Maize Improvement Research Articles

Breeding maize (Zea mays) for Striga resistance: Past, current and prospects in sub-saharan africa.

Striga hermonthica, causes up to 100% yield loss in maize production in Sub‐Saharan Africa. Developing Striga‐resistant maize cultivars could be a major component of integrated Striga management strategies. This paper presents a comprehensive overview of maize breeding activities related to Striga resistance and its management. Scientific surveys have revealed that conventional breeding strategies have been used more than molecular breeding strategies in maize improvement for Striga resistance. Striga resistance genes are still under study in the International Institute for Tropical Agriculture (IITA) maize breeding programme. There is also a need to discover QTL and molecular markers associated with such genes to improve Striga resistance in maize. Marker Assistance Breeding is expected to increase maize breeding efficiency with complex traits such as resistance towards Striga because of the complex nature of the host‐parasite relationship and its intersection with other environmental factors. Conventional alongside molecular tools and technical controls are promising methods to effectively assess Striga in Sub‐Saharan Africa.

Improving architectural traits of maize inflorescences

The domestication and improvement of maize resulted in radical changes in shoot architecture relative to its wild progenitor teosinte. In particular, critical modifications involved a reduction of branching and an increase in inflorescence size to meet the needs for human consumption and modern agricultural practices. Maize is a major contributor to global agricultural production by providing large and inexpensive quantities of food, animal feed, and ethanol. Maize is also a classic system for studying the genetic regulation of inflorescence formation and its enlarged female inflorescences directly influence seed production and yield. Studies on the molecular and genetic networks regulating meristem proliferation and maintenance, including receptor-ligand interactions, transcription factor regulation, and hormonal control, provide important insights into maize inflorescence development and reveal potential avenues for the targeted modification of specific architectural traits. In this review, we summarize recent findings on the molecular mechanisms controlling inflorescence formation and discuss how this knowledge can be applied to improve maize productivity in the face of present and future environmental challenges.

Genetic and molecular control of grain yield in maize.

The online version contains supplementary material available at 10.1007/s11032-021-01214-3.

Modern Approaches for the Genetic Improvement of Rice, Wheat and Maize for Abiotic Constraints-Related Traits: A Comparative Overview

After a basic description of the different sets of genetic tools and genomic approaches most relevant for modern crop breeding (e. g., QTL mapping, GWAS and genomic selection; transcriptomics, qPCR and RNA-seq; transgenesis and gene editing), this review paper describes their history and the main achievements in rice, wheat and maize research, with a further focus on crop traits related to the improvement of plant responses to face major abiotic constrains, including nutritional limitations, drought and heat tolerance, and nitrogen-use efficiency (NUE). Remarkable differences have been evidenced regarding the timing and degree of development of some genetic approaches among these major crops. The underlying reasons related to their distinct genome complexity, are also considered. Based on bibliographic records, drought tolerance and related topics (i.e., water-use efficiency) are by far the most abundantly addressed by molecular tools among the breeding objectives considered. Heat tolerance is usually more relevant than NUE in rice and wheat, while the opposite is true for maize.

Genetic diversity and population structure of early and extra-early maturing maize germplasm adapted to sub-Saharan Africa

BackgroundAssessment and effective utilization of genetic diversity in breeding programs is crucial for sustainable genetic improvement and rapid adaptation to changing breeding objectives. During the past two decades, the commercialization of the early and extra-early maturing cultivars has contributed to rapid expansion of maize into different agro-ecologies of sub-Saharan Africa (SSA) where maize has become an important component of the agricultural economy and played a vital role in food and nutritional security. The present study aimed at understanding the population structure and genetic variability among 439 early and extra-early maize inbred lines developed from three narrow-based and twenty-seven broad-based populations by the International Iinstitute of Tropical Agriculture Maize Improvement Program (IITA-MIP). These inbreds were genotyped using 9642 DArTseq-based single nucleotide polymorphism (SNP) markers distributed uniformly throughout the maize genome.ResultsAbout 40.8% SNP markers were found highly informative and exhibited polymorphic information content (PIC) greater than 0.25. The minor allele frequency and PIC ranged from 0.015 to 0.500 and 0.029 to 0.375, respectively. The STRUCTURE, neighbour-joining phylogenetic tree and principal coordinate analysis (PCoA) grouped the inbred lines into four major classes generally consistent with the selection history, ancestry and kernel colour of the inbreds but indicated a complex pattern of the genetic structure. The pattern of grouping of the lines based on the STRUCTURE analysis was in concordance with the results of the PCoA and suggested greater number of sub-populations (K = 10). Generally, the classification of the inbred lines into heterotic groups based on SNP markers was reasonably reliable and in agreement with defined heterotic groups of previously identified testers based on combining ability studies.ConclusionsComplete understanding of potential heterotic groups would be difficult to portray by depending solely on molecular markers. Therefore, planned crosses involving representative testers from opposing heterotic groups would be required to refine the existing heterotic groups. It is anticipated that the present set of inbreds could contribute new beneficial alleles for population improvement, development of hybrids and lines with potential to strengthen future breeding programs. Results of this study would help breeders in formulating breeding strategies for genetic enhancement and sustainable maize production in SSA.

Thermal Stresses in Maize: Effects and Management Strategies

Climate change can decrease the global maize productivity and grain quality. Maize crop requires an optimal temperature for better harvest productivity. A suboptimal temperature at any critical stage for a prolonged duration can negatively affect the growth and yield formation processes. This review discusses the negative impact of temperature extremes (high and low temperatures) on the morpho-physiological, biochemical, and nutritional traits of the maize crop. High temperature stress limits pollen viability and silks receptivity, leading to a significant reduction in seed setting and grain yield. Likewise, severe alterations in growth rate, photosynthesis, dry matter accumulation, cellular membranes, and antioxidant enzyme activities under low temperature collectively limit maize productivity. We also discussed various strategies with practical examples to cope with temperature stresses, including cultural practices, exogenous protectants, breeding climate-smart crops, and molecular genomics approaches. We reviewed that identified quantitative trait loci (QTLs) and genes controlling high- and low temperature stress tolerance in maize could be introgressed into otherwise elite cultivars to develop stress-tolerant cultivars. Genome editing has become a key tool for developing climate-resilient crops. Moreover, challenges to maize crop improvement such as lack of adequate resources for breeding in poor countries, poor communication among the scientists of developing and developed countries, problems in germplasm exchange, and high cost of advanced high-throughput phenotyping systems are discussed. In the end, future perspectives for maize improvement are discussed, which briefly include new breeding technologies such as transgene-free clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas)-mediated genome editing for thermo-stress tolerance in maize.

Growth and yield improvement of maize by ACC deaminase producing bacteria under dry soil conditions

The beneficial effects of plant-microbe interactions have been widely studied. This study aimed to examine the ability of ACC deaminase producing bacteria to improve maize plant growth and yield under dry soil conditions. The study consisted of laboratory analyses, a greenhouse trial, and field experiments. Eight strains of Pseudomonas and Bacillus from previous studies were formulated into four groups of bacterial consortia (PC1, PC2, PC3, and PC4) in peat-based carriers. The bacteria were evaluated for their ability to grow in osmotic stress conditions using Polyethylene Glycol. Greenhouse experiment tested the consortia to improve maize growth in soil with 50, 75, and 100% water-filled pore space (WFPS). A field experiment was conducted in a farmer’s field using bacterial consortia in combination with organic fertilizer. The results showed that most bacterial strains were able to grow in osmotic stress conditions up to -2.0 MPa. Under different WFPS levels, the four consortia tested appeared to prevent maize from further stress of water shortages, although not significantly different from the uninoculated. The highest increase of maize yield under field soil condition was shown by plants inoculated with PC3 consortium. Therefore, the PC3 consortium needs further evaluation as a promising biofertilizer for dry soil conditions.

Neurovascularization In Patients with Type 2 Diabetes Mellitus Using Different Methods of Magnetic Resonance Perfusion

GA 2-oxidases (GA2oxs) are a class of enzymes that inhibit the biosynthesis of bioactive GAs in plants. Although GA2oxs have clear roles in the development and defence responses in Arabidopsis, rice, and wheat, their potential effects on maize remain unclear. This study identified thirteen ZmGA2ox genes in maize and further characterized them using phylogenetic, gene structure, genomic locus, expression pattern analyses and GA content determination. Phylogenetic relationship analysis clearly divided the ZmGA2ox family into three groups—seven in C19-GA2ox class I, three in C19-GA2ox class II, and three in C20-GA2ox class. Evolutionary analysis suggested that ZmGA2ox1;1 and ZmGA2ox1;2, ZmGA2ox3;1 and ZmGA2ox3;2, and ZmGA2ox7;1 and ZmGA2ox7;2 are three pairs of segmental duplicated genes. Prediction of cis-regulatory elements in promoters suggested that ZmGA2ox genes were mainly associated with growth, development, hormones, and biotic/abiotic stress. Therefore, their spatial and temporal expression patterns and responses to various stress treatments were analysed on the basis of published RNA-seq data. Moreover, the changes of ZmGA2ox expression in leaves and roots of maize seedlings was detected under salt, alkali, dehydration, and cold stresses by qRT-PCR. The ZmGA2oxs exhibited obvious expression tendencies or characteristics in various organs under different abiotic stresses. The variations in the expression of three ZmGA2ox genes in the C20-GA2ox class in maize seedling roots showed significant regularity and a clear negative correlation with bioactive GA contents under cold and drought conditions, indicating that these three genes might exert key effects on the regulation of GA synthesis and the response to drought and cold stress. Taken together, this study is useful for further dissection of the effect of ZmGA2oxs on abiotic stress responses and might provide potential targets for the genetic improvement of maize.

Environmental impact and genetic expressions of new drought tolerant maize genotypes in derived savannah agro-ecology

Reduced water resources in sub-Saharan Africa will not only pose threat to the livelihood of poor resource farmers, but also food security in the region. Drought tolerant (DT) maize varieties hold promise to reducing poor resourced farmers’ vulnerability and improve food security in sub-Saharan Africa. Ten maize genotypes obtained from the International Institute of Tropical Agriculture (IITA), were evaluated in 2015 and 2016 using a randomized complete block design experiment with three replications to estimate their genetic variability and predict their genetic advances in the derived savannah agro-ecology. Growth, phenological and yield data were collected from 10 middle row plants. Genetic advance, genotypic, phenotypic and environmental coefficients of variations and their variances were estimated. Principal component and hierarchical cluster analyses were also performed. The dendrogram showed that at 80% dissimilarity point, the genotypes were grouped into clusters A, B and C in both years. The first two principal components explained 91.8% and 93.3% of the total variation in 2015 and 2016, respectively. Number of grains cob-1, plant height and number of days to physiological maturity were consistent in explaining the variations observed in the maize population. Heritability estimates in broad sense ranged from 1.35% for number of leaves to 87.43% for grain yield per hectare. The genetic parameters studied showed significant variations among the growth, phenological and yield data collected that warrants selection and maize improvement program using the DT maize inbred lines in derived savannah agro-ecology.

Water productivity improvement in summer maize – A case study in the North China Plain from 1980 to 2019

Improving water productivity (WP) in grain production (WPg) is critical for maintaining food supply in regions with water shortage. A long-term field experiment from 1980 to 2019 was used to investigate the changes in WPg and its influencing factors for summer maize in the North China Plain (NCP). The results showed that grain yield increased from 5.1 t ha−1 to 8.8 t ha−1 and WPg from 1.35 kg m−3 to 2.36 kg m−3 during the past four decades under full irrigation condition. Overall, a 75% increase in yield and a 73% increase in WPg were achieved. Further analysis indicated that in 1980 s and 1990 s, the improvements in yield and WPg were mainly associated with a significant increase in biomass production which was related to the increase in fertilizer use and the improvement in soil fertility. In 2000 s and 2010 s, the increase in yield and WPg was due to a significant increase in harvest index (HI) which was related to the introduction of modern hybrid maize. Overall, increased HI contributed to 65% of the WPg increase for the past 40 years. The results also indicated that during the recent years, large seasonal yield variation was observed which was related to some deteriorating weather factors such as the reduced sunshine hours and the large variation in temperature. Based on the linear positive correlation of grain yield with WPg, management practices that can minimize the negative effects of weather on grain production would favor an improved WPg in future.

Mapping genomic regions for red flour beetle (Tribolium castaneum (Herbst)) resistance in teosinte (Zea mays L. subsp. parviglumis H. H. Iltis & Doebley) derived maize backcross inbred line population

The development of maize germplasm with resistance to red flour beetle requires identification of donors of resistant traits and understanding of the genetic mechanisms underlying resistance. As resistance sources are scarce in elite maize lines, teosinte (Zea mays ssp. parviglumis; 2n = 20) following insect bioassay was found to be resistant and therefore used as parent in a cross with flour beetle susceptible but superior maize inbred line DI-103 for development of backcross inbred line (BIL) mapping population with a view to identify genomic regions conferring resistance. Data on four resistance parameters namely, weight loss (WL), number of insect progeny emerged, kernel damage (KD) and flour produced (FP) were collected on 141 BILs. Highly significant differences were found amongst BILs for all the parameters indicating substantial variability in the population for the traits probably contributed by teosinte. Based on cumulative susceptibility index (CSI), 83 BILs were scored as resistant and can be utilized as donor for flour beetle resistance in maize improvement programs. Principal component analysis was conducted and first three principal components contributing 92.36% of the total phenotypic variation were identified. Highly significant positive correlations were found between all trait combinations except for correlation between WL and KD which was positive but non-significant. A total of 18 marker linked genomic regions were found to be significantly associated with red flour beetle resistance. Two major quantitative trait loci (QTLs) were detected on chromosome 1 and 3 for KD and they explained 11.17% and 14.88% of the total phenotypic variation, respectively. Highest number of colocalized QTLs i.e., 3 were detected for KD and FP. These linked markers after further validation can be used in future for indirect selection for resistance to red flour beetle in maize.

Preliminary Phenotypic and SNP-Based Molecular Characterization of Maize (<i>Zea mays</i> L.)-Mexicana (<i>Zea mays</i> SSP. <i>Mexicana</i>) Introgression Lines under Inbred Background of 48-2

Wild relatives possess potential genetic diversity for maize (Zea mays L.) improvement. Characterization of maize-mexicana introgression lines (ILs) is of great value to diversify the genetic base and improve the maize germplasm. Four maize-mexicana IL generations, i.e. BC1, BC2, BC3, and RIL, were constructed under the elite inbred background of 48-2, elite inbred line that is widely used in maize breeding in Southwestern China, and were phenotyped in different years and genotyped with 56110 SNPs. The results indicated that 48-2 had higher phenotypic performances than all the characterized ILs on most of the agronomic traits. Compared with other ILs, BC2 individuals exhibited more similar performance to 48-2 on most traits and possessed the highest kernel ratio (66.5%). Population structure and principal component analysis indicated that BC3 individuals gathered closer to 48-2 and exhibited the lowest mexicana-introgression frequency (0.50%), while BC2 (29.06%) and RIL (18.52%) showed higher introgression frequency. The high level of genetic diversity observed in the maize-mexicana ILs demonstrated that Z. mays ssp. mexicana can serve as a potential source for the enrichment of maize germplasm.

Yield Responses of Maize (Zea maysL.) and Successive Potato (Solanum tuberosumL.) Crops to Maize Stover co-compostedwith Calliandra CalothyrsusMeisn Green Manure

The present investigation aimed at evaluating the effect of Calliandra calothyrsus Meisn green manure on the quality improvement of maize (Zea mays L.) stover compost. To that end, two field experiments were installed with maize (Zea mays L.) and a successive potato (Solanum tuberosum L.) crop, which was specifically set up to investigate the potential residual effects of tested organo-mineral fertilizers. The potato (Solanum tuberosum L.) crop did not receive any fertilizer, either organic or mineral. The experimental design was a randomized complete block with three replicates. The basic experimental plot was 1.6 m wide and 3 m long (4.8 m²). Treatments under evaluation were: T1=Control, T2=Maize stover co-composted with mineral fertilizer, T3=Maize stover co-compost with Calliandra calothyrsus Meisn green manure; T4=Farm manure+45-60-30; and T5=Maize stover co-composted with Calliandra calothyrsus Meisn green manure+45-60-30. Evaluated parameters were grain yields, root biomass, above-ground biomass, Harvest Index, and Root/Shoot ratio for maize (Zea mays L.). Potato yields were categorized into small size ( 65 mm). Significant effects (p 0.05) of fertilizer treatments could be noticed on the harvest index (HI=0.31-0.38) or R/S ratio (0.079-0.088). For the successive potato crop, a significant effect (p < 0.001) of tested treatments was only observed for the seed-oriented medium size tubers (MST) potato yield. Overall, the most relevant observation of the maize experiment is that treatments T4 and T5 gave higher and equivalent grain and biomass yields. From there, we derive that maize stover co-composted with Calliandra calothyrsus Meisn green manure could be a sound substitute to farm manure. Additionally, the potato experiment highlighted the residual effects of the T3 treatment, statistically equivalent to that of T2. Consequently, we advise that the effects of compost-based organo-mineral fertilizers on crop yields should be evaluated beyond a single seasonal crop, in order to fully catch their residual fertilizer potentials.

Pest Risk Analysis and Quarantine Precautions for Maize Importation into Ethiopia: A Case of Eleven Source Countries

Maize improvement program in Ethiopia utilizes a large amount of germplasm from external sources. Seed samples were imported from eleven different countries Mexico, Kenya, Zimbabwe, India, Norway, Colombia, Thailand, Zambia, South Africa, Nigeria and Egypt from 2011 to 2020. During maize importation, regular inspection was carried out at Holetta Agricultural Research Center for freedom from pests of insects, pathogens and weed seeds. In order to be effective in this important regulatory pest management undertaking, this review attempts to provide a concerted approach for effecting pre- and post-entry regulatory measures for maize importation into Ethiopia based on pest risk analysis (PRA) to safeguard the country. A total of 18 pests (including 12 arthropods, 3 fungi, 1 bacterium, 1 virus and 1 Spiroplasma) are of quarantine concern when importing maize seed into Ethiopia from the eleven major germplasm source-countries considered in this PRA. Three fungi (Cocliobolus, Fusarium and Mycosphaerella), one bacterium bacterial wilt of maize (Pantoea stewartii) and the virus maize chlorotic dwarf virus and corn stunt Spiroplasma (Spiroplasma kunkelii) and also twelve arthropods are of quarantine concern to the country. The number and species of pests of quarantine concern for the country vary depending on country of origin the highest in Mexico with 11 pests followed by India (7 pests) and then Colombia (6 pests). The rest consists of only 1–5 pests of quarantine importance for Ethiopia. Therefore, this review describes quarantine precautions in the import control scenarios and presents PRA based on pathway analysis for importing maize seed into Ethiopia from eleven major source-countries. Generally, the importers of maize into Ethiopia need to strictly consider the information provided in this paper before, during and after arrival of maize samples for research.

Detection of Non-Additive Gene Action within Elite Maize Populations Evaluated in Contrasting Environments under Rainforest Ecology in Nigeria

Proper understanding of the mode of gene action in open-pollinated varieties (OPVs) maize parents helps breeder in the choice of appropriate breeding method to improve its genetic value. The objectives of the present study were to determine gene action controlling grain yield and other agronomic traits of late maturing elite OPVs and classify the varieties into heterotic groups. Ninety-one hybrids generated from 14 elite OPV parents using diallel mating design were evaluated with their parents plus three commercial checks under marginal rainfall, drought, and optimal environments in Nigeria from 2017 to 2018. The experiment was laid out in a 9 × 12 alpha lattice with three replications in each environment. Results showed that there were significant mean squares for grain yield and most agronomic traits. Significant general combining ability (GCA) and specific combining ability (SCA) mean squares for some of the traits indicated that additive and non-additive genetic gene actions were important in the inheritance of yield and those traits among this set of genotypes. However, non-additive genetic effects were more important than additive for grain yield and other agronomic traits in all research environments. Only TZL Comp-3 C3 DT had significant and positive GCA effects (0.336*) while three hybrids had significant and positive SCA for grain yield across research environments. Because of the preponderance of non-additive gene action over additive gene action, distinct heterotic groups could not be identified but four tester groups were identified by HSGCA (Heterotic grouping based on Specific and General Combining Ability) and three groups by HGCAMT (Heterotic grouping based on the GCA of Multiple Traits). Results of grouping were not related to the endosperm colour but grouping based on HGCAMT was related to the pedigree of the varieties. In conclusion, this study has demonstrated preponderance of non-additive gene action over the additive gene action for all measured traits. The presence of the non-additive gene action present in the studied materials can enhance identification of outstanding varietal hybrids and population testers that can serve as base genetic materials for future maize improvement through reciprocal recurrent selection program in SSA.

Characterization of a source of resistance to aflatoxin accumulation in maize

AbstractAflatoxinproduced by the fungus Aspergillus flavus (Link:Fr) can accumulate in maize (Zea mays L.) and poses serious human health and economic concerns, especially in sub‐Saharan Africa. Genetic resistance against A. flavus infection and spread, and subsequent production of aflatoxin, is a key tool for reducing the problem. Some resistant inbred donor lines carry quantitative trait loci (QTL) for resistance that have a sufficiently large phenotypic effect to be used for marker assisted introgression. New sources of resistance, unrelated to previously characterized resistant lines, could carry unique QTL with large phenotypic effect on resistance to complement the previously identified QTL. To this end, CML69, derived from Caribbean Composite germplasm unrelated to previously released resistant lines, was used in QTL mapping to identify and characterize new resistance QTL. Seventeen QTL were identified, although some may be the same genetic region causing QTL identified in more than one environment, indicating that these QTL are stably expressed across environments. These QTL explained 1.8–12.6% each and jointly up to 55% of the phenotypic variation. The largest effect QTL, in particular the QTL in bin 4.08, are most likely the same as has been reported in QTL mapping studies of other resistant maize lines, suggesting both environmental and genetic stability. This stability will be very useful when these QTL are used in maize improvement programs, and single nucleotide polymorphism (SNP) markers linked to these QTL were identified to facilitate this use. CML69, and other lines related to it by pedigree, may make good parents for new aflatoxin resistant hybrids.

Characterization of elite bread wheat (Triticum aestivum L.) germplasm for spot blotch Bipolaris sorokiniana (Sacc.) Shoemaker resistance

AbstractGenetic resources are of paramount importance for developing improved crop varieties, particularly for biotic and abiotic stress tolerance. Spot blotch (SB) is a destructive foliar disease of wheat prevalent in warm and humid regions of the world, especially in the eastern parts of South Asia. For the management of this disease, the most effective measure is the development of resistant cultivars. Thus, the present investigation was carried out to confirm SB resistance in 200 germplasm accessions based on phenotypic observations and molecular characterization. These elite breeding lines obtained from the International Centre for Maize and Wheat Improvement, Mexico, are developed deploying multiple parentages. These lines were screened for SB resistance in the field under artificially created epiphytotic conditions during 2014–15 and 2015–16 along with two susceptible checks (CIANO T79 and Sonalika) and two resistant checks (Chirya 3 and Francolin). Eighty-two out of 200 germplasm accessions were found resistant to SB and resistance in these lines was confirmed with a specific SSR marker Xgwm148. Three accessions, VORONA/CNO79, KAUZ*3//DOVE/BUC and JUP/BJY//URES/3/HD2206/HORK//BUC/BUL were observed possessing better resistance than the well-known SB-resistant genotype Chirya3. These newly identified resistant lines could be used by wheat breeders for developing SB-resistant wheat varieties.

Genome-wide association studies and whole-genome prediction reveal the genetic architecture of KRN in maize

BackgroundKernel row number (KRN) is an important trait for the domestication and improvement of maize. Exploring the genetic basis of KRN has great research significance and can provide valuable information for molecular assisted selection.ResultsIn this study, one single-locus method (MLM) and six multilocus methods (mrMLM, FASTmrMLM, FASTmrEMMA, pLARmEB, pKWmEB and ISIS EM-BLASSO) of genome-wide association studies (GWASs) were used to identify significant quantitative trait nucleotides (QTNs) for KRN in an association panel including 639 maize inbred lines that were genotyped by the MaizeSNP50 BeadChip. In three phenotyping environments and with best linear unbiased prediction (BLUP) values, the seven GWAS methods revealed different numbers of KRN-associated QTNs, ranging from 11 to 177. Based on these results, seven important regions for KRN located on chromosomes 1, 2, 3, 5, 9, and 10 were identified by at least three methods and in at least two environments. Moreover, 49 genes from the seven regions were expressed in different maize tissues. Among the 49 genes, ARF29 (Zm00001d026540, encoding auxin response factor 29) and CKO4 (Zm00001d043293, encoding cytokinin oxidase protein) were significantly related to KRN, based on expression analysis and candidate gene association mapping. Whole-genome prediction (WGP) of KRN was also performed, and we found that the KRN-associated tagSNPs achieved a high prediction accuracy. The best strategy was to integrate all of the KRN-associated tagSNPs identified by all GWAS models.ConclusionsThese results aid in our understanding of the genetic architecture of KRN and provide useful information for genomic selection for KRN in maize breeding.

Silicon Coating on Maize Seed Mitigates Saline Stress in Yermosols of Southern Punjab

Silicon (Si) has been identified as a key nutrient in plants to lower the pressures of environmental stress. In pot experiment, seeds of different maize hybrids (Pioneer-1543, Monsanto-6103 and Monsanto-6724) were coated with different concentrations of Si viz. 0, 5, 10, 15 and 20 mg kg− 1 seed using H2SiO3. Salinity was imposed by adding NaCl (120 mM) into the soil. Saline stressed (without Si coating) plants were observed with a significant decrease in growth and yield, Chl a and b, soluble contents of sugars and proteins, contents of free amino acids and phenols, leaf relative water content (LRWC), superoxide dismutase, catalase, peroxidase and brings only increased in proline contents. However, plants developed from Si coated seeds were recorded with significant improvements in growth and different physiological parameters. Moreover, among Si coated maize, coating with 20 mg Si proved maximum growth and yield in saline condition, which was came with the improvement in photosynthetic contents, osmoprotectants and antioxidant. Furthermore, Si coated plants have significantly lower proline compare than saline stress alone. Taken above results together, it is concluded that Si has significant role in reducing adverse behavior of NaCl in maize growth through bringing a improvement in leaf relative water contents, keeping normal working of chl a and b that enhanced the osmoprotectants concentration rather than proline and motivate the antioxidant system. Thus, our study suggested that Si coating is a viable strategy that can be implemented to bring a significant improvement in maize under saline condition.

English

Wheat rusts, stem rust, leaf rust, and stripe or yellow rust are the major biotic constraints in all wheat-growing regions of Ethiopia. Therefore, the main objective of this study is to identify the temporal-spatial hot spot pattern of wheat rust incidence and severity in Ethiopia. A GIS-based hotspot analysis tool was employed to identify the spatial distribution of hot spot patterns and temporal trends using survey data collected by the International Maize and Wheat Improvement Center and the Ethiopian Institute of Agricultural Research from the fields of smallholder farmers in Ethiopia. The analysis identified seven hot spot pattern categories; no trend detected, new hot spot, consecutive hot spot, diminishing hot spot, oscillating hot spot, persistent hot spot and a sporadic hot spot for yellow and stem rusts distributed in different parts of the country. For instance, the persistent hot spot is observed in west Arsi and Bale zones, which are the potential wheat-growing areas of the country while new hot spots are emerging in central and northern parts of the country. Generally, areas where these two hot spot patterns occurred, are requiring special attention to minimize yield loss due to rust and tackle food insecurity. Key words: Emerging hotspot, stem rust, yellow rust, leaf rust.