Question

Disease resistant varieties can be produced by ___________
(a) Crossing a plant with a wild variety
(b) Treating with colchicine
(c) Crossing with hormones
(d) Treating with low temperatures

Answer 1

Hint: Plant disease resistance defends plants in two ways from pathogens: by pre-formed structures and chemicals, and through the immune system's infection-induced responses. Disease resistance is the reduction of pathogen growth on or in the plant relative to a susceptible plant, while the term disease tolerance describes plants that, despite significant pathogen levels, show little disease damage. The outcome of the disease is determined by the three-way pathogen, plant, and environmental interaction.

Complete answer:
To produce new crop varieties or disease-resistant high yielding plants, classical plant breeding uses the intentional crossing of closely or distantly related individuals. To introduce traits/genes from one variety or line into a new genetic history, plants are crossbred. The aim of the cross is to add disease resistance without sacrificing the features of high yield. To ensure that the offspring is most like the high-yielding parent, progeny from the cross would then be crossed with the high-yielding parent (backcrossing). The progeny from that cross would then be tested for yield and resistance to illness and would be further established by high-yielding resistant plants.

Additional information:
Plant Breeding Methods For Disease Resistance: Breeding is achieved either by traditional techniques or by the breeding of mutants. In general, a traditional breeding system for disease resistance follows the same steps as that of a normal hybridization program.
The measures would be sequential:
(i) Germoplasm screening for resistance origin.
(ii) Hybridization, accompanied by hybrid selection and assessment.
(iii) Testing and release of a newly developed hybrid variety resistant to disease.
However, the above approaches are limited to the availability of genes resistant to diseases in different crops and other associated plants.

So, the correct answer is ‘(a) Crossing a plant with wild variety’.

Note: Many wild varieties of today's crops have been found with certain resistant features. Yet their yield is very small. These resistant genes are introduced by hybridization into high yielding varieties, e.g., resistance to the bhindi yellow mosaic virus (Abelmoschus esculentus) has been transferred from its wild relative, A. Hey, Manihot. As a result, the name Parbhani Kranti has developed as a yellow mosaic virus-resistant variety of bhindi.