Abstract
Quality Protein Popcorn (QPP) BC2F5 inbred lines were produced through an interpopulation breeding system between Quality Protein Maize dent (QPM) and elite popcorn germplasm. In 2019, five QPP F1 hybrids were selected for further evaluation due to superior agronomics, endosperm protein quality, and popping quality traits. Though these BC2F5 QPP hybrids were phenotypically similar to their popcorn parents, the QPP cultivars conveyed slightly inferior popping characteristics when compared to the original popcorn germplasm. The objective of this study was twofold. First, BC2F5 inbred lines were crossed to their popcorn parents and BC3F4 inbred lines were produced for hybridization to test the agronomic, protein, and popping trait effects from an additional QPP by popcorn backcross. Second, BC2- and BC3-hybrids were simultaneously evaluated alongside ConAgra Brands® elite cultivars and ranked for potential commercialization in the spring of 2020. These 10 QPP hybrids were grown alongside five ConAgra Brands® elite popcorn cultivars in three locations and agronomic, protein quality, and popping quality traits were evaluated. Significant improvements in popcorn quality traits were observed in the QPP BC3 cultivars compared to their BC2 counterparts, and yield averages were significantly lower in BC3-derived QPP hybrids compared to the BC2 population. Protein quality traits were not significantly different between QPP backcrossing populations and significantly superior to ConAgra elite popcorn varieties. Utilizing a previously published ranking system, six QPP hybrids, three from the BC2F5 population and three from the BC3F4 population, were evaluated as candidates for final selection. The successful evaluation and ranking system methodology employed is transferable to other hybrid production and testing programs. Incorporating this analysis with concurrent sensory studies, two QPP hybrids were chosen as premier cultivars for potential commercialization.
Highlights
Popcorn [Zea mays L. ssp. everta (Sturt.) Zhuk] is a type of flint corn characterized by its ability to expand and form light flakes under high heat
Since BC3F4 inbred lines were achieved through the backcross of BC2F5 Quality Protein Popcorn (QPP) with original popcorn parents, improved vitreousness of BC3 cultivars compared to their BC2 counterpart was not attainable (Supplementary Figure 1)
Equation 3 estimates from test weight and moisture content revealed a decreased seed size in BC3F4-derived QPP hybrids compared to BC2F5 hybrids, and original popcorn parental hybrids had significantly smaller seeds than both QPP populations
Summary
Popcorn [Zea mays L. ssp. everta (Sturt.) Zhuk] is a type of flint corn characterized by its ability to expand and form light flakes under high heat. Intra-subspecies crosses between dent maize and popcorn, one avenue for increasing diversity in the popcorn germplasm pool, have shown to enhance popcorn’s agronomic fitness and flavor profile at the cost of deficient popcorn quality traits such as popability and expansion volume (Robbins and Ashman, 1984; Sprague and Dudley, 1988; Dofing et al, 1991; Ziegler and Ashman, 1994) To negate these undesired side effects, a study in 2018 described an inter-subspecies breeding program crossing highly vitreous dent Quality Protein Maize dent (QPM) varieties with proprietary popcorn lines to produce highly vitreous, high lysine Quality Protein Popcorn (QPP) BC2F5 inbred lines (Ren et al, 2018). Since the rest of the endosperm modifier genes are unspecified (though genetic locations have been postulated), phenotypic evaluation of vitreousness and zein profiling still serve as the best means for selecting vitreousness, and popping traits, in an opaque-2 background (Holding et al, 2008; Wu et al, 2010; Holding, 2014; Parsons et al, 2020)
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