Junming Li: Molecular Wheat Breeding

Physiological Evaluation and Molecular Cytogenetic Identification of Drought Tolerant Germplasm from T. aestivum -Ae.biuncialis

Jing Wang , Furong Li, Zhiguo Wang, Jun Ji and Junming Li

Aegilops biuncialis (2n=4x=48) contains UUMM genome, which originated from Aegilops umbellulata (U genome) and Aegilops comosa (M genome). Ae. biuncialis is an annual herb and widely distributed in Mediterranean and western Asiatic areas characterized by a dry summer seasons. The successful adaptation of some Ae. biuncialis

accessions to a dry habit may take them useful for the genetic improvement of wheat against drought stress.

Because the high genetic diversity of Ae. biuncialis existed in different accessions,it is necessary to set up a generalized ideogram to identify the U, M chromosomes and to trace their transmission in wheat background. Three accessions of Ae. biuncialis were used and C-banding and FISH ideogram of 14 pair chromosomes was established (Figure 1 ).

Crossing and limited-backcrossing was made to develop wheat-Aegilops hybrids between Chinese Spring (CS) and Ae. biuncialis accessions, and 213 lines of BC2F3 with characteristics of Ae. biuncialis were obtained. A preliminary physiological evaluation during drought stress and rewatering was given and 24 lines showed desirable drought tolerance. Using CS as control, one line 131-1 demonstrated higher superoxide dismutase (SOD) and peroxidase (POD) activity, higher relative water content of leaf (RWC) and stronger modulation ability. Meanwhile, significant difference in decrease of stomata closure between l31-1 and CS was observed; but photosynthetic rate of the former was little affected (Figure 2). All the physiological parameters manifested that 131-1 has better drought tolerance than CS.

The chromosomal constitution of 131-1 was identified by C-banding and FISH. The and one 6U chromosome from Ae. biuncialis (Figure 3). Considering the fact that only one 6U chromosome is different between 131-1 and CS, it is reasonable to postulate that 6U chromosome carry the  rought tolerance gene.