Exploitation of Heterosis in Pearl Millet : Rakesh K Srivastava
by Senior Scientist Rakesh Rakesh K. Srivastava (Ph.D, FRSM, FRSPH) ProfessorThe phenomenon of heterosis has fascinated plant breeders ever
since it was first described by Charles Darwin in 1876 in the vegetable kingdom
and later elaborated by George H Shull and Edward M East in maize during 1908.
Heterosis is the phenotypic and functional superiority manifested in the F1 crosses over
the parents. Various classical complementation mechanisms gave way to the study
of the underlying potential cellular and molecular mechanisms responsible for
heterosis. In cereals, such as maize, heterosis has been exploited very well,
with the development of many single-cross hybrids that revolutionized the yield
and productivity enhancements.
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Pearl millet (Pennisetum glaucum (L.)
R. Br.) is one of the important cereal crops with nutritious grains and lower
water and energy footprints in addition to the capability of growing in some of
the harshest and most marginal environments of the world. In this highly
cross-pollinating crop, heterosis was exploited by the development of a
commercially viable cytoplasmic male-sterility (CMS) system involving a
three-lines breeding system (A-, B- and R-lines). The first set of male-sterile
lines, i.e., Tift 23A and Tift18A, were developed in the early 1960s in Tifton,
Georgia, USA. These provided a breakthrough in the development of hybrids
worldwide, e.g., Tift 23A was extensively used by Punjab Agricultural
University (PAU), Ludhiana, India, for the development of the first
single-cross pearl millet hybrid, named Hybrid Bajra 1 (HB 1), in 1965. Over
the past five decades, the pearl millet community has shown tremendous
improvement in terms of cytoplasmic and nuclear diversification of the hybrid
parental lines, which led to a progressive increase in the yield and
adaptability of the hybrids that were developed, resulting in significant
genetic gains.
Lately, the whole genome sequencing of Tift 23D2B1 and
re-sequencing of circa 1000 genomes by a consortium led by the International
Crops Research Institute for the Semi-Arid Tropics (ICRISAT) has been a
significant milestone in the development of cutting-edge genetic and genomic
resources in pearl millet. Recently, the application of genomics and molecular
technologies has provided better insights into genetic architecture and
patterns of heterotic gene pools. Development of whole-genome prediction models
incorporating heterotic gene pool models, mapped traits and markers have the
potential to take heterosis breeding to a new level in pearl millet. This
review discusses advances and prospects in various fronts of heterosis for
pearl millet.
Keywords: genome sequence;
genomic selection; heterosis; heterotic gene pools; hybrid vigor; pearl millet.
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Created on Nov 1st 2021 13:26. Viewed 285 times.