Long‐Term Selection in Hybrid Sorghum Breeding Programs

Abstract

Estimating genetic gains in sorghum [Sorghum bicolor (L.) Moench] is necessary to assess whether the current rates of improvement will meet future production demands. The current study was conducted to determine the rate of genetic gain in yield and associated traits over the commercial hybrid era using sorghum germplasm from the Texas A&M sorghum breeding program and a US sorghum seed company. From the Texas A&M AgriLife program, 60 hybrids that represented a 50‐yr span of hybrid breeding were grown and evaluated in five environments across Texas in 2016. In a separate set of trials, 14 commercial hybrids representing a similar timespan were evaluated in three Texas environments in 2016. In both programs, grain sorghum yields increased 0.008 t ha−1 annually over their respective timespans. Traits that increased over time included yield potential per plant, heterosis, test weight, panicle size, and grain number per panicle, whereas leaf angle, days to maturity, plant height, and yield stability demonstrated little to no change. Overall, ∼60% of total yield gains in US sorghum production are attributed to genetic improvement through sorghum breeding. Compared with other major US field crops, the rate of genetic gain in sorghum has been slower, presumably due to a combination of factors, which include continually shifting production environments, changing priorities in traits, reduced research investments (compared with other crops), and less‐than‐optimized heterotic groups.

Assessing combining abilities, genomic data, and genotype × environment interactions to predict hybrid grain sorghum performance

“…Since the development of sorghum hybrids, sorghum breeding programs have focused on improving the performance of A‐ and R‐lines in a concurrent and complementary mean with the expectation that hybrid combinations between elite inbred lines derived from complementary heterotic groups will maximize heterosis. There is some evidence that this has occurred over the past 60 yr (Assefa & Staggenborg, 2010; Gizzi & Gambin, 2016; Pfeiffer et al., 2019).…”

“…This strategy has increased the performance of hybrids, but these increments have been modest, and continual modification to the production environments has exacerbated the selection priorities in sorghum breeding programs (Monk et al., 2014; Pfeiffer et al., 2019). Technow et al.…”

Back to the future: implications of genetic complexity for the structure of hybrid breeding programs

“…However, the reduction of N e was also caused in part by the effects of selection, particularly once the majority of the genetic variation was additive. This has not generally happened in commercial breeding programs, where genetic gain continues apace ( Rasmusson and Phillips 1997 ; Duvick et al 2004 ; Fischer et al 2008 ; Pfeiffer et al 2019 ). Several factors that maintain diversity in practical programs were not included in the simulation model.…”

The AGCVIII kinase Dw2 modulates cell proliferation, endomembrane trafficking, and MLG/xylan cell wall localization in elongating stem internodes of Sorghum bicolor

“…The current study also raises the possibility that reduced panicle length and lower grain yield could be due in part to reduced cell proliferation or altered endomembrane activity. Increases in the yield of grain sorghum have been very slow over the past 30 years (Pfeiffer et al, 2019), suggesting a limitation has been reached with the current dwarf hybrid crop genotypes that are used commercially. This study suggests that developing grain hybrids containing dominant alleles of Dw2 could be useful, while selecting for increased stalk strength similar to the development of bioenergy sorghum.…”