Screening Of Nitrogen Efficient Germplasm And Minning Of Elite Allele In Cassava

Cassava (Manihot esculenta Crantz) is one of the important cereal crops, it is significant to screen Nitrogen(N) high-efficient germplasms and identify elite alleles in cassava. In this study, phenotypic variation of 30 cassava were obtained by using different nitrogen source under low N treatment and high N treatment in cassava pot culture experiment. N-efficiency of 135 cassava were evaluated by The fuzzy membership function under low N treatment and high N treatment in cassava field experiment. The low N treatment to high N treatment ratio was defined as N-efficiency, genetic resources and marker locus were discovered by SNP and SSR technique. It provides the original material and theoretic support for N high-efficient germplasms breeding and N high-efficient utilization mechanism in cassava by this study. The main results were as follows:1. Cassava biomass could be significantly influenced by increasing soil N concentration, but it was variant in different source of N. Supplying nitrate nitrogen was more suitable for growing than ammonium nitrogen for cassava by the comparison of biomass.2. Increasing soil N concentration in a certain scope could significantly improve the content of nitrogen forms in cassava. But continue to supply a large number of ammonium nitrogen or nitrate nitrogen could lead to the ammonium nitrogen content decreased in leaves.3. Increasing soil N concentration could enhance activity level of N-metabolism enzymes in cassava, especially the glutamine synthetase(GS). It showed that GS was the strongest responsed to N and played an important role in cassava N-metabolism pathways.4. By correlation analysis, we found ammonium nitrogen, nitrate nitrogen and total nitrogen were very positively associated with biomass in cassava, it showed that nitrogen concentration in cassava body could significantly affect the growth of plants.5. By evaluating N-efficiency of 135 cassava, it showed that the order of effect on N- efficiency:the tuber weight> the number of tubers> the fresh weight of aerial part> the dry matter ratio> the numbre of main stem branch> the plant height. And we screened 5 N high-efficient germplasms, they were FB-2, G5,11K, Indonesia spire and G5. At the same time, we selected 5 N low-efficient germplasms, they were COL764, SG6386, BV-8, COL269 and Indonesia.6.29 SSR polymorphic locus were associated with N-efficiency by association mapping method, it had average 3.72 allelic variation. And we screened elite allele for cassava N-efficiency, they were ESSR14e, ESSR51c, ESSR31c and EME489d.7. By Sequence of field containing GS beta-Grasp SNP analysis, we found that the sequence had 35 polymorphism loci and 21 InDel mutation. There were 3 synonymous variation and 2 nonsynonymous variation in exon. By association mapping method, there were 1 synonymous variation were associated with N-efficiency, elite allele was A→T.