INDUCED POLYPLOIDY 



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past the second or third leaf stage, a hardiness to cold counteracts unfavorable 

 soil conditions (Eigsti and Dustin, 1955). 



Reduced fertility of the tetraploid seed parent reduces the seed production. 

 Since the tetraploid must be used as the seed parent there is no prospect for 

 increasing seed production by reciprocal crosses. The fertility shown by the 



Fig. 2. Triploid fruit in cross section showing ovules. 



tetraploid parent is directly related to "seedlessness" in the subsequent tri- 

 ploid hybrid. 



Consumer acceptance rises when good-quality seedless fruit can be brought 

 to the market. Where seedless fruit is produced in volume, the wholesale 

 market awards premium prices over the price of regular fruit. Plant breeders 

 have new approaches with polyploidy and watermelon improvements (fig. 2). 



Induced polyploidy has contributed another significant achievement in 

 tobacco improvement. Cultivated tobacco is attacked by a serious mosaic, a 

 disease to which many varieties of Nicotiana tabacum are susceptible. An- 

 other species, A^. glutinosa, carries disease resistance, but it is otherwise unfit 

 for cultivation. If the resistance factor could be transferred to the commercial 

 varieties, a long step in tobacco improvement could be taken. A review by 



