Breeding seed sterility

Male sterility due to deleterious nuelear genes is common in the cultivated potato (Howard, 1970). Because the marketable product is not seed, there is no selection pressure for high fertility in breeding programs. In fact, fruit development may partition resources away from tuber deld, so breeders may inadvertently select against high fertility (Jansky and Thompson, 1990). In addition, deleterious recessive alleles can accumulate in tetraploid potato cultivars because they are more easily masked than in diploids. 

Emasculation of the female parent is used for the production of artificial hybrids. Acid-induced male sterile plants pollinated without emasculation are also used. These hybrids were produced by natural crossing in seed production fields (breeding nursery), with the two parents planted in alternating groups of rows. The first hybrid cultivars were introduced in Canada for commercial production in 1946 (4). 

In spite of these hopeful pronouncements and intentions, if one examines carefully many of the agricultural innovations of the twentieth century—innovations that seemed purely technical and hence neutral —one cannot but conclude that many of them created commercial and political monopolies that inevitably diminished the autonomy of the farmer. The revolution in hybrid seeds, particularly corn, had this effect. Since hybrids are either sterile or do not breed "true, the seed company that has bred the parents of the hybrid-cross has valuable property in hybrid seed, which it can sell every year, unlike the open-pollinated varieties which the farmer can select himself. ... 

Seedless hops command a higher price than those with seeds but it will no doubt be some time before all other English hop-growing areas only produce seedless hops. An alternative approach to the production of seedless hops is the breeding of triploid varieties which are sterile and thus do not produce seed even in the presence of male hops. In America most hops are grown seedless but in Oregon they are fertilized. 

For the majority of crops which are not strict cross-pollinators, hybrid seed formation itself is a technical problem. We have developed a universal hybrid seed system based on the rubICON gene fragmentation technology which allows for the breeding of male sterile female lines as fertile crossing partners (8). This hybridization system can easily be combined with a switchable gene expression onset in cross-pollinated seeds. 

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