seedling stage (WL₁), and tasseling stage (WL₂)] were studied under waterlogging lasting 10 days. Maize growth and development were significantly (p?≤?.05) reduced by waterlogging stress under WL₁ than WL₂. Waterlogging stress at WL₁ adversely affected (p?≤?.05) the protein and relative water contents. The nitrogen (N) content among the plant partitions (leaves, stems, and grains) were reduced (p?≤?.05) at both silking and harvest. The beneficial effect of BR was more pronounced in Oba-98 with higher protein contents, dry matter yield, N-uptake and harvest index than IKW. Oba-98 was also better yielding than IKW. Thus, in a waterlogged soil, treatment of maize plants with BR at WL₁ could induce some tolerance.     

Genotype-by-environment interaction of elite heat and drought tolerant bread wheat (Triticum aestivum L.) genotypes under non-stressed and drought-stressed conditions

ABSTRACT

The selection of relatively high and stable yielding genotypes is key in wheat breeding programs to improve yield performance under heat and drought-stressed environments. This study determined grain yield response and stability among elite heat and drought tolerant bread wheat genotypes under simulated drought-stressed (DS) and non-stressed (NS) environments to select promising parents for breeding. Twenty-four elite bread wheat genotypes selected from the International Maize and Wheat Improvement Centre (CIMMYT) drought and heat tolerant nursery were assessed under NS and DS conditions using a 7?×?4 alpha-lattice design under rainout shelter (RS) and glasshouse (GH) environments. Grain yield data was subjected to analysis of variance (ANOVA), the additive main effect and multiplicative interaction (AMMI) and genotype and genotype-by-environment (GGE) biplot analyses. ANOVA and AMMI revealed highly significant (p?≤?0.001) differences among test genotypes (G), environments (E) and G?×?E interaction effects suggesting differential responses for selection. The GGE biplot explained 83.76% of total variation and aided in selection of high-yielding and stable heat and drought tolerant wheat genotypes such as LM13, LM22, LM95 and LM100. These selections are recommended for breeding for yield gains under heat and drought-stressed environments.     

Hand planter for maize (Zea mays L.) in the developing world

Third world maize (Zea mays L.) production is characterized by having extremely low yields, attributed in part to the poor planting methods employed. Maize planting in most third world countries involves placing 2–3 seeds per hill, with hills being roughly 30 cm apart. The variability in seeds per hill and distance between hills result in heterogeneous plant stands that are directly responsible for lower yields. Oklahoma State University (OSU) has developed a durable hand planter with a reciprocating internal drum that delivers single maize seeds per strike and that can also be used for mid-season application of urea fertilizer. The hand planter is 1.4 m in length, 5.8 cm in diameter, and weighs 1.9 kg when empty. The seed hopper has the capacity to hold 1 kg of seed and the tip has a sharp pointed shovel which can deliver seed to a planting depth of 5 cm in no-till and tilled soils. The current prototype has been comprehensively tested and evaluated to deliver at least 80% single seeds (singulation), with 0% misses and work well across varying seed sizes (2652–4344 seeds/kg) and different operators. Using the OSU hand planter, third world maize producers with average yields of 2.0 Mg ha^?1 could increase yields by 20%.     

Soil temperature,growth and yield of maize (Zea mays L.) as affected by wheat straw mulch

Maize crop is grown mostly in tropical/subtropical environments where drought adversely affects its production. A field experiment was conducted on sandy loam soil for four years (1999 – 2002) to study the effect of wheat straw mulch (0 and 6 t ha^?1) and planting methods (flat and channel) on maize sown on different dates. Maximum soil temperature without mulch ranged from 32.2 – 44.4°C in channel and 31.6 – 46.4°C in flat planting method. Mulching, however, lowered soil temperature by 0.8 – 7.0°C in channel and 0 – 9.8°C in flat planting. Mulching, on an average, improved leaf area index by 0.42, plant height by 14 cm, grain yield by 0.24 t ha^?1 and biomass by 1.57 t ha^?1, respectively. Mulching improved grain yield only in flat sowing. Interaction between sowing date and planting method was significant. Seasonal variation in biomass were significantly correlated (p = 0.05) with mean air temperature during 0 – 45 days after planting (DAP) (r = ?0.95), pan evaporation during 0 – 15 DAP (r = 0.79) and negative correlation with rainfall in entire cropping season (r = ?0.89), whereas biomass increase with mulch in different cropping seasons had negative relation (r = ?0.74) with amount of rain during 0 – 15 DAP.     

Prediction of maize (Zea mays L.) population using normalized-difference vegetative index (NDVI) and coefficient of variation (CV)

The process of improving crop management inputs by use of remote sensing devices is a new technology. This study presents the use of the normalized-difference vegetative index (NDVI) combined with the coefficient of variation (CV) to predict plant populations in corn (Zea mays L.) over different growth stages and different locations. About 76 plots were selected from the two sites to conduct this research. The results showed that we were not able to reliably predict plant population at lately growth stages because the canopy covered the soil with overlapping leaves. However, at early growth stages, the results suggest that as the corn plant emerged from the soil, the biomass per unit area was small and the sensor technology application for prediction of plant population was possible. Further studies may be designed based on this observation to investigate the possibility at early growth stages such as V2 and V3.     

Kinetics of 15N-labelled nitrate uptake by maize (Zea mays L.) root segments

Abstract

Isotherms and kinetic constants of nitrate uptake by excised root segments from the apical root zone of 6-d-old maize seedlings pretreated with nitrate were investigated using ¹⁵N-labelled nitrate. The isotherms were resolved into two systems namely a multiphasic saturable system at substrate concentrations lower than 2 mol m^?-3 and a linear system at higher concentrations. The detailed analysis of the multiphasic saturable system suggested the existence of at least three phases, which followed the Michaelis-Menten kinetics. The I _max and K _m of each phase increase from the lower phase to the upper phase. The distance from the root tip and the presence of stele affected considerably the linear system but only slightly the saturable system.     

Effect of nitrogen fertilizer source on corn (Zea mays L.) optical sensor response index values in a rain-fed environment

The use of optical sensors to detect nitrogen (N) deficiencies and determine in-season fertilizer recommendations has grown. Nitrogen responses are difficult to detect early in the growing season. The objective of this experiment was to determine if different N sources could deliver early season detection of N deficiencies. Four N fertilizer sources were applied at rates of 90 and 180 kg N ha^?1 across three site-years. A Greenseeker and SPAD sensor were used to measure in-season fertilizer response index (RI). When differences in sensor RI values between N rates were present, they did not occur until the V9/10 growth stage. No specific N source provided superior results that led to a reliable, early season detection of N deficiency. Reliable differences in response index values could be detected beyond the V7/V8 growth stages. For earlier detection of N responsiveness, and potential N deficiency, other management strategies should be investigated.     

Evaluation of analytical methods for carotenoid extraction from biofortified maize (Zea mays sp.)

Biofortification of maize with beta-carotene has the potential to improve vitamin A status in vitamin A deficient populations where maize is a staple crop. Accurate assessment of provitamin A carotenoids in maize must be performed to direct breeding efforts. The objective was to evaluate carotenoid extraction methods and determine essential steps for use in countries growing biofortified maize. The most reproducible method based on coefficient of variation and extraction efficiency was a modification of Kurilich and Juvik (1999). Heat and saponification are required to release carotenoids from biofortified maize and remove oils interfering with chromatographic analysis. For maize samples with high oil content, additional base may be added to ensure complete saponification without compromising results. Degradation of internal standard before carotenoids were released from the maize matrix required the addition of internal standard after heating to prevent overestimation of carotenoids. This modified method works well for lutein, zeaxanthin, beta-cryptoxanthin, alpha-carotene, and beta-carotene.     

Kinetics of zinc uptake by mycorrhizal (VAM) and non-mycorrhizal corn (Zea mays L.) roots

Summary The kinetics of Zn absorption were studied in mycorrhizal (Glomus macrocarpum) and non-mycorrhizal roots of corn (Zea mays L.) at pH 6.0 at Zn concentrations of 75 mol to 1.07 mol m^-3. Five concentration-dependent phases of Zn absorption were recognized; phase 0 (1.5–4.0 mmol m^-3) was linear but the other four phases (4.0 mmol to 1.07 mol m^-3) obeyed Michaelis-Menten kinetics. At low concentrations (less than 4 mmol m^-3), sigmoidal kinetics of Zn absorption were observed. The absorption of Zn by mycorrhizal maize was greater at low concentrations but decreased at higher levels. This appeared to be a result of a higher maximal uptake rate in phase 1 and lower K _m values in the subsequent phases. Kinetic models yielding continuous isotherms could not account for the observed multiphasic pattern.Research paper no. 6820 through the Director, Experiment Station, G.B. Pant University of Agriculture and Technology, Pantnagar 263 145, UP, India     

After effects of metals derived from a highly metal-polluted sludge on maize (Zea mays L.)

High Cd and Ni concentrations in sandy soils were built up in a field experiment, receiving an unusually metal-polluted sewage sludge between 1976 and 1980, at Bordeaux, France. The study evaluates the availability of metals and their after effects on maize at one point in time, the 8th year following termination of sludge application (1988). Plant parts (leaves, stalks, roots, grains) and soil samples were collected from plots which received 0 (Control), 50 (S1) and 300 Mg sludge DW ha^?1 (S2) as cumulative inputs. Dry-matter yield, plant metal concentrations, total, and extractable metals in soils were determined. Metal inputs resulted in a marked increase in total and extractable metals in soils, except for extractable Mn and Cu with either 0.1 N Ca(NO₃)₂ or 0.1 N CaCl₂. Total metal contents in the metal-loaded topsoils (0–20 cm depth) were very often lower, especially for Cd, Zn, and Ni, than the expected values. Explanation was partly given by the increases of metal contents below the plow layer, particularly for Cd at the low metal loading rate, and for Cd, Ni, and Cu at the high one (Gomez et al., 1992). In a control plot beside a highly metal- polluted plot, Cd, Zn, and Ni concentration in soil increased whereas the concentration of other metals was unchanged; lateral movement, especially with soil water, is plausible. Yield of leaves for plants from the S2 plot was reduced by 27%, but no toxicity symptoms developed on shoots. Yields of stalks for plants in both sludge-treated plots numerically were less than the controls but the decrease was not statistically significant. Cd and Ni concentrations increased in all plant parts with metal loading rate while Mn concentrations decreased. Leaf Cd concentration in plants from sludge-treated plots (i.e. 44 and 69 mg Cd kg^?1 DM for S1 and S2) was above its upper critical level (i.e. dry matter yield reduced by 10%: 25μg Cd g^?1 DM in corn leaves, Macnicol and Beckett, 1985). Yield reduction at the high metal-loading rate was probably due to 3 main factors: Mn deficiency in leaves, the accumulation of Ni especially in roots, and the increase of Cd in leaves. The amount of metal taken up by plants from the control plot ranked in the following order (mole ha^?1): Fe(22)? Mn(7)>Zn (5.6)?Cu (0.7), Ni (0.6), Cd (0.4). For sludge-treated plots, the order was (values for S1 and S2 in mole ha ^?1): Fe (16, 15)>Zn (7.9, 7.7)>Ni (4.3, 4.7)>Cd (1.9, 2.1)>Cu (1.0,1.2), Mn (1.5, 1.1). Zn and Cd had the greatest offtake percent from the soil to the above ground plant parts. Cd or Ni uptake by maize were correlated with extractable metals by unbuffered salts (i.e. 0.1 N Ca(NO₃)₂ and 0.1 N CaCl₂). It is concluded that part of the sludge-borne Cd and Ni can remain bioavailable in this sandy soil for a long period of time (e.g. 8 yr) after the termination of metal-polluted sludge application.     

Hormonal interactions in the rhizosphere of maize (Zea mays L.) and their effects on plant development

The phytohormones indole acetic acid (IAA), abscisic acid (ABA), isopentenyladenosine (iPA), dihydrozeatin riboside (DHZR), and zeatinriboside (ZR) were determined quantitatively using monoclonal antibodies by an enzyme immunoassay in the following samples: a) culture filtrates of known bacterial species, growing naturally in close, loose or without contact with higher plants; b) culture filtrates of heterogeneous populations of microorganisms, isolated from the rhizoplane and rhizosphere of maize as well as from root-free soil; c) sterile and nonsterile maize root exudates; d) in the rhizosphere of field-grown maize plants and in soil fractions distant from the roots (bulk soil). ABA was not detected in the culture filtrates of bacteria and ZR was not found in bulk soil and rhizosphere soil of field-grown maize. All phytohormones were present in the other samples analyzed. Bacterial cultures with cell concentrations roughly equal to those in the rhizosphere of field-grown maize may produce under optimal laboratory conditions phytohormone concentrations comparable to those measured in the rhizosphere of field-grown maize. During the whole vegetation period there was a steep phytohormone gradient in the first centimeter of soil around a maize root in the field. Inoculation of maize seedlings growing in nutrient solution with rhizosphere bacteria resulted in a synergistic increase in phytohormone concentration in comparison to the sum of hormone production by sterile plant roots and by bacteria cultures. Using regression analysis, the relationship between phytohormone concentration changes in the rhizosphere and different morphological characteristics of the maize plant were shown to be highly significant.     

N-utilization by maize (Zea mays L.) as influenced by crop rotation and field pea (Pisum sativum L.) residue management

Abstract. A five year field experiment was conducted to assess the influence of crop rotation and field pea residue incorporation into the soil on maize yield. The data indicated a 30% increase in maize yield grown in rotation with field pea compared to when it was grown after wheat and a further increase of 35% when field pea residues were incorporated into the soil. The effect of field pea and residue incorporation was greater in the presence of fertilizer nitrogen indicating the enhanced capacity of the crop to utilize N from the residue. Legume residue management in sub-tropical regions of the world, having coarse textured soils low in organic matter, could help to increase the yield of cereals besides saving some of the expensive fertilizer input.     

Response of maize (Zea mays L.) and mungbean (Vigna radiata L.) to tillage in relation to water table depth in tropical lowland rice soils

The effects of zero, minimum and conventional tillage on soil physical properties and on the growth and yield of mungbean (Vigna radiata L.) grown after lowland rice (Oryza sativa L.) were studied in field experiments conducted during the 1984 and 1985 dry seasons (DS) at two Philippine sites (clay loam, Vertic Tropaquept, with shallow water table and sandy loam, Aeric Tropaquept, with deep water table). Effects on maize (Zea mays L.) were studied only in 1984 on clay loam soil.All parameter measurements were not significantly different with minimum and conventional tillage. Tillage, averaged over minimum and conventional and in both seasons, significantly lowered bulk density (10%) and increased aeration porosity (120%) of the 0–0.10 m clay loam soil layer. In sandy loam soil in 1985, it decreased bulk density by 7% and increased aeration porosity by 61%. Tillage only slightly affected the matric suction, strength and temperature of both soils.Maize seedling emergence was 15% higher with zero tillage than with minimum and conventional tillage. Tillage, however, did not affect mungbean emergence. It significantly increased maize plant height (42%) and root length (61%) as compared with no tillage. In mungbean, tillage increased plant height (18%) and root length (60%), as averaged over both sites and seasons. In clay loam soil, tillage increased grain yield of maize by 242%. On the same field, tillage increased mungbean grain yield by 78% in 1984 and 20% in 1985. In sandy loam, tillage produced 38% more mungbean grains than without tillage.     

Variation among maize (Zea mays L.) accessions of Bendel State,Nigeria

Summary Variability in maize zein protein band mobilities in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was characterized to classify 27 maize accessions (OTUs) collected from Bendel State, Nigeria. The classification of the OTUs was achieved using two numerical procedures: average linkage cluster analysis and principal component analysis (PCA). Five clusters were delineated by the cluster analysis whereas the PCA complemented the cluster analysis by separating the OTUs with yellow kernels into one group and OTUs with early maturity into another. OTUs from the same geographical contiguity commonly grouped together. However some regional overlappings of the OTUs occurred. Results of the PCA revealed that zein bands that stained less intensely more strongly separated the OTUs into various clusters than did those that stained more intensely.     

整地时期对东北雨养区土壤含水量及玉米产量的影响

以东北雨养区春玉米农田为研究对象,分析春季和秋季2个整地时期对农田土壤含水量、土壤物理性状、土壤养分含量以及玉米产量等的影响。结果表明:秋整地可显著提高玉米产量,与春整地相比增产8.7%(P<0.05)。秋整地处理下土壤水分状况得到显著改善,播种前和苗期耕层土壤(0-20cm)含水量分别比春整地高18.9%和5.6%。整地时期对种子层土壤(0-10cm)的物理特性影响不明显(P>0.05),但秋整地可显著改善10-40cm的根层土壤物理性状,其中土壤孔隙度比春整地平均提高10.0%,而土壤容重则比春整地平均下降11.6%。整地时期对0-40cm层次的土壤硬度和土壤养分含量影响不显著。可见,秋整地主要通过改善土壤物理蓄水性能和减少水分散失提高土壤水分含量,保证较高的成株率和成穗率,进而利于玉米高产稳产。