Evaluation of the Performance of Three Onion Genotypes, Transplants Age and Plant Population Density on Yield, Premature Bolting and Doubling

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Abd El Hafiz, Ali Mohamed
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To investigate the performance of genotypes , transplant age and plant population density on yield , premature bolting and doubling of onion , two experiments were conducted during 1996/1997 season , one in the University of Khartoum at Shambat Experimental Farm (Sudan) and the other at the Foundation Seed Farm of the National Center for Seed Multiplication , Sieyun( Yemen). Three onion genotypes ( Baftaim Improved-1 " BAIM-1" , Baftaim improved-2 " BAIM2" and the landrace Baftaim) were transplanted at the ages of 80, 60, or 40 days in Shambat and 33 plants/m2 obtained from plant population densities of 100, 50 and 33 plants/m2 obtained from spacings at 5,10 and 15 cm between plants and 20 cm between rows were used. The experimental design used in both experiments was split-split plot design with population assigned to the main plot, transplant age in sub-plot and genotype to the sub-subplot. Growth and yield characteristics namely number of leaves/plant , plant height ( taken at bulbing ratio =2) , total bulb yield , marketable yield , average bulb weight , premature bloting (%) , doubling(%) , total soluble solids and dry matter contents were measured. The studied genotypes were found significantly different with respect to the investigated parameters in both experiments. The landrace " Baftaim" produced higher leaf number /plant than either Baftaim improved -1 (BAIM-1) or Baftaim improved -2 (BAIM-2) whereas , the highest plants were produced by BAIM-2 in Shambat experiment , but in Sieyun the landrace overscored BAIM-1 and BAIM-2. Genotypes BAIM-1 and BAIM-2 significantly (p=0.01) gave higher total yield , marketable yield (%) and average bulb weight than the landrace in both experiments . In general , "Baftaim" showed more tendency to premature bloting and doubling than either BAIM-2 except in Shambat experiment where BAIM-2 showed higher percentage of doubling . The genotypes were not significantly different in either bulb shape index , TSS and dry matter contents except in Shambat experiment where "Baftaim" gave significantly lower percentage TSS compared to the others (p=0.01). Transplant age had significant effect on growth traits only in Shambat where medium and young transplants showed higher leaf number. The use of old transplants significantly (p= 0.01) increased total yield, percentage of premature bloting and average bulb weight compared to either medium and young ages in both experiments. Marketable yield was significantly (p=0.01) enhanced by using young and medium transplants in Shambat while marketable yield was not effected by transplant age at Sieyun. In Sieyun, the percentage of doubling significantly (p=0.01) increased with decreased age of transplant, but at Shambat, doubling was not affected by transplant age. No significant effect of the transplant age on bulb shape index, TSS and dry matter was observed in both experiments. Plant population density showed significant effect (p=0.01) on the leaf number in Shambat. Medium and low plant densities increased significantly (p=0.01) the leaf number / plant than higher plant population density. Total and marketable yield were significantly (p=0.01) increased with increased plant population density, whereas bloting, doubling and average bulb weight increased with the decrease of plant density. Bulb shape index, total soluble solids and dry matter percentages were not affected by plant population density. The differences in soil type, irrigation, the level of infestation by the onion thrips (Thrips tabaci) and climatic conditions could explain the differences shown in parameters measured in Shambat and Sieyun experiment.
University of khartoum