Title of Thesis

Genetics of Drought Tolerance in Maize (Zea mays L.)

Author(s)

Imtiaz Hussain

Department of Plant Breeding And Genetics/ University of Agriculture Faisalabad

Subject

Plant Breeding And Genetics

Abstract
Fifty maize inbred lines were screened at seedling stage under drought and normal conditions for various seedlings parameters under controlled conditions in growth chamber, three drought tolerant and three susceptible inbred lines were selected. These six genotypes were crossed in full diallel fashion. F1 seed was planted in the field using randomized complete block design in three replications under drought and irrigated conditions. All the cultural and other practices were kept uniform to both plantings except irrigation. Various agronomic and physiological parameters were recorded. There was 20 to 40% reduction in almost all parameters was observed. Co-efficient of variability was more under water stress than normal for most of the seedling traits. In field experiment, additive gene action with partial dominance was revealed for plant height, leaf area,  leaf number, biological yield, harvest index, stomatal frequency and stomata size under both conditions. Over-dominance type of gene action was found for kernels per ear row, 100-grain weight, leaf temperature and cell membrane thermostability. Additive gene action for relative water content under normal condition was changed to over-dominance under water stress condition. The best combinations on the basis of mean performance under normal condition were Y-74×F-141, Y-74×F-128, Y-74×Y158 F-128×Y-158. Under water stress condition best performing crosses were, Y-74×F-141, Y-158×Y-74, F-128×Y-74 and F-141×B-34. These crosses might be useful as transgressive segregants in subsequent generations. Inbred lines Y-74 and F-141 were found best parents. These inbred lines may be exploited in future breeding programme for drought conditions. On the basis of different inheritance pattern of each parameter, it was suggested that overall performance of the inbred lines and their all possible combinations might be more useful while selecting for water stress condition.

REVIEW OF LITERATURE

2.1 Drought

2.2 Physiological Attributes

2.3 Agronomic Attributes

2.4 Selection Criterion

2.5Combining Ability

MATERIALS AND METHODS

3.1 Experiment 1

3.2 Experiment 2

3.3 PHYSIOLOGICAL TRAITS

3.4 STATISTICAL ANALYSIS

3.5 COMBINING ABILITY ANALYSIS

RESULTS AND DISCUSSION

4.1 EXPERIMENT 1

4.2 FIELD STUDY

4.3 GENETIC ANALYSIS

4.4 EXPERIMENT 2

4.5 COMBINING ABILITY ANALYSIS