Horticulture and Crop Improvement
Horticulture and improving crops
Horticulture is the intensive cultivation of fruits (pomology), vegetables (olericulture) and flowers (floriculture). You must describe nursery practice: site selection, sterilised media, seedbeds or trays, shading, watering, pricking out, hardening off, and transplanting at the right spacing and depth.
Learn vegetative propagation - cuttings, layering, budding, grafting, division, suckers and tissue culture - and why it is used: identical offspring, earlier bearing and the ability to combine a scion (the fruiting top) with a rootstock (a disease-resistant or dwarfing root system). Budding inserts a single bud under the bark; grafting joins a shoot piece. Sexual propagation gives variation, useful in breeding but not for reproducing a named cultivar.
Crop improvement: know the sources of variation (mutation, recombination, introduction), methods (selection, pure-line, hybridisation, backcrossing, genetic engineering), pollination, and the difference between self- and cross-pollinated crops. Define variety, cultivar, hybrid vigour and pure live seed. Hybrid seed must be bought each season because saved seed loses vigour and uniformity.
Traps: confusing variety with cultivar, assuming a grafted plant breeds true from seed, and forgetting to test seed viability.
Worked example - pure live seed: a lot has 90% purity and 80% germination, so PLS = 0.90 × 0.80 = 72%. To sow 50 kg/ha of pure live seed, use 50 ÷ 0.72 = 69 kg/ha of this lot.