SEARCH OF MUNGBEAN (Vigna radiata (L.) Wilczek) GENOTYPES FOR OPTIMAL AND SUB-OPTIMAL NITROGEN LEVELS
A series of three experiments were conducted in the Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh during the period of 1999 to 2001 to assess mungbean genotypes in terms of growth, yield, nitrogen uptake kinetics and use efficiency under sub-optimal and optimal nutrient environments. Seedlings of 7, 15 and 21 days of 200 mungbean genotypes of native and exotic origin were evaluated under sub-optimal nutrient conditions in the first experiment in the series. In the second experiment six genotypes viz. VC6153B, GK3, VC6144A PDM54, IPSA25 and VO1443A-G were evaluated for nitrogen uptake dynamics, growth and yield under high (154ppm) and low (34ppm) N levels employing solution culture technique. Nitrogen was supplied through Hoagland solution 3(N-154ppm) and Hoagland solution 1(N-34ppm) over time.
Two mungbean genotypes GK3 and IPSA25 were evaluated in the third experiment to determine the N uptake kinetics and N use efficiency of the genotypes employing nutrient depletion technique under high (154 ppm) and low N (34 ppm) levels. GK3 maintained consistently higher growth and N uptake than IPSA25 over time irrespective of N level. GK3 was relatively efficient in N use at both levels of N supply. From the results of the experiments it was observed that wide diversity exists among mungbean genotypes in adapting under sub-optimal and optimal nutrient environments which could be exploited in screening high yielding genotypes that would best fit under nutrient stress environment. GK3 and IPSA25 may prove to be the target genotypes. This result may have important implications with regard to effects of genetic selection under specific levels of N fertility.