Bulb development in garlic – a review

Many factors including cold conditioning, temperature, photoperiod, plant population, clove weight, soil nutrients, irrigation, plant growth regulators, and genetic responses influence bulb development in garlic. Garlic produces poor bulbs in warm and short-day conditions but cool and long-days induce flowering. Bulbs exposed before planting from 0° to 10°C for 8 weeks accelerate growth as the low temperatures modify the hormonal balance. Large cloves (>2–4 g) yield heavier bulbs than small (1–2 g) cloves. Plant population has an impact on bulb size: the higher the plant population, the smaller the bulb size. Garlic is sensitive to moisture stress especially during bulb initiation and development. Depending upon cultivar, soil type, and fertility status, NPK fertilisation for enhancement of bulb yield varies from 60–200, 20–75, and 40–166 kg ha−1, respectively. Low-temperature pre-treatment (4°C) increases salicylic acid (SA) concentration in the leaf sheath and enhances bulbing. Injecting garlic plants with gibberellin (GA3) solution increases clove number per bulb. Like onion, flowering and bulb formation in garlic are controlled by different (Flowering Locus T) FT genes. Two antagonistic FT-like genes regulate bulb formation. AsFT1 enhances bulb formation, while AsFT4 prevents AsFT1 up-regulation and inhibits bulbing.