Resistant Maize Varieties Research Articles

Comparative genomics of Fusarium species causing Fusarium ear rot of maize.

Fusarium ear rot (FER), caused by the fungal pathogen Fusarium verticillioides, stands as one of the most economically burdensome and pervasive diseases affecting maize worldwide. Its impact on food security is particularly pronounced due to the production of fumonisins, toxic secondary metabolites that pose serious health risks, especially for livestock. FER disease severity is complex and polygenic, with few resistance (R) genes being identified for use in breeding resistant varieties. While FER is the subject of several breeding programs, only a few studies have investigated entire populations of F. verticillioides with corresponding virulence data to better understand and characterize the pathogenomics. Here, we sequenced and compared the genomes of 50 Fusarium isolates (43 F. verticillioides and 7 other Fusarium spp.) that were used to inoculate a diverse maize population. Our objectives were to elucidate the genome size and composition of F. verticillioides, explore the variable relationship between fumonisin production and visual disease severity, and shed light on the phylogenetic relationships among the isolates. Additionally, we conducted a comparative analysis of the nucleotide variants (SNPs) and the isolates' effectoromes to uncover potential genetic determinants of pathogenicity. Our findings revealed several promising leads, notably the association of certain gene groups, such as pectate lyase, with disease severity. These genes should be investigated further as putative alleles for breeding resistant maize varieties. We suggest that, beyond validation of the alleles identified in this study, researchers validate each phenotypic dataset on an individual basis, particularly if considering fumonisin concentrations and when using diverse populations. Our study underscores the importance of genomic analysis in tackling FER and offers insights that could inform the development of resilient maize cultivars. By leveraging advances in genomics and incorporating pathogen populations into breeding programs, resistance to FER can be advanced.

Distinctive physiological and molecular responses of foxtail millet and maize to nicosulfuron.

Nicosulfuron is the leading acetolactate synthase inhibitor herbicide product, and widely used to control gramineous weeds. Here, we investigated the metabolic process of nicosulfuron into foxtail millet and maize, in order to clarify the mechanism of the difference in sensitivity of foxtail millet and maize to nicosulfuron from the perspective of physiological metabolism and provide a theoretical basis for the breeding of nicosulfuron-resistant foxtail millet varieties. We treated foxtail millet (Zhangzagu 10, Jingu 21) and maize (Nongda 108, Ditian 8) with various doses of nicosulfuron in both pot and field experiments. The malonaldehyde (MDA) content, target enzymes, detoxification enzymes, and antioxidant enzymes, as well as related gene expression levels in the leaf tissues of foxtail millet and maize were measured, and the yield was determined after maturity. The results showed that the recommended dose of nicosulfuron caused Zhangzagu 10 and Jingu 21 to fail to harvest; the yield of the sensitive maize variety (Ditian 8) decreased by 37.09%, whereas that of the resistant maize variety (Nongda 108) did not decrease. Nicosulfuron stress increased the CYP450 enzyme activity, MDA content, and antioxidant enzyme activity of foxtail millet and maize, reduced the acetolactate synthase (ALS) activity and ALS gene expression of foxtail millet and Ditian 8, and reduced the glutathione S-transferase (GST) activity and GST gene expression of foxtail millet. In conclusion, target enzymes, detoxification enzymes, and antioxidant enzymes were involved in the detoxification metabolism of nicosulfuron in plants. ALS and GST are the main factors responsible for the metabolic differences among foxtail millet, sensitive maize varieties, and resistant maize varieties. These findings offer valuable insights for exploring the target resistance (TSR) and non-target resistance (NTSR) mechanisms in foxtail millet under herbicide stress and provides theoretical basis for future research of develop foxtail millet germplasm with diverse herbicide resistance traits.

Screening of Promising Maize Varieties Against Maize Weevil (Sitophilus zeamais Motschulky) Under Storage Condition

The maize weevil (Sitophilus zeamais Motschulsky) causes significant quantitative and qualitative losses during storage. To identify resistant varieties of maize against this pest, an experiment was conducted in a Completely Randomized Design (CRD) with 11 varieties in free and no-choice conditions. The study measured weight loss, mean bored grain, debris, and weevil numbers at 30, 60, and 90 days. The findings showed that BG13Y-POP, Manakamana-7, and RML-19/RML-6 were the most resistant varieties, with weight loss percentages of 1.99%, 1.47%, and 1.74%, respectively, and final weevil numbers of 104, 72, and 73. Ganesh-2 and ZM-401 were the most susceptible varieties, with weight losses of 7.34% and 6.05%, respectively. The maximum debris weight was found in RML-761/RL-105 (1.98 g), while the minimum was found in Manakamana-7 (0.26 g). The highest number of bored grains was observed in Ganesh-2 (81), while the lowest number was observed in Rampur-4 (51). Similarly, ZM-401 (158) and Ganesh-2 (165) exhibited the highest weevil population, while the lowest count was found in Rampur-4 (72). Overall, using resistant varieties, such as Manakamana-7, BG13Y-POP, and RML-19/RML-6, can be an effective approach for reducing post-harvest losses from weevil infestation.

3D-based precise evaluation pipeline for maize ear rot using multi-view stereo reconstruction and point cloud semantic segmentation

Maize ear rot poses a severe threat to maize yield and quality. Breeding and cultivating highly resistant maize varieties is a crucial approach for preventing and controlling maize ear rot. However, traditional methods of visually grading the severity of maize ear infection and resistance lack objectivity and repeatability. To meet the requirement of precise breeding and resistance assessment scenarios, a novel pipeline based on three-dimensional (3D) point clouds of maize ear was developed for ear rot precise evaluation. First, multi-view stereo (MVS) reconstruction was employed to obtain high-precision dense point clouds of maize ears. And the coordinate correction and circular sampling approaches were proposed to optimize the data structure of the input maize ear samples. Next, a specialized network called the ear rot segmentation network (ERSegNet) was proposed to detect the infected area of maize ears. This network incorporated an orientation-encoding (OE) module and point transformer (PT) attention, which effectively boosted the performance of PointNet++. The proposed ERSegNet achieved impressive results, including a mean intersection over union (mIoU) of 85.83%, a mean precision (mPrec) of 92.34%, a mean recall (mRec) of 92.23%, a mean F1-score of 92.28%, and an overall accuracy (OA) of 93.76%. This demonstrated the feasibility of using semantic segmentation algorithms to predict 3D point clouds of maize ears. Furthermore, a point cloud resampling method was suggested to enhance the spatial uniformity of maize ear point clouds and a point-level quantitative assessment approach based on the 3D point cloud data was provided for evaluating the severity of ear rot. The results showed an average evaluation error of 1.55% in the testing set, indicating the accuracy of the proposed method. This study provides a reliable and objective method for maize ear rot precise assessment, offering potential and valuable support for the identification of resistant varieties in breeding programs.

Genetic response of hybrid maize line to downy mildew caused by Peronosclerospora spp. infection

Maize is the second staple food commodity in Indonesia. Apart from being the main source of carbohydrates and protein, the production of maize continues to increase along with the escalation of population growth and animal feed requirements in the last few years. The potential to increase the national production of maize is still feasible because of the yield gap between the potential yields of new superior varieties and the level of yields obtained by farmers. The yield gap caused by biotic stress in maize is mainly caused by pathogens such as downy mildew due to Peronosclerospora spp. Downy mildew distribution is sporadic that can infect a wide area. In Indonesia, it spreads widely and significantly reduces yields in the areas of maize production centres in East Java, Central Java, South Sulawesi, North Sulawesi, Gorontalo, Lampung, and Sumatera. These obstacles can be overcome by integrated pest and disease control technology. One strategy is to discover downy mildew-resistant varieties that can be combined with other control treatments. The phenomenon of resistance to downy mildew infection of several hybrid maize strains began to be detected in the vegetative growth phase, with symptoms beginning at 14 days after planting (DAP), increasing with plant age, and reaching its peak after 28-35 DAP and then the symptoms will gradually disappear until no infection after 42 HST. This study analyses the resistant maize varieties from 2020 to 2022. The data showed the susceptible comparison variety (Anoman) was infected with 88.94% to 100%. In 2020, BMD73 showed a resistant reaction to Philippinensis species, other strains were classified as susceptible in P. maydis except BMD 76. All strains showed highly susceptible and susceptible reactions. In 2021, in P. philippinensis all strains FCP10-FCP16 showed a resistant reaction, but line FCP10-FCP16 had a resistance response that was classified as moderately resistant to P. maydis. The incidence of genetic response in 2022, except BMD86, strains BMD81-BMD85 were classified as resistant, as well as in the P. maydis endemic area all strains showed the same reaction.

Rapid screening for resistance of maize inbred and hybrid lines against southern corn leaf blight

AbstractBipolaris is one of the most important phytopathogenic fungal genera to cause disease in cereal crops. Southern corn leaf blight (SCLB) is a pandemic and widespread disease; it's found everywhere corn is grown, causing a noticeable reduction in crop yield. Most cultivated varieties of maize do not resist SCLB disease where it is reported. Nevertheless, previous researchers have reported some resistant varieties of maize. In this study, we tested inbred and hybrid lines collected from ICAR‐IIMR based in Ludhiana against the disease. The field experiment was setup using a Randomized Block Design with three replications in natural conditions. Here we evaluated lines by quantifying disease pressure, yield, and their attributes. Moreover, model‐based clustering allowed the identification of five groups. For the SCLB disease confirmation, infected maize leaves were collected and used for pathogen isolation, and a pure culture was maintained. Both disease assessment and data analysis focused more specifically on characters that showed significant differences between means, especially leaf area, percentage of leaf infection, disease incidence, disease severity, disease index by plot basis, number of grain rows formed per ear, weight of maize kernels per ear, each corn ear weight, shelling percentage, and grain yield. The two best clusters identified, namely Group 1 and Group 2, together comprise 11002, 11009, 11026, 11030, 11069, 11149, 11153, 11185, 11328, 11333, 11337, 11347, 11370, 11385, 11074, 11351, 11356, 11357, 11608, and Karav‐8523 lines. As per disease reaction, CM‐500 is individually one of the best lines in terms of SCLB resistance. Specific symptoms were clearly found on leaves, and pseudo‐septate conidia were observed under the microscope. Thus, several lines exhibited highly resistant reactions against SCLB, especially 11002, 11009, 11026, 11069, 11074, 11337, 11347, 11385, and CM‐500, and can still be recommended for farmers and in breeding programmes, for future usefulness as industries are complaining of maize shortages, and they present a great commercial potential.

Impact assessment of Striga resistant maize varieties and fertilizer use in Ghana: A panel analysis

AbstractThis study analyzes the impact of a component of climate‐smart agriculture (CSA) technology—Striga‐resistant maize (SRM) varieties and mineral fertilizer—on maize yield and food security using two rounds of panel data in Ghana. The study employs a multinomial endogenous switching regression model and finds that joint adoption of SRM varieties and mineral fertilizer increased maize yield by 872 kg/ha, food consumption scores by 17, and consumption per adult equivalent unit by 38 kg/ha. The positive impact of maize yield is high among adopters of multiple CSA technologies. The result is robust to an alternative endogeneity‐correcting model and the implications of the findings are discussed.

Relationship between yield and lodging traits of maize under different planting densities

AbstractMaize (Zea mays L.) is one of the main food crops in China but the problems with lodging have seriously affected the quality and production. In this study, lodging resistant and density tolerant varieties of maize were screened. The relationships between rind penetration strength (RPS), stalk breaking strength (SBS), and yield under two different planting densities were studied. Eight hybrid combinations were set up under the planting densities of 75,000 and 90,000 plants ha–2 and their effects on yield were determined with a regression equation method. The results showed that density had a greater effect on yield through its effect on lodging rate. Finally, high‐yielding maize varieties JKY143 and JKY182 with stronger planting density tolerance were selected to provide reference points and technical support for maize‐breeding programs focusing on plant density tolerance and lodging resistance.

Screening of Maize Genotypes against Maize Leaf Aphid [Rhopalosiphum maidis (Fitch)] under Field Condition at Chitwan, Nepal

Thirty maize genotypes including five hybrids, eight quality protein (QPM) and seventeen full season open pollinated (OP) were screened for their resistance against maize leaf aphid (Rhopalosiphum maidis Fitch) at the research field of National Maize Research Program, Rampur, Chitwan, Nepal during the year 2019 and 2020. The design of the experiment was randomized incomplete block with three replications. The plot size was 2 rows of 5 m long with the spacing of 60 cm × 25 cm. The recommended dose of fertilizer for full season OP and QPM were 120:60:40 and for hybrid maize 180:60:40 N: P2O5:K2O kg/ha with farmyard manure 10 t/ha and seed rate was 20 kg/ha. Data on aphid incidence, severity, yield and yield components were recorded. Maize hybrids RML-95/RML-96 (18%) and Rampur Hybrid-10 (22%), two quality protein maize (QPM) S00TLYQ-AB (22%) and S99TLYQ-A (23%) and two full season OP genotypes TLBRS07F16 (24%) and ZM 627 (26%) were less susceptible to aphid infestation and resulted in higher grain yield. The findings could aid in the selection of maize genotypes for the development of aphid resistant and high-yielding maize varieties.

The Significance of the Hungarian Wheat Production in Relation to the Common Agricultural Policy

Maize is one of the major crops of Hungary. This can be used in various ways, most notably for human consumption, feeding purpose, and ethanol production that is used as a fuel additive. The major indicator of its market competitiveness is the maize yield which varied over the years. This was mostly caused by the weather conditions. The use of more resistant maize varieties, as well as the proper amount of fertilizer (especially nitrogen and potassium as active ingredients), would help to stabilize yields. On the sales side, the price determines the efficiency of production. The Common Agricultural Policy plays a key role in this regard as direct payments contributed to the gross revenue of the crop producers by 57.2% on average in Hungary. The article aims to provide a detailed overview of these issues from 2010 to 2020. Based on our results, we formulated policy recommendations. Regarding maize trade, processing and, therefore, a higher share of value-added products would be essential (canned products, gluten, corn germ oil, gluten) on the export side. This would further increase Hungary’s agri-food trade surplus as well as create new jobs in this sector. However, the exceptional (roughly 47%) price increase in 2021 may not be motivating enough for the different market players in the supply chain.

Sources of tolerance to low soil nitrogen in some Striga resistant and quality protein maize (Zea mays L.) varieties

Sources of tolerance to low soil nitrogen in some Striga resistant and quality protein maize (Zea mays L.) varieties

Evaluation of maize genotypes against post flowering stalk rot under terai region of Nepal

The inadequate source of resistance materials in maize against major biotic stresses is one of the main reasons for considerable loss of grain yield in Nepal. Post flowering stalk rot disease caused by Fusarium moniliforme is a serious disease that exposes high incidence at grain filling stage of maize in terai region of Nepal during summer season. This study was done to evaluate level of resistance, or tolerance in selected genotypes against the post flowering stalk rot disease of maize. Accordingly, thirty maize genotypes were tested for maize stalk rot resistance during summer season of 2016 and 2017 at National Maize Research Program, Rampur (NMRP), Chitwan. The experiment was done under natural epiphytotic condition at hot spot of the disease by using Randomized Complete Block design with 2 replications for each treatment. The package of practices was followed as per national recommendation. The summer season of 2016 and 2017 were affable for post flowering stalk rot of maize at NMRP, Rampur. Out of 30 genotypes, most of the tested entries showed susceptible reaction during both the years; however, RML-95/RML-96, Across-9942/Across-9944, ZM-401, Rampur 34, RamS03F08 and TLBRS07F16 showed resistant reaction against the disease and might be useful for the development of post flowering stalk rot resistant maize varieties for terai region of Nepal.

Drivers, Barriers and Success Factors in Climate Change Adaptation for Smallholder Farmers: A Case Study in Thai Nguyen Province, Vietnam

This paper aims to identify appropriate approaches and interventions of local governments and extension services through identifying the most potential adaptive measures in agricultural production of local farmers in Thai Nguyen province (Vietnam) and analyses of key drivers, barriers and success factors for climate change adaptation (CCA).The study was conducted during October 2019 – April 2020 in Thai Nguyen and two selected communes with 92 smallholder farmers and relevant stakeholders from the provincial to commune levels using both quantitative and qualitative methods.Results showed a highly vulnerable situation of the local farmers under the context of climate change with 60.9% and 44.6% of the interviewed farmers stating reduced crop/livestock productivity and crop losses, and reduced arable production land and number of crop seasons/year respectively.Ten most potential livelihood models and production practices were identified. For example, animal husbandry (pigs, cattle) combined with biogas digester installation; intercropping between fruit crops and annual crops; use of drought and disease resistant maize varieties; changes of crop patterns and calendars; water saving production techniques, etc. Driver, barriers and success factors for CCA suggestguiding actions for the local government and extension services to plan adequate approaches and interventions for embracing and upscalingthe CCA initiatives towards climate resilient farming communities.The guiding actions include:strengthening capacity of extension staff; providing update market information to farmers for their decisions of crops and livestock; disseminating new and locally appropriate CCA models and practices together with on-field demo-plots and farmer field schools; and building capacity for community organisations, production groups/cooperatives to promote community learning for wider adoption and thus sustainability of their farming systems in response to the changing environment.

Evaluation of Genetic Diversity of QPM, Provit-A, and Elite Maize Inbreds Resistant to Downy Mildew Disease Using Simple Sequence Repeats

<p>Functional maize tends to be more susceptible to major maize diseases, particularly Downy mildew. Among the functional maize are Quality Protein Maize (QPM) and Provit A maize. The presence of higher amino acid and beta carotene in functional maize might have caused these types of maize more susceptible to Downy mildew disease. The objective of the research was to identify the heterotic pairs among maize inbreds i.e. QPM, Provit A, and local maize varieties resistant to Downy mildew disease using Simple Sequence Repeats (SSR) marker. The research was conducted from April to July 2017 at the Molecular Biology Laboratory of Indonesian Cereals Research Institute. A total of five QPM inbreds, 15 Provit A inbreds, and 11 Downy mildew resistant local varieties of maize were used in the experiment using 34 SSR markers. Results indicated that among 34 SSR locus analysed, variation of allele lengths ranged from 74 bp to 500 bp. A total of 125 alleles ranging from two to nine alleles per locus with an average of 3.68 alleles were generated. The data indicated wide genetic variations among characters. DNA band profile showed that nc130 marker produced the highest PIC (over 0.83) and allele value (8.00). Genetic distance analysis found a total of 21 heterotic genotypes with genetic distance exceeds 0.65. </p>

Molecular Evolution of Maize Ascorbate Peroxidase Genes and Their Functional Divergence.

Ascorbate peroxidase (APX) is an important antioxidant enzyme. APXs in maize are encoded by multiple genes and exist as isoenzymes. The evolutionary history and functional divergence of the maize APX gene family were analyzed through comparative genomic and experimental data on the Internet in this paper. APX genes in higher plants were divided into classes A, B, and C. Each type of APX gene in angiosperms only had one ancestral gene that was duplicated along with the genome duplication or local (or tandem) duplication of the angiosperm. A total of eight genes were retained in maize and named APXa1, APXa2, APXa3, APXb1, APXb2, APXc1.1, APXc1.2, and APXc2. The APX genes of class A were located in the chloroplasts or mitochondria, and the class B and C genes were localized in the peroxisomes and cytoplasm, respectively. The expression patterns of eight APXs were different in vegetative and reproductive organs at different growth and development stages. APXa1 and APXb1 of maize may participate in the antioxidant metabolism of vegetative organs under normal conditions. APXa2, APXb2, APXc1.1, and APXc1.2 may be involved in the stress response, and APXb2 and APXc2 may participate in the senescence response. These results provide a basis for cultivating high-yield and resistant maize varieties.

Mycofloral study of cultivated maize seed in district Poonch Azad Jammu and Kashmir

The current study was carried out on the prevalence of mycoflora associated with maize seeds using blotter paper method. Maize seed samples were collected from six different locations of district Poonch, Azad Jammu and Kashmir. Objective of this study was to determine the fungi associated with maize seeds. A total of seven species of fungi were isolated. Penicillium spp., Fusarium spp., Aspergillus niger, A. flavus, Fusarium spp., Fusarium oxysporum and Pythium spp., were identified. Davigali had the infection percentage of 72 % in all locations. Occurrence frequency and type of fungi isolated varied with location. Prevalence of pathogenic fungi with maize seeds of district Poonch was found variable. Resistant varieties of maize, maintaining temperature, relative humidity and their treatment is suggested to reduce disease and increase yield.

Varietal susceptibility of maize to larger grain borer, Prostephanus truncatus (Horn) (Coleoptera; Bostrichidae), based on grain physicochemical parameters.

Maize (Zea mays L) is one of main nutrients sources for humans and animals worldwide. In Africa, storage of maize ensures food resources availability throughout the year. However, it often suffers losses exceeding 20% due to insects such as the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera; Bostrichidae), major pest of stored maize in the tropical countries. This study aims to select resistant varieties to reduce maize storage losses and explain the physicochemical parameters role in grains susceptibility. In the first study, maize grains were artificially infested under no-choice method with insects. Susceptibility parameters such as weight loss, grain damage, number of emerged insects, median development time and susceptibility index varied significantly through maize varieties. Dobie susceptibility index (SI) was assessed as a major indicator of resistance. The most resistant varieties were Early-Thaï, DMR-ES and Tzee-Yellow. Conversely, Synth-9243, Obatampa and Synth-C varieties were susceptible. SWAN, Across-Pool and Tzee-White were classified as moderately resistant varieties. The insect reproductive potential was significantly different in the nine maize varieties and Early-Thaï, DMR-ES and Tzee-Yellow varieties were the least favourable host. To assess the relationship between grains physicochemical characteristics and varietal susceptibility, moisture, total phenolics, palmitic acid, proteins, amylose, density and grain hardness were evaluated according to standardized methods. Palmitic acid, SI, insects emerged and grain damage were significantly and positively correlated with each other, and negatively correlated with grains hardness, phenolics and amylose contents. Maize susceptibility index was significantly and negatively correlated to amylose, and phenolics contents and positively correlated to palmitic acid content. This study identified three resistant maize varieties to P. tuncatus and revealed that the major factors involved in this resistance were hardness, phenolic and amylose contents of grains.

Structural parameters for X-ray micro-computed tomography (\u03bcCT) and their relationship with the breakage rate of maize varieties

BackgroundHigh grain breakage rate is the main limiting factor encountered in the mechanical harvest of maize grain. X-ray micro-computed tomography (μCT) scanning technology could be used to obtain the three-dimensional structure of maize grain. Currently, the effect of maize grain structure on the grain breakage rate, determined using X-ray μCT scanning technology, has not been reported. Therefore, the objectives of this study are: (i) to obtain the shape, geometry, and structural parameters related to the breakage rate using X-ray μCT scanning technology; (ii) to explore relationships between these parameters and grain breakage rate.ResultIn this study, 28 parameters were determined using X-ray μCT scanning technology. The maize breakage rate was mainly influenced by the grain specific surface area, subcutaneous cavity volume, sphericity, and density. In particular, the breakage rate was directly affected by the subcutaneous cavity volume and density. The maize variety with high density and low subcutaneous cavity volume had a low breakage rate. The specific surface area (r = 0.758*), embryo specific surface area (r = 0.927**), subcutaneous cavity volume ratio (0.581*), and subcutaneous cavity volume (0.589*) of maize grain significantly and positively correlated with breakage rate. The cavity specific surface area (− 0.628*) and grain density (− 0.934**) of maize grain significantly and negatively correlated with grain breakage rates. Grain shape (length, width, thickness, and aspect ratio) positively correlated with grain breakage rate but the correlation did not reach statistical significance. The susceptibility of grain breakage increased when kernel weight decreased (− 0.371), but the effect was not significant.ConclusionsThe results indicate that X-ray μCT scanning technology could be effectively used to evaluate maize grain breakage rate. X-ray μCT scanning technology provided a more precise and comprehensive acquisition method to evaluate the shape, geometry, and structure of maize grain. Thus, data gained by X-ray μCT can be used as a guideline for breeding resistant breakage maize varieties. Grain density and subcutaneous cavity volume are two of the most important factors affecting grain breakage rate. Grain density, in particular, plays a vital role in grain breakage and this parameter can be used to predict the breakage rate of maize varieties.

Genetic Diversity and Responses of Some Selected Yellow Maize Genotypes to Stem Borer (Sesamia calamistis Hampson) Infestation

Aims: Identification of promising resistant parents against stem borer infestation for the development of high yielding maize hybrids.
 Study Design: Ten yellow maize genotypes selected for yield potential and durable level of tolerance to stem borer infestation were used in this study. A stem borer resistant yellow maize variety was crossed with nine stem borer (not necessarily resistant) maize varieties in a top-cross mating design.
 Place and Duration of Study: The study was conducted in 2017 and 2018 at the Institute of Agricultural Research and Training, OAU, Ibadan, Nigeria.
 Methodology: The resulting nine F1 hybrids along with the ten parents were evaluated under irrigation using a Randomized Complete Block Design (RCBD) with three replications in a stem borer endemic area. Data collected were subjected to combined analysis of variance (ANOVA), principal component analysis (PCA) and hierarchical clustering analyses.
 Results: Results obtained showed significant differences for year and genotype, as well as their interaction for some traits measured. Maize varieties were delineated into three groups. The first two PCA with Eigen values greater than 1.0 accounted for 73.0% of the variation; where PC1 was responsible for 52.5% of the variation and was associated with percentage stem borer infestation, leaf damage, plant aspect, stem tunneling ratio and dead heart. PC2 accounted for 20.5% and associated with only grain yield (GY). Also, maize hybrids had higher GY and better resistance to stem borer than their parents by 24.3% and -14.3%, respectively. BR9928-DMR-SR-Y was identified as resistant to stem borer with high GY in hybrid combinations. Positive and significant correlation was obtained among infestation parameters.
 Conclusion: Genes from promising donor parents may be introgressed into other desirable maize germplasm for the development of stem borer resistant maize hybrids.

Characterization and Molecular Mapping of Two Novel Genes Resistant to Pythium Stalk Rot in Maize.

Pythium stalk rot caused by Pythium inflatum is becoming a more and more serious disease in maize, and it has caused severe yield loss in China in recent years. Deployment of resistant maize varieties is the most effective way to control this disease. Searching for the resistant maize germplasm and identifying the resistance genes are the vital processes in the breeding program. The maize inbred line X178 previously showed high resistance to Pythium stalk rot. Thus, this study aimed to reveal the gene(s) resistance to Pythium stalk rot in X178 by resistance inheritance analysis using the derived F2 and F2:3 genetic populations. The results showed that two independently inherited dominant genes, designated RpiX178-1 and RpiX178-2, carried by X178 are responsible for its resistance relative to the susceptible parent Ye107; they are located on regions of maize chromosome (chr.) 1 bin 1.09 and chr. 4 bin 4.08, respectively, and flanked by markers umc2047 and bnlg1671 as well as bnlg1444 and umc1313, respectively, by linkage analysis. Subsequently, RpiX178-1 was finely mapped between markers SSRZ8 and IDP2347, with genetic distances of 0.6 and 1.1 cM, respectively, and the physical distance of the target region was about 700 kb. RpiX178-2 was also further located between markers bnlg1444 and umc2041, with a genetic distance of 2.4 cM. Moreover, we confirmed that the two genes RpiX178-1 and RpiX178-2 were newly identified and different from those genes known on chrs. 1 and 4 according to results of allelism testing. Herein, we newly identified two genes resistant to P. inflatum, which provided important genetic information for resistance to Pythium stalk rot in maize.