Resistance to early blight of tomato with respect to various parameters of disease epidemics

Abstract

Resistance to early blight in the tomato was assessed by examining various parameters of the progress of the disease. Artificial inoculation and the scoring technique were standardized. Test plants were inoculated with 125 cfu/ ml of a 12-day-old culture of a pathogenic isolate of Alternaria solani. Screening under artificial conditions was more informative than that under natural epidemic conditions. Tomato cultivars CLN-2071-C, CLN-2070-A, BSS-174, and DTH-7 with resistance expressed as slow blighting against four pathogenic isolates of A. solani, were selected for cultivation in disease-prone areas. Disease intensity increased with the age of plants under the same inoculum load. The area under the disease progress curve (AUDPC) was positively correlated with the percentage disease index and negatively with resistance. Calculation of the apparent infection rate (r) was more informative for natural epidemics than for artificial conditions. The sequential apparent infection rate between observation periods was better correlated with disease progress than was the total apparent infection rate between the first and last observations. A double sigmoidal disease progress curve during the same cropping season was characteristic of some varieties when fungal infection took place during the vegetative phase of crop growth.

Tomato early blight (Alternaria solani): the pathogen, genetics, and breeding for resistance

“…Heavily infected fruits frequently drop before they mature. On susceptible genotypes, the calyx and blossom may also be infected (Pandey et al 2003).…”

“…Occasionally the disease curve is bimodal, which could be due to the emergence of new healthy leaves after the first cycle of infection (Pandey et al 2003). Therefore, a once-only evaluation can underestimate or overestimate the actual level of resistance of a particular host, and field assessments must be based on several observations over time that are used to calculate the area under the disease progress curve (AUDPC).…”

“…Therefore, a once-only evaluation can underestimate or overestimate the actual level of resistance of a particular host, and field assessments must be based on several observations over time that are used to calculate the area under the disease progress curve (AUDPC). The AUDPC integrates the host, pathogen, and environmental effects during the epidemic (Pandey et al 2003).…”

Impact of Weather Parameter on Early Blight Epidemiology in Tomato Crop

“…The standard method was used for other cultural practices. The disease severity was recorded from 20-tagged plants on 0-5 scale as suggested by Pandey et al, (2003).The disease severity index (DSI) was calculated using the formula (Wheeler, 1969).…”

VARIATION IN AGGRESSIVENESS AND AFLP AMONG Alternaria solani ISOLATES FROM INDONESIA

“…Leaves that were not completely unfurled during the inoculation were not assessed. The disease scales were converted into percentage of early blight index (PEBI) for each plant using the following formula (Pandey et al 2003): PEBI = (sum of all ratings × 100)/(no. of leaves sampled × maximum disease scale).…”