LAUSR

AIMS Green bean (Phaseolus vulgaris L.) is a popular vegetable worldwide. The use of beneficial fungi is a simple and effective way to improve the biological nitrogen fixation (BNF) of this leguminous vegetable. METHODS AND RESULTS A micro-plot was conducted to investigate the enhancement of BNF using 15 N natural abundance technology and agronomic performances of green bean caused by wood-rot fungus Ceriporia lacerata HG2011. The results showed the soil for frequently growing green bean featured abundant native rhizobia, and newly inoculated rhizobia may have to compete with them in nodulation and only highly competitive rhizobia can succeed. The addition of C. lacerata HG2011 to the soil increased the population of ammonia oxidizers, nitrifiers, and phosphorus (P)-mobilizing microbes in rhizosphere, accelerated nitrification and P mobilization, creating a favorable soil environment with high P and low ammonia for BNF. Green bean received C. lacerata HG2011 had higher dehydrogenase activity in roots and higher nodulation rate and large nodules. These phenomena implied abundant supplies of adenosine triphosphate, nicotinamide adenine dinucleotide hydrogen or nicotinamide adenine dinucleotide phosphate hydrogen for BNF in the roots, a large proportion of N2 fixation tissues, and a greater sink for receiving photosynthates. As a result, C. lacerata HG2011 considerably increased the percentage of N derived from the atmosphere, BNF, and plant nutrient uptake (including N, P, and potassium), leading to 15.58-28.51% of biomass increasment and 9.82-17.03% of peapod yield increasment along with quality improvement compared with non-fungal application. CONCLUSIONS C. lacerata HG2011 increased the nodulation and BNF of green bean, accelerated the nutrient uptake (NPK) and therefore improved the yield and peapod quality of green bean.