Additive Main Effects and Multiplicative Interaction Analysis of Two International Maize Cultivar Trials
The methodology used by the International Maize and Wheat Improvement Center (CIMMYT) to develop and improve its maize (Zea mays L.) germplasm involves evaluation of families or experimental varieties in extensive international testing trials. The genotype‐environmental interaction is produced by differential genotypic responses to varied environmental conditions. Its effect is to limit the accuracy of yield estimates and complicate the identification of specific genotypes for specific environments. The objective of this study was to use the Additive Main effects and Multiplicative Interaction (AMMI) method, with additive effects for genotypes and environments and multiplicative terms for genotype‐environment interaction, for analyzing data from two international maize cultivar trials. Results from the first trial were: (i) predictive assessment selected AMMI with one principal component axis, (ii) AMMI increased the precision of yield estimates equivalent to increasing the number of replications by a factor of 4.30, (iii) AMMI provided much insight into genotype‐environment interactions, and (iv) AMMI selected a different highest‐yielding genotype than did treatment means in 72% of the environments. Results for the second trial were that predictive assessment selects the AMMI with none of the principal component axes, which increased precision equivalent to increase the number of replications by a factor of 2.59. 
Soil Type and Maize Cultivar Affect the Genetic Diversity of Maize Root–Associated Burkholderia cepacia Populations
Burkholderia cepacia populations associated with the Zea mays root system were investigated to assess the influence of soil type, maize cultivar, and root localization on the degree of their genetic diversity. A total of 180 B. cepacia isolates were identified by restriction analysis of the amplified 16S rDNA (ARDRA technique). The genetic diversity among B. cepacia isolates was analyzed by the random amplified polymorphic DNA (RAPD) technique, using the 10-mer primer AP5. The analysis of molecular variance (AMOVA) method was applied to estimate the variance components for the RAPD patterns. The results indicated that, among the factors studied, the soil was clearly the dominant one in affecting the genetic diversity of maize root–associated B. cepacia populations. In fact, the percentage of variation among populations was significantly higher between B. cepacia populations recovered from maize planted in different soils than between B. cepacia populations isolated from different maize cultivars and from distinct root compartments such as rhizoplane and rhizosphere. The analysis of the genetic relationships among B. cepacia isolates resulted in dendrograms showing bacterial populations with frequent recombinations and a nonclonal genetic structure. The dendrograms were also in agreement with the AMOVA results. We were able to group strains obtained from distinct soils on the basis of their origin, confirming that soil type had the major effect on the degree of genetic diversity of the maize root–associated B. cepacia populations analyzed. On the other hand, strains isolated from distinct root compartments exhibited a random distribution which confirmed that the rhizosphere and rhizoplane populations analyzed did not significantly differ in their genetic structure. 
Dynamics of the bacterial community structure in the rhizosphere of a maize cultivar
Rhizosphere bacteria have significant contributions to crop health, productivity and carbon sequestration. As maize (Zea mays) is an important economic crop, its rhizosphere bacterial communities have been intensively investigated using various approaches. However, low-resolution profiling methods often make it difficult to understand the complicated rhizosphere bacterial communities and their dynamics. In this study, we analyzed growth-stage related dynamics of bacterial community structures in the rhizosphere of maize using the pyrosequencing method, which revealed an assembly of bacteria enriched in the rhizosphere. Our results revealed that the rhizosphere of maize was preferentially colonized by Proteobacteria, Bacteroidetes and Actinobacteria, and each bacterial phylum was represented by one or two dominating subsets of bacterial groups. Dominant genera enriched in the rhizosphere included Massilia, Burkholderia, Ralstonia, Dyella, Chitinophaga and Sphingobium. Rhizosphere bacterial community structures significantly changed through different growth stages at lower taxonomic ranks (family, genus and OTU levels). Genera Massilia, Flavobacterium, Arenimonas and Ohtaekwangia were relatively abundant at early growth stages, while genera Burkholderia, Ralstonia, Dyella, Chitinophaga, Sphingobium, Bradyrhizobium and Variovorax populations were dominant at later stages. Comparisons of pyrosequencing data collected in Illinois, USA in this study with the available data from Braunschweig, Germany indicated many common bacterial inhabitants but also many differences in the structure of bacterial communities, implying that some site-specific factors, such as soil properties, may play important roles in shaping the structure of rhizosphere bacterial community. 
Agronomic Performance of Corn Cultivars as a Function of Phosphorus Use
Aims: The research was carried out to evaluate the agronomic performance of corn cultivars in contrasting phosphorus environments in the state of Pará, Brazil.
Study Design: The experimental design was randomized blocks with ten treatments and three replications. The treatments were composed of ten cultivars: AG 1051, AG 8088PRO2, BR 206, BRS 3046, PR 27D28, 2B655PW, AL BANDEIRANTE, ANHEMBI, CATIVERDE 02 and ORION
Place and Duration of Study: In the 2017/18 crop, two competition trials of corn cultivars were carried out at Sítio Vitória, municipality of Santa Maria das Barreiras, state Pará, Brazil.
Methodology: Two competition trials of corn (Zea mays L.) cultivars were carried out under contracting conditions of phosphorus: high P (100 kg ha-1 of P2O5) and low P (50 kg ha-1 of P2O5), using simple superphosphate (18% P2O5) as the source. The agronomic efficiency of phosphorus use was obtained by the difference between grain yield in both levels, divided by the difference between doses. The variables evaluated were: ear height, plant height, ear diameter, number of rows per year, number of grains per rows and grain yield.
Results: The mean grain yield of the cultivars ranged from 5,446 kg ha-1 (low P) to 11,486 kg ha-1 (high P), and the means of all cultivars were higher in high P. The means agronomic efficiency ranged from 25.1 kg kg-1 (AL BANDEIRANTE) to 96.6 kg kg-1 (AG 1051).
Conclusion: The highest phosphorus dose (100 kg ha-1 of P2O5) resulted in higher values in the variables studied. The cultivars that stood out the most, under high and low phosphorus, were AG 8088PRO2, AG 1051 and BRS 3046, the last two being agronomically efficient. 
Influence of Deficit Irrigation at Silking Stage and Genotype on Maize (Zea mays L.) Agronomic and Yield Characters
Maize is considered susceptible to drought stress, when occurs at flowering stage. Thus, the development of drought tolerant maize cultivars is of important priority for plant breeders. The objectives of the present study were: (i) to assess the effect of maize genotype (G), irrigation (I) regime and their interaction on agronomic and yield characters and (ii) to identify drought tolerant and high yielding genotypes under water stress conditions. Six divergent inbred lines in drought tolerance were crossed in a diallel fashion. Inbreds (6), F1’s (15) and checks (2) were evaluated in the field for two seasons under two irrigation regimes, i.e. well watering (WW) and water stress (WS) via withholding the 4th and 5th irrigations to induce water stress at flowering stage. A split plot design in randomized complete blocks arrangement with three replications was used. Data analyzed across two seasons revealed that significant reduction in grain yield of maize (25.53%) due to water stress was accompanied with significant reductions in ears/plant (2.76%), 100-kernel weight (8.41%), rows/ear (4.23%), kernels/row (6.82%), kernels/plant (12.57%) and plant height (4.37%) and increases in days to silking (3.50%), anthesis silking interval (21.17%), barren stalks (26.18%) and leaf angle (9.41%). Interaction between genotypes and irrigation treatments was significant, indicating that selection is possible to be practiced under a specific irrigation treatment. Reduction in grain yield and its components due to water stress differed from genotype to genotype. The inbreds L20, L53 and Sk5, and the F1 crosses L20 × L53, L53 × Sk5 and L53× Sd7 were the most drought tolerant and highest yielders under WS and the WW environments. Mean grain yield/acre (GYPA) of drought tolerant (T) was greater than sensitive (S) inbreds and crosses by 170.18 and 54.73%, respectively under water stress (WS) conditions. Under water stress, T×T crosses were generally superior in most studied characters over T×S and S×S crosses, indicating that the most tolerant cross to water stress should include two tolerant parents and assures that water stress tolerance trait is quantitative in nature. 
 Crossa, J., Gauch Jr, H.G. and Zobel, R.W., 1990. Additive main effects and multiplicative interaction analysis of two international maize cultivar trials. Crop Science, 30(3), pp.493-500.
 Dalmastri, C., Chiarini, L., Cantale, C., Bevivino, A. and Tabacchioni, S., 1999. Soil type and maize cultivar affect the genetic diversity of maize root–associated Burkholderia cepacia populations. Microbial Ecology, 38(3), pp.273-284.
 Li, X., Rui, J., Mao, Y., Yannarell, A. and Mackie, R., 2014. Dynamics of the bacterial community structure in the rhizosphere of a maize cultivar. Soil Biology and Biochemistry, 68, pp.392-401.
 Maciel, L. C., Santos, W. F. dos, Peluzio, J. M., Junior, O. J. F., Barbosa, A. S., Silva, R. M. da, Sodré, L. F. and Oliveira, M. D. (2020) “Agronomic Performance of Corn Cultivars as a Function of Phosphorus Use”, Annual Research & Review in Biology, 35(6), pp. 99-108. doi: 10.9734/arrb/2020/v35i630241.
 Al-Naggar, A. M. M., Atta, M. M. M., Ahmed, M. A. and Younis, A. S. M. (2016) “Influence of Deficit Irrigation at Silking Stage and Genotype on Maize (Zea mays L.) Agronomic and Yield Characters”, Journal of Agriculture and Ecology Research International, 7(4), pp. 1-16. doi: 10.9734/JAERI/2016/25438.