Insight into genetic potential of male sterile sweet sorghum A-lines for agroindustrial traits using tester R-lines

There is a growing demand for the development of alternative fuels from renewable sources, thus sweet sorghum an autogamous species has potential for bioethanol production. Traditionally recommended cultivars were varieties, however, with the development of cytoplasmic male sterile sweet sorghum lines, sweet sorghum hybrids have become economically viable. The sweet sorghum breeding program of the Brazilian Agricultural Research Corporation (Embrapa Milho e Sorgo) has been developing sweet sorghum hybrids for bioethanol production according to the scheme of A, B and R-lines are used, where A-lines are used as females in the production of hybrid seeds. A and B-lines are isogenic, which differ only its cytoplasm source, sterile and normal, respectively, and fertility restorers R-lines. Thus the objective of this work was to evaluate the genetic potential of new male-sterile sweet sorghum A-lines using testcross hybrids developed with two sweet sorghum R-line as testers for agroindustry characteristics for bioethanol production. Forty testcross hybrids were developed using 20 experimental A-lines and two testers sweet sorghum R-lines. Experiments were conducted at experimental stations in Sete Lagoas-MG and Nova Porteirinha-MG, to evaluate 20 A-lines, two 2 R-lines, the resulting 40 testcross hybrids, and two controls. The 64 treatments were evaluated for days to flowering, fresh biomass yield and total soluble solids (Brix). The data obtained were analyzed using the ASReml package, for the estimation of variance components and the prediction of genetic and non-genetic values via REML/BLUP. Two models were adopted, called Multi-Tester and Single-Tester. The genotypic values of the A-lines when crossed with tester T2, were positive for nine A-lines (12, 17, 6, 20, 18, 16, 19, 11 and 3) with emphasis on A-lines 12, 17 and 6, which were the highest values, respectively, the same tester for the trait FLOW, ten A-lines were positive values (3, 16, 17, 4, 12, 15, 5, 6, 8, 20) with emphasis on 3, 16 and 17. The genotypic values for TSS (Brix) trait of the A-lines when crossed with tester T1 were positive for A-lines (19, 18, 20, 16, 1, 5, and 6) with emphasis on lines 19, 18, 20, and 16, with the highest values, respectively. Only two A-lines showed positive genotypic values for three traits, A-line 16 and 20. These results indicate the need for continuing simultaneous improvement of A-lines for FLOW, FBY, and TSS. A-lines from the sorghum breeding program of Embrapa Milho e Sorgo have the potential for use as parents in the development of superior sweet sorghum hybrids for bioethanol production. The A-lines 6 and 20 have positive genotypic values for three traits, this A-lines has a potential for producing hybrids dedicated to bioethanol production. The T1-L tester was more efficient in discriminating the genetic values between the A lines for TSS, while the T2-L tester for FBY and FLOW. The development of a tester with genotype "drydry" and "Ma₁Ma₁" is important in order to develop superior hybrids to produce bioethanol involving the A, B and R scheme.