^42 Journal of Agricultural Research voi. xii, no. 9 



INOCULATION OF OKRA 



No difficulty was experienced in securing typical wilting okra plants 

 (PI. 21, 22) by the inoculation of the soil or of the plants through wounds 

 at the hypocotyl with pure cultures of V. albo-airum isolated from okra, 

 eggplant, potato, or snapdragon. By the inoculation of the soil in the 

 vicinity of 17-day-old plants with strain 171 7 isolated from okra, 88 

 per cent of wilting plants were obtained in 2 1 days. Inoculations of the 

 soil with this strain before planting the seed resulted in 59 per cent of 

 wilt. Inoculation of S7- to 90-day-old okra plants with this strain through 

 the hypocotyl gave from 75 to 100 per cent of wilting plants. The 

 reisolated strains of V. alho-atrum 171 7 gave the following results: Strain 

 2943, 40 per cent; strain 3075, 66 per cent; strain 3076, 16 per cent; 

 strain 3156, 71 per cent. V. alho-atrum, strain 2821, isolated from a 

 wilting okra plant from Middle River, Cal., produced 100 per cent of 

 wilting plants through hypocotyl inoculations. 



The introduction of V. alho-atrum into wounds of the pedicel and the 

 stem of okra plants was without apparent effect, thus indicating that 

 there is no danger of carrying the wilt disease from plant to plant by the 

 cutting knife. 



The inoculation of okra plants with V alho-atrum from hosts other 

 than okra gave the following results: Strain 2985, isolated from snap- 

 dragon, produced from none to 45 per cent of wilt through hypocotyl 

 inoculation; strain 2784 from potato gave 73 per cent through hypocotyl 

 wounds and 55 per cent through soil inoculation previous to planting the 

 seed; strain 1685, isolated from eggplant, gave 43 per cent of wilt through 

 the inoculation of 60-day-old plants at the hypocotyl. 



The results of inoculating okra plants with F. vasinfectum were for 

 some time disappointing. However, after an insight was gained into 

 the conditions necessary to induce the Fusarium-wilt of okra, better 

 results were obtained. With the' species of Fusarium from okra in two 

 trials, 50 and 55 per cent of wilting plants were secured by inoculation 

 through the hypocotyl (PL 23). But with the species of Fusarium from 

 cotton only i per cent was obtained. However, the cotton inoculated 

 with the species of Fusarium (3592) from okra and the strain (1855) from 

 cotton gave a high percentage of wilting plants in a parallel test of the 

 two strains (PI. 24-26). 



INOCULATION OF COTTON 



Fusarium vasinfectum strain 1855 from cotton, when introduced into 

 wounds at the hypocotyl of 21-day-old plants, gave 50 per cent of wilt 

 in 17 days and a total of 89 per cent in 5 weeks (PI'. 25). Similarly, in a 

 parallel test, F. vasinfectum strain 3592 from okra gave 42 per cent of 

 wilt in 17 days and a total of 87 per cent in 5 weeks (PI. 26). In contrast 

 to these results are those secured with these strains on okra in the parallel 



