Teosinte (Zea mays subsp. parviglumis H. H. Iltis & Doebley) has greater genetic diversity than maize inbreds and landraces (Z. mays subsp. mays). There are, however, limited genetic resources to efficiently evaluate and tap this diversity. To broaden resources for genetic diversity studies in maize, we developed and evaluated 928 near-isogenic introgression lines (NILs) from 10 teosinte accessions in the B73 background. Joint linkage analysis of the 10 introgression populations identified several large-effect quantitative trait loci (QTL) for days to anthesis (DTA), kernel row number (KRN), and 50-kernel weight (Wt50k). Our results confirm prior reports of kernel domestication loci and identify previously uncharacterized QTL with a range of allelic effects enabling future research into the genetic basis of these traits. Additionally, we used a targeted set of NILs to validate the effects of a KRN QTL located on chromosome 2. These introgression populations offer novel tools for QTL discovery and validation as well as a platform for initiating fine mapping.
Reduced seedling emergence of low‐phytate (LP) soybean [Glycine max (L.) Merr.] lines with the pha1 and pha2 alleles has been a limiting factor in the development of LP cultivars. Crosses between normal‐phytate (NP) and LP soybean lines have produced progeny with improved emergence. The objective of this study was to determine if LP lines with improved emergence are capable of producing progeny with equal or higher emergence when crossed to NP parents. Low‐phytate lines with improved emergence were crossed to NP cultivars and the LP progeny were evaluated with seed produced at three 2007 locations and five 2008 locations. A field test of the lines was conducted in 2008 with one 2007 seed source. An extended cold test (ECT) was developed to evaluate all the lines with the three 2007 seed sources and selected lines and parents with the five 2008 sources. There were LP progeny with significantly less emergence than the LP parent when evaluated in the field and with the ECT. One single‐cross line had significantly greater emergence than the LP parent and emergence equal to the NP parent. Genetic variation among the single‐cross and backcross lines was attributed to the segregation of favorable and unfavorable alleles for emergence from both the NP and LP parents. Multiple seed sources should be used to identify LP lines with superior emergence based on field evaluations or the ECT.
The mutant su1‐ref allele is of interest in the commercial sweet maize (Zea mays L.) industry. It was the only starch synthesis mutation used for sweet maize until the 1960s and is still used today, especially in combinations with other loci. The wild‐type Su1 allele produces a starch debranching‐type isoamylase, ISA1, required for normal amylopectin and starch granule crystal formation in maize endosperm. Five naturally occurring mutant alleles have been identified at the su1 locus, but they have not been characterized for seedling emergence, field traits, mature kernel composition, or ISA1 enzyme activity. These five alleles were backcrossed to A619 and A632, two modern field maize inbreds. The su1 inbreds and wild‐type checks were grown in El Monte, Chile, in 2009 to 2010 and Madison, WI, in 2010 to 2011 for seed production to evaluate seedling emergence, field traits, and mature kernel composition. In a greenhouse in Madison, WI, in 2011 to 2012, the su1 inbreds were grown and kernels were harvested at 20 d after pollination (DAP) for enzymatic analysis. Significant differences were identified among the su1 inbreds, where su1‐ne was consistently poorer for emergence and field traits and the su1‐pu allele was consistently better than the other su1 mutant alleles for the evaluated traits. Differences were observed in the presence of ISA1 enzyme; however, no functional ISA1 enzyme activity was observed. Further research is necessary to elucidate the differences for appearance, carbohydrate composition, and seed germination and emergence traits in lines with no functional ISA1 enzyme activity.
Reduced seedling emergence of low‐phytate (LP) soybean [Glycine max (L.) Merr.] lines with the pha1 and pha2 alleles has been a limiting factor in the development of LP cultivars. Crosses between normal‐phytate (NP) and LP soybean lines have produced progeny with improved emergence. The objective of this study was to determine if LP lines with improved emergence are capable of producing progeny with equal or higher emergence when crossed to NP parents. Low‐phytate lines with improved emergence were crossed to NP cultivars and the LP progeny were evaluated with seed produced at three 2007 locations and five 2008 locations. A field test of the lines was conducted in 2008 with one 2007 seed source. An extended cold test (ECT) was developed to evaluate all the lines with the three 2007 seed sources and selected lines and parents with the five 2008 sources. There were LP progeny with significantly less emergence than the LP parent when evaluated in the field and with the ECT. One single‐cross line had significantly greater emergence than the LP parent and emergence equal to the NP parent. Genetic variation among the single‐cross and backcross lines was attributed to the segregation of favorable and unfavorable alleles for emergence from both the NP and LP parents. Multiple seed sources should be used to identify LP lines with superior emergence based on field evaluations or the ECT.
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