Inheritance of leaf resistance to Sclerotinia sclerotiorum in Brassica napus and its genetic correlation with cotyledon
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Inheritance of leaf resistance to Sclerotinia sclerotiorum in Brassica napus and its genetic correlation with cotyledon resistance Muhammad Azam Khan . Wallace Cowling . Surinder Singh Banga . Ming Pei You . Vikrant Tyagi . Baudh Bharti . Martin J. Barbetti
Received: 23 July 2020 / Accepted: 15 October 2020 Ó Springer Nature B.V. 2020
Abstract Research to control yield losses from Sclerotinia (Sclerotinia sclerotiorum) in oilseed rape (Brassica napus) has focused on stem resistance. However, resistance to leaf infection against this pathogen would also be beneficial, both in limiting additional plant leaf damage and in reducing inoculum build up within-crop and resultant spread onto stems. Three B. napus breeding populations, C2 (NC-8 9 RQ-001-NCA-8 NC2-7), C5 (cv. Charlton 9 RQ-001NCA-8 NC2-7) and C6 (cv. Charlton 9 NC4-5), were screened for leaf resistance (based on mean lesion diameter) under controlled environment conditions. Each population consisted of parents (P1 and P2), F1, F2, BC1P1 and BC2P2, except for C5 that lacked BC1P1. Moderate broad sense heritability for leaf resistance (0.45) to S. sclerotiorum was only found in population C6, where genetic variance was mostly non-additive. Analyses of generation means and M. A. Khan W. Cowling M. P. You M. J. Barbetti (&) UWA School of Agriculture and Environment, and The UWA Institute of Agriculture, The University of Western Australia, 35 Stirling Highway, Perth, WA 6009, Australia e-mail: [email protected] M. A. Khan University of Agriculture, Faisalabad 38000, Pakistan S. S. Banga V. Tyagi B. Bharti Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana, Punjab 141004, India
variances indicated that both dominance and complex epistatic interactions were present in C6. Bivariate analysis revealed a positive genetic covariance between the non-additive effects for mean leaf lesion and cotyledon lesion diameters, and significant negative covariance of residuals, which supports a common genetic control of cotyledon and leaf resistance to S. sclerotiorum. These results will guide breeders in selection and development of genotypes with both cotyledon and leaf resistance against this important pathogen worldwide. Keywords Sclerotinia sclerotiorum Brassica napus Additive-dominance model Bivariate
Introduction Sclerotinia stem rot (Sclerotinia sclerotiorum) is a devastating disease affecting host oilseed rape (Brassica napus L.) and mustard (B. juncea L.) worldwide, including in Australia, North America, China and Europe. In Australia, it causes up to 24% yield loss (Garg et al. 2008), translating into an estimated AU$10 million yield loss per annum (Murray and Brennan 2012). The mode of germination for this pathogen is usually myceliogenic or carpogenic; the former of these causes direct stem infection, generally from soil, while the latter infects through airborne
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ascospores (Singh et al. 2008a, b, 2010). In Western Australia, up to 29%
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