Performance of interspecific derivatives of Arachis species in Uganda and identification of quantitative trait loci associated with resistance to groundnut rosette and late leaf spot
Essandoh, Danielle Ama
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The study was conducted to determine the usefulness of interspecific derivatives of Arachis from Advanced backcross lines and chromosome segment substitution lines derived from four different wild species. The objectives of this study were to i) Evaluate Interspecific derivatives of groundnuts for yield and yield component traits in Uganda ii) Determine the response of interspecific derivatives of groundnuts to groundnut rosette disease (GRD) and late leaf spot (LLS) infection and iii) Identify candidate genes associated with resistance to late leaf spot and groundnut rosette disease in Interspecific derivatives of groundnuts. A total of 376, three local checks and one recurrent parent, Fleur 11 were evaluated at National Semi-Arid Resources Research Institute (NaSARRI) in Serere under controlled and natural conditions and also in Nakabango, in Jinja under natural field conditions. A 19×20 alpha lattice experimental design was used. Data was collected on yield and its component traits as well as phenotypic traits. The pooled analysis of variance revealed that genetic variability for quantitative traits was influenced by genotype, environment as well as genotype × environment interaction effects. Several lines out-performed the best checks for yield traits which indicates the usefulness of interspecific derivatives as parents in crosses to broaden the genetic base of cultivated groundnut. Individuals from population (Fleur11 x (A. valida × A. duranensis)4x were particularly useful as they showed high to moderate broad sense heritability estimates with high to moderate genetic advance of the mean for all traits except number of pods per plant and shelling percentage. The interspecific derivatives were evaluated across two hotspots of GRD and LLS diseases; NaSARRI and Nakabango for two seasons. Moderate levels of resistance were recorded for late leaf spot and four interspecific lines from (A. valida ×A. duranensis) and two from (A. batizocoi and A. duranensis) showed the highest resistance to LLS and hence are recommended for use in groundnut breeding programmes targeting LLS resistance. Similarly, 5% of the lines were resistant to GRD, with lines from population (Fleur11 x (A. valida x A. duranensis) 4x recording the highest number of these lines. Interspecific lines, B7-32-8-4 and B7-25-22-8 from F (Av × Ad) were resistant to both LLS and GRD in high-yielding background and are best recommended for breeding purposes. As expected, yield and GRD incidence were negatively correlated. A molecular map was developed using 1440 SNP in the (Fleur11 x (A. batizocoi x A. duranensis)4x population. QTL analysis revealed two resistance QTLs for LLS on linkage group, LG B03; Araip.B04_17705669 (phenotypic variance explained, PVE= 9.43) and Araip.B04_9708846(PVE=9.60%). Four resistance QTLs were identified for GRD on LG A08(PVE=7.90), B01(PVE=11.04), B04(PVE=12.56) and B05(PVE=11.51). The QTLs identified for GRD and LLS are novel and can be used to develop markers that could be validated for Marker Assisted Selection in groundnut breeding efforts. With the exception of GRD severity, all the other lower trait values for GRD and LLS disease were contributed by the wild alleles. This finding of the wild alleles’ contribution for GRD and LLS disease resistance offers new opportunities for exploiting the wild Arachis species for cultivated groundnut crop improvement.