Which nematodes possess only one generation in a year?

✅Explanation: Heterodera avenae, the cereal cyst nematode, generally has one generation per year, although it can sometimes complete two generations under favorable conditions (warm temperatures and sufficient moisture).

🔑Key Points:
(a) Meloidogyne spp. (Root-knot nematodes): These nematodes have very short life cycles, typically completing multiple generations within a single growing season (20-40 days per generation, depending on conditions).
(c) Tylenchulus semipenetrans (Citrus nematode): This nematode generally has a longer life cycle, but it can complete multiple generations per year in warm climates.
(d) Rotylenchulus reniformis (Reniform nematode): Similar to root-knot nematodes, reniform nematodes have short life cycles and can have multiple generations in a year.