A major challenge in the protected cultivation of fruit crops is the increasing threat of:

Correct option is D

Nematodes (Root-knot nematodes, Meloidogyne spp.)

• Nematodes are indeed a serious hidden problem in polyhouse soils.
• They attack roots, reduce plant vigor, and predispose plants to other infections.
• Their problem is more severe in vegetables (tomato, cucumber, capsicum) grown under protected cultivation than in fruit crops.