Agriculture Reference
In-Depth Information
Chapter 8
In Vitro Haploid Production—A Fast and
Reliable Approach for Crop Improvement
Rashmi Rekha Hazarika, Vijay Kumar Mishra and Rakhi Chaturvedi
1 Introduction
1.1 Overview of Haploidy
Haploids have attracted great interest of plant physiologists, embryologists, geneti-
cists and breeders ever since the discovery of the first natural haploid embryos and
plants in
Datura stramonium
in 1922 by Blakeslee et al. Subsequently, haploidy has
been reported in many species, but at low and variable frequencies and was regard-
ed as a special biological phenomenon. The low frequency of spontaneously arising
haploid plants severely limited the utilization of haploids for crop improvement
and genetic studies. The remarkable discovery that haploid embryos and plants can
be produced through in vitro culture of anthers of
Datura
(Guha and Maheshwari
1964
,
1966
) brought renewed interest to haploidy. This method of androgenic hap-
loid production was quickly attempted in many species to hasten the breeding pro-
gramme in several economically-important plants.
The life cycle of angiosperms (higher plants) is characterized by alternating gen-
erations of sporophytes and gametophytes. The gametophytic phase arises when the
diploid cells undergo meiosis (reduction division) to form male and female gametes.
This phase is shortlived as fertilization of the egg re-establishes the diploid spo-
rophytic phase. The sporophytic phase characterized by diploid (2n) chromosome
number is the product of fertilization of male and female gametes, containing the
haploid (n) set of chromosomes from each parent (Forster et al.
2007
). Therefore,
haploid is a generalized term for plants that contain the gametic chromosome num-
ber (n). This is in contrast to diploid plants, which contain two sets (2n) of chromo-
somes. Haploids are sexually sterile and, therefore, doubling of the chromosomes is
