Reducing the build‐up of Plasmodiophora brassicae inoculum by early management of oilseed rape volunteers

Abstract

Clubroot of oilseed rape (OSR), caused by Plasmodiophora brassicae, is a disease of increasing economic importance worldwide. Previous studies indicated that OSR volunteers, Brassica crops and weeds play a critical role in the predisposition of the disease. To determine the effect of timing of foliar application of the herbicide glyphosate or mechanical destruction of OSR volunteers in reduction of clubroot severity and resting spore production, a series of studies was conducted under controlled conditions with a susceptible OSR cultivar and an isolate of P. brassicae. Plants were inoculated by injecting a spore suspension beside the root hairs at growth stage 11–12 (BBCH scale) and were terminated at 7 (early) or 21 (late) days post‐inoculation (dpi). Under controlled conditions, the first symptoms on roots were observed as early as 7 dpi. The early application of glyphosate as well as early mechanical destruction resulted in significant (P ≤ 0.05) reduction in the development of clubroot symptoms, root fresh weight and the number of resting spores⁄g root. Furthermore, the effect of volunteer management on clubroot severity in the succeeding OSR was studied by inoculating plants with the resting spores obtained from treated clubbed roots. Inoculated OSR exhibited root clubs similar to the initial symptoms after 35 dpi. Plants that were inoculated with spore suspension from early treated roots resulted in significant reductions in clubroot incidence and severity. Conversely, plants inoculated with the spore suspension from the late treated roots displayed levels of clubroot similar to the plants inoculated with the spore solutions of positive controls.

Greenhouse Evaluation of Clubroot Resistant-Brassica napus cv. Mendel and Its Efficacy Concerning Virulence and Soil Inoculum Levels of Plasmodiophora brassicae

“…In contrast to the less virulent pathotype, growing plants in soil infested with the high virulent P. brassicae isolate induced the most rapid increase in root fresh weight, resulting in a statistically significant increase in the number of new resting spores inside the roots. These findings were very similar to our previous study under controlled conditions, where we showed that the first symptoms of clubroot are observed as early as 7 days post-inoculation, and that the severity of symptoms and the root fresh weight of inoculated plants both increased over time and were strongly correlated with higher numbers of pathogen resting spores [25].…”

“…Besides the susceptible oilseed rape crop, oilseed rape volunteer seedlings as well as other Brassica crops and weeds can play a critical role in the maintenance of resting spores in infested fields. As such, early destruction of oilseed rape plants and volunteers in clubroot-infested fields has been shown to limit the increase of P. brassicae resting spore numbers in the soil [ 25 , 26 , 27 , 28 , 29 ].…”

QTL Mapping and Inheritance of Clubroot Resistance Genes Derived From Brassica rapa subsp. rapifera (ECD 02) Reveals Resistance Loci and Distorted Segregation Ratios in Two F2 Populations of Different Crosses

“…The erosion of the effectiveness of CR genes has also occurred in cruciferous vegetables in Asia ( Bhattacharya et al, 2014 ; Chai et al, 2014 ). The elevated infection in clubroot-resistant cultivars and volunteers would lead to increased spore load of the pathogen in the soil ( Zamani-Noor and Rodemann, 2017 ). Hence, clubroot remains a huge problem and poses by far the most significant threat to cruciferous crop production worldwide.…”

The Phenological Growth Stages of Sapindus mukorossi According to BBCH Scale

“…Vegetative growth spanned three principal stages at our location in southern China: bud (00-09), leaf (10)(11)(12)(13)(14)(15)(16)(17)(18)(19) and shoot (31)(32)(33)(34)(35)(36)(37)(38)(39) development. The growth cycle of S. mukorossi differed from those of longan and lychee trees in southern China; these latter species have a period of dormancy in winter after completing the growth of shoot and then start the reproductive period in the spring of next year.…”