Abstract
Capsicum baccatum, commonly known as ají, has been reported as a source of variation for many different traits to improve common pepper (C. annuum), one of the most important vegetables in the world. However, strong interspecific hybridization barriers exist between them. A comparative study of two wide hybridization approaches for introgressing C. baccatum genes into C. annuum was performed: i) genetic bridge (GB) using C. chinense and C. frutescens as bridge species; and, ii) direct cross between C. annuum and C. baccatum combined with in vitro embryo rescue (ER). A diverse and representative collection of 18 accessions from four cultivated species of Capsicum was used, including C. annuum (12), C. baccatum (3), C. chinense (2), and C. frutescens (1). More than 5000 crosses were made and over 1000 embryos were rescued in the present study. C. chinense performed as a good bridge species between C. annuum and C. baccatum, with the best results being obtained with the cross combination [C. baccatum (♀) × C. chinense (♂)] (♀) × C. annuum (♂), while C. frutescens gave poor results as bridge species due to strong prezygotic and postzygotic barriers. Virus-like-syndrome or dwarfism was observed in F1 hybrids when both C. chinense and C. frutescens were used as female parents. Regarding the ER strategy, the best response was found in C. annuum (♀) × C. baccatum (♂) crosses. First backcrosses to C. annuum (BC1s) were obtained according to the crossing scheme [C. annuum (♀) × C. baccatum (♂)] (♀) × C. annuum (♂) using ER. Advantages and disadvantages of each strategy are discussed in relation to their application to breeding programmes. These results provide breeders with useful practical information for the regular utilization of the C. baccatum gene pool in C. annuum breeding.
Highlights
Crop relatives have been used for decades for breeding, in particular to transfer genes of resistance or tolerance to pests, diseases or abiotic stress to the cultivated species [1, 2]
C. pubescens and C. baccatum represent separate taxons from the annuum complex and, they have been widely grown in the Andean region and Brazil for millennia, they are very rare outside this area nowadays [9, 10]
A total of 18 accessions from four cultivated species of Capsicum were utilized in the present study: C. annuum (12 accessions), C. baccatum (3 accessions), and the bridge species C. chinense (2 accessions) and C. frutescens (1 accession)
Summary
Crop relatives have been used for decades for breeding, in particular to transfer genes of resistance or tolerance to pests, diseases or abiotic stress to the cultivated species [1, 2]. Breeding programmes in the economically important common Capsicum peppers (Capsicum annuum L.) have made little use of related species for breeding as reviewed by Mongkolporn and Taylor [5] This limitation has been mainly due to the presence of different pre-zygotic barriers which avoid fertilization (e.g. pollen-pistil incompatibilities) and/or post-zygotic barriers, which prevent the achievement of fertile hybrids, e.g. embryo/endosperm abortion, hybrid weakness or sterility [6, 7]. Due to prezygotic barriers which prevent the growth of the pollen tube through the style, and possible postzygotic barriers, it does not cross with any of the other four species [9, 11] The latter, commonly known as ají (with white flowers and yellow spots), has showed an extremely low/nil cross compatibility with C. annuum [6], it has been reported as source of variation for a range of traits with potential interest for the genetic improvement of this species. Successful wide hybridization attempts to introgress these traits in C. annuum have been scarce [12, 22]
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