• Bacterial Wilt Disease Complexes in Carnation (Dianthus caryophyllus):
• Statement (I) is correct: Root-knot nematodes (Meloidogyne spp.) penetrate carnation roots and establish metabolic sinks, compromising host defense and dramatically increasing the incidence, severity, and rate of wilting caused by Burkholderia caryophylli.
• Statement (II) is correct: Spiral nematodes (Helicotylenchus spp.) feeding ectoparasitically/semi-endoparasitically create cortical lacerations and feeding wounds that provide direct ingress avenues for Burkholderia caryophylli, aggravating bacterial wilt.
• Conclusion: Both Statement (I) and Statement (II) are correct (Option 1).

• Etiology of Tundu / Yellow Ear Rot Disease of Wheat:
• Synergistic Association: Tundu disease (yellow slime rot) is a classic disease complex requiring the obligatory interaction between a nematode vector and a bacterium:
• Nematode Vector: Anguina tritici (wheat gall nematode).
• Bacterial Pathogen: Clavibacter tritici (now classified as Rathayibacter tritici).
• Mechanism: $J_2$ juveniles of Anguina tritici carry bacterial cells adhering to their cuticles as they migrate upward on dew films into the floral meristem, where the bacterium proliferates and exudes copious bright yellow gum/slime that glues the earhead.
• Conclusion: The bacterium carried is Clavibacter tritici (Option 3).

Correct option: (3) Clavibacter tritici