Eleven genotypes of sugarcane (ten genotypes and one commercial variety G.T.54-9 as a control) were evaluated at twelve environments; three locations (Agric. Res. Stations of Kom-Ombo, Aswan governorate, El-Mataana, Luxor governorate and Shandaweel, Sohag governorate and two harvesting dates; 11 and 12 month-old in 2015/2016 (plant-cane) and 2016/2017 (first-ratoon).The differences among genotypes, locations and between harvesting dates were significant for all studied traits; stalk length, stalk weight, cane yield, brix, sucrose and sugar yield. The interaction of locations × genotypes was highly significant in plant-cane and first-ratoon for all studied traits. Locations × harvesting dates interaction was significantly for stalk length in plant-cane crop and for stalk weight, sucrose and sugar yield in first-ratoon crop. Mean squares due to interaction between genotypes, harvesting dates and locations were significantly for all studied traits, except cane and sugar yields in plant-crop and stalk length in first-ratoon. Mean cane yield ranged from 54.23 and 52.61 to 57.61 and 56.71t/fed at harvesting dates and from 46.66 and 50.12 to 60.71 and 58.69 t/fed under locations in plant-cane and first-ratoon, respectively. Late harvesting date increased cane yield and its components. The stability analysis of variance for cane yield showed that the intermediate yielding genotypes (G.2003-47, G.2004-27 and G.2011-82) were more stable than the rather responsive high yielding ones. However, the genotype G. 2004-27 was stable for cane yield and its components. In addition, it was considered to be superior for cane yield under different environments. However, the highest yielding genotype (G.99-103) was unstable.

The research reported was conducted during 2016 and 2017 at the breeding station of Sugar Crops Research Institute, Agriculture Research Center (ARC), Giza, Egypt (30° 0' N latitude, 31° 12' E longitude),to examine the response of three sugarcane clones (Co1129, IK76-99, and NCo339) and the commercial cultivar GT54-9, to four photo-initiation treatments of constant 12.5-h days of 15-, 21-, 30-, and 60-days length followed by a declination of 30 s/d to 11 h 30 min.. The four sugarcane clones varied considerably in their initiation response. None showed any flowering response to the 15-day treatment. However, they revealed differential responses regarding their flowering dates for the 21-, 30-, and 60-day photo-initiation treatments. Their flowering dates were delayed by increasing the number of initiation cycles. The cultivar GT54-9 responded only to the 21-day treatment. Co1129 responded best to the 30-day treatment with 50% flowering but produced no flowers in the 21-day treatment. IK76-99 and NCo339, with 50% flowering, responded best to the 30-day treatment. Increasing the length of the inductive cycle reduced pollen viability. This resulted in decreased seed germinability and germination speed. We suggest all germplasm be screened under different photo-initiation cycles to define and select parents for sugarcane breeding program so all cross combinations can be made among synchronized flowering parents.

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