الفهرس 
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Abstract
The present investigation was carried out at Sids Agricultural Research Station, Agricultural Researsh center, Beni-Suef, Governorate, Ministry of Agriculture, Egypt, during the two successive growing seasons of 2003/2004 and 2004/2005. Selected local and some exotic onion gentoypes were used. These genotypes are respresenting broad genetic base and all of them have been maintained for number of years in Egypt by Onion Research Section, A.R.C. Egypt. The am of the study was to determine phenotypic stability of yield and other economic traits in onion genotypes.
Twenty one genotypes of onion across four environments (two transplanting dates by two growing seasons) were tested in. a randomized complete block design with three replications. Standard analysis of variance according to Snedecor and Cochran (1967) was used to analyze genotype performance in estimating phenotypic and genotypic stability parameters according by Eberhart and Reussel (1966) and Tai (1971) models.
Seeds of the twenty one genotypes were planted in the nursery in two different sowing dates. The first sowing date was in Sep.10 , and the second was in 13 Oct. in both seasons. The transplants were transplanted in 15th Nov. in the first date and 18 th Dec. in the second one respectively in both seasons. Irrigation, pest & weed control, and other and normal cultural treatments were done as the recommended in commercial production.
The results of these investigations can be summarized as follow :
I- Agronomic characters :
Plant height (cm) :
Highly significant differences were observed among the tested genotypes and between the two transplanting date on plant height in both seasons. The performance of the tested genotypes indicated that ”Beharry 1866”, ”Texas Early Grano” and ”Ehnacia Red” cvs. had the heighest plants in both seasons , While ”Dronka” and ”Hegaza” gave the lowest values in both seasons. The early transplanting date gave the heighest value, while the second date gave the lowest value in both season. The interaction effect between the genotypes and planting date was only significant in 2003/2004 season. ”Beharry 1866” cv. gave the tallest plant in the first date while ”Hegaza” and” Dronka” gave the lowest value in the second.
Bulb height (cm) :
Data revealed that bulb height was significantly affected by transplanting date, the first date gave the higher means in both seasons. The effect of tested cultivars was high significant on bulb height. ”Texas Early Grano” gave highest bulb followed by ”Beharry Red” cv. in both seasons while ”Dronka” gave the lowest values. Also the interaction (genotypes X sowing dates) showed significant differences. The highest means were given by ”Texas Early Grano” in the first date in both seasons. While ”Dronka” cv. gave the lowest values in the second date in both seasons.
Number of leaves / plant :
Number of leaves per plant was affected significantly by the different transplanting dates in both seasons. The first date gave the highest mean in both season. This character differed significantly among the genotypes. ”Texas Early Grano” gave the higher means in both seasons followed by ”Cepolla Bianca Apriliatica”. In the meantime, the cultivar ”Shandaweel 1” gave the lowest number of leaves per plant in both seaon. The interaction between planting date and genotype was highly significant for number of leaves per plant. ”Texas Early Grano” in the first sowing date, gave the highest mean in both seasons, followed by ”Cepolla Bianca Apriliatica” cv. in both seasons. While the landrace ”Dronka” gave the lowest mean value in the second date in both seasons.
Bulb diameter (cm) :
The effects of transplanting date, genotypes and their interaction (sowing date X genotype) were highly significant in both seasons. ”Texas Early Grano” gave the highest value in both seasons, while ”Hegaza” gave the lowest value. Also the first date gave the highest value in both seasons. In the meantime, ”Texas Early Grano” cv. in the first transplanting date gave the highest bulb diameter in both seasons.
Neck bulb diameter (cm) :
Data indicated that the differences in the performance of 21 genotypes for neck bulb diameter was highly significant. Also, the first planting date gave higher values in both seasons, compared to the other date. Cultivar ”Beharry Red” gave highest neck diameter in both seasons. But ”Dronka” cv. gave the lowest value. The interaction (sowing date X cultivar) effect was highly significant. Thus, ”Beharry Red” when planted in early sowing date gave the highest value in both seasons.
Bulbing ratio :
Data showed that there were highly significant differences among the studied cultivars for bulbing ratio in both seasons. ”Texas Early Grano” gave the lowest value in both seasons. The interaction (sowing date X cultivar) was highly significant in both seasons and ”Texas Early Grano” in the first transplanting date gave the lowest bulbing ratio in both seasons.
Bulb shape index :
Mean values of bulb shape index were highly significant under different transplanting dates in both seasons. The late date, gave the high value. The interaction between transplanting dates and growing was significant in both season, Generally ”Hegaza” in early date gave the highest shape index in both seasons .
Whole Plant fresh weight (g) :
Effects of transplanting dates, genotypes, and their interaction (transplanting date X genotype) were highly significant in both seasons. The first date gave the highest plant weight in both seasons .
”Beharry Red” and ”Texas Early Grano” cvs. gave the highest weight in both seasons, respectively. Also, cultivar ”Texas Early Grano” in the first planting date the heaviest plant weight in both seasons, while ”Shandaweel 1” in the second date gave the lighter weight in both seasons.
Bulb fresh weight (g) :
Transplanting dates, genotypes, and their interaction effects were highly significant in the two season. The first date gave heaviest bulb weight in both seasons. Also, cultivar ”Texas Early Grano” scored the heaviest weight in both season, compared to ”Cepolla Bianca Apriliatica” cv. that gave lighter weight in both seasons. Also the interaction between genotypes and planting dates indicated that cv. ”Texas Early Grano” in the early sowing date recorded the heaviest bulbs in both seasons, while ”Cepolla Bianca Apriliatica” cv. gave a lighter bulb weight in both dates in both seasons.
TSS :
Clearly, TSS content of onion was affected significantly by the tested genotypes. Cultivar ”Giza 20” gave the highest values in both seasons, while ”Cepolla Bianca Apriliatica” cv. gave the lowest value in both seasons. Moreover, TSS of onion cultivars was significantly different at various transplanting dates. The first date gave higher value in both seasons than the second date. Also the interaction between genotypes and planting dates had a significant effect on TSS values in both seasons. ”Giza 20” cv. gave the highest TSS in the early date in both seasons, while ”Cepolla Bianca Apriliatica” gave the lowest values in the second date.
Percentage of dry matter (D.M.) :
Percentage dry matter of onion was significantly affected by the growing cultivars at different planting date. ”Composite 16” cv. gave higher percentage, followed by ”Giza 20” cv. The first planting date gave the highest values in both seasons.
Number of days from transplanting to maturity :
Data indicated that the number of days from transplanting to maturity of all cultivars were significantly affected by transplanting date. The first date needed longer growth period, also the maturity was significantly affected by the growing genotypes. Landrace ”Dronka” was the earlist one in both seasons, followed by cv. ”El-Maragha”. On the other hand ”Cepolla Bianca Apriliatica” cv. was the latest one in both seasons. The interaction was significant, ”El-Maragha” cv. when planted in the second date was the first cultivar shown ripening signs in both seasons, while ”Cepolla Bianca Apriliatica” cv. was the in both seasons for both transplanting dates.
II- Yield and its componants :
Data indicated that the transplanting date, cultivars, and their interaction were significant for culls yield, marketable yield, total yield, % of bolting , % of doubling , and % of culls yield to total yield in both seasons.
1- Culls yield (ton/fed) :
The first date gave the highest culls yield than the second date in both seasons, ”Cepolla Bianca Apriliatica” cv. gave higher culls yield, followed by ”Texas Early Grano” cv. in both seasons, compared to ”Giza White” cv. which gave the lowest value in both seasons. Also the interaction (transplanting dates X cultivars) showed that ”Cepolla Bianca Apriliatica” cv. in the late date scored the higest culls yield in both seasons.
Marketable yield (ton/fed) :
The first transplanting date gave the highest marketable yield than the second date in both seasons. ”Ehnasia Red” cv. gave higher marketable yield, followed by ”Beharry Red”, while ”Hegaza” cv. gave the lowest marketable yield in both seasons. Also ”Ehnasia Red” in the first sowing date, gave higher marketable yield in both seasons, compared with ”Hegaza”. when planted in the late planting dates which gave lowest marketable yield in both seasons.
Total yield (ton/fed) :
First transplanting date gave the highest total yield compared with the second date in both seasons. ”Ehnasia Red” genotype gave the highest value compared with ”Hegaza” which gave the lowest total yield in both seasons. Generally ”Ehnasia Red” in the first sowing date gave the highest total yield, while ”Hegaza” gave the lowest total yield when planted in the second sowing date in both seasons.
Percentage of bolting :
The first transplanting date gave the highest values, compared with the second date in both seasons. ”El-Maragha” gave the highest percentage in both seasons, while ”Giza 20” cv. gave the lowest percentage. Also ”Texas Early Grano” cv. gave the highest bolting percent when planted in the first sowing date in both seasns.
Percentage of culls yield to total yield :
The highest percentages of culls were given by planting onions in the first transplanting date compared with the late date, in both seasons. In this regard, ”Cepolla Bianca Apriliatica” gave the highest percentage compared with ”Giza White” cv. who gave the lowest percentage. Cultivar ”Cepolla Bianca Apriliatica” in the second sowing date gave the highest percentage of culls yield, while ”Giza White” cv. gave the lowest values when planted in the second date.
Percentage of doubling :
The first transplanting date gave the higest percentage of doubles compared with the second date.” Cepolla Bianca Apriliatica” cv. gave the highest percentage of doubles, compared with ”Dronka” cv. which gave the lowest percentage . ”Cepolla Bianca Apriliatica” cv. when planted in the first date gave the highest percent, while ”Dronka” cv. gave the lowest percentage when planted in the second date.
III. Storability :
Percentage of weight loss in storage :
Transplanting date had insignificant effect on % weight loss after 2, 4 and 6 months of storage for all tested genotypes. On their hand the effects of genotypes and interaction (transplanting dates X genotypes) were highly significant after 2, 4, and 6 months of storage.
After 6 months of storage, ”Cepolla Bianca Apriliatica” cv. gave the highest losses in both seasons. But ”Giza 6 M.D.M.R”(Giza 6 Mohassan Downy Mildew Resistance) gave the lowest values.
TSS content :
Total soluble solids (TSS) content decreased after six months of storage in both seasons. ”Texas Early Grano” cv. had the lowest TSS values in both seasons, while the highest TSS values were obtained by ”Assiut Globe” cv. in the first season, and ”Phulkara” cv. in the second one.
Percentage of of dry matter :
Percentage dry matter content increased with increasing storage periods for all tested genotypes.
IV. Phenotypic and genotypic stability parameters :
The stability of the performance of each 21 genotypes across four environments were determined. Three of genotypes showed above average degree of genotypic stability for most of the tested traits. Hence, these three genotypes, ”Composite El-Bostan” , ”Composite 16”, and ”El-Maragha” may be recommended to be released as commerical stable for high yielding and/or incorporated into a breeding stock in any future breeding program. Sound golden onions are among the desired characteristics which the breeders shouls search for.
V. Phenotypic correlations :
Highly significant and positively correlation coefficients were detected between total yield, and the following traites : plant hight, bulb hight, number of leaves per plant, bulb diameter, neck bulb diameter, plant weight, bulb fresh weight, period untill maturity, number of growing points per bulb, number doubling bulbs per plot, and % doubling. Also total yield was significant and positively correlated with TSS and number of single bulbs per plot. On other hand it was highly significant and negatively correlation coefficients between total yield and the bulb shape index, and % bolting bulb. Moreover, there was significant and negative association between total yield and % culls yield.
F- Economic evaluation :
According to this study fresh yield of marketting was more profitable for most of the tested genotypes. On the other hand the “Synthetic 346”, after 6 months of storage gave the high estimations for gross field incom, gross margin, and benefit cost ratio (B/C).
VI. Conclusion
Genotypes “Beharry Red.”, showed high adaptation to all environments (ideal genotype) and had above averag stability – Composite 16 and Giza 20 were alternatives for “Beharry Red”, “Ehnasia Red” showed good adaptability but had low stability. Growers should check with potential buyers before harvesting so the yield can be moved out rapidly. The best way to market the bulb yield of most genotypes as soon as possible.