Obtaining pepper F2:3 lines with resistance to the bacterial spot using the pedigree method

Abstract

The economic importance of sweet pepper is rising in Brazil and abroad. Nevertheless, diseases, such as the bacterial spot (Xanthomonas campestris pv. vesicatoria or Xanthomonas euvesicatoria) jeopardize its yield. An efficient method for controlling the disease is the use of resistant varieties. The objective of this work was to select sweet pepper genotypes with resistance to the bacterial spot on a segregating population (Capsicum annum accessions UENF 1421, susceptible, x UENF 1381, resistant), advanced using the pedigree method. Three selection procedures, " selection between and within families" , " mass selection" , and " combined selection" were compared. Fifty-six F2:3 families (40 plants per family) were planted in the field, without replication. Ten plants of each genitor were used as controls in each line, between families. Plants were inoculated (isolate ENA 4135) 42 days after transplanting and leaves were collected and digitalized three weeks after. Images were analyzed to obtain the percentage of leaf tissue damaged (RMB%) and leaf damaged area (RMBcm²). Since similar results were achieved using either RMB% or RMBcm², we suggest using RMB% in further studies instead of RMBcm², which values remain close to zero. Eleven lines had promising results when selection within and among F2:3 families was used (genetic gains = 40%). Considering mass selection, eleven individuals (three lines), were selected (genetic gains = 28%). Based on combined selection, three lines (11 individuals within the lines) were selected (genetic gains = 266%). There were three lines (105, 475, and 517) in common between selection among and within families and mass selection, and another three (111, 260, and 313), between selection among and within families and combined selection. Combined selection was 6.6 (RMB%) and 6.5 (RMBcm²) times more efficient than selection among and between families, and 9.6 (RMB%) and 9.5 (RMBcm²) times more efficient than mass selection.