Abstract:

Screening for germplasm with tolerance to low nitrogen and high nitrogen efficiency （NE）is of great significance for breeding green and high-yielding new varieties of potatoes. In this study，a pot experiment with nutrient solution control was conducted to measure the leaf gas exchange parameters，relative chlorophyll content，aboveground dry matter accumulation，and yield-related traits of 180 potato germplasms under low nitrogen（0.1 mmol · L^-1 NH₄NO₃，LN）and normal nitrogen（10 mmol · L^-1 NH₄NO₃, NN）treatments. The study analyzed the variation，correlation，and low-nitrogen sensitivity of each trait，screened for low nitrogen tolerant and high NE germplasms，and conducted physiological mechanism analysis and field validation experiment. The results showed that，there was significant variation in photosynthesis and yield-related traits among the 180 potato germplasms. Under NN and LN treatments，the coefficient of variation for the 9 traits ranged from 11.76% to 73.04% and 13.48% to 112.13%，respectively. Moreover，the variation in traits under LN treatment was higher than under NN treatment. Most of the traits showed a clear correlation with each other，and to some extent，were influenced by nitrogen treatment. Low nitrogen significantly affected the leaf photosynthesis and yield-related traits of potatoes，with single plant yield（SPY）being the most suppressed by low nitrogen，but also showing the greatest variation of low nitrogen tolerance index（LNTI），with a coefficient of variation of 57.53%. By clustering the LNTI of SPY，10 low nitrogen tolerant germplasms were selected，of which CIP8，CIP52，E33，CIP10，CIP16，T1 and CIP66 had high NE both under LN and NN treatment （DNHE）；under field conditions of low nitrogen，DNHE germplasms also had higher yield. Analysis found that，low nitrogen tolerant germplasms had higher net photosynthesis rates，chlorophyll content，aboveground dry matter，and tuber number per plant than sensitive germplasms. The results of this study can offer valuable materials for further exploration of excellent genetic resources and the breeding of varieties with high-yield and high NE.

Key words: potato, germplasm, low nitrogen tolerant germplasm, nitrogen efficiency, yield, pot experiment