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B. MEENA KUMARI* AND K. GANESAMURTHY
Centre for Plant Breeding and Genetics, Tamil Nadu Agricultural University, Coimbatore – 641 003.
An experiment was conducted to study the expression of heterosis for ten characters in forty five crosses of sesame developed by crossing five lines with nine testers in Line x Tester mating design. The analysis of variance revealed significant differences among the genotypes for all the characters studied except for number of secondary branches. Heterosis was worked out over midparent, better parent and standard parents viz., CO 1 and TMV 7. For days to fifty per cent flowering and days to maturity, none of the crosses exhibited significant relative heterosis and heterobeltiosis. The cross TMV 5 × ORM 7 expressed significant and positive heterosis over mid-parent, better parent and two standard parents for single plant yield along with high per se performance. The crosses TMV 5 × ORM 7, TMV 6 × VRI 1 and TMV 3 × CO 1 expressed highly significant standard heterosis for most of the traits studied including single plant yield and hence could be exploited for developing superior hybrids and varieties.
Heterobeltiosis, Relative heterosis, Sesame, Standard heterosis, Yield.
Sesame (Sesamum indicum L.) (2n=26), the most ancient oilseed crop of the world, mainly cultivated in tropical and subtropical conditions. It is regarded as the ‘Queen of Oilseeds’ as the quality of oil is of high nutritional and therapeutic value combined with stability. Sesame is the sixth most important oilseed crop of the world, occupying an area of 9.4 m.ha, with a production of 4.5 m.tons and its average productivity being 515 kg ha-1. India is the largest sesame growing country in the world with an area of 1.86 m.ha, producing 0.64 m. tons but productivity wise, it is among the lowest with 345 kg ha-1 (FAOSTAT, 2013), much lower than the world average productivity. This can be overcome by the commercial exploitation of heterosis.
Since this crop has epipetatious flower nature, easy emasculation and pollination procedure, pollen transfer by honey bee activity, more number of seedset in a capsule, more number of capsules per plant, low seed rate (5.0 kg ha-1) and high multiplication ratio, it has more scope for manual hybrid seed production to exploit heterosis. Also, several researchers already reported the presence of significantly high heterosis for yield and yield components, like Anandakumar (1995), Saravanan and Nadarajan (2002), Mothilal and Ganesan (2005), Anuratha and Lakshmi Kantha Reddy (2008). Hence the present
investigation was carried out to study the magnitude of heterosis for yield and yield components to exploit in our breeding programme.
The material for the present study consisted of five female parents, viz., TMV 3, TMV 4, TMV 5, TMV 6, Paiyur 1 and nine males viz., CO 1, SVPR 1, TMV 7, VRI 1, VRI 2, Jaumer, ORM 7, ORM 14 and ORM 17. Crosses were made in Line × Tester mating design to develop 45 hybrids at the Department of Oilseeds, Tamil Nadu Agricultural University, Coimbatore during Rabi-Summer 2012-13. Individual cross combinations along with their parents were raised in Randomized Block Design along with two checks viz., TMV 7 and CO 1 in two replications, each in two rows of four meter length with the spacing of 30 × 30 cm, during Kharif, 2013. The recommended package of practices for sesame was followed throughout the crop growing period. Observations were recorded for ten traits viz., days to first flowering, days to maturity, plant height (cm), number of primary branches, number of secondary branches, number of capsules in main stem, total number of capsules per plant, number of seeds per capsule, single plant yield (g) and 100 seed weight (mg). Ten plants in parents and
hybrids were randomly selected in each replication and observations on the quantitative traits were recorded. The mean values were used for estimation of heterosis over mid parent, better parent and standard check as per the standard method.
The analysis of variance revealed significant differences among parents for the ten quantitative characters studied (Table 1). This indicates the presence of significant variation in the experimental material for the traits observed. Significant variation was also observed among hybrids for all the characters observed in this study except for days to maturity, indicating the variability among the crosses for the other observed traits. The interaction among the crosses and parents recorded significant variation for all the observed traits except for number of secondary branches per plant indicating the possibility of exploiting heterosis for most of the traits. Similar results were also observed by Kar et al. (2002), Thiyagu et al. (2007), Jadhav and Mohir (2013) for most of the characters studied in this experiment.
Heterosis for single plant yield ranged from -69.57 to124.18, from -71.54 to 104.13 per cent over mid parent and better parent respectively and from -68.75 to 98.66 and from -74.12 to 64.51 per cent over standard varieties i.e., TMV 7 and CO 1, respectively. The cross TMV 5 × ORM 7 expressed significant and positive heterosis over mid parent, better parent and two standard varieties with the mean seed yield of 44.5 g plant-1. The crosses TMV 3× CO 1, TMV 5 × ORM 14 and TMV 6 × VRI 1 recorded significant and positive relative heterosis, heterobeltiosis and standard heterosis over CO 1 alone for seed yield per plant. Among forty five crosses studied, significant and positive relative heterosis was observed in eleven crosses, heterobeltiosis in nine crosses, standard heterosis in one cross (TMV 5 × ORM 7) over the standard variety TMV 7 and four crosses over the standard variety CO 1 for seed yield per plant. Minimum number of crosses exhibiting standard heterosis as compared to relative heterosis and heterobeltiosis was already observed by Jayaprakash and Sivasubramanian (2000); Mothilal and Manoharan (2004), Padmasundari and Kamala (2012) and Jawahar lal Jatothu et al. (2013).
The number of crosses with significant heterotic performance and range of heterosis for yield and yield components are given in Table 2 and the crosses are given in Table 3. For earliness, none of the crosses exhibited significant relative heterosis and heterobeltiosis, while the crosses TMV 4 × Jaumer, TMV 5 × ORM 7 and Paiyur 1× ORM 17 showed significant and negative standard heterosis over CO 1. For days to maturity, TMV 6 × ORM 17, TMV 3 × SVPR 1 and TMV 6 × SVPR 1 showed significant and negative standard heterosis over CO 1. For plant height, TMV 3 × CO 1 expressed significant and positive heterosis over midparent, better parent and over two standard varieties used. Significant positive heterosis for plant height was reported by Ananda Kumar (1995), Navadiya et al. (1995), Mishra and Sikarwar (2001), Mothilal and Ganesan (2005) and Parimala et al.(2013). For number of primary and secondary branches, TMV 6 × VRI 1 showed significant and positive relative heterosis and heterobeltiosis. TMV 3 × CO 1 expressed significant values of standard heterosis over TMV 3 × CO 1 for number of secondary branches.
For the number of capsules in main stem, Paiyur 1 × ORM 7 and Paiyur 1 × ORM 14 had the significant and positive heterosis over mid and better parent, while TMV 5 × ORM 7, TMV 3 × ORM 7 and TMV 5 Jaumer was significantly heterotic over the standard varieties CO 1 and TMV 7. The cross Paiyur 1 × ORM 7 recorded significant and positive relative heterosis, heterobeltiosis and standard heterosis for total number of capsules per plant. For number of seeds per capsule, Paiyur 1 × ORM 7 and TMV 3 × VRI 1 expressed significant and positive heterotic values on all the three bases. Significant heterosis for number of seeds per capsule was also reported by Mishra and Yadav (1996), Mishra and Sikarwar (2001), Mothilal and Ganesan (2005) and Parimala et al. (2013). For single plant yield, TMV 5 × ORM 7, Paiyur 1 × SVPR 1 expressed significant and high relative heterosis and heterobeltiosis, while TMV 5 × ORM 7 showed significant and positive heterosis on all the three bases. Similar results were also reported by Padmavathi (1998), Deepa Sankar and Ananda Kumar (2001), Saravanan and Nadarajan (2002) and Thiyagu et al. (2007). For 100 seed weight, Paiyur 1 × VRI 1, TMV 3 × Jaumer and TMV 5 × VRI exhibited positive and highly significant heterosis on all the three bases.
The crosses showing standard heterosis for single plant yield and other contributing traits are given in Table 4. The hybrid TMV 5 × ORM 7 expressed high heterosis for single plant yield, number of capsules in main stem, total number of capsules per plant, while the cross TMV
6 × VRI 1 showed heterotic vigour for three traits viz., single plant yield, number of secondary branches, 100 seed weight. The hybrid TMV 3 × CO 1 was superior for single plant yield, plant height and number of secondary branches. For number of primary branches, number of capsules in main stem and number of seeds per capsule, the cross TMV 3 × VRI 1 was identified as highly heterotic over standard parents. The cross TMV 5 × Jaumer expressed high heterosis for three traits viz., plant height, total number of capsules per plant and number of capsules in main stem. For number of primary branches and total number of capsules per plant, the hybrid Paiyur 1 × ORM 14 had expressed high heterosis. These highly heterotic crosses can be utilized for yield improvement through heterosis breeding.
