GENETIC BEHAVIOUR OF SOME AGRONOMIC AND PHYSIOLOGICAL TRAITS IN BARLEY DIALLEL CROSSES UNDER MARYOUT CONDITIONS

Abstract

The main objectives of this study were to (1) evaluate performance and degree of drought stress tolerance of six barley genotypes and their F1's for some agronomic and physiological traits under well watered and rainfed conditions, (2) identify the traits which can be used as selection criteria for drought stress tolerance, (3) estimate of some genetic parameters specially heterosis, combining ability and heritability as bases of improving barley under rainfed conditions at Maryoutregion and (4) study the interrelationships among traits under the two irrigation regimes. Six parents of barley (Hordeumvulgare L.) namely: the cv. G126 (P1), L Su12303 (P2)(are local genotypes), L 105/20 (P3), L105/27 (P4), L105/32 (P5) and L 105/36 (P6) (are introduced from ICARDA) were chosen to achieve the present study. The experiments of the present study were carried out at the Maryout Agriculture Experiment Station of Desert Research Center (North Western Coast of Egypt). In 2008/09 season, the six parents were handy crossed in all possible combinations, excluding reciprocals and seeds of the 15 F1’s were obtained. In 2009/10 season, two adjacent field trials each included the 15 F1 crosses and their respective parents (21 genotypes) were conducted in a randomized complete block design with three replications. Each experiment was devoted to one of the followingtwo irrigation treatments; a) rainfall treatment (drought stress treatment) and b) rainfall + 2 supplemental irrigations given at sowing date and flowering stage (well watered treatment). Experimental unit consisted of one row for each genotype. Row was 3.5 m in length and rows spacing and distance between plants within row were 30cm and 10cm, respectively. Sowing date was on 20th November.Plants were thinned at one plant per hill after about three weeks from sowing date. Days to heading and maturity were recorded. Also, flag leaf area, flag leaf angle, as well as relative water content (RWC), proline content, chlorophyll a (chl.aand b)content and carotenoids content as physiological traits were recorded at anthesis stage. At harvest, ten guarded plants randomly taken from each plot were used for recording data of the following traits; plant height, no. of spikes/plant, spike length, number of spikelets/spike, number of grains/spike, 100-kernel weight, grain yield/plant, straw yield/plant and harvest index. Data of all traits recorded from each experiment were subjected to the ordinary analysis of variance and combined analysis over the two irrigation regimes was done when the homogeneity test was insignificant. Significant differences between means were tested by using the least significant differences (L.S.D) test at 5% level of probability. Heterosis, combining ability and heritability were estimated for the studied traits.Estimates of combining ability effects were made by applying Griffing's(1956) method 2 and model 1. Different groups of phenotypic correlation were estimated between the studied traits under both irrigation treatments.

The obtained results can be summarized as follows: A. Analysis of variance The results revealed that irrigation regimes mean squares were highly significant for all studied traits, indicating that the genotypes performance