Studies on combining ability and gene action for heat stress tolerance traits in Indian mustard (Brassica juncea L.)

Abstract

In order to identify parents for suitable use in a breeding programme for development of high yielding varieties of Indian
mustard with heat stress tolerant traits, the combining ability and gene action for certain physiological traits were
investigated in half-diallel crossings among eight parental lines. The cultivars investigated were NRCHB 101, GM-2,
NRCDR-601, BPR-543-2, BPR-549-9, JN-032, Urvashi and BPR-541-2 possess different tolerance levels to heat stress.
Heat stress conditions were achieved through early sowing under conserve moisture condition. On the date of seeding
(September, 28) of the year 2013-14, the maximum soil temperature at 0- 10 cm depth was 39.0oC. Data were subjected to
analysis of variance and combining abilities factor analysis. Analysis of variance for general combining ability (GCA)
and specific combining ability (SCA) displayed significant general and specific combining effects for the seven seed
yield and physiological traits i.e. population survival (%) 10 DAS, population survival (%) 25 DAS, membrane stability
index (%), excised- leaf water loss (%), relative water content (%), water retention capacity of leaves (%) 24hrs and seed
yield per plant (g). For all the traits the GCA effects were relatively more important than the SCA effects, indicating that
additive genetic effects were predominant. Crosses displaying high SCA effects for relative water content (%), membrane
stability index (%) and seed yield per plant (g) were observed to be derived from parents having various types of GCA
effects (high x high, high x low, low x low and medium x low).The single seed descent method can be applied to exploit
additive gene effects whereas dominance gene effects could be valuable in hybrid mustard breeding programmes.
Among the parents, genotypes BPR-549-9, BPR-543-2 and Urvashi were found to be superior general combiners for seed
yield and heat stress tolerance traits. Likewise, crosses involving diverse parents showed significant SCA effects for
seed yield and other heat stress tolerance traits.