Plant Pathology

Rhizopus fungi are heterothallic, meaning they require two opposite mating strains (plus + and minus - strains) to undergo sexual reproduction and form zygospores. When you start a culture from a single spore, you only have one strain present. Without both plus and minus strains coming into contact, sexual reproduction cannot occur and zygospores cannot form. This is a fundamental characteristic of their reproductive biology.

Puccinia graminis is an obligate parasite causing black rust of wheat. It is a heteroecious fungus that completes its life history on wheat and barberry plants leaves.

Phytophthora infestans is a fungus-like organism (oomycete) that causes late blight of potato, which was responsible for the Irish Potato Famine. Loose smut of wheat is caused by Ustilago tritici, wilt of pigeon pea by Fusarium udum, and blight of chickpea by other pathogens.

Eucarpic fungi are those where only a portion of the thallus (vegetative body) is converted into reproductive structures, while the rest continues to perform somatic functions. This is the defining characteristic. Option C correctly states this. Option A describes habitat incorrectly (eucarpy is about reproduction, not habitat). Option B describes holocarpic fungi, not eucarpic.

The question asks for the FALSE statement. Dwarf pea plants have mutations that REDUCE gibberellin production or sensitivity, which is why they're dwarf. Therefore, they would have LOWER levels of active gibberellin, not higher. Option D correctly identifies this as false by stating they would have 'higher levels' - this is the lie. Options A, B, and C are all true statements about gibberellins.

Earcockle disease of wheat is caused by Anguina tritici (a nematode). Puccinia tritici causes stem rust of wheat, not earcockle. Corynebacterium tritici causes bacterial leaf streak. 'Angunia' appears to be a typo for 'Anguina' but given the options, C is clearly intended as the correct answer.

Quarantine regulations are designed to prevent the entry of diseased plants, pathogens, or invasive species into a country or region. This is a fundamental biosecurity measure. It has nothing to do with promoting dry farming, growing fruit trees, or spraying insecticides - those are agricultural practices, not quarantine measures.

Though witches' broom is caused by bacteria but in legumes it is caused by fungus.

Cauliflower Mosaic Virus (CaMV) is one of the few plant viruses that contains DNA (specifically, double-stranded DNA). In contrast, Tobacco Mosaic Virus (TMV), Tomato Mosaic Virus, and Potato Mosaic Virus are all RNA viruses. This is an important distinction in virology.

Root-knot nematodes use their stylet (a needle-like mouthpart) to pierce plant cell walls and establish feeding sites. The stylet is a specialized structure for penetration and feeding. They do not use teeth (nematodes don't have teeth) or saliva (they secrete substances through the stylet, but the stylet itself is the penetrating organ).

Norin – 10 gene is associated with wheat cultivation.

Dee-geo-woo-gen is a well-known dwarfing gene from rice (Oryza sativa). It was identified in Taiwanese rice varieties in the 1950s and contributed to the development of semi-dwarf rice varieties during the Green Revolution. The name appears to be a transliteration from Chinese.

Loose smut of wheat is caused by Ustilago tritici (1-c). White rust of crucifers is caused by Albugo candida (2-d). Crown gall is caused by Agrobacterium tumefaciens (3-b). Pierce's disease of grape is caused by Xylella fastidiosa (4-a). Option B matches all pairings correctly.