Heterosis and Combining Ability of F₁ Hybrid Sweet Sorghum in Thailand

Abstract

Sweet sorghum [Sorghum bicolor (L.) Moench] is a sugar‐based biofuel crop that is well‐suited to tropical environments. Most sweet sorghum cultivars are open‐pollinated, but hybrids could offer yield and seed production advantages. Fifteen hybrids were generated among five female and three male parents. The hybrids, parents, and three inbred checks were evaluated for sugar yield and related traits under two environments in Thailand in 2013: Field Crop Research Station at Khon Kaen University, Khon Kaen, and National Corn and Sorghum Research Center, Nakhon Ratchasima. Theoretical sugar yield was positively correlated with juice dissolved solids (Brix), plant height, stalk diameter, biomass yield, stripped stalk yield, and theoretical juice yield. Grain yield was negatively correlated with juice dissolved solids and theoretical sugar yield. Positive heterosis for juice dissolved solids was not observed, though five hybrids had negative mid‐parent heterosis for this trait. Positive heterosis for biomass yield, theoretical juice yield, and grain yield was observed in some hybrids. General combining ability was observed for most traits, but specific combining ability (SCA) effects were of greater importance. Overall, the hybrids KKA‐11 × BJ248, KKA‐11 × KKU40, KKA‐139 × BJ248, KKA‐14 × KKU40, and KKA‐53 × Theis had the greatest SCA for theoretical sugar yield. In producing ethanol from both sugar and grain fractions, two of the hybrids in this study (KKA‐11 × BJ248 and KKA‐139 × BJ248) could produce approximately 4600 L ha−1 ethanol in Thailand.

Heterosis in sweet sorghum

“…This fact indicates that in the genetic control of these traits, nonadditive genes are involved, with the possibility of obtaining promising hybrid combinations. When estimating the combining ability, Bunphan et al (2015) pointed out the nonadditive gene action for plant height, total biomass production, juice extraction, total soluble solids, sugar yield, and ethanol production. In a detailed analysis of the manifested heterosis, the traits showed significance for the average heterosis ( Table 3), indicating that there is a divergence in the allelic frequencies in the lines, which results in a favorable situation for breeding (Cruz & Vencovsky, 1989).…”

“…In general, the heterotic effect in autogamous species is less effectively manifested than in allogamous ones; however, there are some examples of success, such as in rice (Pereira et al, 2008) and grain sorghum (Scapim et al, 1998). Studies on sweet sorghum have shown the existence of heterosis for traits directly or indirectly related to the ethanol production, including soluble solids content, green mass production, and juice yield (Pfeiffer et al, 2010;Bunphan et al, 2015;Reddy et al, 2007).…”

“…Thus, the establishment of heterosis-based breeding of sweet sorghum has been shown to be a viable alternative. In general, studies on sweet sorghum have shown the presence of genes with additive and nonadditive gene action, in the expression of traits related to ethanol production (Bunphan et al, 2015), emphasizing the justification of breeding to obtain hybrid cultivars.…”

General and specific combining ability in sweet sorghum

“…The method of diallel analysis proposed by Griffing (1956) is widely used in the choice of parents since it allows estimation of general combining ability (GCA) and specific combining ability (SCA), previously defined by Sprague and Tatum (1942). Sweet sorghum has been studied in this manner in several countries, with emphasis on characterizing combining ability to produce ethanol (Makanda et al 2009, Indhubala et al 2010, Sandeep et al 2010, Vinaykumar et al 2011, Umakanth et al 2012, Bunphan et al 2015. These studies have encouraged breeding sorghum to obtain hybrids.…”

Dedicated Herbaceous Biomass Feedstock Genetics and Development

“…In addition, potential parental lines with high sugar yields and disease resistance were identified within a collection of sweet sorghum lines from multiple international sources [20]. Male sterile female parents (A-lines) have been tested with high-sugar male parents for heritability of sugar traits [10,95]. A number of sweet sorghum A-lines were crossed with several high-yielding pollen parents in both studies.…”