Govindaraj, M
(2011)
Genetics of grain iron and zinc concentration in pearl millet (Pennisetum glaucum (L.) R. Br.).
PHD thesis, Tamil Nadu Agricultural University.
Supervisors
| Supervisors Name | Supervisors ID |
|---|
| Shanmugasundaram, P | TNAU |
| Rai, K N | ICRISAT |
Abstract
Pearl millet (Pennisetum glaucum (L.) R. Br.) is an important staple crop for
millions of poor rural households in the semi-arid tropics of Asia and Africa. Owing
to its importance for addressing micronutrient malnutrition problem, especially iron
(Fe) and zinc (Zn) concentration, considerable global efforts are under way to
improve its Fe and Zn levels through genetic enhancement. Hence, this dissertation
was aimed at investigating some of the factors that have direct bearing on breeding
efficiency. These includes gene action, combining ability and heterosis for Fe and Zn,
intra-population variance, efficiency of single plant selection, association of grain Fe
and Zn concentration with grain yield and key agronomic traits (1000-grain mass and
flowering), and response to recurrent selection.
In two sets of line x tester studies, parents were observed having a
wide range of genetic variability for both grain Fe (34 -102 mg kg-1) and Zn
(34 - 84 mg kg-1) concentration and this was also reflected in both sets of
hybrids. over two season, ICMB 93222, ICMB 98222, 863 B, ICMB 95333,
ICMB 96333 among seed parents (lines) and IPC 774, IPC 616, IPC 1650,
IPC 1178, IPC 536 and IPC 735 amongst pollen parents (testers) were found
to have >60 mg kg-1 Fe and >55 mg kg-1 Zn concentration. All these inbreds
are designated seed/pollinator parents in elite genetic backgrounds, indicating
good scope for their effective use in hybrid and hybrid parents breeding.
The predictability ratio was around unity for all traits, revealing the
predominance of GCA (additive) variance controlling these traits in both the
sets. Highly significant positive correlation between mid-parent value and per
se performance of hybrids further confirmed the predominant role of additive
gene action for these traits. using both parameters (per se performance and
positive significant gca effect), ICMB 93222, ICMB 98222, 863b, ICMB
91222, IPC 1650, IPC 843, IPC 774, IPC 1178, IPC 689 and IPC 735 were
identified as good general combiners for grain Fe and Zn in hybrid breeding.
similarly, 863 B x IPC 404 and ICMB 95333 x IPC 404 for both grain Fe and
Zn, while ICMB 94111 x IPC 1178 and ICMB 89111 x IPC 843 for grain Zn
had positive significant sca effects. Low level of heterosis over mid-parent
for grain Fe and Zn, no hybrid with significant heterosis over better-parent,
and largely additive genetic variances would imply that there would be little
opportunity, to exploit heterosis for these traits. In fact, to breed hybrids with
high Fe and Zn levels, these micronutrients will have to be incorporated in
both parental lines.
Higher degree of positive and highly significant correlation between S0
plants and their respective S1 progenies both for grain Fe and Zn in all four
populations indicated that individual plant performance for these
micronutrients can be as effectively used for selection as the S1 progeny
performance. Highly significant positive correlation between Fe and Zn revealed
good prospects of concurrent genetic improvement for both micronutrients. Recurrent
selection for high grain Fe and Zn in two populations increased Fe concentration by 2.4%
to 8.0% and Zn concentration by 5.4% to 7.9%. It also increased 1000-grain mass by
4.8% and 14.2%, changed flowering time from -2.3% to 0.8% and had no adverse effect
on grain yield. This would indicate that selection for Fe and Zn concentration can be
made without compromising on grain yield and other agronomic traits such as large seed
size and earliness.
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