Epidemiology of beet necrotic yellow vein virus in sugar beet at different initial inoculum levels in the presence or absence of irrigation

Abstract

Abstract.A field experiment was set up in 1988 to study the development of rhizomania disease of sugar beet at different inoculum levels of beet necrotic yellow vein virus (BNYVV) in soil. Five, tenfold different, inoculum levels were created by addition of the approximate amounts of 0, 0.5, 5, 50 and 500 kg infested soil per ha (the latter corresponding to 0.01% v/v calculated to the tillage layer). A drip irrigation treatment was applied to study the influence of soil moisture on disease. Susceptible sugar beet, cv. Regina, was grown for three consecutive years.In the first year, root symptoms were not observed, but BNYVV-infected plants were detected by ELISA in low numbers at all inoculum levels at harvest. After late drilling in 1989, high numbers of infected plants, up to 90-100% in plots with the highest inoculum level, were detected already in June. Root symptoms were also observed from June onwards. In both these years disease incidence increased in time and was significantly influenced by the initial inoculum level. In the third year, the whole field was heavily diseased, and only for the non-irrigated plots incidence differed for different initial inoculum levels. The expression of symptoms by BNYVV-infected plants was influenced by initial inoculum level, thus by the amount and timing of primary infection.Root weight at harvest was not affected, but sugar content decreased with increasing inoculum level already in 1988, leading to a reduction in sugar yield of 10% at the highest inoculum level. In 1989, both root weight and sugar content decreased progressively with increasing inoculum level, resulting in sugar yield reductions of 11-66% (down to approximately 3000 kg ha -1) for low to high inoculum levels compared to the control. As the control plots became contaminated, all yields were low in 1990, still showing a decrease with increasing inoculum level in the non-irrigated plots, but an overall mean sugar yield of 3323 kg ha -1 for the irrigated ones.Sodium and c~-amino nitrogen content of the root, additional quality parameters determining extractability of sucrose, showed an increase and decrease, respectively, with increasing initial inoculum level already in the first year. The relative differences in contents compared to those from the control were largest for Na content. A significant negative correlation was found between Na (mmol kg -I root) and sugar content (% of fresh weight); linear for 1988, exponential for 1989 and 1990. In spring 1989, the infestation of individual plots was assessed using a quantitative bioassay estimating most probable numbers (MPNs) of infective units of BNYVV per 100 g 20 dry soil. The relationship between the MPNs determined and root weight, sugar content and sugar yield at harvest could be described by Gompertz curves. The increase in disease incidence with increasing MPN in 1989 was adequately fitted with a logistic equation.

Evaluation of rhizomania infection on sugar beet quality in multi‐year field assessment

“…The root yield and sugar yield of susceptible cultivars 1114 and 1213 were severely reduced (about 2.5 times, Figure 5 ). Such root yield reduction is in conformity with the similar finding made earlier by Tuitert ( 1994 ), in which root yield decreased from 70 t/ha under normal condition to 26 t/ha under high rhizomania infection. An increase in root yield could have been expected under low incidence of the disease.…”

“…According to the results derived from the Spearman correlation matrix (Figure 3 ), positive and highly significant correlations were observed between root yield, sugar yield, white sugar yield, sugar content, white sugar content, and extraction coefficient of sugar. However, the above‐mentioned traits showed a negative correlation with sodium, potassium, amino‐N, and molasses sugar, as also reported by Heijbroek ( 1989 ), Tuitert ( 1994 ), and Ahmadi et al. ( 2022 ), under rhizomania stress.…”

“…Sodium content can be suggested as a sensitive indicator of rhizomania, showing significant variation at low and high infection levels (1.82 in Mashhad versus 4.66 meq.100/g in Shiraz). The present results are in agreement completely with those reported by Heijbroek (1989), Tuitert (1994), Kuzevski et al (2000), and Campbell et al (2008) that under rhizomania infection, sodium and invert sugar accumulation increases in the root. An increase in potassium content (1.28 times) was observed with an increase in infection level, especially in Shiraz.…”

“…In some trials in Shiraz, the adjusted mean of sugar content was high, which is in contrast to other studies (Henry, 1996 ; Kuzevski et al., 2000 ), and may be attributed to smaller root size and an increase in dry matter (data not shown). Muller and Gosswein ( 1987 ) cited by Tuitert ( 1994 ) evaluated the effect of irrigation on rhizomania in naturally infected fields. Their results showed that irrigation mounted sugar content.…”

Impact of scale on the effectiveness of disease control strategies for epidemics with cryptic infection in a dynamical landscape: an example for a crop disease

“…Details of the soil-temperature dependence are given by Stacey et al (2004). In brief, data for seven different classes of soil type modulated by insolation (obtained from MAFF) were input to the model on a granularity value of 1 km: the parameter l m , and hence l(T ), were linearly scaled according to soil type-climate class and parameterized from published data (Blunt et al 1991;Tuitert 1994;Tuitert & Hofmeester 1994). The principal qualitative results from the model presented below are robust to fine detail concerning temperature and soil insolation.…”