Authors:R. Singh, R. Behl, P. Jain, N. Narula, and K. Singh
The present investigation was conducted to investigate the impact of bio-inoculants on the magnitude and direction of gene effects and mean performance for root length density, root biomass per plant, AMF colonization in roots and micronutrient uptake (Cu, Fe, Mn, Zn) in wheat under low input field conditions. The material for study comprised three wheat cultivars, WH 147 (low mineral input), WH 533 (drought-tolerant), Raj 3077 (high mineral input) and six generations (P
) of three crosses, namely WH 147 × WH 533, WH 533 × Raj 3077 and WH 147 × Raj 3077. The experiment was conducted in a randomized block design with three replications having three treatments, i.e. (i) control; (ii) inoculation with arbuscular mycorrhizal fungi (AMF,
); (iii) dual inoculation with AMF and
). The fertilizer doses in all three treatments were 80 kg N + 40 kg P + 18 kg ZnSO
. Root length density, root biomass per plant, AMF colonization in roots and Zn and Mn content were found to be maximum after dual inoculation with AMF+
in all three crosses. Joint scaling tests revealed that additive-dominance gene effects were mainly operative in governing the expression of root biomass, Cu and Zn content in all three crosses for all three treatments (i.e. control, AMF and AMF +
). Pedigree selection in crosses WH 147 × WH 533 and WH 147 × Raj 3077 could be effective for breeding pure lines of wheat for sustainable agriculture (low input genotypes responsive to biofertilizers such as AMF and
Heat stress is an important production constraint of wheat during grain-fill period in India and in other parts of the world where the temperature become high during anthesis to maturity (grain-filling) stage of plant growth. This study determined the genetic control of heat tolerance through half diallel analysis of selected wheat genotypes. Heat induced damage of plasma membrane was assayed by membrane thermo-stability (MTS), which measure electrolyte leakage from leaf tissues after exposure to high temperature. Eight genotypes comprising heat tolerant and sensitive response to high temperature stress were hybridized in a half diallel. Electrolyte leakage or MTS was conducted at grain-filling stage of plant growth as ambient temperature become high enough to cause heat hardening of leaves. The mean square for GCA was higher in magnitude than that of SCA, but the components of genetic variance indicated considerable influence of dominance variance in determining inheritance of this trait. Results suggested that the selection for heat tolerant inbred lines based on MTS in this material may be more effective by reducing the dominance variance after a few generation of selfing particularly in a self-pollinated wheat crop. The varieties, Hindi 62 and NIAW 34 were good general and specific combiners in the tolerant group, while HD 2687 and WH 147 were good specific combiners in the heat sensitive group.
Gene effects were analyzed using mean excised-leaf water loss and relative water content of 12 populations viz., both parents (P
, first back cross generations (BC1 and BC2), second back cross generations (B
) and back cross-selfed generations (B
s and B
s) of four crosses involving three drought tolerant and three drought susceptible cultivars of
L. to determine nature of gene action governing excised-leaf water loss (ELWL) and relative water content (RWC) through generation mean analysis under rainfed (E1) and irrigated (E2) environments. Both additive-dominance and digenic epistatic model were found to be inadequate in all the crosses for ELWL and in most of the crosses for RWC to explain genetic variation among the generation means. Additive gene effects were predominant for RWC, while for ELWL both additive and dominance component of variance were important. Epistatic effects, particularly dominance × dominance (1) type of interaction was more predominant for RWC, while additive × additive(i) for ELWL. Duplicate type of epistasis was observed in the crosses Hindi 62/HS240 and VL421/HS240 for RWC and in the cross S4/HPW89 for ELWL under both the environments. Complementary type of epistasis was observed only in the cross VL421/PBW175 for ELWL under E1. Hybridization systems, such as biparental mating and/or diallel selective mating could be useful for improvement of these traits which would help in isolating drought tolerant progenies.
Authors:Y. Sharma, S. N. Sharma, P. Joshi, and R. S. Sain
The F1 and F2 progenies of a ten-parent diallel cross (excluding reciprocals) were analysed for the combining ability of quantitative traits in six-rowed barley (Hordeum vulgare L.). significant differences were indicated between the parents, F1s and F2s for all the characters studied. The gca and sca components of variance were significant for all the traits. Both additive and non-additive gene effects were involved in the genetic control of the characters; however, non-additive gene effects were observed to be predominant. Among the parents RD 2035, RD 2052, RD 2503 and BL 2 were the best general combiners for grain yield and average to high combiners for other important traits.The parents RD 2552 and RD 387 were the best general combiners for dwarfness. The best specific crosses for grain yield were RD 2503 × RD 2585,RD 2035 × RD 2052, RD 2035 × BL 2, RD 2052 × BL 2, RD 2508 × RD 2552, RD 2552 × RD 2585 and Rd 2052 × RD 2552 in both the F1 and F2 generations. These crosses were higher yielders and in most of the crosses one of the parents involved was a good combiner, indicating that such combinations can be expected to produce desirable transgressive segregants. All the best crosses for grain yield also showed average to high sca effects for most of the yield components. Most of the specific crosses for grain yield involved high × average, average × average and average × poor general combiners. To ensure a further increase in grain yield, the combination of desirable yield components is advocated. The inclusion of F1 hybrids showing high sca, and having parents with good gca, in multiple crosses, bi-parental mating or diallel selective mating could prove a worthwhile approach for further amelioration of grain yield in six-rowed barley.
Authors:J. Alvarez, J. Gómez, A. Martín, and L. Martín
Roem. et Schult. is a South American wild barley that occurs exclusively in Chile and Argentina, where it is a component of natural pastures. This species has been crossed with durum and bread wheats to obtain a new amphiploid, called tritordeum, which presents agronomic traits of a new crop. Two groups represented by H1 and H7 lines have shown differences for spike length and density, number of spikelets per spike and various other characters which are interesting for tritordeum improvement. This study was conducted to investigate inheritance of these three characters in a cross between H1 and H7 lines, including parents, F
generations. The three characters studied fitted the additive model. The dominance effects were less strong than the additive effects, indicating partial dominance of positive sign for number of spikelets per spike; whereas spike length displayed small dominance effects of negative sign and the spike density showed intermediate inheritance, with the inheritance being almost exclusively additive.