1. Drought Resistance Evaluation of Diverse Wheat Germplasm
Habtamu Ayalew1, 2, Hui Liu 1, Guijun Yan1
1 School of Plant Biology, Faculty of Science and The UWA Institute of Agriculture, The University of Western Australia, Crawley, WA 6009, Australia,
2 Department of Horticulture, College of Agriculture and Natural Resources, Debre Markos University, P. O. Box 269 Debre Markos, Ethiopia
Background
Result
Drought is one of the major abiotic stresses limiting wheat production worldwide.
It can happen at any stage of crop development - varying in durations and intensities.
Breeding for drought resistance needs to consider evaluating germplasm at various growth stages and for both above and below ground performances.
Deep root system, fine roots, root length density, leaf rolling, leaf waxy layer, and osmotic adjustment are among the most frequently studied traits that enable plants to avoid dehydration.
Root traits can be screened at early stage to identify useful germplasm for drought resistance improvement.
The major objectives of this research were (1) to develop a screening technique for easy and efficient root phenotyping (2) to identify contrasting genotypes for genetic studies of root length and (3) to use deep rooting genotypes for drought resistance breeding.
Highly significant differences (P<0.001) were observed for root length both under stress and non-stress conditions.
Osmotic stress caused an average reduction of 54% on root length (Fig 1b).
There was also a significant variation based on the various ploidy levels (Fig 2b).
The best control variety for drought resistance was significantly (p<0.05) outperformed by four new entries namely Colotana , Compare, Santa Elena, and Tammarin Rock .
Figure 2. Genotype distribution (a) and , relative reduction in root length among different ploidy levels (b) under stress and non-stress conditions.
The domesticated and high ploidy forms showed longer roots under stress
Genotypes from the respective continents of origin showed significant differences under stress condition but not under normal condition (Fig 3).
Figure 3. The relative reduction in root length among genotypes from different continents of origin under stress and non-stress conditions. a) b)
Materials and Methods
A total of 838 wheat genotypes were evaluated in a constant temperature room in a customized hydroponic system (Fig 1a).
The experiment was setup in an augmented complete block design with seven blocks (planting time) and six released varieties, Drysdale, Gladius, Young, Wyalkatchem, Guardian and Mace were used as checks (controls).
Figure 1. The hydroponic system used for screening non-stressed (left) and stressed (right) wheat plants in figures (a) and (b).
Seeds were first germinated in Petri dishes lined with filter paper and seedlings were transferred to the hydroponic system after 48 hours of germination.
Plants were then grown in water for the first seven days followed by either in half strength Hoagland’s solution alone (control) or half strength Hoagland’s solution and PEG6000 (-0.82 MPa osmotic stress).
The growing condition was adjusted as follows:
pH of the solution
Relative humidity %
Temperature- 25/22oC day/night
Light intensity of 300 µmol.m-2s-1 (using cool florescent lamps )
The solution was being constantly aerated using an electric air bubbler.
Data were collected from 14 days old seedlings.
Conclusion a) b)
Root length was the main focus of this study keeping in mind a situation with an initial rainfall enough for germination followed by a dry spell before the actual rainy season resumes.
Results from this study showed that wheat collections tested did vary significantly (p<0.01) for root length under MPa osmotic stress which is half way to permanent wilting (Fig 2a).
The high genetic variability for seedling water stress resistance can be used for future breeding activities.
The hydroponic system was found to be a handy method for root phenotyping of a large number of genotypes.
Crossing among the most contrasting genotypes was made to analyse the inheritance of root length under water stress and the resulting populations are being advanced to RILs for QTL mapping.
Acknowledgements
The Australian Development Scholarship funded the study of the first author. The Australian Winter Cereals Collection provided us the genotypes.