Post-anthesis development of East African Maize (Zea mays L.) varieties under drought | |
| Author | Hunegnaw, Demelash Kefale |
| Call Number | AIT Diss. no.AS-03-06 |
| Subject(s) | Drought-tolerant plants Corn--Drought tolerance |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Technical Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. AS-03-06 |
| Abstract | Drought stress is the most crucial and important factor limiting crop production in many parts of the world by creating a shortage of plant- available water for optimal economic yield. It is a complex syndrome involving several climatic, edaphic and agronomic factors, usually characterized by timing of occurrence, duration, and intensity. Maize (Zea mays L.) is one of the crop species, which is usually affected by drought under rainfed agriculture. The complexity nature of drought can only be tackled with a holistic approach integrating physiological dissection of the resistance traits and molecular genetic tools together with agronomic practices that lead to better conservation and utilization of soil moisture and matching crop genotypes with the environment. This has been partly addressed through plant breeding. However the selection methods are often conventional and based on the grain yield. Associating drought responses with the expression of specific physiological mechanisms would greatly help in establishing protocols which allow better management of genotype-environment (G x E) interactions. The main objective of this study was therefore, to evaluate the extent of variability and levels of tolerance of selected maize genotypes to drought stress induced at different growth stages and identify adaptive mechanisms and response traits that could be used as selection criteria in developing suitable varieties to the drought-phone areas in Ethiopia. Responses of three Ethiopian grown open pollinated maize varieties (A-511, ACV-6 and Katumani) were evaluated under five watering regimes (viz, water deficit at one week before tasseling – DO, at silking – DS, at grain filling – DG, and throughout the growth – DW, and as a control adequate water supply throughout the growth period - AW). The study was carriedout in 2002 under field conditions on a sandy-loam soil with pH of 7.5 at Awassa in Ethiopia, which has an altitude of 1650m above sea level and mean annual rainfall 800-900mm. The mean temperature during the study period was 21 °C. The study was repeated in 2003 in a greenhouse at Asian Institute of Technology in Thailand where the mean temperature was 28°C during the study period. All plots were equally irrigated at seeding stage for proper root establishment, and later irrigation was withdrawn as per treatments. Irrigation schedules were adjusted and watering suspended to each treatment at predetermined specific stage so as to coincide the induced drought stress with the intended phenological stage of each variety. The results showed that, in general drought stresses induced at different growth stage of the three varieties under field and greenhouse condition significantly reduced the total biomass and grain yield {P=0.001}. Although there were no specific environment x genotype interactions the greenhouse growing condition increased tasseling-silking interval (TSI) of the three varieties. Drought stresses starting at the early vegetative stage (DO and DW) under both field and greenhouse growing conditions had significant impact on aboveground vegetative growth of A-511 and root development of variety Katumani. The reductions in vegetative growth were significantly correlated with grain yield in both varieties i.e. A-511 and Katumani, but not in ACV-6. Significant reduction in the number of grains per cob in variety A-511 under drought stress at grain filling stage in both growing environments proved that, use of early vegetative vigor as a selection criterion for drought resistance is of little importance and could even be Disadvantageous since the stalk competition for assimilate could be of rather higher importance than of young grains. Grain yield in A-511 was highly associated (P=0.001) with plant height than any other traits under greenhouse condition. The grain yield of variety Katumani was significantly correlated with a number of vegetative and generative traits more than of ACV-6, which also has similar growth pattern and yield potential under optimum growing conditions. Katumani maintained the number of grains per cob, but reduced individual grain weight, under drought stress conditions, while variety ACV-6 showed the vise-versa, i.e. a reduction in number of grains and an increase in individual grain weight thus sustaining its grain yield in all the drought stress treatments. Although yield losses in variety Katumani were associated with various traits, hundred grain-weight was the main contributor (P=0.001) among the yield components for gains yield reduction. Drought tolerance mechanisms of Katumani favored securing plant survival under drought stress, while ACV-6 maintained partitioning of assimilates towards yield components with limited water. This indicated the potential of using specific mechanisms and traits of these two varieties in breeding programs to develop drought tolerance varieties and to assist subsistence farming in the drought-prone regions of Ethiopia |
| Year | 2003 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AS-03-06 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Aquatic Systems(AS) |
| Chairperson(s) | Ranamukhaarachchi, S. L.; |
| Examination Committee(s) | Zoebisch, Michael A.;Clemente, R. S.;Stamp, Peter; |
| Scholarship Donor(s) | Agricultural Research and Training Project (ARTP/AUA);Government of Federal Democratic Republic of Ethiopia; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2003 |