Question

Which one of the following, proved effective for biological control of nematode diseases in plants?
A) Gliocladium virens
B) Paecilomyces lilacinus
C) Pisolithus tinctorius
D) Pseudomonas cepacia

Answer 1

Hint: Nematodes are microscopic organisms that are eel-like roundworms. They are parasitic organisms that feed on the fluid of plants or human blood. They have an elongated, unsegmented and a cylindrical body. They do not possess cilia. They possess six lips that surround the mouth. Nematodes are controlled by the fungus that belong to the family Ophiocordycipitaceae.

Complete answer: Paecilomyces lilacinus are filamentous fungus isolated from the soil, sewage sludge, forests, grasslands, deserts, and insects. It is a member of the family Ophiocordycipitaceae. Paecilomyces lilacinus strain 251 is used to control nematodes which affect plant roots in the soil. Crops recommended for the use of P. lilacinus are banana, capsicum, tomato, brinjal, onion, chilli, etc. The species grows at a wide range of temperatures, i.e. from 8 to 38 °C for a few isolates, with optimal growth in the range 26 to 30 °C.
a) Gliocladium virens is a saprophytic fungus which is mycoparasitic on a wide variety of fungi. These are also known as Trichoderma virens. These are useful in controlling Pythium ultimum and Rhizoctonia solani.
b) Pisolithus tinctorius is an earth-ball like fungus. Its inoculation enhances the germination of plants like Scots pine. It is an ectomycorrhizal basidiomycete.
c) Pseudomonas cepacia is also known as Burkholderia cepacia. It is a group of bacteria that are catalase-producing, lactose-non fermenting, and gram-negative. It is used to promote the growth of crops.
Thus, the correct answer is Option B.

Note: Some of the nematodes causing diseases in the plants are root-knot nematodes, root lesion nematodes, Citrus nematode, etc. Symptoms of nematode infection are nutrient deficiency, incipient wilt, poor yield, and sometimes may cause the death of the plant as well.