Tuber Rots

Biology and Chemistry of Jerusalem Artichoke Helianthus tuberosus L. 

Snowdon, 1992). Approximately 20 organisms have been shown to cause tuber rots (Table 11.3), although losses for many can be circumvented through proper storage conditions. 

Blue mold rot, caused by Penicillium, results in decay only at relatively high temperatures (e.g., 20°C). The organism is only weakly virulent and gains access through wounds or lesions made by other fungi. 

Fusarium rot is caused by several Fusarium species and is frequently isolated from diseased tubers (McCarter and Kays, 1984). Rots were most severe at 25 to 30°C and can be prevented with temperatures below 5°C. 

Gray mold rot is caused by Botrytis cinerea, which results in a pale brown discoloration and sunken lesions on the tuber surface. At high relative humidities, the surface becomes covered with white mycelium and subsequently with gray-brown spores (Johnson, 1931). The interior of the tubers discolors and softens. The organism can cause serious storage losses even at low temperatures. 

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Sclerotium rot is a serious tuber rot in the field and storage (McCarter and Kays, 1984), caused by S. rolfsii. The tubers display robust white to light brown mycelium with numerous spherical sclerotia. Postharvest losses can be largely prevented with low-temperature storage (Johnson, 1931 Thompson, 1928). 

Leaves roll, wrinkle, and blister. Lower stem disintegrates and can be foulsmelling. Tubers can also be attacked, resulting in a gray slimy rot. Can affect isolated individual plants and even Isolated stems on one plant. It is more likely during prolonged wet conditions. 

The dose required to inhibit sprouting of onions, shallots, and garlics is 0.03-0.12 kGy. For good sprout control of tubers such as potatoes and yams, somewhat higher doses, 0.08-0.14 kGy, are required. Because of decreased wound-healing ability after irradiation, doses in excess of 0.15-0.2 kGy may induce increased microbial rot in storage [24]. 

Carputo, D., Cardi, T., Palta, J. P, Sirianni, P, Vega, S., Fruseiante, L. (2000b). Toleranee to low temperatures and tuber soft rot in hybrids between Solanum commersonii and Solanum tuberosum obtained through manipulation of ploidy and endosperm balanee number (EBN). Plant Breeding, 119, 127-130. 

Carputo, D., Speggiorin, M., Garreffa, P, Raio, A., Monti, L. M. (1996). Sereening for resistanee to tuber soft rot and blaekleg in diploid Solanum speeies and S. tuberosum haploids. Journal of Genetics and Breeding, 50, 221-226. 

Carputo, D. C. T., Speggiorin, M., Zoina, A., Frusciante, L. (1997). Resistance to blackleg and tuber soft rot in sexual and somatic interspecific hybrids with different genetic background. American Potato Journal 74, 161-172. 

McGrath, J. M. W., Christie E.,Haberlach, Geraldine T., Wielgus, SusanM.,Uchytil, ThomasF.,Helgeson, John R (2002). Introgression and stabilization of Env/ma tuber soft rot resistance into potato after somatic hybridization of Solanum tuberosum and S. brevidens. American Journal of Potato Research 79,19-24. 

McGuire, R. G., Kelman, A. (1984). Reduced severity of Erwinia soft rot in potato tubers with increased calcium content. Phytopathol., 74,1250-1256. 

Figure 1 2.3 Soft rot of potatoes developed in storage due to storage of wet tubers, condensations and anaerobic conditions in the storage.

Khanbari, O. S., Thompson, A. K. (1994). The effect of controlled atmosphere storage at 4°C on crisp color and on sprout growth, rotting and weight loss of potato tubers. Potato Research, 37, 291-300. 

Parlow Rot — German origin. Red tubers. Late maturing. Honermeier et al 1996. 

S. rolfsii also causes storage rots in tubers that appear sound at harvest (Thompson, 1928). The fungus produces a silky white mold on which numerous spherical sclerotia appear (Snowdon, 1992). Postharvest losses can be controlled by low-temperature storage or, in the absence of refrigeration, through the use of prestorage fungicide dips (Thompson, 1928). 

Rhizoctonia rot results in a brown discoloration of the tubers, caused by Rhizoctonia solanii. While occasionally isolated from diseased tubers, it is not a serious postharvest pathogen of Jerusalem artichoke. 

Watery soft rot caused by S. sclerotiorum and S. minor often develops on tubers that appear sound at harvest but subsequently succumb in storage (Gaudineau and Lafon, 1958). The tubers become covered with a dense white mycelium and irregular sclerotia, which progress from white to dark brown or black. Though storage at low temperatures repressed development, S. sclerotiorum can cause serious losses at low temperature (Johnson, 1931). 

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