"Crown gall" is caused by

The most extensively studied plant-microbe interaction is:

The $RNAi$ stands for

Main objective of production/use of herbicide resistant $GM$ crops is to
$(A)$ -Reduce herbicide accumulation in food articles for health safety.
$(B)$ -Eliminate weeds in the field without the use of herbicides.
$(C)$ -Eliminate weeds from the field without the use of manual labour.
$(D)$ -Soil pollution and biomagnification caused by herbicides.
Which of the following statements are correct?

Consider the following statements about $Bt$:
$I.$ The bacteria $Bacillus$ $thuringiensis$ $(Bt)$ are used to control butterfly caterpillars.
$II.$ Fresh spores of $Bt$ are mixed with water and sprayed on crops such as brassicas and fruit trees.
$III.$ Insect larvae,after eating these,are killed by the toxin released in their gut.
$IV.$ $Bt$ toxin genes have been introduced into plants to provide resistance to pests.
Which of the statements given above are correct?

The toxin produced by the gene of $Bacillus \text{ } thuringiensis$ is effective against which of the following?