Breeding Maize Exotic Germplasm

Betrán, F. J.; Mayfield, Kerry; Isakeit, Thomas; Menz, Monica A.

doi:10.1002/9780470752708.ch26

Cited by 7 publications

(9 citation statements)

References 31 publications

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“…These lines have many agronomic traits that could serve as bases for reduced aflatoxin accumulation. Examples of these traits include improved husk coverage, increased grain hardness, and maintenance of kernel integrity (Odvody et al, 1997; Betrán et al, 2006). In our tests, Tx739 and Tx740 testcrosses had higher grain moisture contents than the commercial hybrids.…”

Section: Discussionmentioning

confidence: 99%

“…This higher moisture content is probably caused in part by a combination of increased husk coverage and a later flowering date. These two traits are more common in tropical maize than in temperate maize; their presence should be acceptable for maize grown in areas with longer growing seasons, such as Texas (Betrán et al, 2006). Although husk coverage was not specifically measured in trials with Tx739 and Tx740, both testcrosses and inbred lines have husks that are tight and extend past the tip of the ear.…”

Section: Discussionmentioning

confidence: 99%

“…Balanced bulks were created within a generation when selections of a few ears having a similar phenotype (kernel texture, grain color, and cob color) were bulked together. This method was used because it has the simplicity of a bulk method while still “maintaining genetic variability” through the heterogeneity of the pedigree method (Betrán et al, 2006).…”

Section: Methodsmentioning

confidence: 99%

“…Unfortunately, tropical maize cultivars commonly lack the adaptation and suitable agronomic performance to be used directly in hybrids for U.S. production environments. Specific limitations include delayed flowering and maturity, photoperiod sensitivity, and unacceptably high ear height (Holland et al, 1996; Betrán et al, 2006). This general lack of adaptation and acceptable agronomic characteristics results in lower yield than that produced with temperately adapted maize (Castillo‐Gonzalez and Goodman, 1989).…”

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confidence: 99%

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Registration of Maize Germplasm Lines Tx736, Tx739, and Tx740 for Reducing Preharvest Aflatoxin Accumulation

Mayfield

Betrán

Isakeit

et al. 2012

J of Plant Registrations

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Maize (Zea mays L.) production in Texas, the southern United States, and much of the developing world is constrained by preharvest contamination from aflatoxins—potent mycotoxins produced by the fungus Aspergillus flavus. When consumed, aflatoxin can lead to impaired growth, liver cancer, or death of both humans and livestock. Because of these effects, the presence of this mycotoxin is tightly regulated in the U.S. food supply. No complete resistance to A. flavus or aflatoxin is known to exist in maize; however, multiple quantitative traits and some sources of resistance have been identified. We propose the release of three maize lines that demonstrate reduced preharvest aflatoxin accumulation. Tx736 (Reg. No. GP‐578, PI 662937) is a germplasm line derived from modified pedigree selection of a cross between Tx772, a line with reduced aflatoxin accumulation, and T246, a temperate line with good yield and Texas adaptation, backcrossed to Tx772 once. Lines Tx739 (Reg. No. GP‐579, PI 662938) and Tx740 (Reg. No. GP‐580, PI 662939) were selected by pedigree methods from S3 plants selfed out of heterotic groups A, C, and E from Agricomseeds (Santa Cruz, Bolivia). These three lines were field tested as lines per se and as testcross hybrids with introduced inoculation in multienvironmental field trials. In trials, these lines and hybrids had between 30 and 73% lower aflatoxin content than commercial checks. These germplasm lines will serve as unique sources for novel traits and alleles that reduce aflatoxin in elite temperate and subtropical maize.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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Registration of Maize Germplasm Lines Tx736, Tx739, and Tx740 for Reducing Preharvest Aflatoxin Accumulation

Mayfield

Betrán

Isakeit

et al. 2012

J of Plant Registrations

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“…Similar results have been obtained for general resistance to tropical maize viruses such as maize mosaic virus and to other tested pathogens and insect pests (Brewbaker et al, 1989; Kim et al, 1988a). Despite the common reference to tropical maize as “exotic,” it is temperate maize that must be viewed as a relatively narrow germplasm base that is truly exotic among the ∼300 races of maize (Goodman, 1992; Betrán et al, 2006). Temperate maize was developed largely from the Corn Belt Dent and Northern Flint races, and temperate sweet corns are even more narrowly derived.…”

Section: Discussionmentioning

confidence: 99%

General Resistance in Maize to Southern Rust (Puccinia polysora Underw.)

Brewbaker

Kim

et al. 2011

Crop Science

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Southern corn rust (Puccinia polysora Underw.) is a major tropical disease that can iead to severe yield losses in the tropics. Occasionally it becomes of concern in temperate regions, as in 2010. We summarize 45 yr of research on the occurrence, genetic basis, and breeding of general resistance. Trials were conducted in Colombia, Hawaii, Nigeria, the Philippines, Texas, and Thaiiand. Temperate maize proved uniformly susceptible. No racially specific monogenes were effective. Resistance varied continuously among tropical inbreds and many of these showed stable intermediate toierance.Two diallel populations revealed high correlations of inbred values with hybrid array means and slight heterosis for resistance. Narrowsense heritabilities were 51% and 66%, and mean square ratios for gênerai to specific combining ability (GGA:SCA) were 7.8 and 10.7 to 1. Generation mean analyses were performed on six sets of families. Mean and additive effects were significant across families, while significant nonadditive effects were rare. Heritability values ranged from 19% to 49%. A set of recombinant lines segregated a primary susceptibility locus on chromosome 6. Studies of 137 near-isogenic inbred lines (NILs) of resistant tropical inbred HÍ27 revealed a dominant susceptibility quantitative trait locus (QTL) in the NIL for dwarf-1 locus, but linkage could not be confirmed. Premature senescence was associated with rust infections in many NILs, emphasizing the ubiquity of modifying genes. No correlation existed between resistance to southern and common rusts. Resistant tropical inbreds and populations were bred to serve as sources for future improvement.

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Mapping quantitative trait loci for aflatoxin accumulation resistance in two populations containing resistant maize inbred Mp717

et al. 2022

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Mp717, a maize germplasm line resistant to aflatoxin accumulation, served as the resistant parent in two bi‐parental quantitative trait loci (QTL) mapping populations: Mp717 × Va35 and Mp717 × PHW79. Both populations were phenotyped for concentration of total aflatoxins following artificial inoculation in replicated field trials grown in four environments. In all four environments in which the Mp717 × Va35 population was evaluated, the majority of the explained phenotypic variance was due to QTL for which the aflatoxin‐reducing allele was contributed by Va35, not Mp717. When the data were combined across environments, Mp717 contributed the beneficial allele for four QTL, but those QTL individually explained only 2.5 to 5.4% of the phenotypic variance. In contrast, Mp717 was the source of the resistance allele for the majority of the QTL observed in the Mp717 × PHW79 population in all four environments. When the data were combined across environments, Mp717 was the source of the resistance allele for eight QTL that individually explained 3.5 to 8.7% of the phenotypic variance. Three of those QTL individually explained 7.7 to 8.7% of the phenotypic variance, but none of those three QTL were observed in the Mp717 × Va35 population. Due to the small effect size of most observed QTL and the inconsistency across genetic backgrounds of the few medium‐effect QTL that were detected, it was concluded that no resistance QTL suitable for marker‐assisted introgression of the resistance present in Mp717 were detected in these two populations.

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Breeding Maize Exotic Germplasm

Cited by 7 publications

References 31 publications

Registration of Maize Germplasm Lines Tx736, Tx739, and Tx740 for Reducing Preharvest Aflatoxin Accumulation

Registration of Maize Germplasm Lines Tx736, Tx739, and Tx740 for Reducing Preharvest Aflatoxin Accumulation

General Resistance in Maize to Southern Rust (Puccinia polysora Underw.)

Mapping quantitative trait loci for aflatoxin accumulation resistance in two populations containing resistant maize inbred Mp717

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