The flowering plants
(Angiosperms) are widely distributed across the earth, representing the most
diverse group of terrestrial plants. The land dwelling plants due to their
sessile nature, are unable to escape the various stressful environmental
conditions. Hence, they adapt themselves accordingly and possess a quite
complex biology in contrast to animals, which allows them to change their
reproduction, growth and development to survive in respective habitat. To
undergo such adaptation, the plants prevent selfing to limit the deleterious effects of
inbreeding, and promotes
outcrossing by employing several strategies for securing their future survivality.

The Self-Incompatibility
(SI), a genetically controlled mechanism is one of the most extensively adopted
strategy by plants, to attain the heterogeneous
nature and thus expanding the plant diversity (de Nettancourt, 1997).
In the course of evolution, the SI plants possess an evolved genetic system to
prevent self-fertilization by recognizing the self-pollen/Pollen Tube
(PT) and arresting their germination/growth. The recognition determines the
allelic specificity of pollen/PT and pistil differentiating the self or cross
pollen based on the haplotype they possess (Chapman and Goring, 2010).
In case if they possess the same S-haplotype (same allelic specificity), then
self-pollen germination or PT growth is arrested leading to pollen pistil
incompatibility, either in the vicinity to ovule near micropyle (ovular
incompatibility or late acting incompatibility) or by post zygotic
incompatibility, wherein the self-fertilized zygotes were aborted inhibiting
seed set (Gibbs, 2014). During the
various seminal studies, three distinct types of genetic control mechanisms of
Self-incompatibility (homomorphic sporophytic, homomorphic gametophytic and
heteromorphic self-incompatibility) were established, prominently occurring in
the angiosperm breeding system (Lewis, 1951). In spite of
being extensively studied in the angiosperms, the molecular insight behind SI
remained limited to Brassicaceae, Plantaginaceae, Rosaceae, Solanaceae and
Papaveraceae (Gibbs, 2014). After knowing about
the Pros of SI, the major con is about beyond the realms of possibility in
raising and maintaining the quality lines of many heterozygous crops. One such
crop is Tea, the most widely consumed profitable aromatic beverage across the
world.

Tea (Camellia
sinensis (L) Kuntze) belonging to family Theaceae is
indigenous to India and China, and is appreciated for its role as stimulant and
health benefits (Preedy, 2012), (Chen et al.,
2008). Based on well-defined taxonomic
traits, the commercially important tea species have been classi?ed into three
types as China (Camellia sinensis
var. sinensis), Assam (Camellia sinensis var. assamica) and Cambod (Camellia sinensis var. assamica subssp. lasiocalyx) (Balasaravanan et
al., 2003),(Mondal, 2002). In spite of
having high economic value, breeding efforts have been made for its genetic
improvement, though still obtuse due to certain bottlenecks. These includes
obligate outcross nature, imparting high level of  heterozygosity with profuse phenotypic
variation; perennial nature; long gestation periods and self-incompatibility (Mondal et al.,
2004). Among these bottlenecks, the major problem
faced during tea breeding is about raising and maintaining the elite quality
lines, which gets depressed in its offspring due to its profuse outcross nature
(allogamy) contributing profuse heterogeneous nature to tea (Kaundun and Matsumoto, 2002),. Thus,
clonal propagation is preferred over natural propagation in maintaining the
quality lines (Sharma et al.,
2011).

To
unravel the genome-wide molecular insights, the Next-Generation Sequencing
(NGS) approach have been revolutionized in many of the non-model plants,
yielding high throughput sequencing data in cost effective manner. Thus
Utilizing transcriptome approach, the expression pattern of functional region
of the genome is targeted and their relative abundance is estimated (Unamba, Nag and Sharma, 2015). Recently, some
studies were led to comprehend the type of incompatibility existing in tea, demonstrating
the role of S-RNase in late acting self-incompatibility (Chen et al.,
2012),(Zhang et al.,
2016). Also the draft genome of Camellia sinensis was sequenced
enriching the genomic assets of tea (Xia et al.,
2017) however, genome-wide studies to
unravel the molecular genetics behind fertilization and late acting
gametophytic self-incompatibility is yet obscure in tea.

Thinking
about the limitations in the past investigations and anticipating the open
doors in tea, the doctoral studies was conducted with the accompanying objectives:

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