Q.Write outline the life cycle of Agaricus.

Step 1. Germination and primary mycelium. A haploid basidiospore, of either '+' or '-' strain, germinates to produce the primary mycelium - septate, uninucleate and monokaryotic (one nucleus per cell).

Step 2. Formation of secondary mycelium. When primary mycelia of opposite strain meet, they fuse by somatogamy (direct fusion of ordinary hyphal cells, since Agaricus has no dedicated sex organs). This is plasmogamy only - the two nuclei do not fuse yet - producing a dikaryotic secondary mycelium in which each cell carries one '+' and one '-' nucleus side by side.

Step 3. Rhizomorphs and the basidiocarp. The dikaryotic secondary mycelium develops into hyphal cords called rhizomorphs, which can persist in the soil for long periods; dense knots of this dikaryotic tissue eventually develop into the basidiocarp (the visible mushroom fruiting body), whose tissue is the tertiary mycelium. …

Trace the cycle through its four stages: primary mycelium -> secondary (dikaryotic) mycelium -> basid …

• Placing karyogamy right after somatogamy instead of after the long dikaryotic phase - in Agaricus, karyogamy is deliberately delayed until inside the basidium. …