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Improvement of a local onion variety through selection

Sitesh Chandra Biswas and Monjur Hassan

BRAC Agricultural Research & Development Centre, Jogitola, BRRI, Joydebpur, Gazipur-1702

Abstract

In order to improve a popular local variety of onion fresh onion bulbs of ‘Taherpuri Local’ was brought to BRAC Agricultural Research and Development Centre (BARDC) and subjected to selection process. Continued selection improved the bulb weight and increased their shape and size respectively. Storage quality of this newly developed line ‘Improved Taherpuri’ has also been found to be increased. Especially its consumer acceptance has been increased due to its larger size, greater uniformity rate very good flavour and excellent taste. Positive attitude has also been observed among the seed producers towards this new line as its seed production is also profitable.

Key words: Allium cepa L., Keeping quality, Onion, Onion bulb, Seed production, Selection, Yield.

Introduction

Onion (Allium cepa L.) is an important rabi season crop in Bangladesh and it is generally used as a spice crop here although sometimes it is used as vegetables particularly in the form of salad. Different types of onion varieties viz. Taherpuri, Faridpuri, Shuk Sagar, BARI Pianj-1, BARI Pianj-4, Bahadur, Lalima, Ranga etc. are grown here for either as spice crop or for vegetables. Some of these varieties have very good flavour, pungency, taste and keeping quality besides their excellent shape and size. Very recently an imported type of onion having extra large size bulb having the wt. 180-260 gm ( diameter = 8-9 cm.) is also being observed in the vegetable market of township areas in Bangladesh. Based on the above characteristics ‘Taherpuri’ variety (named after the name of Taherpur Upazilla of Rajshahi district) is very popular in Bangladesh and most of the onion growers usually show their interest for growing ‘Taherpuri’ variety than any other onion variety due to its good market demand and storage quality. It can be mentioned here that every year huge onion bulbs are imported into Bangladesh particularly from India to meet up the growing demand of fresh onion in Bangladesh. Since the bulbs of onion can be stored 3 to 4 months easily there is a trend of storage of onions in the countryside in Bangladesh and the preserved bulbs are either sold at higher price in the monsoon season to get more profit or used for home consumption to cut down the cost of onion during its higher price in the market. As the storage quality of other varieties including Indian onion varieties are not good enough this is why there is a good demand of ‘Taherpuri’ variety among the people who want to preserve onion for longer period. Moreover, its cultivation is easy and matures earlier as well. Since there is a very good demand of high quality onion seeds in Bangladesh and there are few excellent varieties of onion available here in the market, a program on the improvement of a local variety ‘Taherpuri Local’ was initiated at BRAC Agricultural Research and Development Centre (BARDC) very recently and a brief account of the development process and the performance of new line ‘Improved Taherpuri’ has been described in the present communication.

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Materials and methods

The experiment was carried out in the experimental field of BRAC Agricultural Research and Development Centre (BARDC) Gazipur. Initially, fresh bulbs of local ‘Taherpuri’ variety collected from a local market were used as plant material and seeds derived from these bulbs were used for the varietal improvement process. Selection on the basis of ‘Greater Initial Capital’ theory postulated by Ashby (1930) followed by ‘Recurrent Selection’ process proposed by Hayes & Garber (1919) and East and Jones (1920) was adopted for the varietal improvement method. Standard cultural practices were followed for bulb as well as seed production. Data were collected accordingly and analyzed statistically. Results & Discussion

Actually the breeding activities of ‘Taherpuri Local ‘onion variety were started at BARDC during the year 2005-2006 by collecting original ‘Taherpuri’ variety bulb. Following are the excerpts of breeding activities have been made so far for its improvement in size & quality:

Fig. 1. Onion seed production plot at BARDC.

Table. 1. Year wise activities for varietal improvement of ‘Taherpuri’ variety .

Year Activities Remarks 2005 - 2006 Collection of bulbs of ‘Taherpuri Local’ onion

variety and planting them in the experimental field of BARDC. Off type plants were removed through rouging and diseased plants were eradicated.

Uniformity was found to be increased and healthy plant population was formed.

2006 -2009 Purification of the local variety through selection.

More or less purified stock was produced as a result of continued selection.

2010-11 Seed production from selected medium size single bulb (18-20 gm) at BARDC from the purified germplasm stock of ‘Taherpuri Local’ variety. Diseased & weaker plants were removed through rouging.

Good quality seeds were harvested from healthy plants.

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2011-12 Seed grading (selection), categorizing into different groups according to seed size (e.g. Larger seed stock, Medium size seed stock and smaller size seed stock) seedling raising from each stock, transplantation, rouging & bulb as well as seed production from selected stocks maintaining isolation distance. Healthy type single bulbs after harvesting were selected and bulbs were preserved in suitable condition. Most of the selected bulbs were sent to Thakurgaon (well known region for vegetable seed production) for growing them in farmer’s field and good quality seeds were obtained from these bulbs.

Variations in overall plant vigour, growth, flowering pattern, bulb size and in other characteristics were recorded among the different stocks; noticeable improvement in the bulb size & quality was also recorded.

2012-13 Seedling raising from seeds obtained from different stocks, seedling selection for transplantation & bulb production accordingly maintaining suitable isolation distance. Selection of good quality single bulb having higher storability. Bulbs were preserved for planting at Gazipur BARDC, in 2013-14.

Again variations in the phenotype between the different stocks were noticed while uniformity in the populations within each stock was observed. Compared to original stock larger size bulbs were harvested from each group and big size bulbs were harvested from ‘Larger Seed Stock’ and ‘Medium size Seed Stock’.

2013-14 Planting of superior quality bulbs from different stocks maintaining uniform distance and suitable isolation distance, rouging & seed production. Bulbs were also produced from super quality seeds obtained from medium size seed stock along with larger seed stock.

Seeds were collected from each of the different stocks and stored separately. Seeds were sent to Dinajpur for bulb production & evaluation. Good quality bulbs were also sent to Thakurgaon for commercial seed production. Good quality bulbs and seeds were produced at Dinajpur & Thakurgaon.

2014-15 Raising of seedlings from different stocks, seedling selection, transplantation of selected seedlings in separate plots maintaining suitable isolation distance and keeping uniform spacing, bulb production & selection of bulbs in the field & also during post harvest operations. Good quality bulbs were sent to Thakurgaon for commercial seed production for evaluation. At BARDC, super quality bulbs were planted for high quality seed production.

Again superior performances of the selected stocks were noticed and single bulbs were being stored separately for next course of breeding activities. Excellent quality seeds were also obtained at BARDC from super quality bulbs.

2015-2016 OYT of ‘Improved Taherpuri’ will be conducted in the current ‘Rabi season’ using popular commercial variety. Good quality ‘Basic Seed’ will also be produced side by side.

Better performance of ‘Improved Taherpuri’ is expected.

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From Table 2 it is clear that selection on seed size has made an impact on bulb size and larger

size bulbs were produced in the improved stock as a result of selection. The bulb size of improved stock

was found to be increased considerably in the year 2012 and in 2015 compared to original stock (Table 2

& 3). Near about 31.20 % increased diameter was also recorded in the ‘Improved Stock’.

Table. 2. Bulb weight (gm) variations of local and Improved ‘Taherpuri’ variety (at the time of planting).

Year 2011 2012 2015 Stock Original Stock Improved stock

Size category Wt. of big size bulb (gm)

Wt. of medium size bulb (gm)

Wt. of big size bulb (gm)

Wt. of medium size bulb (gm)

Wt. of big size bulb (gm)

Wt. of medium size bulb (gm)

Mean ± S.D (range)

*18.40 ± 1.84 (16-20)

14.00±1.33 (12-16)

35.36±2.74 (31.2-40.7)

25.87±3.04 (20.1-30.3)

39.60±2.55 (34-44)

27.50±1.78 (24-31)

% increased than original stock

- - 92.17 84.78 115.21 96.42

*Very close to wt. of bulb of ‘Taherpuri’ variety of ‘Lal Teer’ Company = 20 gm (Ref: Recent catalog of 2012).

Table. 3. Bulb diameter (cm) variations of local ‘Taherpuri’ variety at different stages of improvement.

Year 2011 2015 Stock Original Stock Improved stock Mean ± S.D (range)

3.20 ± 0.24 (2.90 -3.60)

4.22 ± 0.37 (3.60 - 4.60)

% increased than original stock

- 31.20

Bulb characteristics of ‘Improved Taherpuri’ was also compared with other 3 commercial

vegetable type onion having larger bulb size ‘Lalima’, ‘Ranga’ and ‘Bahadur’. All the 3 vegetable type

commercial onion varieties exhibited higher bulb weight than the Improved Taherpuri (Table.4). But it is

interesting to note that highest bulb diameter was recorded in ‘Improved Taherpuri’ compared to all

other commercial vegetable type onion varieties. Higher pungency was also recorded in ‘Improved

Taherpuri’.

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Table. 4. Comparative studies on fresh bulb weight (gm) & diameter (cm) of ‘Improved Taherpuri’, ‘Lalima’ (check), ‘Ranga’ (check) & ‘Bahadur’ (Check) ( data of the year 2012). Parameters Improved Taherpuri Lalima Ranga Bahadur Characters Bulb

weight (gm)

Bulb dia-meter (cm)

Bulb weight (gm)

Bulb dia-meter (cm)

Bulb weight (gm)

Bulb dia-meter (cm)

Bulb weight (gm)

Bulb dia-meter (cm)

Mean

62.96 7.02 118.78

6.85 104.73

5.50 131.24

6.70

± S.D

± 9.10 ±0.62 ±17.06 ±0.44 ±18.41 ±0.49 ± 13.49 ±0.52

(range) (49.55- 77.67)

(6.2-7.3) (99.12-161.01)

(6.2-7.5) (74.14-139.35)

(5.0-6.6) (117.35-163.11)

(5.8-7.5)

% increased or decreased than ‘ Imp. Taherpuri’

- - +88.65 -2.42 +65.23 -27.66 +68.28 -4.77

Pungency

High Low Low Low

Taste Better Normal Normal Normal

Fig.2. ‘Lalima’ and ‘Bahadur’ Fig. 3. ‘Bahadur’ and ‘Taherpuri Local’

To find out the difference between ‘Taherpuri Local’ and ‘ Improved Taherpuri ‘; after

harvesting a good crop of ‘Improved Taherpuri’ in 2014-15 at BARDC, bulbs were categorized into 3

groups and were compared accordingly with the recommended size for ‘Taherpuri Local’ variety

(Table.5). Increased size was also observed in all the groups than the recommended size for ‘Taherpuri ‘

onion variety.

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Table. 5. Bulb wt. and diameter of different categories of bulb of ‘ Improved Taherpuri’ onion variety (2014-15).

Parameters Category of bulbs Remarks Bigger size Medium size Smaller size

Bulb wt. (gm) 39.60 ± 2.55 (34.00 - 44.00)

27.50 ± 1.78 (24.00-31.00)

14.70 ± 1.36 (13.00 - 17.00)

Recommended bulb diameter of ‘Taherpuri’: for bigger size, medium size and smaller size- 3.8 cm, 2.50 cm & 1.80 cm respectively .

Bulb diameter (cm) 4.22 ± 0.37 (3.60 - 4.60)

3.06 ± 0.16 (2.80 - 3.50)

2.61 ± 0.11 (2.50 - 2.80)

Increased over recommended diameter (%)

+ 11.05 + 22.40 +45.00

Fig.4. Three different sizes of bulbs of ‘Improved Tagerpuri’. Main characteristic features of ‘Improved Taherpuri’ are:

1. High yielding variety having excellent bulb quality with good flavour.

2.Improved stock of original 'Taherpuri' having larger size uniform bulbs with

shiny brown colour (bulb wt. 40-45 gm).

3. Pitcher shaped uniform size single bulb and the neck region is very narrow.

4. Higher keeping quality and looses water very slowly during storage period.

5. Pungency is very much similar to the original 'Taherpuri' variety but taste is

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better than that of 'Taherpuri Local'.

6. Tolerant to major diseases and yield per acre is around 10-12 mt.

7. Seed yield per acre 270-300 Kg.

Fig.5. High quality of bulbs of ‘Improved Taherpuri’.

Bulb production

Onion bulbs are generally produced in Bangladesh by 2 popular methods: 1) Through the raising of seedlings on seed bed followed by transplanting them in the main plot or by 2) By planting bulbs.

Onion bulb production from good quality seeds of ‘Improved Taherpuri’: Good quality seeds harvested from selected bulbs were sown on seed beds on 31.10.14 after germinating them initially within a piece of moist cloth tied for stimulating dormant seeds for germination. Better seedling emergence was noticed and 40 days old selected healthy seedlings were transplanted in the main plot on 15.11.14. Standard cultural practices were provided to ensure better growth of onion plants. Almost all the plants grew uniformly and produced good quality bulbs at the end of the season. No off type plants were recorded in the population of ‘Improved Taherpuri’ variety. The plot was also found to be unaffected by major diseases. At the end of the season good quality larger uniform size bulbs were harvested and

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interestingly most of these harvested bulbs were found to be fleshy type single bulb. Not only these bulbs were found to be increased in size and shape; these bulbs had better taste as well.

Onion seed production from good quality bulb of ‘Improved Taherpuri’: With a view to produce high quality seeds of ‘Improved Taherpuri’ larger size bulbs were planted on 07.11.2014 in 0.25 decimal of land. Within few days healthy plants having excellent vigour came out from the bulbs and a disease free population of the line was developed providing standard cultural practices of onion cultivation. These plants were came into flowering on 05.12.14 (at 38 DAP) and a high quality almost uniform umbels were produced by these plants. At maturity, these healthy umbels produced fine quality seeds. It can be mentioned here that a wide variation in the production of umbel per bulb was noticed during the seed production of ‘Improved Taherpuri’ and this is very important for seed production as the quantity of seeds per plot is very much dependent on the production of umbels by each bulb. Umbels produced from each bulb have been presented in the table below (Table 6).

Table.6. Data on nature of umbel formation during seed production. Name of the line

Total no. of bulbs planted

% non bolting bulb

Frequency of umbels from each bulb (%)

1- umbel

2 -umbels

3 -umbels

4- umbels

5 -umbels

6- umbels

7 -umbels

8- umbels

Improved Taherpuri

69 1.44 4.35 2.89 5.79 10.14 36.23 23.18 13.04 2.89

It is interesting to note that during last year i.e. in 2014-15 season highest frequency of umbel per bulb was noticed as 5 umbels per bulb (36.23 %) and the 2nd highest frequency was recorded as 6 umbels per bulb (23.18%). No off type plants were noticed in the ‘Improved Taherpuri’ population and the plot was found to be disease free. Finally excellent quality of seeds was produced from this plot at the rate of 270 Kg per acre. In conjunction with this experiment good quality bulbs of ‘Improved Taherpuri’ were also sent to Thakurgaon district well known for onion seed production and was tested at the farmers level for its acceptance and also the farmer’s reaction towards the new line. Alongside its performance was also compared with the local ‘Taherpuri’ variety in the same location as the said farmer also grew ordinary ‘Taherpuri’ variety purchasing bulb from the local market. Compared to local variety the plants of ‘Improved Taherpuri’ were found to be healthier and gave higher seed yield than the local variety although the farmer harvested 40 Kg of good quality seeds from 25 decimal of land.

Fig.6. Onion seed production plot at BARDC. Fig. 7. An umbel of ‘Improved Taherpuri’.

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Normally onion seed production is a 2 years process. Good quality bulbs are produced during the 1st year. These bulbs are stored under suitable environment for a period of 7-8 months and finally selected good quality bulbs are used as planting material for seed production in the next year. However, in a separate experiment at BRAC Agricultural Research & Development Center it was possible to produce seeds from bulbs within a year instead of 2 years using selected seed lots of ‘Taherpuri’ variety and manipulating seeding & transplanting dates (during the year 2011-12).

Bulb production from inferior quality bulbs in the early season: Since onion seed production is a 2 years process consequently bulbs are stored for a longer period (almost 7-8 months) and during this bulb preservation process a considerable number of bulbs (near about 30-40%) loose water gradually and become unfit for producing seeds and these extremely shriveled bulbs cannot be used for consumption as well. If these poor quality bulbs are planted in the early part of the onion growing season and suitable production technique is followed, good quality bulbs can be produced within a shorter period (within 70-75 DAT) and these bulbs fetches higher prices in the early season market. To validate this technology 3.00 kg of poor quality bulbs of ‘Improved Taherpuri’ were planted in 0.30 decimal of land on 10.07.2014 and finally 13.5 Kg of fresh bulbs were produced within 73 days after planting.

Fig.6. Good quality bulb of ‘Improved Taherpuri’ (Left). Fig.7. Poor quality bulb of ‘Improved Taherpuri’ (right).

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Fig.8. Healthier plants from poor quality bulb (shrivelled bulbs) in the early season ( 2014-15).

Fig.9. Bulb production from poor quality bulb in the Fig.10. Fresh bulbs harvested from poor early season. quality bulb. Conclusion

A new advance line of a local onion variety ‘Improved Taherpuri’ has been developed through selection at BARDC to meet up the growing demand of a good quality onion variety. This line has been found to be superior to the existing variety ‘Taherpuri Local’ both in terms of size and quality. Through the study of its bulb & seed production performances it seems that it will be a profitable variety if it is released for commercial production.

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References:

Ashby, E. 1930. Studies in the inheritance of physiological characters. I. A physiological investigation of the nature of hybrid vigour in maize. Annals of Botany. 44 : 457-467.

East, E.M., and D.F.Jones. 1920. Genetic studies on the protein content of maize. Genetics. 5: 543-610.

Hays, V.B., Garber, R.J. 1919. Synthetic production in relation to breeding. Journal of American society of agronomy. 11: 309-319.

Address:

Dr. Sitesh Chandra Biswas Program Specialist (Vegetable Research) BRAC Agricultural Research & Development Centre (BARDC) Jogitola, BRRI, Joydebpur, Gazipur BANGLADESH Mobile Phone: +8801730349845 E-mail: sitesh.cb@brac.net

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