Phenotypic and molecular evaluation of a recurrent selection program for a polygenic resistance to Phytophthora capsici in pepper

Abstract

'Criollo de Morelos 334' (CM334) is one of the most promising sources of resistance to Phytophthora capsici in pepper. This Mexican accession is distantly related to bell pepper and its resistance displays a complex inheritance. The QTLs involved in resistance to P. capsici were previously mapped. In order to transfer the resistance factors from CM334 into a bell pepper genetic background, a modified, recurrent breeding scheme was initiated. The breeding population was divided into three sub-populations which were screened by distinct phenotypic tests of increasing severity. The plants from the first sub-population were screened with low-severity tests and backcrossed to the susceptible bell pepper; the plants from the second and third sub-populations were screened by more severe resistance tests and crossed with the plants from the first and second sub-populations, respectively. In this study, the phenotypic data for the three sub-populations during five screening/intermating cycles were analysed. In parallel, the changes in allelic frequencies at molecular markers linked to the resistance QTLs were reported. The resistance phenotype and allelic frequencies strongly depended on the sub-population and screening severity. Regarding allelic frequency changes across the selection cycles, a loss of resistant QTL alleles was observed in the first sub-population, particularly for the low-effect QTLs, whereas a better conservation of the resistant QTL alleles was observed in the two other sub-populations. The same trend was observed in the phenotypic data with an increasing resistance level from the first to the third sub-populations. The changes in the allelic frequencies of loci not linked to resistance QTLs and for horticultural traits across the breeding process indicated that the recovery of the recipient parent genome was not significantly affected by the selection for resistance.

The inheritance of late blight resistance derived from Solanum habrochaites

“…Race-specific and polygenic resistance have been characterized and exploited in breeding providing an efficient control of disease severity (Thabuis et al 2004). The high variability in P. infestans populations throughout the world, especially for virulence, has made race-specific resistance genes almost useless in disease control (Andrivon 1994).…”

Effects of grafting combinations on the nutritional composition of pepper fruit

“…In previous work [12] we tested, as putative rootstocks of sweet pepper, the pepper hybrids 'Foc' and 'Charlo' − which share the parent Serrano Criollo de Morelos (SCM334) [10], a common source of resistance to Phytophthora capsici Leonian [24,25]. Both hybrids showed resistance to P. capsici and good agronomic performance [12].…”

Mapping of the ms8 male sterility gene in sweet pepper (Capsicum annuum L.) on the chromosome P4 using PCR-based markers useful for breeding programmes

“…NuMex RNaky indicate that the ms8 locus is located on the lower arm of the pepper chromosome P4. In addition to the ms8 locus, a number of other important traits of pepper were mapped to the P4 chromosome: the pvr2 locus for PVY resistance (Caranta et al 1997;Lefebvre et al 2002), the C2 locus for fruit color (Thorup et al 2000), QTLs for fruit weight and shape (Barchi et al 2009;Zygier et al 2005), and QTL for Phytophthora capsici resistance (Thabuis et al 2004). It has to be considered in the breeding programmes aimed to introgress ms8 gene into the different breeding lines.…”