Ola Omar Moustafa
General Commission for Scientific Agricultural Research-
Administration of Field Crops Research, Section of Technology
Package of Agronomy
Aleppo University, Faculty of Agriculture
2010

Abstract

Durum wheat (Tritcum turgidum L var. durum) is one of the most widespread grown wheat in the Mediterranean region, where drought is the main environmental stress that determines its productivity. Understanding of drought tolerance basics relies on the study of morpho-physiological traits that can be used in genotypes selection based on the correlation of these traits to grain yield under drought conditions, in addition to determining gene loci responsible for them through finding a molecular marker close to the gene or genetic loci associated with an impartial trail under drought condition, which can be used by plant breeder as a selection tools “Marker Assisted Selection MAS”, to develop  drought tolerant varieties.
This research was conducted within the joint scientific collaboration program between ICARDA, GCSAR, and Faculty of Agriculture / University of Aleppo,  aiming at determining the most important morpho-ophysiological traits  genetically correlated to grain yield  and drought tolerance, determining the molecular  markers associated with drought in the studied lines of the  “Lahn x cham1” population,  using microsatellite technique liking between the morpho-physiological trait and the molecular markers related to drought, and then studying the genetic compatibility relationship between the morphophysiological trait correlated to drought in selected gene loci.
The field experiments were carried out in two different locations. In terms of environmental and climatic conditions which are Tel Hadya (supplementary irrigation), and Breda (rainfed Zone C) in 3 seasons (2004/05-2005/06-2006/07) .
In 2004/05 growing season, the plant material studied consisted of 112 uniform durum genotypes which originated from the cross Lahn x Cham1. The parent Lahn is characterized by high grain yield under irrigated conditions and high grain quality. Cham1 is characterized by high grain yield and yield stability in different environments.
Eighteen lines were selected based on their yield and stability, and were studied during two growing seasons (2005/06 and 2006/07)
Augmented design was used in the first season, while in the next two seasons randomized completed block design was used.
The results indicated that there was a significant difference in the grain yield between locations, and that drought reduced grain yield by 89% and decreased the values of yield components and morphological characters in addition to different physiological responses.
The results of studying the correlation between grain yield and morpho-physiological traits studied revealed a significant positive correlation in dry location to peduncle length, straw length, leaf color during filling period, stomata resistance, and leaf temperature at 45 zadoks. While grain yield was significantly and negatively correlated to days to heading. The results also showed that the best physiological criterion positively correlated with yield is sensitivity tolerance index (STI) which is in turn linked to number of grains per spike, which was proven by the results to the yield component that is most associated with grain yield in the dry location. The line LC2106 was the most drought tolerant. The results showed that stress tolerance trait of durum wheat and yield stability were reached by reduced number of days to heading and to maturity and increased peduncle length, which  makes these traits important indicators for selection of stable, high- yielding lines und drought stress conditions.
The study of grain yield and most of morphophysiology traits under study have significant degree of Transgressive Inheritance which indicates to the possibility to reaching lines with morpho-physiological characteristics better than their parents.
Concerning the molecular study using micro-satellite technique, SSR markers were distributed over all durum wheat chromosomes to correlate the morphophysiological traits with Gene loci. The results revealed the existence of many gene loci associated with most of the morpho-physiological traits related to drought (pedunde length, leaf color, stomata resistance, leaf temperature at 45 stage, STI, days to heading). These loci are located on the chromosome 4B (gwm160bp172, gwm006bp180, gwm495bp155, wmc048bp190, gwm368bp287) which contains a great number of gene loci for drought tolerance (BM816121, BM816640, BM816848). Including the marker (gwm160bp172) which is correlated to grain yield and number of grains per spike which can be used in marker-assisted selection.
Our results confirmed the correlation of gene locus (XBM816640) located on chromosome 4B to leaf color, and indicated to the correlation of several  morpho-physiological traits related to drought with the gene locus (GWM129) located on chromosome 5A whose near the gene locus (XBM816474) associated with drought.