STUDIES ON THE REACTION OF SOYBEAN CULTIVARS TO Alectra vogelii (Benth), MECHANISM OF RESISTANCE AND CONTROL USING ANTI-TRANSPIRANTS

STUDIES ON THE REACTION OF SOYBEAN CULTIVARS TO Alectra vogelii (Benth), MECHANISM OF RESISTANCE AND CONTROL USING ANTI-TRANSPIRANTS

Abstract:

Screen-house, field and laboratory trials were conducted between 1995 and 1998 at Samaru in the northern Guinea savanna ecological zone of Nigeria to study the reaction of soybean cultivars to Alectra vogelii, mechanism of resistance and control using anti-transpirants. Results of the response of soybean cultivars to Alectra vogelii showed that TGX 1649-11F. TGX 1681-3F, TGX 1674-3F. TGX 1636-7F. TGX 1670-1F. TGX 1670-3F and TGX 1660-191- exhibited resistance to Alectra by support for low and delayed Alectra shoot emergence both in the screen-house and field trials. Also, exhibited low crop syndrome reaction score, reduction in nodulation, shoot dry matter production, plant height, and days to first crop flowering and produced high seed yield. TGX 1740-7F and TGX 1740-2F exhibited low to moderate resistance by support for low to moderate and delayed Alectra shoot emergence. These cultivars exhibited low crop reaction score, low reduction in crop parameters and produced seed yield comparable to the highest and significantly higher than the least in all the field trials. Inspite of support for high Alectra shoot emergence, exhibition of moderate to high crop syndrome reaction score and high reduction in crop parameters. TGX 1660-15F. TGX 1485-1D. SAMSOY 2. TGX 1440-IE and TGX 536-02D produced high seed yield, thus exhibiting obvious tolerance. However, soybean cultivars. TGX 1019-2EB. M-351, TGX 87D-516. TGX 849-313D and TGM 344 exhibited susceptibility to Alectra parasitism through support for high Alectra shoots in all the trials. Also, these cultivars exhbited high crop syndrome reaction score, high reduction in crop parameters and produced low seed yields in all the field trials Alecrra shoot emergence was negatively correlated with the number of branches. 100-seed weight, seed yield and percentage reduction in crop parameters. Seed yield was positively correlated with the number of pods and branches and 100-seed weight. 100- seed weight and number of pods per plant and their combined contributions were the major yield determinants in soybean. In the mechanism of resistance study. TGX 1649-1 IF, TGX 1681-3F. TGX 1740- 7F, TGX 1660-IF. TGX 1740-2F. TGX 1670-3F and TGX 1660-19F exhibited multiple mechanism of resistance through the stimulation of low Alecrra seed germination and were insensitive to Alectra produced ‘toxins’. SAMSOY 2 stimulated high Alecrra seed germination but was insensitive to Alecrra produced ‘toxins’. Results of the control of Alecrra using anti-transpirants in the screen-house trial showed that abscisic acid at all concentration did not affect Alecrra plants. However. shea butter and paraffin oils resulted to over 90 and 100% death of Alecrra shoots at 5 and 10 days after application, respectively. Gum arabic, vaseline, kaoline and talcmagnesite also caused between 68 and 90% control of Alecrra within 10 days afterapplication. The loeal anti-transpirants used in this investigation are promising and cheap but require further work under field condition for confirmation.

STUDIES ON THE REACTION OF SOYBEAN CULTIVARS TO Alectra vogelii (Benth), MECHANISM OF RESISTANCE AND CONTROL USING ANTI-TRANSPIRANTS

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