Elementary plant Biochemistry and Biotechnology (2+1)

Anther Culture

 
• The impact of haploid production in genetics and plant breeding has long been realized. Homozygous lines of the cross pollinating species and hybrids are highly desirable to increase the efficiency of selection and production of homozygous plants. The conventional method to produce homozygous plants is lengthy and laborious, requiring 7-8 recurrent cycles of inbreeding. Moreover, this approach is impractical for self-incompatible and male sterile and tree species. On the other hand, homozygous plants can be obtained in a single generation by diploidization of the haploid. This kind of production of stable, homozygous dihaploids or doubled haploids (DH) in a single generation equivalent to the Fα generation of pedigree breeding and thus considerably shortens the breeding cycle. However, their exploitation remained restricted because of the extremely low frequency with which they occur in nature.


• Spontaneous production of haploids usually occurs through the process of parthenogenesis (embryo development from unfertilized egg). Rarely, they reproduce male parent alone. This suggest that their origin through ‘ovule androgenesis’ (embryo development inside the ovule by the activity of the male nucleus alone). In vivo occurrence of androgenic haploids has been reported in Antirrhinum, Nicotiana etc. the artificial production of haploids was attempted through distant hybridization, delayed pollination, application of irradiated pollen, hormone treatments and temperature shocks.


• However, none of these methods are dependable. The development of numerous pollen plantlets in anther culture of Datura innoxia, first reported by two Indian Scientists (Guha and Maheswari) was a major breakthrough in haploid breeding of higher plants. This technique of haploid production through anther culture (anther androgenesis or simply androgenesis) has been extended to numerous plant species including cereals, vegetables, oil and tree species.


• The anthers may be taken from plants grown in the field or in pots, but ideally these plants should be grown under controlled temperature, light and humidity. Often the capacity for haploid production declines with age of donor plants. Flower buds of the appropriate developmental stage are collected, surface sterilized and their anthers are excised and placed horizontally on culture medium. Care should be taken to avoid injury to anthers since it may induce callus formation from anther walls. Alternatively, pollen grains can be separated from anthers and cultured on a suitable medium.