Tropical Corn Research Articles

Investigation on types of corn rust in eastern Yunnan ecology and analysis of population genetic structure of its rusts

ABSTRACT Corn rust disease can be classified into four types: common corn rust, southern corn rust, tropical corn rust and stem corn rust. In this paper, 270 samples of corn rust gathered from Yunnan province were identified by observation of symptom and pathogen morphology, detection of specific molecular markers between Puccinia sorghi Schw and Puccinia polysora Unedrw. The results showed that 180 samples of corn rust collected form Qujing, Zhaotong, Kunming, Honghe (Mile, Kaiyuan and Jianshui) were common corn rust caused by Puccinia sorghi Schw; and 90 samples of corn rust collected form Wenshan and Honghe (Pinbian) were southern corn rust. Morphology and aspect ratio compared Puccinia sorghi Schw with Puccinia polysora Unedrw. The uredospores of Puccinia polysora Unedrw were oval and the aspect ratio of 81.6% of all uredospores from Puccinia polysora Unedrw was greater than 1.2. The uredospores of Puccinia sorghi Schw were nearly round, and their aspect ratio was 1.0-1.3. In addition, the population genetic structure of all corn rust samples was analyzed by ISSR molecular marker. Concerning Puccinia polysora Unedrw, the genetic diversity was larger in Wenshan than in Honghe. In Puccinia sorghi Schw, the population genetic diversity was larger in Zhaotong and the lowest in Kunming.

Seed yield of simple and tri-linear corn (Zea mays L.) hybrids for the mexican humid tropics

The objective of the work was to evaluate the agronomic performance and seed yield of tropical corn (Zea mays L.) of single and tri-linear crosses. In the spring-summer of 2015 and 2016, two essays were established in the states of Veracruz and Tabasco, Mexico. In the first essay, a group of 12 single crosses was evaluated, and in the second, a group of 18 tri-linear crosses was evaluated. In both essays, the treatments were distributed under a completely randomized block design with three replicates in 5 m long, two-row plots and 0.8 m between rows, with an initial population density of 62.500 plants ha-1. Within the simple cross trial, hybrids HE-3W, COMERCIAL 1, LT-164xLT-165, and HE-1W presented seed yields above the general mean (3384 kg ha-1). Within this outstanding group is the LT-164xLT-165 cross, which participates as a female parent in the formation of the recently released commercial hybrid H-567. In the tri-linear crosses essay, a group of varieties and hybrids including H-567, (LT-164xLT-165) xLT-156, (LT-164xLT-165) xLT-155, (LT-154xLT-155) xLT-165, VS-536, H-520, VS-563, (LT-154xLT-155) xLT-170, (LT-171xLT-172) xLT-156, (LT-164xLT-165) xLT-164, and (LT-171xLT-172) xLT-170 recorded seed yields of 6669.8, 6515.4, 6498.6, 6431.1, 6260, 6024.7, 5935.4, 5664.3, 5580.8, and 5527.1 kg ha-1, respectively. The LT-154, LT-155, and LT-156 lines are common as a male and female parent, suggesting a good genetic combination. The prevailing environmental conditions during the development of the experiments did not significantly influence the productivity of the crosses. There is genetic variability that can be used to continue developing lines, open pollination varieties, and corn hybrids.

Colchicine-induced mutation for new line development of tropical maize (Zea mays L.)

This research aimed to identify colchicine-induced tropical Yellow Corn characters and their potential in superior traits development. Single cross was applied to colchicine mutant line with tester line, INOAXM2 yellow and white seeds, to observe and test the characters enrichment of colchicine mutant, while pure line tester of sweet corn (OP-SBX) was used to observe the enhancement of germination and growth rate. Analysis of various quantitative data was determined using F test at the level of 5%, continued with Least Significant Difference Test (LSD) at the level of 5%. Potential characters and its inheritance pattern were determined by a descriptive statistical approach. Overall, germination and growth test of mutant show significant improvement when mutant crossed with tester lines. According to qualitative characters analysis of mutant line and its single way, it is found that glum colour is influenced by the male parent (Paternal Effect), while seed colour is determined by the female (Maternal Effect). From mutant M1 to M4, quantitative mutant (INFM) characters showed significant differences between lines within one generation and revealed improvements in single cross progeny. Single cross between colchicine line and tester mutant (IONAXM2) presents significant differences in all cobs characters (cob length, number of seeds in a row, number of rows, cob dry weight, and weight of 100 seeds (g) and reveals higher value compared to other lines. Mid-parent heterosis of single cross progeny of mutants was high for cob dry weight, those were 202.38% and 166.67%. The chromosomes observation of pink and yellow seeds of colchicine mutants revealed the presence of diploid, triploid, and euploid chromosomes, which verify chromosomal changes inside colchicine mutant lines.

Genomic-wide association study for white spot resistance in a tropical maize germplasm

White spot is an important maize disease, prevalent in most high production tropical regions with a severe negative impact in grain yield. Breeding for white spot resistance is the most effective mechanism to control the disease. The objectives of this research include identifying and mapping chromosomal regions and putative genes associated to the maize response to white spot. We performed an association mapping with phenotypic data collected in two environments located at South region of Brazil, and by using a set of 355,972 high-quality single nucleotide polymorphism markers in a panel composed by 183 tropical field corn and popcorn inbred lines. Nine SNPs were significantly associated with white spot, five of them co-localized on previously reported quantitative trait loci regions, while remaining regions are novel. The total phenotypic variance explained (r2) by the nine SNPs associated with white spot severity was 64.3%, while the variance explained by each SNP ranged from 0.72 to 25.54%. The identified putative gene models are promising candidates associated with white spot resistance. Once these SNPs were validated, they can be useful for selecting superior genotypes.

Testers in supersweet corn lines

ABSTRACT: The purpose of this study was to evaluate the discriminatory capacity of tester lines for tropical corn lines converted to supersweet shrunken (sh2) gene, for the development of hybrids adapted to tropical conditions. Lines were used as female parents in crosses with three testers: open-pollinated mixed variety; supersweet line L4; supersweet commercial hybrid Tropical Plus. Four trials were carried out to evaluate topcrosses in Maringá - PR e Sabáudia - PR, Brazil in the main growing season of 2015/16. The following traits were evaluated: total ear weight (TEW, in kg), commercial ear weight (CEW, in kg) and total soluble solids (TSS, in °Brix). The GCA estimates for TEW and CEW were highest for L4. The lines Balu-114 and UEM-25 were selected based on the effects of g ̂ ifor the traits studied and should be used in the establishment of base populations for the breeding of superior lines. The s ̂ ijvalue for TEW was highest for cross BALU-182 x Tropical, while for CEW was the highest value for cross BALU-94 x Mista.

Phenology and Biomass Production of Adapted and Non‐Adapted Tropical Corn Populations in Central Iowa

Core Ideas The accuracy of the Leaf Collar Method was refined.Tropical corn adaptability investigated in central Iowa.Non‐adapted tropical corn had greater non‐grain and total biomass as compared to their non‐adapted counterparts.Taller tropical corn populations had the greatest biomass.Greater non‐grain biomass occurs at the expense of grain yield.Tropical corn biomass has potential as Gen2 biofuel feedstock. Biofuel production in the midwestern United States has largely focused on corn (Zea mays L.) grain for ethanol production and more recently, corn stover for lignocellulosic ethanol. Tropical corn refers to corn adapted from tropical regions. Growing tropical germplasm in temperate environments is not attractive for grain yield, but shows promise for biomass production through taller and more vigorous plants with thick stems and long leaves. The comparison between tropical corn populations and their temperate adapted counterparts with a focus on biomass production has not yet been explored under Iowa growing conditions. This study refines the accuracy of the leaf collar method, and characterizes the adaptation of the populations by evaluating crop development and biomass production. Therefore, field trials were established in central Iowa during the 2014 and 2015 growing seasons. Adapted and non‐adapted versions of three populations, Tuxpeño, Suwan, and Tuson, were planted at three dates to evaluate their phenology and potential for biomass production under midwestern U.S. conditions. Plant height correlated well with vegetative development and total biomass. Adapted tropical corn had advanced grain development, while non‐adapted tropical corn had advanced vegetative development and greater biomass yield. Non‐adapted tropical corn flowered later, had 22% greater total biomass on average (4.6 Mg ha−1 greater than adapted), and had 43% greater non‐grain biomass on average, up to 20 Mg ha−1 (6 Mg ha−1 greater than adapted), while adapted populations yielded more grain. Non‐adapted tropical corn has a high potential as feedstock for Gen2 biofuels in central Iowa.

280 Isolation and identification of lactic acid bacteria that colonize tropical whole-plant corn silage during the fermentation process

280 Isolation and identification of lactic acid bacteria that colonize tropical whole-plant corn silage during the fermentation process

282 Effect of Lactobacillus buchneri isolated from tropical corn silage on fermentation and aerobic stability of sugarcane silage

282 Effect of Lactobacillus buchneri isolated from tropical corn silage on fermentation and aerobic stability of sugarcane silage

281 Effect of Lactobacillus buchneri isolated from tropical corn silage on fermentation and aerobic stability

281 Effect of Lactobacillus buchneri isolated from tropical corn silage on fermentation and aerobic stability

Selección en cruzas interraciales tropicales de maíz de México para adaptación a valles altos

The response of the selection, and its adaptation at high plateaus, of five generations of tropical corn race crosses from Mexico, with a 0- 700 masl altitude range, was evaluated. An assay was planted at Montecillo, Mexico (locale with high plateaus) using four generations of 22 tropical interracial crosses, nine race progenitors and four local populations as controls. Besides of the grain yield per stalk, 15 characters were studied, some as yield components and others as of agronomic interest for its adaptation. The selection for high platea u adaptation with tropical corn inter-racial crosses was efective to increase grain yield per stalk, achiering an average response of 18% per selection cycle, in five cycles. Although with smaller increments, the number of ears per stalk, lenght, diameter and grain percentage of the ear, volume and weight of 100 seeds were modified. Ear and plant height showed undesirable agronomic responses, while days to tasselling, blooming coincidence and plant health improved with the selection. Six crosses in F8 were identified as matching the yield and other characters to the best local control Huamantla (conical race). According to the progenitors used in these crosses, it is deduced that the Tuxpeño race was the largest gene contributor for yield and Vandeño for adaptation genes, while Tepecintle showed a very poor gene contribution to the selection response.

Effect of bacterial endophyte on expression of defense genes in Indian popcorn against Fusarium moniliforme

An endophytic Bacillus amyloliquefaciens subsp. subtilis was isolated from surface sterilized seedlings of tropical corn. To evaluate the hypothesis that this endophyte is defensive in nature and determine the mechanisms of host defense we examined the effects of the endophyte on pathogens and host disease resistance genes. The bacterial endophyte showed antifungal activity against fungal pathogens Fusarium moniliforme, Colletotrichum gloeosporioides and Aspergillus flavus. Plant protection activity was also observed in Indian popcorn seedlings inoculated with the endophyte against F. moniliforme. Gene expression analysis was conducted and demonstrated that up-regulation of several defense genes in corn was greater after 48 hours of pathogen challenge than 24 hours. Plant defense pathways triggered by the endophytic bacterium appeared to be SA (salicylic acid) independent. The abundance of the zm Jasmonic acid-induced gene expression was greater in pathogen challenged plants pre-treated with the endophytic bacterium than in the plants challenged only with pathogen. Pre-treatment with the endophytic bacterium resulted in a more intense induction of maize pathogenesis related protein genes PR-1 and PR-10 during interaction with F. moniliforme compared to plants that were treated only with the fungal pathogen.

Induction of salt tolerance and up-regulation of aquaporin genes in tropical corn by rhizobacterium Pantoea agglomerans.

Bacteria were isolated from surface disinfected seeds of eight modern corn types and an ancestor of corn, 'teosinte' and identified using 16S rDNA sequences. From each of the modern corn types we obtained Bacillus spp. (including, Bacillus amyloliquefaciens and Bacillus subtilis); while from teosinte we obtained only Pantoea agglomerans and Agrobacterium species. Of these bacteria, only P. agglomerans could actively grow under hypersaline conditions and increase salt tolerance of tropical corn seedlings. In laboratory and greenhouse experiments where plants were watered with a 0.2 mol l(-1) NaCl solution, P. agglomerans was found to enhance the capacity of tropical corn to grow compared to uninoculated controls. The total dry biomass was significantly higher in P. agglomerans-treated plants compared to controls under saline water. Gene expression analysis showed the up-regulation of the aquaporin gene family especially plasma membrane integral protein (ZmPIP) genes in P. agglomerans-treated plants. The plasma membrane integral protein type 2 (PIP2-1) gene in tropical corn seedlings was highly up-regulated by P. agglomerans treatment under salt stress conditions. Microscopic examination of P. agglomerans inoculated seedlings revealed that the bacterium colonized root meristems densely, and as roots developed, the bacterium became sparsely located in cell junctions. The enhancement of salt tolerance capacity in tropical corn, an important food crop, has the capacity to increase its cultivation area and yield in saline soils. The application of rhizobacteria to improve salt tolerance of tropical corn is ecofriendly and cost effective. We show that P. agglomerans isolated from teosinte (an ancestor of corn) induces salt tolerance in tropical corn and up-regulation of aquaporin genes. This study shows that microbes that increase salt tolerance may be used to enhance crop growth in saline soils.

Quantitative trait loci associated with resistance to gray leaf spot and grain yield in corn

The main objectives of hybrid development programs include incorporating genetic resistance to diseases and increasing grain yield. Identification of Quantitative Trait Loci (QTL) through the statistical analysis of molecular markers allows efficient selection of resistant and productive hybrids. The objective of this research was to identify QTL associated with resistance to gray leaf spot and for grain yield in the germplasm of tropical corn. We used two strains with different degrees of reaction to the disease; the genotypes are owned by GENESEEDS Ltda, their F1 hybrid and the F2 population. The plants were evaluated for gray leaf spot resistance, for grain yield and were genotyped with 94 microsatellite markers. Association of the markers with the QTL was performed by single marker analysis using linear regression and maximum likelihood analysis. It was observed that the additive effect was predominant for genetic control of resistance to gray leaf spot, and the dominant effect in that of grain yield. The most promising markers to be used in studies of assisted selection are: umc2082 in bins 4.03 and umc1117 in bins 4.04 for resistance to gray leaf spot; for grain yield umc1042 in bins 2.07 and umc1058 in bins 4.11.

Demarcation of informative chromosomes in tropical sweet corn inbred lines using microsatellite DNA markers

A study of genetic variation among 10 pairs of chromosomes extracted from 13 tropical sweet corn inbred lines, using 99 microsatellite markers, revealed a wide range of genetic diversity. Allelic richness and the number of effective alleles per chromosome ranged from 2.78 to 4.33 and 1.96 to 3.47, respectively, with respective mean values of 3.62 and 2.73. According to the Shannon’s information index (I) and Nei’s gene diversity coefficient (Nei), Chromosome 10 was the most informative chromosome (I = 1.311 and Nei = 0.703), while Chromosome 2 possessed the least (I = 0.762 and Nei = 0.456). Based on linkage disequilibrium (LD) measurements for loci less than 50 cM apart on the same chromosome, all loci on Chromosomes 1, 6 and 7 were in equilibrium. Even so, there was a high proportion of genetic variation in Chromosomes 4, 5, 8, 9 and 10, thereby revealing their appropriateness for use in the genetic diversity investigations among tropical sweet corn lines. Chromosome 4, with the highest number of loci in linkage disequilibrium, was considered the best for marker-phenotype association and QTL mapping, followed by Chromosomes 5, 8, 9 and 10.

Role of dehydrodiferulates in maize resistance to pests and diseases.

Phenolic esters have attracted considerable interest due to the potential they offer for peroxidase catalysed cross-linking of cell wall polysaccharides. Particularly, feruloyl residues undergo radical coupling reactions that result in cross-linking (intra-/intermolecular) between polysaccharides, between polysaccharides and lignin and, between polysaccharides and proteins. This review addresses for the first time different studies in which it is established that cross-linking by dehydrodiferulates contributes to maize’s defences to pests and diseases. Dehydrodiferulate cross-links are involved in maize defence mechanisms against insects such as the European, Mediterranean, and tropical corn borers and, storage pest as the maize weevil. In addition, cross-links are also discussed to be involved in genetic resistance of maize to fungus diseases as Gibberella ear and stalk rot. Resistance against insects and fungus attending dehydrodiferulates could go hand in hand. Quantitative trait loci mapping for these cell wall components could be a useful tool for enhancing resistance to pest and diseases in future breeding programs.

Resistência ao acamamento de plantas e ao quebramento do colmo em milho tropical

O objetivo deste trabalho foi avaliar genótipos de milho quanto à resistência ao acamamento e ao quebramento do colmo e apresentar metodologia para avaliar essas características. Os ensaios foram realizados em blocos ao acaso, com 85 genótipos tropicais de milho e quatro repetições, em cinco locais. Foram avaliadas: as forças necessárias para o arranquio da planta e para o quebramento do colmo e o ângulo no momento do quebramento. As medições foram realizadas com equipamentos desenvolvidos para essas finalidades. Foram realizadas análises de variância e teste de Scott-Knott quanto às características. Asforças de arranquio da planta, de quebramento do colmo e ângulo no momento do quebramento do colmo interagiram significativamente com a localidade. As médias variaram de 49,43 a 76,03 kgf para a força de arranquio da planta, de 1,07 kgf a 2,76 kgf para força de quebramento do colmo, e de 16,15 a 41,18º para o ângulo de quebramento do colmo. Existe variabilidade genética para seleção quanto à resistência ao acamamento e ao quebramento do colmo em genótipos tropicais de milho. A metodologia apresentada é eficiente para a avaliação e discriminação de genótipos.

Epidermal cell response to rust hyphae and the resistance mode of tropical maize to southern corn rust (Puccinia polysora underwood)

Southern Corn Rust (SCR), caused byPuccinia polysora Underwood, is found primarily in the tropics, occurring especially during wet and cool winters in Hawaii. Whereas Hi38-71, a tropical Hawaiian super sweet corn, is resistant to SCR, the G24 inbred is susceptible. Anatomical traits are distinct in these two lines, with differences evident in their epidermal cell shapes, cell types, epidermal cell walls, hairs, and bulliform cells. Trichomes are found on the leaves of Hi38-71 plants and their epidermal surface cells are flat. In contrast, the epidermal surfaces of G24 leaves are circular, rough, and woolly, and are uniform in their size and pattern. These woolly epidermal leaf surfaces on the susceptible G24 provide access for disease infection while the trichomes and smooth leaves may confer more resistance in Hi38-71. Our genetic study utilized Generation Mean Analysis (GMA) of progenies derived from crosses of these two inbred lines. Resistance to SCR was scaled from 1 (resistant) to 9 (susceptible) in the winter and spring in Hawaii. Average scores for Hi38-71 and G24 were 3.1 and 6.9 respectively, while the F1 and F2 hybrids were both highly resistant to the rust. Both additive and dominant effects for SCR resistance were highly significant, as were their epistatic interactions [aa] and [dd]. However, the additive x dominance interaction was not. Therefore, a single dominant gene in inbred line Hi38-71 might be involved in determining its high resistance to SCR.

High temperature and water stress during flowering in tropical corn populations

High temperature and water stress during flowering in tropical corn populations

Corn Hybrids for Late Planting in the Southeast

Delayed planting dates in the U.S. Southeast often result in insect and disease problems on corn (Zea mays L.). The objectives of this study were to determine the effects of corn hybrid (type) and planting date on yields and the extent of injury resulting from insects and pathogens. Tropical, Bt (Bacillus thuringiensis var. kurstaki Berliner), and non‐Bt corn hybrids were evaluated for grain and silage yields and insect damage at planting dates from March to August from 1998 to 2001. Averaged across years, corn silage yields were greatest at March and April planting dates (16.1 Mg ha−1) and least from July (6.1 Mg ha−1) and August (4.5 Mg ha−1) planting dates. Silage yields of tropical corn were 26 and 17% higher than non‐Bt and Bt hybrids, respectively, because of less yield reduction at later planting dates. Corn grain yields were greatest at the March planting date (9.6 Mg ha−1) and least at July and August planting dates (0.9 and 0.4 Mg ha−1, respectively). Grain yields of tropical corn were 15 and 10% higher than those of Bt and non‐Bt, respectively. Fall armyworm (Spodoptera frugiperda J.E. Smith), corn earworm (Helicoverpa zea Boddie), and southern corn rust disease (Puccinia polysora Underw.) ratings had negative correlations with corn yields. Insect damage was below 6% for Bt hybrids and above 11% for non‐Bt hybrids. Tropical corn had higher silage and grain yields and better silage quality and disease resistance than either Bt or non‐Bt hybrids.

Chemical Composition, Ensiling Characteristics, and Apparent Digestibility of Summer Annual Forages in a Subtropical Double-Cropping System with Annual Ryegrass

A2-yr study was conducted to determine the chemical composition and digestibility of silages made from forage sorghum, pearl millet, and tropical corn managed to optimize forage quality. Silages were ensiled in upright concrete silos lined with plastic and fed to heifers to determine in vivo apparent digestibility. Samples were collected before and after ensiling to determine ensiling characteristics and forage quality. After ensiling, tropical corn had the greatest dry matter (DM), the lowest crude protein, and the greatest water-soluble concentrations. Tropical corn silage had a pH of 3.96. The pH of forage sorghum silage was 4.09, and pearl millet had a pH of 4.50. Pearl millet had the lowest concentration of preensiled water-soluble carbohydrate, which likely caused the high pH in the silage. There were no differences among the forages in DM loss during ensiling in yr 2. Heifers fed pearl millet silage consumed more DM, but digestible DM intake was not different among the three groups of heifers. The results of this experiment indicate that pearl millet would be less desirable as a crop intended solely for silage production. Both forage sorghum and tropical corn could be grown specifically for ensiling based on DM digestibility. The decision on which crop to use should be based on factors such as production costs, forage yields, and local growing conditions rather than silage quality.