Genotypic Variation in Nitrogen Utilization Efficiency of Pepper (Capsicum Annuum L.) Under Different Nitrogen Supply in Hydroponic Conditions

The genotypic differences in nitrogen (N) utilization efficiency of third backcrossed (BC3) progenies of Sena (Capsicum annuum L.; recurrent parent) and Kopan (Chile penguin; donor parent) pepper plants were determined by examining the changes in the shoot growth at agronomical, root growth at morphological and leaf development at physiological levels under high and low N rates. A hydroponic experiment was conducted by using an aerated deep water culture (DWC) technique in a controlled growth chamber in the spring 2015 growing season. As plant materials, five pepper plants (BC3‑1, BC3‑2, BC3‑3, BC3‑4, BC3-5) were selected from the third backcrossed (BC3) progenies of Sena and Kopan. Plants were grown in 8 L pots filled continuously aerated nutrient solution under at low N (0.5 mM N) and high N (3.0 mM N) rates in randomized complete block design (RCBD) with four replications for 6 weeks. At the experiment plant growth, leaf, shoot and root fresh and dry weights, total leaf area, leaf chlorophyll content (SPAD), total root length, total root volume and average root diameter in pepper plants were assessed. Significant differences in N efficiency were observed between the backcrossed pepper progenies and their respective parents. Leaf, and shoot fresh and dry weights, total leaf area, and leaf chlorophyll content (SPAD) of pepper plants were significantly increased with increasing N rate: 3.0 mM N increased leaf fresh weight by 149.8%, shoot fresh weight by 116.4%, shoot dry weight by 119.6%, total leaf area by 94.54%, and SPAD by 21.28% at BC3‑3 plants as compared to progenies of third backcrosses and their respective parents. Regarding root morphological parameters, pepper plants under high N rate displayed a lower performance than plants under low N rate. Increasing N rate led to a decrease in root fresh weight by 37.96%, and root dry weight by 35.93%. Overall, the N efficiency of the progeny of BC3‑3 was highly associated with vigorous root growth (root fresh and dry weight, total root length and volume) and photosynthetically active leaves (total leaf area, and leaf chlorophyll index) under low N conditions, which could be useful to select and breed “N efficient” pepper varieties.