Yield and Fibre Quality Improvement in Cotton ( Gossypium spp) Using Interspecific Hybridization

Interspecific cotton hybrids were developed by crossing eight lines and seven testers and were tested in a line x tester mating design for nine quantitative characters. The parents TCH 1218, TCH MCU 13, TCH BS 279 and TCH 1715 among the lines and ICB 114, ICB 134, ICB CCB 1 and DB 1 among the testers contributed most of the promising hybrids exhibiting high heterotic vigour for most of the characters. Nine hybrids such as TCH 1716 x ICB 134, TCH 1716 x ICB 114, TCH 1716 x CCB 1, TCH 1716 x DB 1, TCH 1715 x CCB 6, TCH 1734 x CCB 6, BS 279 x DB 1, BS 279 x ICB 134, BS 279 x ICB 114 were judged to be promising for seed cotton yield based on their high heterosis percentage and per se performance. Among the 56 F 1 hybrids studied, TCH 1218 x ICB 114, TCH 1218 x CCB 1, TCH1218 x DB 1, MCU 13 x DB 1, TCH 1715 x CCB 1, BS 279 x ICB 137 and TCH 1716 x ICB 114 were superior for yield, yield component and fibre quality traits. These hybrid combinations could be exploited in heterosis breeding.

five randomly selected plants in each genotype were collected for plant height (cm), number of sympodia/ plant, number of bolls/plant, boll weight (g), seed index, lint index, fibre length (mm), fibre strength (g/ tex) and seed cotton yield (kg/ha) . The relative heterosis and heterobeltiosis were calculated as the per cent deviation of mean of the F1 hybrid from the mid and better parental value respectively. The performance of hybrids over mid parent (di) and better parent (dii) was estimated following Fonseca and Patterson (1968) standard procedures using't' test, (Snedecor and Cochran,1967) and tested for its significance.

Results and Discussion
In the present study, superiority of the F1 hybrids was observed over mid parent and better parent for all the nine characters. Heterosis over mid and better parents for each of the characters studied are presented in Table 1 and 2 respectively. Seed cotton yield is a complex trait, dependent on many other component traits such as plant height, number of sympodia per plant, number of bolls per plant, boll weight etc., Highly significant positive relative and better parent heterosis was observed for seed cotton yield in the cross TCH 1716 x ICB 137 (122.2 and 79.6) followed by TCH 1715 x CCB 6 (103.8 and 95.4), TCH 1716 x ICB 114 (75.5 and 74.9), MCU 13 X ICB 134 (87.9 and 55.9) and MCU 13 X CCB 6 (72.7 and 70.4). These top ranking five hybrids over relative and better parent heterosis for seed cotton yield were depicted in Fig.1. Out of 56 hybrids, 26 hybrids showed highly significant relative heterosis and heterobeltiosis for seed cotton yield. This is in  Das and Shanmugavalli (1996) and Swati et al. (2007). The hybrid TCH 1716 x ICB 137 showed maximum percentage of mid parent heterosis for seed cotton yield (122.2). Rauf et al. (2005) evaluated heterosis of 20 crosses for yield and yield component traits and found that most of the crosses manifested highly significant heterosis for seed cotton yield and Desalegn et al. (2004) found that F1 hybrids showed an overall yield advantage over the parental mean of 26.4%.
Plant height plays an important role in determining the morphological framework relating to plant type, duration and productivity in cotton. In this direction, 21 hybrids recorded positive significant over mid parent and 14 over better parent heterosis.
These findings are in agreement with the studies of Patil and Meshram (2002) and Bhatade et al. (1992).    The range of heterosis for boll weight was observed from -65.6 to 33.3 and -70.9 to 14.45 per cent over mid and better parent respectively. Similar trends were evident from the studies of Reddy (2001) and Punitha and Ravikeshavan (2004). With respect to economic traits included in the study, majority of the hybrids recorded significant positive heterosis over mid and better parental heterosis for the traits lint index and seed index. The range of heterosis varied from -63.3 to 27.6 for mid parent heterosis and -64.1 to -23.9 for better parent heterosis for the trait seed index. The hybrids viz., TCH 1715 × CCB 1, MCU 13 × DB1 and TCH 1715 × ICB 134 also exhibited significant positive heterosis for this trait. The results of seed index were in agreement with Rauf et al. (2005) and Desalegn et al. (2004). Out of 56 crosses, TCH 1218 × ICB 114, MCU 12 × ICB 114, MCU 13 × ICB 163 and TCH 1715 × CCB 1 recorded significant positive mid parental heterosis for lint index. However the range was observed between -63.4 and 33.6 for mid parent heterosis and -63. 7 and 13.6 for better parental heterosis respectively and these findings were in accordance

Fig 1. Mid and better parent heterosis for seed cotton yield of best performing hybrids
with Laxman and Ganesh (2003) and Manickam and Gururajan (2004).
With regard to fibre length, relative heterosis ranged from -54.7 to 20.5 and heterobeltiosis from-56.4 to 17.5 per cent. Out of the 56 hybrids, 11 hybrids over mid parents, 4 over better parents recorded significant positive heterosis for 2.5% span length indicating that hybrids possessed better halo length than their parents. The hybrid MCU 12 × ICB 163 recorded the maximum positive relative heterosis of 18.0 per cent and the hybrid TCH 1716 × ICB 114 showed the maximum better parent heterosis of 17.1 per cent. These findings are in accordance with the results obtained by Kajjidoni (1984 and1997). The hybrid BS 279 × CCB 6 recorded the highest mid and better parental heterosis for fibre strength. Range of relative heterosis varied from -50.7 to 40.2 and the better parent heterosis varied from -51.8 to 23.2. Six hybrids recorded positive significant mid parental heterosis.
In the present study, TCH 1218, MCU 13, BS 279 and TCH 1715 among the lines and ICB 114, ICB 134, CCB 1 and DB 1 among the testers contributed to most of the promising hybrids exhibiting high heterotic vigour for yield and fibre quality characters. Involvement of these parents for crossing program may be fruitful for developing desirable hybrids combining high yield potential, high lint index as well as superior fibre properties. The hybrids TCH 1218 x ICB 114, TCH 1218 x CCB 1, TCH 1218 x DB 1, MCU 13 x DB 1, TCH 1715 x CCB 1, BS 279 x ICB 137 and TCH 1716 x ICB 114 exhibited significant heterosis for yield and yield related components like number of bolls/plant, number of sympodia/plant, seed index, lint index and the fibre quality characters like fibre length and fibre strength in desirable direction. From the study, it showed that these crosses could be further evaluated and exploited for commercial cultivation.