The Genetic Analysis For Responses To Nitrogen And Phosphorus Stresses Using Rice Chromosomal Segment Substitution Lines

Nitrogen and phosphorus are crucial plant macronutrient for crop growth.The insufficient supply of nitrogen or phosphorus is a key limitation that restrict crop yield.In the past several decades,researchers consistently devoted self to breed many varieties with higher yield potential under more fertilizer application.The integrated application of fertilizer and high-yield variety has increased the crop production by forcefully.But there is a contradiction between large dosage of fertilizer usage and low fertilizer use efficiency of plant,which has brought enormous energy dissipation and cost of crop production, while the excessive fertilizer application also causes serious environment pollution. Understanding the genetic basis of crop nutrition absorption and utilization,is an important approach to resolve above mentioned problems.In this study we used two sets of chromosomal segment substitution lines(CSSLs) to analyze the genetic basis of rice responses to nitrogen and phosphorus stresses in the field experiment under three treatments of fertilizer application:normal(N),low nitrogen(NO) and low phosphorus(PO).The CSSLs were planted with augmented design and their plant height(PH),panicle length,panicle number and yield were measured at maturity stage. QTLs were identified related to the responses.The main results are as follows:1.Significant negative correlations between relative trait performance and its measurement under normal cultivated condition indicate a general trend that CSSLs in smaller plant size had higher relative performances.It also suggests that the CSSLs with smaller biomass often showed better tolerance to low nitrogen or low phosphorus conditions.However,there were many CSSLs showing higher values both in the relative trait index and the normal performances than that of the recurrent parent.2.In the CSSLs with 9311 genetic background,we detected 14 QTLs for plant height, 8 QTLs for panicle number and 18 QTLs for yield per plant.Qph-5b was a QTL for plant height with the highest(32.5%) variation explained and additive effect of 19.0 cm;All of the detected QTLs for panicle number showed negative effects,and explained phenotypic variations from -42.6%to -62.9%;The maximum phenotypic difference explained for yield per plant and the additive effect by Qyd-4c) is -88.1%and -9.6. In the CSSLs with Zhenshan97 genetic background,we detected 28,19 and 20 QTLs for plant height,panicle number and yield per plant,respectively.Qph-1d is one plant height QTL with the highest(68.9%) variation explained and its additive effect is 24.2cm, Qpn-5 for panicle number with the highest(58.9%) variation explained,Qyd-11a for yield per plant with the highest(137.9%) variation explained.3.The two sets of CSSLs have the common donor of Nipponbare within two different genetic backgrounds,one is 9311,another Zhenshan97.We detected a total of 58 and 93 QTLs in the two sets of population respectively.Most of the QTLs detected in the different two genetic backgrounds had various locations on the genome.Only 12 QTLs had the common locations such as the regions nearby markers RM472,RM211,RM7,RM411.The differences in QTLs number and location suggested that the different two genetic backgrounds might have very tremendous influence to the QTLs expression. Those QTLs repeatedly detected in different background had the characteristic of stability and authenticity,which is very important for MAS in breeding.4.For the CSSLs with 9311 genetic background,three QTLs(Qph-1c,Qph-5b and Qyd-4c) were detected repeatedly in the three kinds of treatments(N,NO and PO),for the CSSLs with Zhenshan97 genetic background,11 QTLs(such as Qph-5b,Qph-6,Qph-11a) were detected repeatedly in the different treatments.We suggest that these QTLs present more contribution to the traits growth and development.18 QTLs were detected under both NO and PO conditions(not detected under N condition),suggesting these stable QTLs across NO and PO treatments may have samiliar response to low nitrogen and low phosphorus stresses and more likely be common loci involving in nitrogen and phosphorus metabolism.The other most of the QTLs were only detected in either NO or PO treatment,suggesting that the loci are certainly more likely linked to the respective nitrogen or phosphorus pathway.The different QTLs detected under NO or PO treatments reflected diverse genetic basis of nitrogen and phosphorus responses.5.A total of 44 relative traits QTLs were detected in the two sets of CSSLs,of which 28 QTLs were common detected under the N,NO and PO treatments,other 16 QTLs were different from those detected under the N,NO and PO treatments.Thus,the genetic basis of the relative performances cannot simply be deduced as compared separate detection of QTLs under nitrogen and phosphorus treatments.For example,Qryd-3b is a QTL for relative yield which detected in the CSSLs of ZS97 genetic background.The material contained this QTL had a stronger tolerance to low phosphorus stress,however colocation QTLs were not detected under each of three fertilizer conditions.