Comparisons of Pathological Responses in Carrot to Root-knot Nematodes

Abstract

Carrot (Dacus carota var. sativus) is one of the top-ten most economically important vegetable crops produced worldwide, and the root-knot nematodes, Meloidogyne spp., are one of the most important pests in the carrot. In Korea, M. hapla and M. incognita are presumed to be the major root-knot nematodes distributing mostly in open carrot fields and greenhouses, respectively. In our study, currently-developed and commercial carrot cultivars and the parental lines were examined for their pathological responses to M. incognita and M. hapla 7 weeks after inoculation with about 1,000 second-stage juveniles (J2) of the nematodes. All the carrot cultivars and lines showed susceptible responses to both nematodes with the gall index (GI) of 2.4–4.4, which were always higher on the carrot plants infected with M. incognita than M. hapla. Gall sizes were remarkably larger with more serious reduction of the root growths in the plants infected with M. incognita than M. hapla, suggesting the carrot lines examined in our study were more susceptible to the former than the latter. In the infection sites of the root tissues, giant cells were more extensively formed, occupying larger stellar regions with the prominent destruction of adjacent xylem vessels by M. incognita than M. hapla. All of these results suggest M. incognita affect more seriously on the carrot plants that are grown in greenhouses, compared to M. hapla that has a major distribution in open carrot fields, which would be used for determining cropping systems based on target nematode species, their damage and pathological characteristics.

Potential Reasons for Prevalence of Fusarium Wilt in Oriental Melon in Korea

“…It is also noticed in our previous studies that remarkably large galls are formed in susceptible carrot lines infected with M. incognita (Seo et al, 2014, 2015). Above-ground symptoms caused by this root-knot nematodes are stunting and yellowing, and sudden wilting especially in hot and dry conditions in summer (Sardanelli et al, 1983).…”

“…In our study, all cucurbitaceous vegetables were susceptible to the root-knot nematode, M. incognita , forming extensively large root-knot galls, which is one of pathological features characteristic to the symptoms formed on vegetable crops infected with M. incognita ( Sardanelli et al, 1983 ). It is also noticed in our previous studies that remarkably large galls are formed in susceptible carrot lines infected with M. incognita ( Seo et al, 2014 , 2015 ). Above-ground symptoms caused by this root-knot nematodes are stunting and yellowing, and sudden wilting especially in hot and dry conditions in summer ( Sardanelli et al, 1983 ).…”

Effects of Soil Textures on Infectivity of Root-Knot Nematodes on Carrot

“…On the other hand, the root penetration rates of M. hapla juveniles were not much increased in 100% sandy soils as compared to M. incognita in our study, although its gall and especially egg-mass formations were significantly increased in the sandy soil over the other soil textures ( Table 1 , 2 ). This suggests that the increased nematode damage (the root-knot gall formation) and reproduction (egg-mass formation) should not be related with the nematode penetration, but with nematode growth and development after infection in the carrot root tissues, which are dependent on the giant cell formation, leading to the enhanced reproduction and root-knot galling ( Seo et al, 2015 ). This may be supported in our study by the results that showed similar penetration rates among b-s mixtures but differentially increased gall and egg-mass formations in 100% sandy soil compared to the other b-s mixtures ( Table 1 , 2 ).…”

“…A commercial carrot cultivar Shinheukjeon-5-chon (hereafter SHC) and the maternal parent of a hybrid carrot line (13–77♀) currently developed in a Carrot Breeding Institute, Korea, were used for screening assays (nematode inoculation) in our experiments as susceptible host plants. The root-knot nematodes M. incognita Race 1 and M. hapla used in our previous studies ( Park et al, 2014 ; Seo et al, 2014 , 2015 ) were also used in this study. Soils used in our study were bed soil (b) (composed of 64.9% coco-peat, 15% peat-moss, 7% zeolite, 10% perlite, 2.6% dolomite, 0.03% wetting agent, and 0.47% N-P-K common fertilizer) and sand (s) at the ratios of 10:0, 7:3, 5:5, 3:7, and 0:10 (hereafter 10:0, 7:3, 5:5, 3:7, and 0:10 b-s mixtures, respectively) were used in this study.…”

Population dynamics of the carrot cyst nematode Heterodera carotae under greenhouse conditions

“…En 2018, México ocupó el lugar 24 entre los más grandes productores de zanahoria a nivel mundial (FAO, 2020;SIAP, 2020). Como ocurre con todos los cultivos, la zanahoria es afectada por un gran número de patógenos, donde destacan, bacterias, hongos, virus, fitoplasmas y nematodos (Davis y Nuñez, 2007;Seo et al, 2015;Groves et al, 2020). El nematodo del quiste de la zanahoria (NQZ), Heterodera carotae Jones (1950a), es un patógeno que se encuentra distribuido en las zonas productoras de zanahoria en Europa, Norteamérica y África del Sur (Subbotin et al, 2010;Yu et al, 2017;Escobar-Avila et al, 2018;Handoo y Subbotin, 2018).…”