Breeding of a new cassava variety GR4 and its cultivation technologies.

【Objective】A new superior cassava variety was bred in order to provide new resources for cassava production in China. 【Method】The cassava variety GR4 was selected through system selection method from the F1 clone self-crossed(SM1600) of variety PAR164 introduced from the International Center for Tropical Agriculture(CIAT). The variety comparative test was carried out from 1991 to 1996, the regional trial of 11 experimental plots was conducted during 1997-1999, and the production test was carried out at 7 experiment plots in Guangxi from 2009 to 2010. The characteristics,germination rate, tuberization traits, yield, starch content and stress resistance of GR4 were investigated and determined.【Result】GR4 was characterized by erect tight plant without branches, 1.8-3.0 m of plant height, strong growth vigor and drought resistance, long cone tuber with uniformity size and smooth thin peel. The tuberization centralized at shallow soil layer and presented horizontal elongation. The germination rate was at a higher level with 95.8%. The starch content of GR4 was ranged from 25.4% to 29.1% with average of 26.8%, which was 1.3% lower than that of SC205. The yield of GR4 in variety comparative test from 1992 to 1993 was 33600.0 and 28440.0 kg/ha,which was 13.1% and 7.2% higher than that of SC205. Its average yield in advanced variety comparative test during 1994-1996 was 34785.0 kg/ha, which increased by 18.8% as compared with the control SC205. During the regional trial of 11 experimental plots in 1997-1999,the average yield of GR4 was 36885.0 kg/ha, which was 21.1% higher than that of SC205. During the production test of 7plots in 2009-2010, GR4 presented 59040.0 kg/ha of average yield, which increased by 50.1% as compared with the control SC205. The GR4 was registered and certified by Guangxi Committee for Crop Variety Registration in 2011 and was acted as mainly extending cassava variety in the 12thFive-Year Plan by the Ministry of Agriculture. 【Conclusion】The new cassava variety GR4 present advanced comprehensive characteristics, and is suited to be planted with high density or be intercropped. It could be extended in cassava planting areas with moderate soil fertility of Sourthern China.