State twenty Plant breeding topics on yield trials of maize hybrids?

1. Evaluation of maize hybrids for grain yield
2. Comparison of yield performance of different maize hybrids
3. Testing the yield potential of new maize hybrids
4. Impact of environmental factors on maize hybrid yield
5. Genetic factors influencing maize hybrid yield
6. Evaluation of maize hybrids for drought tolerance and yield
7. Evaluation of maize hybrids for disease resistance and yield
8. Evaluation of maize hybrids for pest resistance and yield
9. Evaluation of maize hybrids for heat tolerance and yield
10. Evaluation of maize hybrids for cold tolerance and yield
11. Evaluation of maize hybrids for nutrient use efficiency and yield
12. Evaluation of maize hybrids for water use efficiency and yield
13. Evaluation of maize hybrids for early maturity and yield
14. Evaluation of maize hybrids for late maturity and yield
15. Evaluation of maize hybrids for lodging resistance and yield
16. Evaluation of maize hybrids for ear size and yield
17. Evaluation of maize hybrids for kernel size and yield
18. Evaluation of maize hybrids for stalk strength and yield
19. Evaluation of maize hybrids for ear height and yield
20. Evaluation of maize hybrids for overall agronomic performance and yield.

1. Effects of genotype on grain yield under different environmental conditions
2. Stability of grain yield performance across multiple sites and years
3. Heritability and genetic variation for grain yield traits
4. Genotype-by-environment interactions in grain yield
5. Correlation of grain yield with other agronomic traits
6. Optimum plant density and row spacing for maximizing grain yield
7. Influence of nitrogen fertilization on grain yield
8. Water-use efficiency and its impact on grain yield
9. Disease resistance and its association with grain yield
10. Insect resistance and its impact on grain yield
11. Lodging resistance and its influence on grain yield
12. Drought tolerance and its effect on grain yield
13. Heat tolerance and its impact on grain yield
14. Genetic mapping of grain yield QTLs
15. Gene pyramiding for improved grain yield
16. Marker-assisted selection for grain yield traits
17. Yield potential and physiological limitations
18. Yield stability and environmental influences
19. Evaluation of experimental hybrids vs. commercial checks
20. Economic analysis of yield trials