Combinations of a host resistance gene and the CI gene of turnip mosaic virus differentially regulate symptom expression in Brassica rapa cultivars

Abstract

In the pathosystem of Brassica rapa and Turnip mosaic virus (TuMV), the type of symptoms expressed by susceptible plants are determined by the gene combinations between the host cultivar and virus strain. In this study, we found that the resistant reaction and symptoms such as systemic lethal necrosis, leaf malformation and mosaic were differentially determined, depending on the combinations of the genotypes for a host locus or two closely linked host loci and the viral CI gene. Systemic necrosis caused by TuMV-UK1 on some B. rapa subsp. pekinensis cultivars is induced in conjunction with a recessive gene rnt1-2 (resistance and necrosis to tumv 1-2), which is allelic or closely linked to TuMV resistance gene Rnt1-1 on chromosome R6. rnt1-2 is incompletely recessive to rnt1-3, which does not cause any necrotic responses. The genotype rnt1-2/rnt1-3 caused a mild necrosis along leaf veins of severely malformed leaves. A spontaneous mutant TuMV-UK1 (UK1m) with the amino acid substitution (V1827E) in CI broke Rnt1-1 resistance and altered the systemic necrosis and leaf malformation induced by rnt1-2. This single amino acid in the CI protein of UK1 was also associated with severe mosaic and abnormal leaf development, perhaps interacting with a host unknown factor(s). To clarify the relationship of Rnt1-1 with TuRB01b, which was previously reported as a TuMV-UK1 resistance gene on chromosome R6, the B. rapa cultivar Tropical Delight carrying TuRB01b was inoculated with UK1m or the infectious UK1 clone with the CI V1827E mutation. Because Tropical Delight showed resistance to both mutants, Rnt1-1 might be different from TuRB01b.3

An update on the arsenal: mining resistance genes for disease management of Brassica crops in the genomic era

“…TuRB03, a monodominant gene controlling pathotype 4 resistance, was localized to a 7.9 cM region on N6 in B. napus 24 . retr01 represents the first mapped recessive gene in Brassica species 25 ; other recessive genes from B. rapa include rnt1 and trs, which were mapped to R6 and A4, respectively 26,27 . Using bulked segregant analysis by sequencing (BSA-seq), Shopan et al 28 identified another recessive gene, retr03, in B. juncea.…”

TuMV management for brassica crops through host resistance: retrospect and prospects

“…Fujiwara et al . () found that resistance symptoms such as systemic lethal necrosis, leaf malformation and mosaic were differentially expressed in B. rapa infected by the TuMV isolate UK1, according to the genotype at the host locus rnt1‐2 / rnt1‐ 3. In 2013, Qian et al .…”

Correlation Analysis of Expression Profile and Quantitative iTRAQ-LC-MS/MS Proteomics Reveals Resistance Mechanism Against TuMV in Chinese Cabbage (Brassica rapa ssp. pekinensis)

“…In Brassica napus, TuRB01 and TuRB02 were initially mapped (Walsh et al, 1999), afterward, TuRB04 and TuRB05 were identified by Jenner et al (2002Jenner et al ( , 2003, followed by TuRB03 (Hughes et al, 2003). In Brassica rapa, ConTR01, retr01 (Rushholme, 2000;Walsh and Jenner, 2002;Rusholme et al, 2007), BcTuR3 (Ma et al, 2010), Rnt1-1 (Fujiwara et al, 2011), TuRBCH01 (Xinhua et al, 2011), retr02 (Qian et al, 2013), and TuRB01b (Lydiate et al, 2014), have been identified, as well as retr03 (Shopan et al, 2017) in Brassica juncea. Moreover, numerous disease resistance (R) genes also have been identified including the NBS-LRR gene family.…”