GENETIC ANALYSIS OF YIELD AND ITS COMPONENTS IN Brassica rapa L.

Abstract

ABSTRACT

The experiments were carried out at Sher-e-Bangla Agricultural University from October, 2010 to March, 2013 to perform genetic analysis of yield and its components of Brassica rapa genotypes generated through half diallel crosses and back crossing. No parent showed significant positive gca for yield per plant. SAU Sarisha 2 and SAU Sarisha 3 showed significant negative gca for days to maturity. In case of hybrids, the lowest days to the maturity of 79.33 days was observed in SAU Sarisha 3 × TORI 7. The highest yield per plant and 1000 seed weight were observed in the hybrids BARI Sarisha 6 × SAU Sarisha 2 and BARI Sarisha 6 × SAU Sarisha 1 respectively. The life span of the parent SAU Sarisha 3 was the lowest but the yield was moderate in comparism to other parents. The highest yield and 1000-seed weight were noticed in TORI 7 and its 80% maturity was achieved in 81 days. No hybrid showed significant higher yield over better parent. Three hybrids showed significant negative heterosis for days to maturity. Significant additive and dominant, additive × additive, additive × dominant and dominant × dominant gene interaction were present in Tori 7 × SAU Sarisha 2, SAU Sarisha 1 × SAU Sarisha 2, and SAU Sarisha 2 × SAU Sarisha 3.For numbers of siliqua per plant, number of seed per siliqua and length of siliqua, Vr-Wr graph indicated over dominance gene action for controlling these traits. However, partial dominance gene action was found for controlling the yield per plant. The D and H components were significant for all the traits under study suggesting the importance of both additive and dominance components for the inheritance of all the traits in B. rapa. The ratios of H2/4H1 provide an estimate of the average frequency of positive and negative alleles in all the parents. Regression line intersected the Wr-axis below the origin for all the characters except yield per plant indicating the presence of over dominance. There was no evidence of non-allelic interaction for the character plant height which agreed with the conclusion from individual scaling test results. For the remaining crosses at least one of the two (i and l) interaction parameters were significantly different from zero. The dominance × dominance effects were greater in magnitudes that additive × additive and additive × dominance in all cases which recorded non-allelic interaction in case of plant height. The highest heritability was recorded for days to maturity (99.99%) in the hybrid P1 (TORI 7) × P3 (SAU Sarisha 2). In the cross P1 (TORI 7) × P2 (SAU Sarisha 1), length of siliqua showed high narrow sense heritability (58.06%) with very low genetic gain (0.65). High narrow sense heritability with high genetic gain showed better selection in early segregating generations leading to substantial improvement of the character. In this hybrid P2 (SAU Sarisha 1) × P6 (BARI Sarisha 15 ), yield per plant showed high broad sense heritability but the narrow sense heritability was poor which might be due to presence of non allelic interaction for this character. High values for heritability and genetic advance for various traits indicated good genetic potential for selection.