A B73 x Palomero Toluqueño mapping population reveals local adaptation in Mexican highland maize

Generations of farmer selection in the central Mexican highlands have produced unique maize varieties adapted to the challenges of the local environment. In addition to possessing great agronomic and cultural value, Mexican highland maize represents a good system for the study of local adaptation and acquisition of adaptive phenotypes under cultivation. In this study we characterize a recombinant inbred line population derived from the B73 reference line and the Mexican highland maize variety Palomero Toluqueño. B73 and Palomero Toluqueño showed classic rank-changing differences in performance between lowland and highland field sites, indicative of local adaptation. Quantitative trait mapping identified genomic regions linked to effects on yield components that were conditionally expressed depending on the environment. For the principal genomic regions associated with ear weight and total kernel number, the Palomero Toluqueño allele conferred an advantage specifically in the highland site, consistent with local adaptation. We identified Palomero Toluqueño alleles associated with expression of characteristic highland traits, including reduced tassel branching, increased sheath pigmentation and the presence of sheath macrohairs. The oligogenic architecture of these three morphological traits supports their role in adaptation, suggesting they have arisen from consistent directional selection acting at distinct points across the genome. We discuss these results in the context of the origin of phenotypic novelty during selection, commenting on the role of de novo mutation and the acquisition of adaptive variation by gene flow from endemic wild relatives.

Assessment of Smallholder Farmers’ Adaptive Strategies on the Effects of Seasonal Rainfall Variability on Maize Yields in Nyeri County

Maize is the leading food crop produced in most parts of the world and a staple food crop in Kenya. Majority of the maize farmers are smallholders due to reduced land sizes as a result of land fragmentation. Maize farming is rain-fed making it more vulnerable to rainfall variability. Over the years, the farmers have increased their resilience and adaptive potential through indigenous knowledge so as to cope with the climate related risks. However, the increasing rainfall variability, frequency and more severe shocks likely surpass their current adaptive strategies. The study assessed existing adaptive strategies of the small-holder maize farmers in Kieni East sub-County in Nyeri Couny to the seasonal rainfall variability effects. The research adopted a mixed research design. Data was obtained from primary and secondary sources. Primary data was obtained using household structured questionnaires. Data was analyzed using descriptive methods and presented using charts and tables. SWOT analysis analyzed several underlying aspects affecting maize farmers in the sub-County. The study found that the farmers have several specific adaptive strategies to the effects of seasonal rainfall variability at their disposal which include but not limited to the use of varieties of maize seeds, seeking training, water harvesting, use of manure and fertilizers. Farmers also respond to rainfall variability by planting maize varieties that are early maturing and drought resistant as well as engaging in alternative farming activities and other economic activities.

Fertilizer Effects on Endosperm Physicochemical Properties and Resistance to Larger Grain Borer, Prostephanus truncatus (Coleoptera: Bostrichidae), in Malawian Local Maize (Zea mays L.) Varieties: Potential for Utilization of Ca and Mg Nutrition

Maize grain hardness influences storage pest resistance, a key characteristic valued by smallholder farmers. The structural changes in the endosperm determine grain hardness and are influenced by agronomic practices. The purpose of this study was to establish whether supply of calcium and magnesium based fertilizers can alter physicochemical properties of local and hybrid maize varieties and reduce the infestation by larger grain borer (Prostephanus truncatus (Coleoptera: Bostrichidae)) during storage. Two local and one hybrid maize varieties commonly grown by smallholder farmers in Malawi were cultivated under three fertilizer treatments (NPK (nitrogen, phosphorous, potassium), NPK plus gypsum, and NPK plus dolomite). After harvest, the grains were classified into flint and dent types, followed by P. truncatus infestation and determination of their physicochemical properties. The addition of gypsum and dolomite fertilizers led to higher levels of amylose, total zein and β-14 zein, traits associated with kernel hardness, compared to the application of NPK fertilizer. Moreover, local maize varieties showed higher resistance to P. truncatus infestation, hardness and biochemical properties associated with hardness (total zein, α-19 and β-14 zein, starch lysophosphatidylcholine, and non-starch free fatty acid) compared to hybrid variety. Our study suggests the potential for utilizing Ca and Mg nutrition in maize to improve kernel hardness, thus adoption of gypsum and dolomite by smallholder farmers may be beneficial against P. truncatus during storage.

Assessment of carotenoid degradation of grits from orange corn packaged in high barrier thermosealed pouches

Genetically improved maize varieties with high carotenoid levels and dark orange color have been developed to increase dietary consumption of macular carotenoids. However, postharvest and food processing conditions can cause isomerization and oxidation of carotenoids, reducing their potential impact on consumers' health. The purpose of this study was to assess the effectiveness of high barrier pouches in reducing carotenoid losses during the storage of dry-milled corn products. Orange corn grits were packaged in paper pouch bags, and three types of low-oxygen and low-moisture permeable (LOMP) pouches. Grits were packaged in each type of LOMP pouch with (LOMP-oxy) and without (LOMP-noxy) an oxygen scavenger. For six months, all pouches were stored at semi-controlled environmental conditions (22.5 ± 1.3°C, 32 ± 18% RH). After the storage period, orange corn grits stored in paper pouch bags lost 55% of total xanthophylls, whereas grits packaged in LOMP pouches only lost 8% of total xanthophylls. Orange Corn grits packaged in LOMP-oxy pouches had slightly higher carotenoid content than in LOMP-noxy pouches. Relative humidity fluctuation in the storeroom could have caused fluctuation in moisture content in the orange corn grits packaged in paper pouches, which may affect the rate of carotenoid degradation in the orange corn grits. Therefore, an effective control of the moisture content of the packaged dry-milled product and effective control of the temperature of pouches during storage conditions is essential to maximize carotenoid retention during the storage of dry-milled high carotenoid orange corn grits.

Evaluation of Drought Tolerance in Maize Inbred Lines Selected from the Shaan A Group and Shaan B Group

Drought is one of the most prevailing abiotic stresses affecting the growth, development, and productivity of maize. Knowledge of drought tolerance could help in maize improvement. However, less research has been done to comprehensively evaluate the drought tolerance of maize inbred lines. We used 27 elite maize inbred lines selected from Shaan A group and Shaan B group breeding populations to estimate their drought tolerance in 3 years 2 locations under normal field conditions and low irrigation. Using principal component analysis (PCA) and GGE biplots, all inbred lines, including the controls, could be divided into four types. Ten lines could be categorized as the high-yield drought-resistant type (‘KB081’, ‘KA105’, ‘KB417’, ‘KB215’, ‘KB-7’, ‘2013KB-37’, ‘KA203’, ‘2012KA-34’, ‘KA225’, and ‘91227’) because of their stability and wide adaptability. Compared with the controls, a large proportion of the inbred lines selected from Shaan A and Shaan B breeding populations demonstrated higher drought resistance. Our results suggest that multi-year drought screening can be used as a tool to improve the drought resistance of maize inbred lines and provide a scientific basis for making better use of the Shaan A and Shaan B maize inbred lines to breed new varieties and to identify existing drought-resistant maize varieties.

Yield Assessment of Maize Varieties under Varied Water Application in Semi-Arid Conditions of Southern Mozambique

Maize is one of the most important staple food crops in Mozambique. Its production is country-wise dominated by smallholder farmers (more than 90%) under rain-fed conditions, where the risk of crop failure is high, especially under semi-arid conditions in southern Mozambique. Several maize genotypes have been developed for the broad agro-ecological zone adaptation but lack strong evidence about their productivity and yield stability to support decision-making in farming systems. In order to assess the yield and yield stability of maize genotypes under different environments, five identical on-station trials were implemented in the period 2017 to 2019, covering summer and winter seasons in the semi-arid region of southern Mozambique. The trials were established at the experimental station of the Universidade Eduardo Mondlane (UEM) in Sábie and at the Instituto de Investigação Agrária de Moçambique (IIAM) in Chókwe. A strip-plot design in a randomized complete block arrangement with 15 maize genotypes, and three water application (rainfall plus irrigation) levels in four replications was followed in a line-source irrigation arrangement. The water application levels varied from 151 mm to 804 mm, covering different water regimes. Under well-watered summer conditions, the genotypes G6 and G12 showed high yield and high grain yield stability. In the drier conditions, either in summer or winter, the G2 and G11 genotypes produced higher grain yield but with low stability. Both groups of genotypes have a high potential to be included in technology transfer packages to smallholder farmers to address food security or large-scale commercial farmers differently.

Adoption Drivers of Improved Open-Pollinated (OPVs) Maize Varieties by Smallholder Farmers in the Eastern Cape Province of South Africa

This study assesses the determinants of adoption drivers of improved open-pollinated (OPVs) maize varieties by smallholder farmers in the Eastern Cape Province of South Africa. Cross-sectional data of multi-stage random sampling was used to randomly select 150 smallholder farmers in the province. Data collection was conducted through a well-structured questionnaire administered to 150 smallholder farmers. Descriptive statistics and a logistic regression model were used for the analyses. The inferential results reveal that the majority of farmers in the study area were females (70%) with an average age of 45 years and had six people in the households. Smallholder maize farmers spent an average of 10 years in school. The results show that smallholder maize farmers had a farm size of 3 ha and a household income of R 3565.00, which contributes highly to household and farm operations. Farmers had access to extension services and were members of farm organizations. The results show that hybrid is the most used maize variety rather than OPVs. The main reason, among other things, for the poor use and adoption of OPVs is the lack of knowledge about the seeds. The results drawn from the estimations show that socio-economic and institutional factors influenced the adoption of OPVs by farmers in the study area. Therefore, the study recommends strengthening the existing extension services to highlight the benefits of OPVs through training and farmers’ information days.

Differential response of commercial hybrid and open pollinated maize seeds to mechanical damage during seed processing

Hybrids and open pollinated varieties (OPVs) are two commercial maize seed types cultivated in Nigeria. Information on their response to mechanical damage during processing is limited. This study is thus aimed at assessing the response of hybrids and OPVs of maize seeds to mechanical damage which would facilitate fabrication of processing facilities suitable for either of the maize types. Six maize varieties: three hybids (‘New Kaduna’, ‘SDM-1’, and ‘JO-195’) and three OPVs (‘Sammaz 15’, ‘Sammaz 27’ and ‘Suwan-1-stry’) were used for the study. The seed samples were subjected to standard germination, seedling vigour analysis, accelerated ageing, conductivity and fast green tests. The result showed that all the hybrid seed varieties had more damaged seeds than their OPVs counterpart. Shoot length and root length were more affected than other parts of the seedling. There were differences in the magnitude of electrolyte leakage as well as in what time each seed type (hybrid or OPVs) passed through the phases with ‘JO-195’ having the highest rate of electrolyte leakage. Hybrid seeds had lower resistance to mechanical damage and poorer storability when compared with the OPVs. In the overall, for all the traits, ‘Sammaz 15’, the best among OPVs was more promising when compared with ‘SDM-1’ which was the best among hybrid varieties. Processing machine equipment and accessories that are suitable for hybrid seeds might be inappropriate for conditioning OPVs.

The Influence of Parental Heat-Stress Priming on Drought-Tolerant Maize Progenies’ Field Performance

Maize (Zea mays L.) is a staple crop and an industrial crop. Improving its thermotolerance will be a crucial step in ensuring food security. The objective of this research was to assess the influence of the parental growth environment on their progenies in a non-heat stress environment. The progenies evaluated in this field study were obtained from a 2 × 3 × 3 factorial in a completely randomised greenhouse experiment. Two contrasting growth environments, three maize varieties, and three soil amendments were used in the greenhouse study. A randomised complete block design experiment with three replications was used to grow the progenies. The progenies were examined for nineteen morphological attributes. In this study, 69.51% of the yield variation was explained by the first and second principal component axes. Among the studied attributes, grain weight and cob weight explained more variations in the progenies than the other attributes. The interaction of the parental heat-stress and soil amendment conditions elicited different responses from the drought-tolerant maize progenies. Based on the differences in their yield attributes, the progenies were grouped as poor yielders (Cluster IV), good yielders (Cluster I) and high yielders (Clusters II and III). The parental growth environment influenced the progenies’ field performance in a non-heat-stress environment. Further evaluation of the progenies under a heat-stress environment and molecular analyses are required to establish that a transgenerational effect has occurred.

Impact of Different Nitrogen Levels to the Grain Yield and Yield Components of Some Corn (Zea mays L.) Hybrids

Aims: The study was designed to elucidate the effect of different nitrogen (N) fertilizer levels on five different maize cultivars. Study Design: A split plot experimental design in randomized complete blocks (RCBD) with three replicates. Arrangement of seven nitrogen levels and five single cross hybrids were compared. Main plots were nitrogen levels and subplots were varieties. Place and Duration of Study: College of Agricultural Engineering Sciences at the University of Duhok, Iraq. The study was undertaken fromMarch– August 2021. Methodology: At the present research, five single cross-hybrid corn varieties were used, which were: CADZ, DKC6050, DRACHMA, MYIMY and ZP6468D. Arrangement of seven nitrogen fertilizer levels were 0, 50, 100, 150, 200, 250 and 300 kg N ha−1. The following features were studied: plant height, leaf area index, thousand kernel weight, total grain yield, total chlorophyll, protein% and oil %.The collected data were projected to SAS software program for analysis. The significant differences between treatment means were calculated using Duncan’s multiple ranges. Results: It was reveal that there were significant effect of different nitrogen fertilizer levels, maize genotypes as well as the interaction of nitrogen and genotype of maize (P<.01) for plant height, leaf area index, 1000 kernel weight, total grain yield, total chlorophyll and protein %. However, There were no significant differences between different maize genotypes as well as different nitrogen fertilizer levels (P>.05) with oil %, but the interaction of nitrogen and genotype of maize was significant (P<.01). Conclusion: Increasing the amount of nitrogen had better effect on studied characteristics of different maize varieties, in which adding 300 kg nitrogen had optimum results. In considering the response of maize varieties to nitrogen, the best variety was DRACHMA genotype while the worst variety was CADZ genotype, however this hybrids was superior in some traits.