Combining Ability and Testcross Performance for Carotenoid Content of S2 Super Sweet Corn Lines Derived from Temperate Germplasm

Abstract

Understanding the impact of gene action and combining ability on targeted traits in a hybrid breeding program is imperative. The objective of this study was to estimate the genetic effect and combining ability of S2 super sweet corn lines on carotenoid content. Twenty S2 lines were crossed with two hybrid testers by using the line × tester mating design. Regarding parents, forty hybrids and two commercial checks were evaluated for carotenoid content across two different growing seasons between 2019 and 2020. The result indicated that the non-additive gene action governed the inheritance of carotenoid content. Several promising S2 lines for individual carotenoids were identified; only L20 possessed different and positive GCA values for all observed carotenoids. Moreover, genotype T2 was a promising tester to identify superior lines for creating biofortified sweet corn hybrids. Testcross hybrids with satisfactory performance, desirable SCA estimates, and involving at least one of the pairwise parents with positive and high GCA were successfully defined. Hybrid T2 × L20 had high lutein, zeaxanthin, β-cryptoxanthin, and total carotenoids contents (ranging from 12.58 to 74.01 µg/g of dry weight), whereas hybrid T2 × L9 showed the highest content of β-carotene (4.19 µg/g of dry weight). We propose that high GCA and line at least one of the pairwise parents be included in indirect selections for the hybrid breeding of high-carotenoid sweet corn.

The Combining Ability and Heterosis Analysis of Sweet–Waxy Corn Hybrids for Yield-Related Traits and Carotenoids

“…In contrast, parents with poor GCA effects may produce hybrids with high SCA effects due to the involvement of complementary genes. Previous studies found similar findings [ 25 , 27 , 51 ]. The high × low combiner was appropriate for heterosis breeding, whereas the high × high combiner for population improvements via pedigree selection [ 23 ].…”

“…Lutein and zeaxanthin, which are α-xanthophyll or macular carotenoids central to reducing the risk of AMD, were the predominant carotenoids found in our biofortified hybrids (37.8 and 35.3%, respectively, totaling 73.1%), followed by β-carotene (17.1%) and β-cryptoxanthin (8.7%) ( Figure 1 and Supplementary Table S2 ). Previous studies reported that about 30% of lutein or zeaxanthin was found in the F 1 hybrids evaluated [ 11 , 25 ]. However, other studies found only zeaxanthin as the major carotenoid, representing more than 50% of total carotenoids [ 15 , 18 , 23 , 27 ].…”

“…The frozen carotenoid extract was redissolved in 1 mL of methyl tert-butyl ether (MTBE): methanol (75: 25, v / v ) and filtered through a 0.45 µm nylon membrane filter. The composition of solvents and the gradient elution conditions used were described by Wasuwatnakul et al [ 25 ] and Gupta et al [ 64 ] with modifications. Reversed-phase HPLC analysis of carotenoids was performed using a Shimadzu system (Shimadzu Co., Ltd., Tokyo, Japan) equipped with a binary pump (mod.…”

“…Combining ability analysis can also assess the relative importance and modes of gene action involved in the commercial hybrids to desired traits [ 24 ]. While our previous study demonstrated the predominance of non-additive genetic effects governing the inheritance of carotenoids [ 25 ], other studies reported that carotenoids were additively inherited [ 11 , 23 , 26 , 27 , 28 , 29 ]. Both additive and non-additive genetic effects also played significant roles in the expression of carotenoids [ 30 , 31 ].…”

Biofortification as a solution for addressing nutrient deficiencies and malnutrition

“…Corn cultivars with high carotene content have been produced through plant breeding [ 223 ]. Humans who consume carotenoids through their diet have been found to improve eye health in humans and most importantly, prevent age-related macular degeneration.…”