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University of Ghana (2013)

Genetic Analysis of Earliness and Drought Tolerance in Groundnut (Arachis hypogaea L.) in Niger

Mamadou, C.A.

Titre : Genetic Analysis of Earliness and Drought Tolerance in Groundnut (Arachis hypogaea L.) in Niger

Auteur : Mamadou, C.A.

Université de soutenance : University of Ghana

Grade : Doctor of Philosophy (PhD) 2013

Résumé partiel
End-of-season drought, characterized by low and erratic rainfall, is the most important factor limiting groundnut (Arachis hypogaea L.) production in Niger. Information about farmers’ varietal preferences and production constraints are limited. Genotypes have not yet been screened for earliness and tolerance to end-of-season drought. Data on combining ability and heritability estimates are not available. Development of varieties that have better ability to use limited available water or that mature early and avoid drought is needed. A participatory rural appraisal (PRA) through Focus Group Discussion session was conducted in 2011 to assess farmers’ perceptions on groundnut production constraints and to gather information on preferences for elite groundnut varieties. One hundred and fifty genotypes were screened in 2010 under well watered conditions in an alpha lattice design in an unreplicated trial to select five early maturing parental lines for genetic studies. One hundred intermediate maturing genotypes were selected and, evaluated in 2011 off- season under both well watered and end-of-season drought conditions in an alpha lattice design with two replications to select five drought tolerant parental lines for genetic studies. The selected parental lines were crossed with the three farmers preferred varieties in a North Carolina II mating design and 7 F 4 populations for earliness and 7 F 4 populations for drought tolerance were developed by selfing. Seven F 3 populations were evaluated for earliness and agronomic traits in RCBD replicated three times under well watered conditions. Seven F 3 and F 4 populations were evaluated for drought related traits in RCBD replicated three times. Data recorded included : % emergence, 50% plants flowering, pod yield, seed weight, seed number, shelling %, pod length, maturity index, and biomass. Among the physiological traits measured were SPAD chlorophyll meter reading and harvest index. The data were analyzed using appropriate statistical procedures and experimental designs. The PRA survey revealed that drought was a major production constraint followed by low soil fertility. In the study regions, the varieties 55-437, RRB and JL24, were the most grown. There was variation among the genotypes screened for the various characteristics. The PCA analysis revealed that 79.62% of the total variation among the genotypes was explained by maturity, pod yield, biomass, harvest index and 50% plants flowering. Out of the 150 genotypes, two extra early maturing genotypes (75 days) Chico and ICIAR19BT, three early maturing genotypes (80 days) ICG3584, 796, and ICGV02022 and five drought tolerant genotypes ICGV- SM99511, Tainan-9, ICG11249, ICG6703 and ICGIS01820 were identified. In the early maturity experiment, the analysis of variance for the eight traits revealed significant differences (P ≤ 0.01 and P ≤ 0.05) among parents for pod yield, seed weight, pod length and maturity index. Crosses showed highly significant differences for pod yield (P ≤ 0.001), seed number (P ≤ 0.001), shelling % (P ≤ 0.01) and pod length (P ≤ 0.05). Female and male General combining ability (GCA) mean squares were highly significant (P ≤ 0.01) only for pod yield. GCA mean squares (119.26) for females were greater than males GCA mean square (32.11) for pod weight indicating that the major contribution to additive variance for this trait was due to the female parents. Specific combining ability (SCA) mean squares differed significantly (P ≤ 0.01 and P ≤ 0.05) for seed number and shelling percentage indicating the importance of both additive and non-additive variance for these characters. Chico, ICIAR19BT, 55-437 and RRB were the best general combiners. The estimates of phenotypic coefficient of variation (PCV) were greater than genotypic coefficients of variation (GCV) for all the traits studied. None of the traits recorded high PCV and GCV. PCV ranged from 4.36 to 19.34% and GCV from 2.02 to 11.99%. Narrow sense heritability estimates ranged from 35.4 to 95.5% ; for days to emergence (95.5%), pod yield (85%), shelling percentage (84.3%), seed number (80%) and 50% plants flowering (72%).

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