Studies On The Development Of Rhizobium Inoculum Using Moss As Carrier For Bambara Groundnut, Vigha Subterrahea (L) Verdc.

A B S TRACT i v Research was carried out to de v e l o p an effe c t i v e i n o c u l u m carrier of the nodule bacterium, Rhizobium sp., for the inoculation of seeds of bambara groundnut [Vigna subterranea (L.) V e r d e , c o m b . nov. = Voandzeia subterranea (L. ) T h o u a r s ] f r o m a local material. Five out of 16 strains of Rhizobium sp. isolated from soils of legume farms at eight localities within a r a d i u s of 180 k m f r o m L e g o n w e r e u s e d in e x p e r i m e n t s to t e s t the efficiency of the carrier that was developed. Plants infected by these five strains grew well, had high dry weights and high nitrogen content of the shoots and formed many large nodules. A good Rhizobium carrier was developed from the moss, Brachymenium sp. H a r v e s t e d tha ll i w ere s u n - d r i e d for 10 days and de c o m p o s e d for 15 days. W h e n s t o r ed at r o o m t e m p e r a t u r e , the Rhizobium-population of inoculated moss compost of 50 per cent m o i s t u r e c o n t e n t r o s e to a m a x i m u m of 4 . 0 0 x 1 0 ^ c e l l s p e r 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 week without showing any signs of autolysis. Sterile compost inoculated and stored at room temperature for two weeks when the Rhizobium ii population rose to a p p r o x i m a t e l y 1 x 10 ^per gram of compost was used to in ocu la t e the seeds in the v a r i o u s e x p e r i m e n t s . E x - A d a and E x - 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 nodul a t e d . P l a n t s of E x - A d a v a r i e t y d e v e l o p e d b e s t at l o w l i g h t i n t e n s i t y ( 1 1 0 0 - 2 2 0 0 lux at 9 . 0 0 am, 4 0 3 0 - 6 2 0 0 l u x at n o o n a n d 1 6 0 0 - 1900 lux at 3.00 pm). M e d i u m l i g h t i n t e n s i t y (1400 - 2 8 0 0 lux at 9 . 0 0 am, 6 4 0 0 - 9 1 0 0 l u x at n o o n a n d 2 9 0 0 - 3 5 0 0 l u x at 3.00) was less f a v o u r a b l e and h i g h li gh t i n t e n s i t y ( 5 30 0 - 62 00 lux at 9 . 0 0 am, 8 8 0 0 - 1 0 0 0 0 l ux at n o o n an d 4 6 0 0 - 6 4 0 0 l u x at 3.00 pm) was least favourable. After 30 days, the respectiveV mean dry weights of the plants at the low, m e d i u m and high l i g h t i n t e n s i t i e s w e r e 1 , 6 2 - 2 . 9 1 g , 1 . 3 3 - 1 . 8 2 g a n d 0 , 9 1 - l,41g; and the respective mean number of nodules per plant was 54 - 78, 42 - 51 a n d 16 - 21. Plants of Ex-Tamale variety watered once in two days showed the best growth. Those watered once in four days showed moderate growth, and growth of plants watered once in six days was greatly reduced. After 30 days, the r espective mean dry weights of plants watered once in two, four and six days were I . 0 0 - 1 . 6 8 g , 0 . 6 4 - 0 . 9 4 g a n d 0 . 4 8 - 0 . 7 6 g , a n d t h e r e s p e c t i v e m e a n n u m b e r of n o d u l e s per p l a n t w as 43 - 56, 16 - 25 a nd 8 - II. In both tests, c o n d i t i o n s of l i ght and m o i s t u r e w h i c h encouraged higher nodulation also induced the formation of larger nodules. It was c o n c l u d e d that c o m p o s t of Brachyseniua sp. is a g o o d Rhizobium carrier and can be used for routine inoculation of bambara groundnut seeds. To derive the maximum benefit from the inocula ti on, 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 ambara groundnut.