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Inheritance of resistance to blotchy ripening In tomato (Lycopersicon esculentum Mill.) cultivars intended for machine harvest was studied in two diallel crosses using the Hayman and Griffing analyses. Additive effects were most important as indicated by the high level of general combining ability compared with specific combining ability. Some hybrids performed better than the mid-parent mean; however, heterosis for resistance to blotch above the best inbred line was not evident. Epistasis occurred between recessive genes in two parents, resulting in reduced blotch. No significant interaction between the expression of blotch in diallel progeny and K availability was evident. Genotype-environment Interaction was significant, but relative variation in blotch between experiments only occurred in cultivars with an intermediate level of resistance.
Abstract
Rutabaga (Brassica napus L. Group Napobrassica) cultivars were screened for resistance to turnip mosaic virus (TuMV), and the inheritance of resistance was studied. Immunity and resistance were found in four of 49 rutabaga cultivars evaluated. The cultivar ‘Sensation’ was immune to the Ontario strain of TuMV. In crosses between susceptible ‘Laurentian’ and resistant Line 165 and susceptible triazine-resistant ‘Laurentian’ and Line 165, TuMV resistance was determined by a single dominant gene.
Abstract
Ethylene may induce off-flavor in stored carrot (Daucus carota var. sativus) roots and the formation of abnormal phenolic metabolites (3), including 3-methyl-6-methoxy-8-hydroxy-3, 4 dihydroisocoumarin (6-methoxymellein), which is associated with bitterness (4, 5). A similar response has been suggested (P.A. Ferretti, personal communication) to occur in parsnips (Pastinaca sativa). We report here preliminary work to verify this contention.
Field and greenhouse studies were conducted to investigate the effects of low temperature on the starch, sugar, ascorbic acid, and glucosinolate (GS) concentration in turnip [Brassica rapa ssp. rapifera (Metzg.) Sinsk] roots. Field-harvested roots were stored at 0C for 2 and 4 weeks. In the greenhouse, plants were grown at 0 to 12C for parts of 11 days before harvest. Cold-stored roots decreased in both starch and total sugar concentration (sucrose, fructose, and glucose) when compared to freshly harvested roots. Greenhouse-grown plants subjected to low temperatures had roots with a similar starch content but with a higher concentration of total sugars than the control. In both experiments, the cold treatments induced a slight but significant increase in root sucrose concentration. The ascorbic acid concentration of roots was not affected by low temperature. In both the field and greenhouse studies, low temperature did not change the total concentration of the eight major GSs identified in peeled root “and peel tissues, but did alter the concentration of specific GSs.
The influence of low-temperature on the starch, sugar and glucosinolate content was studied in the mature roots of field and greenhouse-grown turnip. A decrease in both starch and sugar levels was recorded in roots after storage at 0°C for 4 weeks. On the other hand, when plants were exposed to a series of cold treatments, the starch level remained constant but the level of sugars increased in roots. In our studies, turnip roots exhibited the capacity to synthesize and degrade specific glucosinolates at low temperatures. The implications of these findings on the sensory characteristics of the root will be discussed.