Research Article
Heterotic Studies for Various Characters in Sunflower (Helianthus annuus L.)
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Muhammad Siraj Swati
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Iftikhar Hussain Khalil
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Amjad Iqbal
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Edible oil is one of the most important food items which is affecting the economy of Pakistan. Pakistan is the third largest importer of edible oil in the world. The domestic oil production does not combat the need of the edible oil in the country. In order to meet the demand of edible oil, a large amount of oil has to be imported each year, which costs a huge amount of foreign exchange. Since the production potential of our traditional oilseed crops such as cotton seed, rape and mustard is limited, efforts are made to supplement the local production through the cultivation of non-traditional oilseed crops such as sunflower, safflower and soybean.
Amongst the non-traditional oilseed crops sunflower can play an important role in narrowing the wide gap between production of edible oils in the country and its import. It can be grown as catch crop in many situations. Being drought resistant it is well suited for rainfed as well as irrigated areas. Moreover, present day sunflower cultivars contain more than 40% oil and 18-20% protein. Sunflower oil is of good quality as it contains high proportion of linoleic acid which is poly unsaturated fatty acid. It is also a good source of calcium, phosphorus and nicotinic acid and vitamin E.
In Pakistan it covered an area of about 113998 ha with a production of 149502 tones in 1999-00 (Agricultural Statistics of Pakistan, 1999-00). Heterosis of these crops has been exploited to increase seed yield only over the past few decades. Utilization of heterosis has allowed sunflower to become the major oilseed in many countries of the globe (Miller, 1998). In spite of having high yield potential, the production of sunflower in Pakistan is very low. One of the reasons for this is the cultivation of exotic hybrids, which are not well adapted to agro-climatic conditions of the country. To make sunflower a successful crop in Pakistan, we need to develop our own hybrids which could mature early, give higher yield and fit easily in our existing cropping pattern. Keeping in view, these facts, this experiment was designed to identify sunflower genotypes which possess desirable combination of genes for higher yield, early maturity and better oil content.
This research was conducted on silt loam soils with medium organic matter at the Agricultural Research Institute, Tarnab, Peshawar, during August 2001. All the inbred lines and the hybrids were supplied by Pakistan Oilseed Development Board, Tarnab, Pakistan.
The following single cross hybrids and their parents were evaluated in this study.
The inbred lines and hybrids were evaluated in a Randomized complete block design (RCBD) using three replications. Each row was 5 m long with row to row distance of 0.75 m and plant to plant distance of 0.25 m.
Three seeds per hill were planted and after germination the seedlings were thinned to one per hill at 3-4 leaf stage. Fertilizer was applied in the form of urea and DAP at the rate of 120 and 60 kg ha-1, respectively. Standard cultural practices were carried out from sowing till harvesting. To study each character three plants were randomly taken from each replication.
The following parameters were studied during this research work.
• | Number of leaves per plant were counted after flowers became visible. |
• | Plant height was measured from the ground level to the attachment point of the head with the stem by means of a meter rod at the time of maturity. |
• | Head diameter was measured from one edge of the head to the other. |
• | Number of seeds per head were counted after manually threshing all the seeds. First of all the seeds were threshed and then counted. |
• | Number of filled seeds per head were obtained by subtracting the number of unfilled seeds from total number of seeds per head. |
• | Number of unfilled seeds per head were determined by counting their number in total number of seeds per head. |
• | Seed yield per hectare was determined after threshing the seeds and allowing it to dry up to 9-10% moisture content using the following formula: |
• | Oil content was determined by taking a representative sample of 1 gram from each replication. Oil was extracted by using petroleum ether (40-60°C) with the help of Soxtech apparatus. The following formula was used to determine oil content (Khalil and Manan, 1990). |
The data, after compiling, was statistically analyzed. Least significance difference test (LSD) was also applied to test the significance of treatment differences. Heterosis for each character was determined by using the following formula:
Results pertaining to different morphological characters of ten sunflower inbred lines and nine hybrids are presented in tabulated form. Mean squares for each character of inbred lines and their hybrids are presented in Table 1. The means and LSD values for each character of inbred lines, hybrids and mid parent heterotic values are given in Table 2 and 3, respectively.
Number of leaves per plant: Highly significant differences (P<0.01) were observed among the inbred lines and hybrids for the number of leaves per plant (Table 1). Mean data for different inbred lines ranged from 12.8 to 20.8, representing a difference of eight leaves per plant (Table 2). The minimum leaves per plant were observed for TF-18 (12.8) while maximum leaves per plant were observed for TR-11 (20.8). The data for hybrids ranged from 17.9 (TS-18 x TR-120) to 24.2 (TS-17 x TR-120) (Table 3). Mid parent heterosis for the number of leaves per plant ranged from 3.2 to 43.9% (Table 3). Maximum heterosis for the character was exhibited by TS-17 x TR-120 (43.9%) followed by TS-4 x R-8 (38.8%). TS-1 x TR-120 showed minimum heterosis of 3.2%.
These results are in accordance with the findings of Sassikumar and Gopalan (1999) and Yilmaz and Emiroglu (1995), who have reported heterosis of 22.7 and 2 to 14%, respectively for number of leaves per plant.
Plant height: The ANOVA regarding plant height showed highly significant genetic differences (P<0.01) among inbred lines and their hybrids (Table 1). The mean values for inbred lines ranged from 61.4 in TR-18 to 108.6 cm in TR-11 (Table 2).
Table 1: | Mean squares and coefficient of variation (CV) for number of leaves per plant (NL), plant height (PH), head diameter (HD), number of seeds per head (NS), number of filled seeds per head (NFS), number unfilled seeds per head (NUFS), seed yield ha-1 (SY) and oil content (OC) of ten sunflower inbred lines and nine sunflower hybrids evaluated at agricultural research institute, Tarnab, Peshawar, during August, 2001 |
Table 2: | Means for the number of leaves per plant (NL), plant height (PH), head diameter (HD), number of seeds per head (NS), number filled seeds per head (NFS), number unfilled seeds per head (NUFS), seed yield ha-1 (SY) and per cent oil content (OC) of ten sunflower inbred lines evaluated at agricultural research institute, Tarnab, Peshawar during August, 2001 |
Table 3: | Means and mid parent hetrosis for number of leaves per plant (NL), plant height (PH), head diameter (HD), number seeds per head (NS), number of filled seeds per head (NFS), number of unfilled seeds per head (NUFS), seed yield ha-1 (SY) and oil content (OC) of nine sunflower hybrids evaluated at agricultural research institute, Tarnab, Peshawar during August, 2001 |
Means sharing the same letter(s) in a column are not significantly different at 5% probability level |
Mean data for different hybrids was found high as compared to the inbred lines. TS-18 x TR-120 showed minimum plant height of 83.5 cm where as TS-1 x TR-12 showed maximum plant height of 131.3 cm (Table 3). The heterotic values for plant height were ranging from 5.4 (TS-17 x R-8) to 44.3% (TS-4 x TR-11).
These results confirm the findings of many researchers. Sassikumar and Gopalan (1999) and Yilmaz and Emiroglu (1995) have reported heterosis of 22.5, 3.5 to 43.1 and 10 to 22%, respectively.
Head diameter: Inbred lines and hybrids showed highly significant genetic differences (P<0.01) for head diameter (Table 1). Mean data recorded for inbred lines varied from 10.0 to 14.4 cm (Table 2). TR-12 had the minimum value (10.0 cm) and was found to be significantly different from all the inbred lines except R-8 (11.9 cm), TR-6023 (10.8 cm) and TF-18 (11.9 cm). Mean data for hybrids was ranging from 16.1 to 22.5 cm (Table 3). TS-4 x TR-11 had the maximum head diameter while minimum head diameter was observed for TS-18 x TR-120. Heterotic effects for head diameter were positive for all hybrids. TS-4 x TR-11 (59.5%) and TS-17 x TR-120 (57.2%) showed the maximum positive heterosis over the mid parent value for head diameter. The lowest heterotic effect of 32.8% was recorded for TS-18 x TR-120.
The results are in line with those of Sassikumar and Gopalan (1999), who have reported 25.2% heterosis and Goksoy (1999) who has reported 10 to 64.5% heterosis for this character. Gill et al. (1998) and Gangappa et al. (1997) have also reported high heterotic effects for this character.
Number of seeds per head: Number of seeds per head revealed highly significant differences (P<0.01) among inbred lines and their hybrids (Table 1). Among the inbred lines, TR-6023 showed minimum number of seeds per head (275) whereas maximum value was recorded for TR-11 (1139) (Table 2). Mean data for hybrids ranged from 780 in TS-1 x TR-12 to 1384 in TS-17 x TR-120 (Table 3). Data pertaining to number of seeds per head revealed that mid parent heterosis was found maximum in TS-17 x TR-120 (197.3) while it was minimum in TS-4 x TR-11 (23.3).
The present work is in accordance with the work of Yilmaz and Emiroglu (1995), who have reported 20 to 77% heterosis for number of seeds per head. In contrast to this work, Limbore et al. (1999) have reported heterosis as low as -72.50% and as high as 166.45% for this character.
Number of filled seeds per head: Highly significant genetic differences (P<0.01) were observed among inbred lines, whereas the differences among hybrids were significant (P<0.05) for this character (Table 1). The number of filled seeds per head for different inbred lines ranged from 230.7 to 977.3 (Table 2). The lowest value was observed for TR-6023, whereas maximum value was observed for TR-11. Mean data for different hybrids ranged from 709.3 to 1166 (Table 3). The hybrid TS-1 x TR-12 had the lowest number of filled seeds per head, whereas TS-4 x TR-110 had the highest number of filled seeds per head. Mid parent heterosis for number of filled seeds per head ranged from 23.3 (TS-4 x TR-11) to 183.6% (TS-1 x TR-120).
The results are in line with the findings of Burli and Jadhav (2001), Lande et al. (1998) and Gangappa et al. (1997).
Number of unfilled seeds per head: The ANOVA revealed highly significant differences (P<0.01) among inbred lines and their hybrids for the number of unfilled seeds per head (Table 1). Among the inbred lines, TR-120 had the minimum number of unfilled seeds per head (15), while TR-11 had the maximum number of unfilled seeds per head (161.3) (Table 2). Among the hybrids, the maximum number of unfilled seeds per head were observed in TS-17 x TR-120 (267.3), while the minimum number of unfilled seeds per head were observed for TS-18 x TR-120 (32) (Table 3). Most of the heterotic effects for the number of unfilled seeds per head were positive except for TS-4 x TR-11 which showed negative heterosis of 27.6%. Maximum positive heterosis of 387.5% was observed for TS-17x TR-120, followed by TS-17 x R-8 with 208.0% heterosis.
Seed yield ha-1: Highly significant differences (P<0.01) were observed among the inbred lines and their hybrids for this character (Table 1). Seed yield ha-1 was minimum in TR-6023 (330 kg ha-1) whereas the maximum value was recorded for R-8 (1492 kg ha-1). The seed yield for the hybrids ranged from 1566 kg ha-1 in TS-17 x R-8 to 3967 kg ha-1 in TS-17 x TR-120 (Table 3). Data pertaining to seed yield ha-1 revealed that heterosis relative to mid parental value ranged from 10.7 to 322.3%. Among the hybrids, maximum heterosis of 322.3 and 292.6% was found for TS-17 x TR-120 and TS-18 x TR-120, respectively. The lowest positive heterotic effect was observed for TS-17 x R-8 (10.7%).
This study is supported by the work of Singh et al. (2002) and Goksoy (1999), who have reported 278.0 and 15.9 to 178.1% heterosis for this character, respectively.
Oil content (%): Analysis of variance revealed highly significant differences (p<0.01) among inbred lines and their hybrids for oil content (Table 1). Mean oil content ranged from 28.3 to 48.6% among the inbred lines (Table 2). The lowest oil content was observed in TF-1 (28.3%) where as highest oil content was observed in TF-17 (48.6%). Mean oil content for the hybrids ranged from 27.1% in TS-4 x R-8 to 50.4% in TS-17 x TR-120 (Table 3). Data regarding oil content revealed that heterosis relative to mid-parental value ranged from -40.7 to 18.3%. The lowest negative heterotic effect was observed in TS-4 x R-8 (-40.7%). Maximum positive heterosis of 18.3 and 6.5% was observed for TS-4 x TR-11 and TS-17 x TR-120, respectively.
The differences among different inbred lines and their hybrids were highly significant for this character supported by the work of Hussain et al. (2000). Heterosis relative to mid-parental value ranged from 40.9 to 18.3%. This is supported by the work of a wide range of researchers around the world i.e Singh et al. (2002), Kumar et al. (1999), Yenice and Arslan (1997) and Cheres et al. (2000).