RATE OF BARLEY YELLOW DWARF VIRUS TRANSLOCATION AND EFFECTS OF ENVIRONMENT ON BARLEY YELLOW DWARF SYMPTOM EXPRESSION IN WHEAT AND OATS
Abstract
Two studies, conducted in the greenhouse and controlled environment chambers, were designed to study barley yellow dwarf (BYD) symptom expression in winter wheat (Triticum aestivum L. em. Thell) and spring oats (Avena sativa L.). The first experiments was conducted in the spring of 1980 in the greenhouse. Hart, OK 7211542, and Abe winter wheats were infested with viruliferous aphids (Rhopalosiphum padi L.) at the one leaf stage prior to vernalization, at the one leaf stage after vernalization and at the six leaf stage. CI9312, Porter, and Clintland 64, spring oats, were infested at the one leaf stage and at the six leaf stage. Non-viruliferous aphids were allowed to feed for 24 hours on emerging and developing leaves as the plants grew and then aphids were transferred to Clintland 64 seedlings. The number of Clintland 64 plants which developed BYD symptoms was recorded. The systemic movement of barley yellow dwarf virus (BYDV) was not a useful measure of BYD resistance. The difference in the severity of BYD due to the plant growth stage at the time of infection, is not related to the location of the virus in the plant. The virus was successfully transferred from the host plant to an indicator plant within 24 hours after the inoculation feeding on the host plant. The virus was detected without any apparent leaf discoloration. The second study was conducted in three experiments. A completely randomized factorial design was used in each of the three experiments. The first experiment was conducted in controlled climate chambers and tested the response of CI 9312 and Clintland 64, spring oats, to two BYDV treatments, two fertility treatments, two moisture treatments, and two light intensity-temperature treatments. The second experiment was conducted in controlled environment chambers with a high light intensity. It measured the response of Hart and Abe, winter wheats, to two BYDV treatments, two fertility treatments, and two moisture treatments. The third experiment was conducted in the green house in the spring of 1981. It measured the response of Caldwell, Hart, and Abe, winter wheats to two BYDV treatments, two fertility treatments and two moisture treatments. Half of the plants in each treatment were infested with viruliferous Rhopalosiphum padi and the other half were noninfested controls. Oat seedlings were infested in the one leaf stage for ten days. In the second experiment the wheat seedlings were infested in the one leaf stage for ten days following vernalization and in the third experiment the wheat seedlings were infested in the one leaf stage for 24 hours prior to vernalization. The fertility trreatments were an additional 135 kg/ha N-P-K (High fertility) and no additional fertilizer (Low fertility). The moisture treatments were field capacity and severe moisture stress. The light intensity-temperature treatments in the first experiment were 400 (mu) Einsteins/m('2)(.)sec -25(DEGREES) and 150 (mu) Einsteins/m('2)(.)sec -18(DEGREES). Two weeks after heading, planz fresh weight, freeze-dried root weight, plant height and number of fertile culms were recorded. BYD reduced the plant fresh weight, root weight, and height and increased the visual scores of infected wheat and oats. BYD symptom expression was more pronounced when plants were moisture or fertility stressed; however, the evaluation of plants for BYD resistance would be more effective when plants are grown with no moisture or fertility stress or in very mild stress conditions than when grown in stress conditions. Stress conditions which enhance BYD symptom expression mask the effects of BYD by stunting and discoloring noninfected.
Degree
Ph.D.
Subject Area
Agronomy
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