Source of Insect Resistance in Plant Breeding


Source of Insect Resistance in Plant Breeding

There are five different source of insect resistance in crop plants, viz. 1) Cultivated varieties, 2) Germplasm collections, 3) Wild species, 4) Mutations, and 5) Microorganism. This are briefly discussed below:

1. Cultivated Varieties:

In some crops, genes for insect resistance may be found in cultivated varieties. For example, cotton varieties SRT1, Khandwa2, DHY286, PKV081, and B 1007 are good source of Jassid resistance. The insect reactions of cultivated varieties are known in almost all the crops. The desirable source of resistance can be selected from the cultivated varieties. Cultivated varieties are the best source of resistance because they have good agronomic characters, besides resistance.

2. Germplasm Collections:

Germplasm or genetic resources are good source of insect resistance. Resistant lines are identified by screening of germplasm for specific insect. In apple, 14 lines resistant to rosy aphid and 3 lines immune to green apple aphid were identified through screening of 2000 apple germplasm lines. Many such examples of insect resistance can be cited from other crops.

3. Wild Species:

In several crop resistant genes for insect are found in the wild species or wild relative of crop plants. Wild species are good source of insect resistance, for example, wild species Gossypium lomentosum, G. anomalum and G. armourianum are good source of Jassid resistance in cotton. Resistance to Rubus aphid of raspberry is found in wild species of raspberry. In tobacco, resistance to root knot nematode is obtained from wild species.

4. Induced Mutation:

Sometimes, insect resistance is obtained through induced mutations. Insect resistance has been obtained in many crops by this method.

5. Micro Organisms:

Now microorganisms are being used as source of resistance to insect pests. In USA, Monsanto Company has transferred a gene from Bascillus thuringiensis (Bt) into the system of cotton plant through genetic engineering. The bt. Gene is believed to provide effective resistance against bollworms. When the bollworm larva punctures the boll, a toxin is secreted by the plant which leads to death of the larvae by a slow process.

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