An attempt was made to associate marker-based clusters with forage quality traits, to enable breeders select parents for crossing purposes in forage breeding programs. A low but positive significant correlation found between SSR based genetic distance (GD between parents of hybrid) and heterosis for most of the forage traits indicated that SSR-based GD can be used for predicting heterosis for GFY, DFY and CP in pearl millet.
GEODIST RADIAN STATA TRIAL
Eighty hybrids evaluated in multi-location trial along with their parents for forage traits showed that significant heterosis can be realized for forage traits. Across two cuts, crude protein (CP) varied from 11% to 15%, while in vitro organic matter digestibility (IVOMD) varied from 51% to 56%. Significant variations were found for forage related morphological traits at different cutting intervals (first and second cut) in hybrid parents. Most of the seed and pollinator parents clustered into two clear-cut separate groups based on marker based genetic distance. Genetic diversity of 130 forage-type hybrid parents of pearl millet was investigated based on multiple season data of morphological traits and two type of markers: SSRs (Simple sequence repeats) and GBS identified SNPs (Genotyping by sequencing-Single nucleotide polymorphism). Regarding the unpredictability and intensity of biotic and abiotic stresses, heterogeneous population and topcross hybrids appear most suitable to sustainably increase pearl millet yields and give maximal benefits to WA farmers. Molecular markers supporting cytoplasmic male sterility (CMS) introgression are available, and genomic tools can improve hybrid prediction. Building on respective groups, reciprocal recurrent selection in combination with integration of further adapted genetic resources is recommended to systematically diversify and build up the heterotic parental pools, increase combining ability to the opposite group, and create a continuous output of OPV and hybrid varieties. Diversity and combining ability studies pointed at eastern and western WA as promising starting points for systematic development of heterotic groups. Observed average better‐parent heterosis ranged from 4–18% and 0–88% in population and topcross hybrids, respectively, across several studies, and the yield stability was comparable with or better than the parental OPVs. This review is therefore meant to summarize information on pearl millet hybrid breeding with emphasis on WA and to suggest a unified strategy as a way forward.
Encouraging initial results with experimental pearl millet population or topcross hybrids and the available diversity in its WA center of origin offer a great opportunity for a regionally coordinated hybrid breeding approach. Smallholder farmers in Sahelian West Africa (WA) grow pearl millet as a staple cereal in harsh and highly variable environments, predominantly relying on landraces or open‐pollinated varieties (OPVs) with an average grain yield of 648 kg ha−1 (2017). Tapping the regional pearl millet genetic diversity seems therefore beneficial for hybrid breeding to increase pearl millet productivity in WA. Their offspring, especially PE02987 × PE05344 and Kapelga × ICMV IS 92222, exhibited a high and stable GY across all test environments. Parental populations PE02987 (Senegal), PE05344 (Mali) and ICMV IS 92222 (Niger) showed large positive GCA for GY. Its lack of adaptation contributed to the predominance of additive effects in the present germplasm set. The parental population from Sudan (IP8679) had strongly negative GCA for GY. Thus, early selection for parental per se performance would be rewarding. General combining ability (GCA) was significant across test environments as reflected by high heritability estimates and high GCA:SCA variance ratios. Grain yield (GY) exhibited an average panmictic mid-parent heterosis (PMPH) of 24%, ranging from -1.51% to 64.69%. The genotypes were evaluated in six environments in WA in 2007. Hence, our objectives were to estimate the combining ability of seven genetically diverse Sahelian pearl millet populations from Senegal, Mali, Benin, Burkina Faso, Niger, Sudan and Nigeria and the heterosis and stability of their 42 diallel-derived population hybrids to inform pearl millet hybrid breeding. Knowledge of combining ability patterns and quantitative-genetic parameters is required for an efficient development of hybrid varieties.
Breeding for high yield and stability is a major challenge in the harsh environments of WA but could be tackled by hybrid breeding. Pearl millet is an important food-security crop to smallholder farmers in West Africa (WA).
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