Q30. Grassy shoot disease of sugarcane is linked to which kind of plant pathogen?
[RPSC Assistant Research Officer (Plant Pathology) — 12 February 2016, Morning]
(A) True fungi
(B) Typical viruses
(C) Phytoplasmas
(D) Nematodes
Answer: (C) Phytoplasmas
Explanation: Phytoplasmas are cell-wall-less bacteria that live largely in plant phloem and are commonly spread by sap-feeding insects. Sugarcane grassy shoot leads to profuse tillering and thin, grass-like shoots, often with poor cane development.
Q29. Stem pitting is a well-known symptom of which citrus disease?
[RPSC Assistant Research Officer (Plant Pathology) — 12 February 2016, Morning]
(A) Citrus exocortis
(B) Citrus tristeza
(C) Citrus greening
(D) Citrus canker
Answer: (B) Citrus tristeza
Explanation: Citrus tristeza virus may produce stem pitting, decline and poor growth depending on the strain, scion and rootstock combination. Aphids are important vectors. Disease severity varies considerably, so not every infected tree displays identical symptoms.
Q28. Excess cell division causing enlargement of infected plant tissues is termed:
[RPSC Assistant Research Officer (Plant Pathology) — 12 February 2016, Morning]
(A) Hyperplasia
(B) Hypertrophy
(C) Hypoplasia
(D) Atrophy
Answer: (A) Hyperplasia
Explanation: Hyperplasia means an increase in cell number through excessive division. By contrast, hypertrophy is enlargement of existing individual cells. Both changes can produce abnormal galls, swellings or distorted plant structures under pathogen influence.
Q27. Wind-borne dispersal of plant pathogens is known as:
[RPSC Assistant Research Officer (Plant Pathology) — 12 February 2016, Morning]
(A) Hydrochory
(B) Zoochory
(C) Anemochory
(D) Anthropochory
Answer: (C) Anemochory
Explanation: Anemochory means dispersal by wind. Many rust and mildew spores travel in air currents, sometimes across considerable distances. Hydrochory concerns water transport, zoochory involves animals and anthropochory refers to movement associated with human activity.
Q26. Brown discoloration of a plant’s vascular bundles is most suggestive of which general disease syndrome?
[RPSC Assistant Research Officer (Plant Pathology) — 12 February 2016, Morning]
(A) Vascular wilt
(B) Smut
(C) Rust
(D) Bunt
Answer: (A) Vascular wilt
Explanation: Fusarium and Verticillium wilts often damage or colonise the xylem, producing internal brown streaking together with external wilting. Vascular discoloration is useful diagnostically but should be combined with field symptoms and laboratory confirmation.
Q25. Striga is best described as which sort of parasitic plant?
[RPSC Assistant Research Officer (Plant Pathology) — 12 February 2016, Morning]
(A) Complete stem parasite
(B) Complete root parasite
(C) Partial stem parasite
(D) Partial root parasite
Answer: (D) Partial root parasite
Explanation: Striga attaches to host roots and withdraws water and nutrients, but its green shoots also photosynthesise. It is therefore a hemiparasitic or partial root parasite. Infestations are particularly damaging in cereal crops grown on poor soils.
Q24. Who is credited with the earliest scientific description of a plant-parasitic nematode in wheat?
[RPSC Assistant Research Officer (Plant Pathology) — 12 February 2016, Morning]
(A) John Needham
(B) Nathan Cobb
(C) Julius Kühn
(D) Anton de Bary
Answer: (A) John Needham
Explanation: John Needham described organisms associated with wheat seed galls in the eighteenth century. Later work identified the seed-gall nematode as Anguina tritici. These observations are important milestones in the history of plant nematology.
Q23. Which of these is recognised as an early systemic fungicide used for treating seed-borne smuts?
[RPSC Assistant Research Officer (Plant Pathology) — 12 February 2016, Morning]
(A) Bordeaux mixture
(B) Captan
(C) Thiram
(D) Carboxin
Answer: (D) Carboxin
Explanation: Carboxin was among the first commercially important systemic fungicides and is particularly associated with seed treatment against smuts. Bordeaux mixture, captan and thiram are mainly protective contact treatments rather than classic internally translocated systemic fungicides.
Q22. Identify the pathogen that causes leaf smut of rice.
[RPSC Assistant Research Officer (Plant Pathology) — 12 February 2016, Morning]
(A) Entyloma oryzae
(B) Urocystis tritici
(C) Ustilago tritici
(D) Ustilago nuda
Answer: (A) Entyloma oryzae
Explanation: Entyloma oryzae causes rice leaf smut, seen as small dark lesions containing fungal spores. It is distinct from rice blast and false smut, which involve different causal organisms and show different symptoms on plant tissues.
Q21. Among these parasitic flowering plants, which one is a total stem parasite?
[RPSC Assistant Research Officer (Plant Pathology) — 12 February 2016, Morning]
(A) Loranthus
(B) Orobanche
(C) Striga
(D) Cuscuta
Answer: (D) Cuscuta
Explanation: Cuscuta, or dodder, winds around host stems and obtains nourishment through haustoria. It has very little functional chlorophyll in most species. Orobanche is mainly a total root parasite, while Striga and many mistletoes retain photosynthetic capacity.
