The correct answer is option 2: Hybridisation. Hybridisation is a breeding technique where two different varieties of plants with desirable traits are crossed to create a new hybrid variety. This process aims to combine the best characteristics of both parent plants, such as high yield, disease resistance, or better taste. By using hybridisation, farmers can produce plants that have improved traits and higher yields compared to their parent plants.

Option 1: Crop rotation involves the practice of growing different crops in sequential seasons in the same area to improve soil fertility and reduce pests. While it can contribute to overall crop health and yield, it is not directly involved in producing high yielding plants.

Options 3 and 4: Inter-cropping and mixed-cropping are practices where different crops are grown together in the same field. These techniques can provide benefits like better space utilization, pest control, and nutrient cycling, but they may not directly result in high yielding plants.