Use of Genomic Estimated Breeding Values Results in Rapid Genetic Gains for Drought Tolerance in Maize.

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More than 80% of the 19 million ha of maize ( L.) in tropical Asia is rainfed and
prone to drought.

The breeding methods for improving drought tolerance (DT), including genomic selection (GS), are geared to increase the frequency of
favorable alleles. Two biparental populations (CIMMYT-Asia Population 1 [CAP1] and CAP2) were generated by crossing elite Asian-adapted yellow inbreds (CML470
and VL1012767) with an African white drought-tolerant line, CML444. Marker effects of polymorphic single-nucleotide polymorphisms (SNPs) were determined
from testcross (TC) performance of F families under drought and optimal conditions. Cycle 1 (C1) was formed by recombining the top 10% of the F families 
based on TC data. Subsequently, (i) C2[PerSe_PS] was derived by recombining those C1 plants that exhibited superior per se phenotypes (phenotype-only selection),
and (ii) C2[TC-GS] was derived by recombining a second set of C1 plants with high genomic estimated breeding values (GEBVs) derived from TC phenotypes of F
families (marker-only selection). 

All the generations and their top crosses to testers were evaluated under drought and optimal conditions. Per se grain yields 
(GYs) of C2[PerSe_PS] and that of C2[TC-GS] were 23 to 39 and 31 to 53% better, respectively, than that of the corresponding F population. The C2[TC-GS]
populations showed superiority of 10 to 20% over C2[PerSe-PS] of respective populations. Top crosses of C2[TC-GS] showed 4 to 43% superiority of GY over that
of C2[PerSe_PS] of respective populations. 

Thus, GEBV-enabled selection of superior phenotypes (without the target stress) resulted in rapid genetic gains
for DT.

Copyright © 2017 Crop Science Society of America.

Vivek BS, Krishna GK, Vengadessan V, Babu R, Zaidi PH, Kha LQ, Mandal SS,
Grudloyma P, Takalkar S, Krothapalli K, Singh IS, Ocampo ETM, Xingming F,
Burgueño J, Azrai M, Singh RP, Crossa J.

Plant Genome. 2017 Mar;10(1). doi: 10.3835/plantgenome2016.07.0070.

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