HETEROSIS AND COMBINING ABILITY ANALYSIS IN Brassica rapa L.

Abstract

An experiment on oleiferous l3rassica rapa L. was conducted to evaluate the heterosis and combining ability for ten different characters. Out of fifteen crosses, the hybrids SAU sarisha2 X SAU sarishal showed desirable negative heterosis for plant height. The hybrids SAU sarisha3 X TORI 7. BARI sarisha IS X TORI 7 and BARI sarisha6 X TORI 7 were the best for early flowering and the hybrids SAU sarisha) X TORI 7 and BARI sarishal5 X TORI 7 were the best for early maturity. The hybrids BARI sarisha6 X TORI 7. BARI sarisha6 X SAU sarishal, BARI sarishal5 X TORI 7. SAU sarisha3 X TORI 7and SAU sarisha3 X SAU sarisha2 showed heterosis for no. of primary branches per plant, no. of secondary branches per plant and no. of siliquae per plant. The crosses BARI sarishal5 X SAU sarisha2 and BARI sarishal 5 X SAU sarishal were heterotic for siliqua length and the crosses BARI sarisha15 X SAU sarisha2, BARI sarisha15 X SAU sarishal, SAU sarisha3 X SAU sarisha2 and SAU sarisha2 X SAU sarishal were the best for seeds per siliqua. For thousand seed weight the hybrids BARI sarishalS X SAl) sarisha3, BARI sarisha15 X TORI 7. BARI sarisha6 X SAU sarishal and SAU sarisha3 X SAU sarisha2 were the best. For seed yield per plant the cross BARI sarisha6 X TORI 7 was found to be the best. The parent BARI sarisha 6 was best general combiner for plant height, early maturity, number of seeds per siliqua, and thousand seed weight. The parent BARI sarishal 5 was best general combiner for number of primary branches per plant and number of seeds per siliqua. The parent TORI 7 was good general combiner for number of secondary branches per plant, number of siliquae per plant and seed yield per plant. The parent SAU sarishal was the best for early flowering. On the basis of average score and rank position, BARI sarisha6 X TORI 7 was the best combination for early flowering, no. of primary branches per plant, no. of siliquae per plant and seed yield per plant. The combination SAU sarishal X TORI 7 was the best for plant height. The hybrid SAU sarisha3 X SAU sarishal was the best for early maturity. The crosses BARI sarisha15 X TORI 7 and SAU sarisha2 X SAU sarisha3 were the best for no. of secondary branches per plant. For siliqua length and number of seed per siliqua. BARI sarishal 5 X SAU sarisha2 was the best combination. The higher magnitude of CICA variance was observed than that of SCA variance for plant height, days to 50% flowering, days to maturity, no. of primary branches/ plant, no. of secondary branches/ plant, no. of siliquae/ plant, seed yield/ plant and 1000 seed weight which indicated the preponderance of additive component in their expression. The Vr-Wr graph indicate over dominance for plant height, days to flowering, primary branches per plant, secondary branches per plant, siliquae per plant, seeds per siliqua, seed yield per plant and thousand seed weight. Partial dominance was observed for days to maturity and length of siliqua. The graphical analysis also indicates wide genetic diversity among the parents.