Registration of three sweet sorghum lines with high tolerance to sorghum aphid (Melanaphis sorghi)

Sweet sorghum [Sorghum bicolor (L.) Moench] stalks contain sugary juice, which is used to produce syrup and has potential for biofuel production. Since 2013, the sorghum aphid (Melanaphis sorghi, previously known as sugarcane aphid, M. sacchari) has become a major pest of sorghum in North America. GTS1903 (Reg. no GP-945, PI 702423), GTS1904 (Reg. no. GP-946, PI 702424), and GTS1905 (Reg. no. GP-947, PI 702425) represent the first publicly released sorghum aphid-tolerant sweet sorghum germplasm. All three derive from the initial cross A1N109 x No. 5 Gambela. In four environments GTS1903, GTS1904, and GTS1905 sustained less aphid damage than the check cultivar Top 76-6', and in one environment they harbored significantly fewer aphids than Top 76-6. Under sorghum aphid infestation the juice Brix, an estimate of sugar content, averaged 17.0, 15.9, and 17.0 degrees Bx for GTS1903, GTS1904, and GTS1905, respectively, all greater than Top 76-6 (12.7 degrees Bx). The juice of these three lines also contains greater trans-aconitic acid concentration (26.8-37.1 mM) than Top 76-6 (5.5 mM), which may contribute to sorghum aphid tolerance. GTS1903, GTS1904, and GTS1905 flower approximately 74, 89, and 76 days after planting, respectively. GTS1905 is the tallest, averaging 279 cm. All three lines have shown resistance to leaf anthracnose (caused by Colletotrichum sublineola). Genetic markers confirmed that all three lines contain the region of SBI-06 from PI 257599 that is associated with sorghum aphid resistance.