A comparison of inoculation methods for determining potato cultivar reaction to black leg

Abstract

SUMMARYTwo methods of inoculating tubers, one by dipping them in an aqueous suspension of Erwinia carotovora subsp. atroseptica, the other by inserting the end of a wooden toothpick charged with undiluted bacteria into the rose‐end near a sprout, were compared over two years for their ability to produce black leg and for their effect on plant growth and yield on a number of cultivars chosen because of expected differences in susceptibility. Although both methods produced a similar rank order for cultivar reaction, the more consistent results were obtained using the toothpick method, clear differences in black leg incidence and yield being evident between the susceptible cultivars Ulster Sceptre and Maris Bard and the more resistant Pentland cultivars. As some cultivars appear more tolerant to black leg than others, yield may be as important a criterion as disease incidence when assessing overall cultivar performance.The inoculation of the base and middle of stems and the infiltration of the bacterium into tubers were also investigated as alternative methods for assessing cultivar susceptibility.

Resistance Behaviour of Potato Cultivars and Advanced Breeding Clones to Tuber Soft Rot Caused by Pectobacterium atrosepticum

“…However, the introgression of the resistance genes into commercial cultivars is difficult because of incompatibility with Solanum tuberosum, complex inheritance, and linkage drag of unwanted traits from the resistant parent (Ahmet et al, 2004;McGrath et al, 2002). Variation for soft rot resistance among S. tuberosum tuberosum cultivars has, however, been shown repeatedly (e.g., Hossain and Logan, 1983;Lapwood and Gans, 1984;Wastie et al, 1988;Rabot et al, 1994). So far, only quantitative variation has been observed (Lyon, 1989), suggesting that resistance to soft rot is primarily of the polygenic, non-specific type.…”

The role of the seed tuber in determining partial resistance to potato blackleg caused byErwinia spp.

“…Methods are only suitable if they are easy to perform, applicable to early vegetative generations and yield reproducible and quantitative data that show good agreement with the resistance of the clones in farmers' fields. Numerous methods for screening of plants in the field [Hossain and Logan, 1983;Lapwood and Legg, 1983;Lapwood and Gans, 1984;Lapwood and Read, 1986a;Gans et al, 1991], or in the glasshouse [Munzert, 1975;Hidalgo and Echandi, 1982;Lapwood and Read, 1986b;Lojkowska and Kelman, 1989] have been described. Field tests correspond most to field conditions but they are expensive to perform and not feasible when only a small amount of seed is available.…”

A comparison of methods to evaluate the susceptibility of potato cultivars to blackleg (caused by Erwinia carotovora subsp. atroseptica) in the field at different sites

“…The high incidence of blackleg in the waterinoculated controls at NIAB suggests that the inoculation procedure may trigger latent infection even when the pathogen is not being introduced. Hossain & Logan (1983) found that the amount of blackleg in inoculated potato cultivars was quite often disproportionate to yield loss and they suggested that some cultivars showed greater tolerance to the disease than others. In our experiments Pentland Crown showed little black-leg but yield loss was often more severe compared to that of other cultivars.…”

“…PtirUulown, Co Armagh BT6.1 s(i|) UK Stem (Lapwood & Read, 1986b). Differences in susceptibility have also been shown in fieldgrown plants, by planting inoculated seed tubers (Hossain & Logan. 1983;Lapwood & Gans.…”

“…Several methods for introducing inoculum into the seed tuber have been proposed. Some rely on breaching the tuber skin with a toothpick (Hossain & Logan, 1983), a needle (Logan, 1969) or a highpressure needleless jet injector (Wastie. 1984).…”