Abstract
Pigeonpea (Cajanus cajan L.) is an important food legume crop of rainfed agriculture. Owing to exposure of the crop to a number of biotic and abiotic stresses, the crop productivity has remained stagnant for almost last five decades at ca. 750 kg/ha. The availability of a cytoplasmic male sterility (CMS) system has facilitated the development and release of hybrids which are expected to enhance the productivity of pigeonpea. Recent advances in genomics and molecular breeding such as marker-assisted selection (MAS) offer the possibility to accelerate hybrid breeding. Molecular markers and genetic maps are pre-requisites for deploying MAS in breeding. However, in the case of pigeonpea, only one inter- and two intra-specific genetic maps are available so far. Here, four new intra-specific genetic maps comprising 59–140 simple sequence repeat (SSR) loci with map lengths ranging from 586.9 to 881.6 cM have been constructed. Using these four genetic maps together with two recently published intra-specific genetic maps, a consensus map was constructed, comprising of 339 SSR loci spanning a distance of 1,059 cM. Furthermore, quantitative trait loci (QTL) analysis for fertility restoration (Rf) conducted in three mapping populations identified four major QTLs explaining phenotypic variances up to 24 %. To the best of our knowledge, this is the first report on construction of a consensus genetic map in pigeonpea and on the identification of QTLs for fertility restoration. The developed consensus genetic map should serve as a reference for developing new genetic maps as well as correlating with the physical map in pigeonpea to be developed in near future. The availability of more informative markers in the bins harbouring QTLs for sterility mosaic disease (SMD) and Rf will facilitate the selection of the most suitable markers for genetic analysis and molecular breeding applications in pigeonpea.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-012-1916-5) contains supplementary material, which is available to authorized users.
Highlights
Pigeonpea [Cajanus cajan (L.) Millspaugh] is the fifth most important pulse crop in the world and represents an important component of semi-arid and sub-tropical farming systems (Shanower et al 1999)
Based on the marker polymorphism data, a genetic map based on the inter-specific mapping population (C. cajan ICP 28 9 C. scarabaeoides ICPW 94) with 239 simple sequence repeat (SSR) loci (Bohra et al 2011) and two genetic maps based on the intra-specific mapping populations that segregate for sterility mosaic disease (SMD) viz. ICP 8863 9 ICPL 20097 and TTB 7 9 ICP 7035, with 120 and 78 SSR loci, respectively, were developed (Gnanesh et al 2011)
Genotyping of four new intra-specific mapping populations: ICPB 2049 9 ICPL 99050, ICPA 2039 9 ICPR 2447, ICPA 2043 9 ICPR 3467 and ICPA 2043 9 ICPR 2671 was done in this study using polymorphic SSR markers identified by Bohra et al (ESM Table 1)
Summary
Pigeonpea [Cajanus cajan (L.) Millspaugh] is the fifth most important pulse crop in the world and represents an important component of semi-arid and sub-tropical farming systems (Shanower et al 1999). Pigeonpea is a diploid species (2n = 2x = 22) and its genome comprises of 833.1 Mbp arranged into 11 pairs of chromosomes (see Varshney et al 2012). It is cultivated in 4.6 Mha with a production of 3.49 Mt. Nearly 70 % of the pigeonpea production and 74 % of the pigeonpea area is in India. Pigeonpea is a hardy and drought tolerant crop. Pigeonpea seeds contain about 20–24 % protein and reasonable amounts of essential amino acids making it an important source of dietary protein, mainly in vegetarian-based diets
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