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Abstract
SUMMARY
Sugarcane (Saccharum spp.) is the main source of sugar production all over the world. About 68 % of the total sugar produced worldwide came from sugarcane.
The welfare and sustainability of the communities depending on sugarcane production and manufacturing depends on maintaining high productivity and high quality of the grown cane. A major factor that contributes to such issue is the availability of suitable varieties that can provide high yield – high quality crops throughout the milling season.
Since 1983, Egypt relays on one single variety, i.e. Giza Taiwan 54-C9 known for short as C9. The variety has very high yielding potential. However, it is dangerous to depend on one cultivar for production because any crises such as diseases could damage the crop and the industry. This indicates the importance of breeding local cultivars suitable for our environment rather than importing them from other countries.
For a successful breeding program of sugarcane, it is crucial to have very good synchronization between the parents used in the crossing campaign. This is of great importance particularly when artificial floral induction is used in order to secure flowering of different varieties at the same time to be able to make pre-planned crosses.
This work was carried out during the crossing seasons of 2002-2004 and 2003-2005 at Hawamedia breeding station of the Egyptian Sugar and Integrated Industries Company. The station is located 15 km south of Giza at latitude 30° 20” N and Altitude 30° E.
Five sets of experiments were used to test the effects of two day-length decline rates. The examined decline rates were 0.5 minute and 1 minute per day. Fifteen sugarcane genotypes of diverse origin were used in this study. Each set of experiment utilized three genotypes that are proved to flower under the assigned induction duration.
Each experiment was laid in a CRD design with two pots containing ten stalks serving as replicates. Factorial arrangement of treatments was used with nesting for varieties within treatment that was used as an error term for testing the significance of varieties.
After the fixed day length period was over in the five experiments day length was decreased by minute per day, while the 0.5-minute decline rate was applied by reducing day-length by one minute every two days.
The following traits were measured:
1. Number of days to first flower opening recorded from the start day of induction treatment.
2. Pollen grain maturity index using iodine staining.
3. Number of germinated seedlings per 0.1 g of fuzz
4. Total fuzz weight per cross
5. Expected number of seedlings per cross
That data was subjected to statistical analysis. Means were compared using LSD at 5% level.
The major findings could be summarized as follows:
I- Number of days to flower:
The statistical analysis revealed that day-length decline rate did not affect this trait for the easy-to-flower or the hard-to-flower genotypes under 45 or 105 days experiments. However, highly significant effects were observed for 60 and 75 days experiments while significant effect was observed for the 90 days experiment.
The use of both 1 and ½ minutes decline rates could be used to extend the chances of conducting bi-parental crosses.
II- Pollen grain maturity
Decline rate treatments had no significant effect on pollen fertility under all induction experiments. This is of great importance as adverse effect of decline rates could minimize the chances of using certain genotype as male parent in crosses. It also provides further chances of conducting bi-parental crosses rather than poly-crosses.
The differences between varieties was highly significant for those subjected to 60 or 75 induction cycles. Such differences could be attributed mainly to the genetic make up of the genotypes under investigation.
III- Seedling germination per 0.1 g
The data revealed that none of the examined factors, or their interaction reached significant level for the five experiments.
IV- Total fuzz weight
The statistical analysis for total fuzz weight per tassel showed insignificant response to the examined factors or their interactions under all induction experiments. Such trait is highly genetic controlled with very little effect of environmental factors.
V- Seedling number per tassel:
Statistical analysis of this trait revealed that decline rates did not exhibit any significant effect of total number of seedlings per tassel for the five conducted experiments. However, genotypes varied significantly under the 45, 60, and 75 experiments. On the other hand, the interaction was insignificant for the five experiments. Varietal differences followed the pattern of seedling germination per 0.1 g fuzz rather than fuzz weight for the 45 and 60 days experiments. However, tassel weight was the main contributor for this trait in the 75 days experiment.
In general, it could be recommended to use both ½ and 1 minute decline rate in the Hawamedia breeding program to synchronize flowering dates without adverse effects on the fertility of pollen or seed setting of genotypes of various induction treatments.