Commercial Heterosis of F1 Hybrids in Oilseed Brassica
Lalji B. Pandey and B.E. Zehr
Mahyco Life Sciences Research Centre, Jalna –Aurangabad Road, Post Box-76, Dawalwadi Jalna 431203 (M.S.) India. E-mail lpande@omni.mahyco.com
Abstract:
For commercial viability, the important criterion is the yield advantage of hybrids against the best pure line varieties. A survey of literature reveals that heterosis has been observed by a large number of researchers in oilseed brassicas under a large range of test conditions. Unfortunately, most of these studies report heterosis over mean parental value or better parental value. Data based on superiority over commercial variety are very rare. Several crop species show heterotic yield increases when hybrids are compared to inbred cultivars, but it remains to be proven that hybrids oilseed brassica offer any economic yield advantages over commercial varieties. The purpose of this study was to investigate the magnitude of commercial heterosis for seed and oil yield in oilseed brassica to determine the potential advantage of hybrid cultivars, especially in cultivated species in India to examine its genetic bases and to observe morphological characters, which may influence seed and oil yields. Field trials were conducted with F1 hybrids of B.juncea, B.campestris var. yellow sarson & toria and B.napus along with their respective of most commercial varieties as checks during 1995-96 to 1997-98 at two different agro-climatic conditions in India. In B.juncea, FMS (functional male sterility) based hybrids appear to be more productive than those based on CMS (cytoplasmic male sterility), which can be attributed to complete fertility-restoration in the FMS system. Advanced and experimental hybrid data based on design trials indicated commercial heterosis increase up to 33.56 and 39.46%, respectively in average seed yield and oil yield over the commercial varieties (hybrid seeding rates half that of varieties), with maximum seed yield of 2602.50 kg/ha, and 41.76% of oil content. Whereas in rapeseed (B.campestris var.yellow sarson & toria and B.napus), hybrids based on either GMS (genetic male sterility) or self-incompatibility systems appear to be more productive than most of today’s commercial varieties. Experimental hybrid data based on design trials exhibited seed yield heterosis up to 27.31, 21.60, and 21.39%, respectively, over most commercial varieties (hybrid seeding rates half that of varieties) of B.campestris var. yellow sarson & toria, and B.napus, respectively. Increased seed yield in hybrids had a greater number of productive branches, siliqua per plant, and seeds per siliquae in all the above species; whereas, hybrids attributed to early maturity in B.campestris var.yellow sarson and B.napus types.
Introduction:
Oilseed Brassica is the major edible oil crop of the Indian subcontinent. Present day cultivars have higher productivity and improved oil quality, so focus has now shifted to F1 hybrids of brassica species. Development of commercial hybrids is the ultimate goal of breeding cross-pollinated crops to exploit the non-additive gene action present in yield heterosis. The basic requirement for developing commercial hybrids in crops like Oilseed brassica is the availability of proven experimental hybrids (preferably with more than 20% standard heterosis), stable performing male sterile (A), maintainer (B), and fertility restoring ( R) lines, good synchrony of flowering in seed and pollen parents and adequate seed setting on male sterile seed parents through natural cross – pollination. Diversity rich germplasm of brassica species and wild relatives are potential sources of cytoplasmic genes for inducting male sterility. A number of cytoplasmic sources have been introgressed to brassica species in order to develop stable male sterility systems with high female fertility (Prakash et al. 1997). Using cytoplasmic male sterility systems, F1 hybrids have been developed. However, no hybrid cultivars have been widely commercialized so far due to unavailability of suitable fertility restoration systems; therefore, alternate sterility systems are needed. Functional male sterility (FMS) was derived from a spontaneous mutation in B.juncea, and Genetic male sterility (GMS) system were used in B.campestris var.yellow sarson & var. toria and B.napus to overcome the problems of fertility restoration in F1 hybrids of Oilseed brassica. In FMS, the sterility is achieved through early and elongated extension of stigma, which is no longer receptive to pollination when corresponding anthers are extruded from flowers and flower buds (Zehr et al. 1997) (Figure 1a, and 1b).
Experimental Materials and Methods:
The present investigation is comprised of four different experiments including all major cultivated species and subspecies of oilseed brassica( B.juncea, B.campestris var. yellow sarson, & var. toria, and B.napus). F1 hybrids based on different systems of male sterility in all above species and subspecies of oilseed brassica were used in the study. The F1 hybrids are based on CMS (oxyrrhina) (Prakash and Chopra, 1988) & FMS (functional male sterility) in B.juncea, GMS (genetic male sterility) in B.napus & B.campestris var. yellow sarson, and self-incompatibility system in B.campestris var. toria. The F1 hybrids of all above species and subspecies were planted in two different agro-climatic conditions of India along with most commercial variety(s) on a national level as checks in their respective species and subspecies. The row to row and plant to plant distances were maintained at 30 and 15 cm, respectively in all above types of hybrids. All other standard agronomic practices were followed in raising a normal healthy field crop. The experimental material consists of: 10 hybrids along with 3 checks (B.juncea), 2 hybrids along with 2 checks (yellow sarson), 4 hybrids along with 1 check (toria), and 4 hybrids along with 1 check (B.napus). All these experimental materials were grown in a randomized complete block design at two locations with appropriate number of replications during the 1995-96 to 1997-98 crop seasons in India. Observations were recorded on days to flowering, days to maturity, plant height (cm), number of siliqua on the main shoot, number of seeds per siliqua, 1000 seed weight (gm), seed yield per plot (kg), and oil content (%). The commercial heterosis was estimated against most commercial variety of respective species / subspecies over all the locations and all the crop seasons in seed yield and oil yield (in %). Pooled analysis of variance and means comparison for all the data was done using SAS software.
Experimental Results and Discussion:
1. Expression of Commercial Heterosis in Indian Mustard (B.juncea)
The commercial heterosis in Indian mustard was calculated over the most popular variety Varuna on seed yield and oil yield (in %). The data is presented in table 1.1. Table 1.1 shows that average seed yield heterosis values vary from 06.23 to 33.56 percent. In this group of material, hybrids based on the functional male sterility system (FMS) has shown comparatively and significantly better seed yield as well as oil yield heterosis than hybrids based on cytoplasmic male sterility system (CMS). The hybrid MRH-104 showed better seed yield and oil yield heterosis than other hybrids over the most popular variety (s), respectively (Figure 2). Advanced and experimental hybrid data based on designed trials indicated up to 39.46 % increase in average oil yield over the most popular variety(s) (hybrid seeding rate half that of varieties), with maximum oil yield of 1084.86 kg/ha, 41.76 % of oil content (Table 1.1). It is very clear from the table that FMS based hybrids appear to be more productive than those based on the CMS system, which can be attributed to complete fertility restoration in the FMS system. In general, all the hybrids based on the FMS system outyielded the most popular variety(s) by a margin of more than 16 % and 21% in seed yield and oil yield, respectively. All the 10 listed F1hybrids showed commercial heterosis over the most popular variety(s), whereas, seed yield heterosis was highest in MRH-104 (33.56%) followed by MRH-102 (27.96 %).
2. Expression of Commercial Heterosis in Yellow Sarson (B.campestris var. yellow sarson)
Two experimental hybrids based on the genetic male sterility system were evaluated for seed yield and its contributing parameters / traits under different agro-climatic conditions of India along with the highest yielding national check and improved variety(s) during 1995-96 to 1997-98. The average commercial heterosis over national check variety NDYS-2 ranged from 21.38 % to 27.36%, while, heterosis over highest yielding improved variety MYSL-201 ranged from 11.50% to 16.95%. The maximum heterosis for seed yield (27.31%) and oil yield (26.50%) was obtained in the hybrid MYSH-29 (Table-1.2). The high amount of heterosis in hybrids is due to greater number of primary and secondary branches per plant, siliquae on the main shoot, length of the main shoot, and number of siliquae per plant than the variety(s). Generally, hybrids have lower oil content than the variety(s), which may be because of nuclear genes associated with the female parent.
3. Expression of Commercial Heterosis in Toria (B.campestris var. Toria)
Four experimental and advanced toria hybrids which were developed through the use of the self-incompatibility system were evaluated for seed yield and its components during the year 1995-96 to 1997-98 at two different locations of India. The commercial heterosis is estimated over the average seed & oil yield of the most popular variety named as T-9. The results show that the average heterosis of toria hybrids ranged from 13.17 – 21.60%, and 13.94 – 22.61% for seed yield and oil yield, respectively over the locations and years. All the hybrids significantly differ from the commercial check variety in both seed and oil yield. The maximum heterosis for seed yield was obtained in the hybrid MRTH-66 (21.60%) followed by MRTH-9 (18.53%) and MRTH-31 (13.64%) against the most popular variety T-9. The high amount of commercial heterosis in hybrids is due to greater number of primary and secondary branches per plant, number of seeds per siliqua, siliqua per plant, and number of productive branches per plant than the check variety.
4. Expression of Commercial Heterosis in Gobhi Sarson (B. napus)
Four experimental hybrids of B.napus (Gobhi sarson) were developed through the use of the genetic male sterility system were evaluated for seed yield and its components during the year 1995-96 to 1997-98 at two different locations of India. The commercial heterosis was estimated against the average seed & oil yield of the most popular variety(s) GSL-1. The results show that the average commercial heterosis of B.napus hybrids ranged from 12.17 – 21.39%, and 12.72 – 22.65% for seed yield and oil yield, respectively over the locations and years. All the hybrids significantly differ from the commercial check variety in both seed and oil yield. The maximum heterosis for seed yield was obtained in the hybrid MGSH- 401 (21.39%) followed by MGSH- 411 (18.46%) and MGSH- 403(13.33%) against the most popular variety GSL-1. The high amount of commercial heterosis in hybrids is due to greater number of primary and secondary branches per plant, number of seeds per siliqua, siliqua per plant, and number of productive branches per plant than the check variety(s). In general, all the listed hybrids are earlier in maturity (130-140 days) and shorter in stature (150 cm plant height) than the check variety GSL-1 (maturity- 160-170 days and plant height – 180-200 cm). Late maturity in B.napus creates lot of problems like seed shattering in countries like India, where temperature is high during the month of March. So, in Indian climatic conditions, farmers need short stature and early maturing genotypes, especially in B.napus to overcome the problem of shattering.
Conclusions:
Hybrid brassica (B.juncea, B.napus, and B.campestris) varieties frequently display commercial heterosis for seed yield but rarely display commercial heterosis for oil yield. In our studies, we found that almost all the hybrids of B.juncea, B.napus, and B.campestris var. toria showed high percent of commercial heterosis in oil yield than the seed yield except few; whereas hybrids in yellow sarson showed low percent of commercial heterosis for oil yield than the seed yield. High parent heterosis for seed yield in mustard is also reported by Pental et al. (1995), Pradhan et al. (1993); whereas, commercial heterosis for seed yield and oil yield in mustard is reported by Zehr et al. (1997).
The levels of commercial heterosis observed for seed yield and oil yield in hybrid oilseed brassica are sufficient to ensure the large scale switch to hybrids at some point in future.
References
Pental, D., Pradhan, A.K., Sodhi, Y.S., Arumugan, N., and Mukhopadhyay, A. (1995). Heterosis breeding in mustard (B.juncea) and rapeseed (B.napus) by a combination of molecular and conventional methods. Proc.9th International Rapeseed Cong., Cambridge (U.K), A-44.
Pradhan, A.K.; Sodhi, Y.S.; Mukhopadhyay, A. and Pental, D. (1993). Heterosis breeding in Indian mustard (B.juncea L.): analysis of component characters contributing to heterosis for yield. Euphytica, 69:219-229.
Prakash, S. and Chopra, V.L. (1988). Male sterility caused by cytoplasm of Brassica oxyrrhina in B.campestris and B.juncea. Theoretical and Applied Genetics, 79: 285-287.
Prakash, S.; Kirti, P.B.; and Chopra, V.L. (1997) Development of cytoplasmic-fertility restoration systems of variable origin in mustard (B.juncea). Proc.10th Crucifer Genetics Workshop, 23-27 Sept. 1997, Rennes, France.
Zehr, B.E.; Rantnalikar, V.P.; Reddy, L.M.M.; and Pandey, L.B. (1997). Strategies for utilizing heterosis in Wheat, Rice, and Oilseed Brassica in India. Symposia on Heterosis in crop plants, Aug.97, CIMMYT, Mexico.
Table-1.1:
Expression of Commercial Heterosis in Indian Mustard (B.juncea) at Multilocation testing:
Hybrids/ Sterility Seed Oil Oil % Commercial Heterosis Seeding
Variety System Yield Yield Over Seed Over Oil Rate
Check (kg/ha) (kg/ha) Yield (%) Yield (%) (kg/ha)
MRH-101 FMS 2361.72 980.95 41.34 21.20 26.10 2.5
MRH-102 FMS 2493.39 1040.11 41.64 27.96 33.71 2.5
MRH-103 FMS 2260.06 945.36 41.76 15.98 21.53 2.5
MRH-104 FMS 2602.50 1084.86 41.66 33.56 39.46 2.5
MRH-105 FMS 2287.22 942.35 41.12 17.38 21.14 2.5
MRH-51 CMS 2069.94 816.40 39.40 06.23 04.95 2.5
MRH-52 CMS 2070.39 816.98 39.41 06.23 05.02 2.5
MRH-53 CMS 2185.78 869.95 39.74 12.17 11.83 2.5
MRH-54 CMS 2248.44 898.58 39.88 15.39 15.51 2.5
MRH-5 CMS 2261.00 925.31 40.84 16.03 18.95 2.5
MAHYCOBOLD VARIETY 2027.67 841.42 41.42 5.0
KRANTI VARIETY 1886.94 742.14 39.22 5.0
VARUNA VARIETY 1948.61 777.91 39.81 5.0
MEAN (Across year & Location) 2207.97 898.64 40.56
CV ( 5%) 2.815 2.983 1.098
LSD (5%) 40.958 17.664 0.293
Table-1.2:
Expression of Commercial Heterosis in Yellow Sarson (B.campestris var. yellow sarson) at Multilocation testing during 1995-96 to 1997-98:
Hybrids/ Sterility Seed Oil Oil % Commercial Heterosis Seeding
Variety System Yield Yield Over Seed Over Oil Rate
Check ( kg/ha) (kg/ha) Yield (%) Yield ( %) (kg/ha)
MYSH-29 GMS 1725.39 727.17 42.09 27.31 26.50 2.5
MYSH-28 GMS 1645.00 690.35 41.91 21.38 20.09 2.5
MYSL-201 VARIETY 1475.28 640.81 43.38 5.0
NDYS-2 VARIETY 1355.28 574.84 41.24 5.0
MEAN(Across Year & Location) 1550.24 658.29 42.15
CV ( 5%) 1.813 5.471 0.981
LSD (5%) 19.003 24.349 0.280
Table-1.3: Expression of Commercial Heterosis in Toria (B.campestris var, Toria ) at Multilocation testing:
Hybrids/ Sterility Seed Oil Oil % Commercial Heterosis Seeding
Variety System Yield Yield Over Seed Over Oil Rate
Check ( kg/ha) (kg/ha) Yield (%) Yield ( %) (kg/ha)
MRTH-9 SIC 1680.44 712.09 42.36 18.53 19.78 2.5
MRTH-66 SIC 1724.00 728.93 42.25 21.60 22.61 2.5
MRTH-31 SIC 1611.11 684.29 42.47 13.64 15.11 2.5
MRTH-110 SIC 1604.44 677.35 42.21 13.17 13.94 2.5
T-9 VARIETY 1417.78 594.49 41.91 5.0
MEAN(Across Year & Location) 1607.56 679.43 42.24
CV ( 5%) 3.357 4.166 2.390
LSD (5%) 36.173 18.971 0.677
Table-1.4: Expression of Commercial Heterosis in Gobhi Sarson (B.napus ) at Multilocation testing:
Hybrids/ Sterility Seed Oil Oil % Commercial Heterosis Seeding
Variety System Yield Yield Over Seed Over Oil Rate
Check ( kg/ha) (kg/ha) Yield (%) Yield ( %) (kg/ha)
MGSH-401 GMS 1720.67 727.96 42.27 21.39 22.65 2.5
MGSH-403 GMS 1606.39 682.55 42.49 13.33 15.00 2.5
MGSH-404 GMS 1590.00 668.99 42.06 12.17 12.72 2.5
MGSH-411 GMS 1679.11 709.51 42.24 18.46 19.54 2.5
GSL-1 VARIETY 1417.50 593.52 41.86 5.0
MEAN(Across Year & Location) 1602.73 676.51 42.19
CV ( 5%) 3.450 3.824 2.401
LSD (5%) 37.054 17.336 0.679
Figure 1a: FMS plant in Flowering stage Figure 2: Field View of Mustard Hybrid MRH –104 {A FMS based hybrid} Figure 1b: FMS plant in flowering and Bud stage
