Examples of the use of male sterility in hybrid seed production

Hibridne sorte so zaradi visokih pridelkov in visoke stopnje uniformnosti zelo zaželene v pridelavi. Pri pridobivanju hibridnega semena si želimo, da do oprašitve pride med dvema točno določenima homozigotnima linijama in da pri ženski rastlini ne pride do samooploditve. Ena od možnih metod preprečevanja le tega je moška sterilnost, pri kateri je onemogočena funkcija produkcije fertilnega peloda. Pri pridobivanju hibridnega semena se uporabljata genska (jedrna) in citoplazemska moška sterilnost. Gensko moško sterilnost povzročajo geni, ki so kodirani v jedrnem genomu, citoplazemsko moško sterilnost pa geni, ki se nahajajo na mitohondrijih, v povezavi z jedrnimi geni. Da se izognejo vedno bolj omejeni genski raznovrstnosti, morajo žlahtnitelji neprenehoma iskati nove vire moško sterilnih linij. V primeru rjave indijske gorčice so pridobili novo moško sterilno linijo, ki je pri križanju z normalnimi linijami dala fertilne potomce. V primeru oljne ogrščice so pridobili sterilno linijo, ki pa pri križanju z normalnimi linijami ni dala fertilnih potomcev in bo zato potrebno iskati opraševalno linijo v divjih genotipih. V primeru sirka so identificirali prvi gen jedrne moške sterilnosti v sirku, ki bo omogočil razvoj dvolinijskih hibridov. V primeru koruze in riža so razvili povsem nov sistem pridobivanja hibridnega semena, pri katerem je potrebna le ena moško sterilna linija, ki se ji fertilnost povrne z vnosom transgena.Because of their high yield and high level of uniformity, hybrid varieties are quite desirable in crop production. Hybrid seed production depends on pollination between two specific homozygous lines and the prevention of self-fertilisation of female plants. Possible prevention techniques include inducing male sterility that disables production of fertile pollen. For hybrid seed production, genic (nuclear) and cytoplasmic male sterility are used. Genic male sterility is caused by the genes encoded in the nuclear genome while cytoplasmic male sterility is caused by the genes found on mitochondria, together with the nuclear genes. To prevent the increasing loss of genic diversity, plant breeders must constantly search for new sources of male sterile lines. In the case of brown/indian mustard, a new male sterile line, which produced fertile offspring when crossbred with normal lines, has been developed. In the case of oilseed rape, a sterile line, which did not produce fertile offspring when crossbred with normal lines, has also been developed recently. To pollinate this line, a wild-type genotype will have to be found. In the case of sorghum, the first gene causing nuclear male sterility has been identified. This will enable the development of two-line hybrids. In the case of maize and rice, a completely new hybrid-seed-production system has been developed. It requires only one male sterile line, the fertility of which is restored by inserting a transgene