Production of Spontaneously Double Haploids for Breeding,Doubled Haploids (DH),Colchicine Doubled Haploids (CDH),Spontaneously Doubled Haploids (SDH),Hagberg,Cytogenetics

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	Production of Spontaneously Double Haploids for Breeding - The utility of haploids in plant breeding eventually requires production of doubled haploids (DH) as discussed above. For this purpose, often efficient colchicine treatments are applied and colchicine doubled haploids (CDH) are obtained. In a system where haploids are detected through genetic markers, we can also identify the spontaneously doubled haploids (SDH), if doubling does occur spontaneously.
This will avoid unnecessary colchicine treatment and the breeder can save time and plant material. Although there are several reports of SDHs produced during haploid production, but at Svalov in Sweden, hap gene is being utilized, not only for the production of haploids, but also for the production of SDHs (Hagberg and Hagberg, 1987). It utilizes a marker gene system for mildew resistance due to an allele (ml-o), which is recessive to susceptibility allele (Ml-o). The breeding scheme used to produce spontaneously doubled haploids. In such a programme, spontaneously doubled haploids (SOH) were three times as many as the normal haploids, which seem to be really promising.
These SOH plants were found to be completely homozygous thus proving their maternal origin due to doubling of chromosome number in the original egg cell. The marker ml -0 is suitable, because it allows screening at the seedling stage, but other gene pairs like K-k (hooded vs normal awns) or V-v (two row vs six row ears) can also be used in barley. It is expected that more work in this direction will be carried out in future to make SOH production system useful to the breeders and cytogenetics.