**12. Mutation breeding**

Literature on mutation breeding of vegetable crops for resistance to insect attack is meager. In IIHR, Bangalore varietal differences, have been indicated for resistance to jassids in the M1and M 2 populations of okra (dry seed irradiated with 55 to 60 KR gamma rays), to aphid in the M population of muskmelon (30–40 KR gamma rays); and to aphid in the MQ population of watermelon (dry seed irradiated with 50 KR gamma rays). This was indicative that there was a great potential in this approach for resistance genes. It is particularly applicable in case of muskmelon to fruit fly, brinjal fruit and shoot borer, tomato fruit borer, melon fruit fly and others where useful source of resistance has not been obtained. Further in cases where one or two sources have been located in nature, it would be desirable to obtain more sources of resistance through mutation breeding. It is evident that very little experience has been gained in the use of induced mutations in resistance breeding against insect pests but the prospects of this approach are great.

Selection of spontaneous and induced mutant plants with resistance through the use of mutagenesis. In germplasm repositories sometimes natural spontaneous mutations may occur. During that occurrence some resistant types will be developed naturally. If such instances does not occur then mutations can be induced by

*Breeding Approaches for Biotic Stress Resistance in Vegetables DOI: http://dx.doi.org/10.5772/intechopen.94983*

artificial methods. The short comings in this method is that mostly duplication of naturally occurring genes will be the outcome and induced mutants will have mono factorial behavior and the inheritance is short-lived [4]. The genetic stability has to be tested by repeated screening of mutants for the confirmation of resistance.

Potato is a major vegetable crop and is infected by many diseases which induces losses in yield and quality. Artificial mutations through irradiations were tried for developing resistant varieties against stem canker and black scurf of potato caused by *Rhizoctonia solani*. The mutants developed were resistant to these diseases. Aslı Kara and Şerife Evrim Arici [42] investigated the effect of gamma radiation on the susceptibility of the potato plant to *Rhizoctonia solani* at 22, 33, 54, 57 and 109 Gy. The best results were found with a dose of 22 Gy. The application of gamma irradition in this study may offer a new approach for potato breeders for developing plants resistant to *R. solani*.
