The Effect of Genotype x Environment Interaction on Traits Associated with Drought Tolerance in Bread Wheat (Triticum aestivum L.)

Khaled Alshreda
Admin. of Field Crops Research-
General Commission for Scientific Agric. Research (GCSAR)
Faculty of Agriculture, Aleppo University,
2010

Abstract

The study was conducted in cooperation between the General Commission for Scientific Agricultural Research, Aleppo University and International Center for Agricultural Research in the Dry Areas (ICARDA) during the two cropping seasons 2007/2008 and 2008/2009. The research aims at evaluating the genotype —environment interaction for different bread wheat (Triticum aestivum L.) genotypes under various environmental conditions and determining the traits associated with yield under drought conditions in addition to identifying the genotypes having had stable yield and drought tolerance for breeding programs and identifying the best locations for testing the genotypes.
Twenty-four bread wheat genotypes were included,  some of them are released varieties and the others are promising lines. The planting was done in a randomized incomplete block design with three replications o four different locations: Tel Hadya, Breda, Yahmool and Hemo. The planting in Tel Hadya was divided into three parts aiming at creating different environments within the same location:
1.    Early planting: where two irrigations were added; the first at planting and the second at heading with an average amount 35-40 mm each irrigation.
2.    Planting with one irrigation: the irrigation was added after heading with an amount of 35-40 mm.
3.    Rainfed planting.
The following characteristics were studied: days to headings, days to maturity, grain filling period, plant height, peduncle length, spike length, awn length, flag leaf area, number of spikes/m², number of grains/spike, thousand kernel weight, harvest index, biological yield and grain yield. Statistical analysis was done using Genstat program to calculate L.S.D among genotypes, locations, the interaction between them and variation coefficient and correlations between traits, GGEBiplot program was used to determine the best environments to test the genotypes (ideal environment) and best genotypes which combined between high and stable performance (ideal genotype).
The results revealed that early heading genotypes were high yielding The genotypes having better plant height were the better yielding in high-stress locations and the correlation between plant height and grain yield was positive while the correlation reduced when the climatic conditions got better. The results also showed that the environments have similar effect on genotypes for plant height i.e. a decrease in genotype
—environment interaction, so it’s easy to find superior genotype in these environments. Thousand-kernel weight was characterized by high heritability and stability across the environments and seasons, and it was less affected by (Gï‚´E) interaction but it’s correlated negatively with number of grains per spike. Number of spikes /m² was correlated positively and significantly with grain yield. In addition, the grains per spike were correlated positively and highly significant with grain yield in much stressed environments. It’s recommended to use these traits as suitable selection criteria in rainfed agriculture. Harvest index values were lower than theoretical estimated, indicating that harvest index still an important trait to improve wheat yield under rainfed conditions. Biological yield was the most correlated character with grain yield in the two seasons.
Grain yield was correlated with a number of traits contributed to increased grain yield at different levels of stress, namely: biological yield, harvest index, spikes per square meter, grains per spike, plant height and earliness.
The following genotypes were combined between high and stable performance through the tested environments, therefore the use of these genotypes is recommended in the breeding programs:
–    DOUMA-2, ACSAD-981, HAMAM-4 for improving earliness.
–    N-AZRAQ-9 ,JAWAHER-14 for improving plant height.
–    DOUMA-4, DURRA-6 for improving peduncle length.
–    CHAM-6, ACSAD-981 for improving number of spikes per square meter.
–    DOUMA-4, BOHOUTH-8 for improving number of grains per spike.
–    BOHOUTH-6, HAMAM-4, CHAM-10 for improving harvest index.
–    DURRA-6, BABAGA-3, N-AZRAQ-9, JAWAHER-14, DOUMA4 for improving biological yield.
–    DOUMA-4, HAMAM-4, JOLAN-2, ACSAD-981 for improving grain yield.
Ideal environment for testing genotypes was identified for every studied trait according to discriminating ability between genotypes and representative of other environments. These environments were:
–   Planting with one irrigation and Hemo location to test genotypes for earliness.
–    Rainfed planting and early planting to test genotypes for plant height.
–    Rainfed planting and Breda location to test peduncle length.
–    Planting with one irrigation and early planting and Hemo location to test genotypes for number of spikes per square meter.
–    Rainfed planting and Yahmool location for number of grains per spike.
–    Yahmool and Hemo locations for harvest index.
–    Early planting and rainfed planting to test genotypes for biological yield.
–    Planting with one irrigation and rainfed planting to test genotypes for grain yield.