Inheritance of resistance to downy mildew in sweet basil

Robert M. Pyne, Adolfina R. Koroch, Christian A. Wyenandt, James E. Simon

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Sweet basil (Ocimum basilicum) is one of the most economically important culinary herbs in the world, yet global production has become increasingly challenging due to the destructive disease downy mildew (Peronospora belbahrii). Although multiple sources of resistance have been identified, there are no resistant sweet basil cultivars with a commercially acceptable chemotype and phenotype available. The commercial basil cultivar Mrihani (MRI) was identified as resistant and crossed with a Rutgers University susceptible sweet basil inbred line (SB22) to generate a full-sibling family. To determine the mode of inheritance for resistance to downy mildew in basil, six related generations of the MRI × SB22 family were evaluated using a disease severity index (DSI) at northern and southern New Jersey locations over 2 years. All siblings in the F1 and BC1P2 generations were resistant (0.33 > DSI) providing strong evidence that inheritance of resistance from MRI was conferred by dominant alleles. Segregation ratios in the F2 and backcross to the susceptible parent (BCP1) generations demonstrated chi-square goodness of fit to the two-gene complementary (F2: P = 0.11, BC1P1: P = 0.04) and recessive epistatic (F2: P = 0.03, BC1P1: P = 0.63) models. Further analyses of gene effects using a weighted six-parameter scaling test provided evidence that nonallelic additive × additive and additive × dominant gene effects were highly significant (P < 0.001) and resistance reducing. This is the first report of heritable genetic resistance that can be introduced to sweet basil without the issue of sterility barriers. Plant breeding strategies using the MRI × SB22 family should exploit dominant gene action and remove recessive, resistance-reducing alleles from the population.

Original languageEnglish (US)
Pages (from-to)396-403
Number of pages8
JournalJournal of the American Society for Horticultural Science
Volume140
Issue number5
DOIs
StatePublished - Sep 1 2015

All Science Journal Classification (ASJC) codes

  • Genetics
  • Horticulture

Keywords

  • Digenic epistasis
  • Genetic resistance
  • Major genes
  • Ocimum basilicum
  • Peronospora belbahrii
  • Plant breeding

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