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Influence of Paclobutrazol and Bulb Sizes on Seed Yield and Yield Attributing Traits of Onion (allium Cepa L) Cv Taherpuri

M. Ashrafuzzaman
Professor
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

M. Nasrul Millat
Researcher
Department of Crop Botany, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

M. Razi Ismail
Professor
Institute of Tropical Agriculture, University Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia

S.M. Shahidullah
Senior Scientific Officer
Rice Farming Systems Division, Bangladesh Rice Research Institute, Gazipur-1701

Abstract/ Executive Summary:

Different doses of paclobutrazol (PBZ) and different bulb sizes of onion were evaluated to determine their effect on growth and seed production of onion. Onion variety ‘Taherpuri’ with three-bulb sizes – small, medium and large – was used. Four doses of PBZ were 0 (control), 20, 40, and 80 mg l71. The two-factor experiment was laid out in a randomized complete block design with three replications. Application of PBZ significantly reduced the plant height, tillers per bulb, leaves per plant and length of scape. However, in other parameters such as the number of flowers, umbels per bulb, umbel diameter, 1000-seed weight and seed yield, there were no significant influences of PBZ concentrations used (p 5 0.05). On the contrary, plant height, number of leaves per plant, length of scape, effective fruits per umbel, percentage of fruit set, and seed yield were positively influenced by different bulb sizes of onion. Higher values were obtained for the above-mentioned parameters from the larger-sized bulbs and values were decreased as the bulb sizes decreased. The maximum seed yield was recorded in plants grown from the large sized mother bulb. The interaction between the PBZ doses and bulb sizes were also significant for some variables while it was not significant for others.

Keywords: Bulb size; Onion seed; Paclobutrazol

Location: Crop Botany Research field, Bangladesh Agricultural University, Mymensingh

Start Date: 01-07-2005

End Date: 30-06-2006

Program Area: Seed Technology

Commodity: Onion

Objectives:

To evaluate the feasibility of using paclobutrazol in onion seed production and to determine its optimal dose for maximizing growth and flowering and ultimately to increase onion seed yield
To determine how bulb size and paclobutrazol could be used to maximize growth and seed yield of onion

Methodology:

The study was conducted at the Crop Botany Research field, Bangladesh Agricultural University, Mymensingh, during 2005–2006. The soil belongs to the old Brahmaputra flood plain Alluvial Tract under AEZ9. A completely randomized block factorial experiment intended to evaluate the effects occasioned by paclobutrazol concentrations and bulb sizes was conducted with the onion cultivar Taherpuri with three replications. Individual plot size was 1 x 1 m. Three bulb sizes were planted: large, medium and small, with average bulb weights of 12, 8, and 5 g, respectively. Paclobutrazol concentrations were 20, 40, and 80 mg L^-1of water. The paclobutrazol solutions were prepared according to label specifications from the concentrated solution (250 g L^-l), and were applied for treating onion bulbs of three sizes with three concentrations of paclobutrazol overnight. Bulbs were treated with distilled water at equivalent volumes for control. The field was prepared by cultivating it three times each followed by leveling. Onion bulbs were planted on 25 November 2005 with 20 x 10 cm spacing. Bulbs were set upright and at a depth of 2.5 cm. Well-decomposed cow dung (10 t ha^-1) was applied three days before the sowing of onion bulbs. Nitrogen, phosphorus and potassium were applied using urea, triple super phosphate (TSP) and muriate of potash (MP) at 350, 500 and 150 kg ha^-1, respectively. All TSP and half urea and potash were applied as a basal dose, while the remaining urea and potash were applied in two equal installments (at 40 and 60 days after planting). The crop was kept weed-free by manual hoeing. All other agronomic practices like irrigation, mulching, earthing-up, plant protection measure, and staking were kept normal and uniform for all the treatments during the entire growth period. The seed heads or umbels were harvested when the seeds became mature. The umbels were considered to be ready for harvest when about 15–20% of the fruit had black seed exposed. It was harvested in several installments by cutting the mature umbels from the stalk. Harvesting was carried out from 9–25 April 2006 in the morning to prevent shattering and loss of seeds. Harvested umbels were sun-dried, threshed manually and the seed yield per plant and per plot were recorded and converted into kg ha^-1. The data on plant height and number of leaves were recorded from five selected plants at 20, 30, 40, 50, 60 and 70 days after planting and averaged. The number of tillers per plant was counted at the maximum vegetative growth stage of the onion plants. The data regarding length of scape, scape diameter, number of umbels per plant, diameter of umbel, number of flowers per umbel, number of effective fruits per umbel, percentage of seeded fruits, weight of seeds per plant, seed yield per plot, seed yield per hectare, 1000-seed weight were recorded from five randomly selected plants from each plot and then averaged. The data were statistically analyzed using the statistical package program MSTAT-C developed by Russel (1986).

Source of Information: Archives of Agronomy and Soil Science, 55:6, 609— 621, 2009

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Paclobutrazol was effective in reducing plant height, leaf numbers and length of scape but did not increase flowering, fruit setting percentages and 1000-seed weight. Since onion plants can be grown in the field, reducing growth is unnecessary if flowering is not increased. Therefore the use of paclobutrazol would not be recommended for this production system. We also recommend further trials with changing PBZ application methods like foliar spray or drench application, etc. The vegetative growth and seed production ability of the plants increased gradually with the increased bulb size. Considering the cost, medium-sized bulbs can be used as the difference in seed yield among large and medium-sized mother bulbs was not so large.

Knowledge Management: Journal