Nematology- ICAR JRF/SRF 2024

• Sexual Dimorphism in Wheat Seed Gall Nematode (Anguina tritici):
• Statement (I) is correct: Anguina tritici exhibits marked sexual dimorphism in adult stages. Mature adult females are large, obese, curved or spiral in shape ($3-5\text{ mm}$ long), with an enlarged prodelphic reproductive tract; adult males are distinctly smaller, slender, and possess an open leptoderan bursa and prominent curved copulatory spicules.
• Statement (II) is incorrect: There is pronounced sexual dimorphism, making statement II false.
• Conclusion: Statement (I) is correct but Statement (II) is incorrect (Option 3).

• Feeding Habits of Strawberry Crimp Nematode (Aphelenchoides fragariae):
• Statement (I) is correct: Aphelenchoides fragariae is a facultative/amphimictic foliar nematode that exhibits dual parasitism: it feeds ectoparasitically in the folded crowns, runner buds, and young leaf primordia of strawberries (causing crimped, crinkled leaves), and also feeds endoparasitically inside the mesophyll of mature leaf blades (causing angular, vein-limited necrosis in ferns and begonias).
• Statement (II) is incorrect: It does not feed exclusively ectoparasitically.
• Conclusion: Statement (I) is correct but Statement (II) is incorrect (Option 3).

• Extreme Anhydrobiosis in Ditylenchus dipsaci:
• Nematode Wool and Quiescence: When infested onion bulbs, garlic cloves, or clover stems dry out, fourth-stage infective juveniles ($J_4$) of Ditylenchus dipsaci aggregate into dense, grayish-white masses known as 'nematode wool'.
• Duration of Survival: Under desiccated, quiescent (anhydrobiotic) conditions, these $J_4$ juveniles enter profound metabolic dormancy. In a classic landmark study by Fielding (1951), dry infested plant material yielded viable, revived D. dipsaci juveniles after 23 years of storage.
• Conclusion: It can survive up to 23 years under quiescence (Option 1).

Correct option: (1) 23

• Historical Discovery of Nematode-Fungal Disease Complexes:
• Atkinson's Landmark Discovery (1892): In 1892, the American plant pathologist George F. Atkinson published the first definitive experimental evidence demonstrating the synergistic role of nematodes in plant disease complexes.
• The Cotton Wilt Complex: Atkinson proved that root-knot nematodes (Meloidogyne sp.) wound host roots and physiologically predispose cotton plants to severe wilt caused by Fusarium oxysporum f. sp. vasinfectum, whereas cotton plants grown in Fusarium-infested soil without nematodes developed significantly less wilt.
• Conclusion: The first record of a nematode disease complex was reported in 1892 (Option 4).

Correct option: (4) 1892

• Resistance Profile of Tomato Cultivar 'Hisar Lalit':
• Origin: Developed at CCS Haryana Agricultural University (HAU), Hisar, through pedigree selection involving root-knot resistant parentage.
• Root-Knot Nematode Resistance: Statement (II) is correct because 'Hisar Lalit' carries the Mi resistance gene, conferring high resistance against root-knot nematodes (Meloidogyne incognita and M. javanica).
• Reniform Nematode Reaction: Statement (I) is incorrect because 'Hisar Lalit' is not resistant to the reniform nematode (Rotylenchulus reniformis).
• Conclusion: Statement (I) is incorrect but Statement (II) is correct (Option 4).