Studies On The Development Of Rhizobium Inoclum Using Moss As Carrier For Bambara, Vigna Subterranean (L) Verdc.

Abstract

Research was c a r r i e d out to d e v e l o p an e f f e c t i v e i n o c u l u m carrier of the nodule b a c terium, Rhizobium sp., for the inoculation of seeds of b a m b a r a g r o u n d n u t [Vigna subterranea (L.) Verde, comb. nov. = Voandzeia subterranea (L.) Thouars] from a local material. Five out of 16 strains of Rhizobium sp. isolated from soils of legume farms at eight l o c a l i t i e s w i t h i n a radius of 180 km from Legon were used in e x p e r i m e n t s to test the e f f iciency of the c a r r i e r that was de v e l o p e d . Plants infected by these five strains grew well, had hig h dry w e i g h t s and high nitrogen content of the shoots and formed m a n y large n o d u l e s . A good Rhizobium c a r r i e r was d e v e l o p e d from the moss, Brachymenium sp. H a r v e s t e d thalli were s u n - d r i e d for 10 days and decomposed for 15 days. Whe n stored at room t e m p e r a t u r e , the Rhizobium-p o pulation of i n o c u l a t e d moss c o m post of 50 per cent m oisture content rose to a m a x i m u m of 4.00 x 1 0 ^ cells per gram of compost after 10 weeks. The p o p u l a t i o n r e m a i n e d stationary thereafter till the end of the 14th w e e k w i t h o u t showing any signs of autolysis. Sterile c o m post i n o c u l a t e d and stored at room t e m p e r a t u r e for two we e k s when the Rhizobium population rose to a p p r o x i m a t e l y 1 x 10 ^pe r gram of c o m p o s t was used to inoculate the seeds in the v a r i o u s e x p e r i m e n t s . Ex-Ada and Ex-T a m a l e v a r i e t i e s of b a m b a r a g r o u n d n u t inoculated with the five strains of Rhizobium sp. all n o d u l a t e d . Plants of Ex-Ada v a r i e t y d e v e l o p e d best at low light i n t e n s i t y (1100 - 2200 lux at 9.00 am, 4030 - 6200 lux at noon and 1600 - 1900 lux at 3.00 pm). M e d i u m light i n t e n s i t y (1400 - 2800 lux at 9.00 am, 6400 - 9100 lux at noon and 2900 - 3500 lux at 3.00) was less favourable and high light i n t e n s i t y (5300 - 6200 lux at 9.00 am, 8800- 10000 lux at noon and 4600 - 6400 lux at 3.00 pm) was least favourable. After 30 days, the r e s p e c t i v e mean dry weights of the plants at the low, m e d i u m and hi g h light intensities were 1,62 - 2.91g, 1.33 - 1.82g and 0,91 - l,41g; and the r e s p e c t i v e mean n u m b e r of n o d u l e s per pl a n t was 54 - 78, 42 - 51 and 16 - 21. Plants of E x - T a m a l e v a r i e t y w a t e r e d once in two days showed the best growth. Those w a t e r e d once in four days s howed moderate growth, and growth of plants w a t e r e d once in six days was greatly reduced. After 30 days, the r e s p e c t i v e m e a n dry wei ghts of plants w a tered once in two, four and six days were I.00 - 1.68g, 0.64 - 0.94g and 0.48 - 0.76g, and the r e s p e c t i v e mean number of nodules per plant was 43 - 56, 16 - 25 and 8 - II. In both tests, c o n d i t i o n s of light and m o i s t u r e w h i c h e n c ouraged higher n o d u l a t i o n also i n d u c e d the f o r m a t i o n of larger nodules. It was concluded that compost of Brachyseniua sp. is a good Rhizobium carrier and can be used for r o utine i n o c u l a t i o n of bambara groundnut seeds. To derive the m a x i m u m b e n e f i t from the inoculation, it is d e s i r a b l e to i d e n t i f y the best s t r a i n of Rhizobium sp, for each v a r i e t y of b a m b a r a groundnut.