Inheritance And Mechanism Of Resistance To Fusarium Verticillioides Ear Rot In Maize

Fusarium ear rot is a serious disease caused by fungi which happened in maize planting region around the world.Fusarium verticillioides（FV）is the predominant pathogens in China,which not only makes the kernel and spike-stalk rot,but also generates the secondary metabolite FB and MON that posing a potential threat to animal and human health after infecting com.The basic solution to control the disease is to breed and grow the disease-resistant var.It is important to identify and utilize new resistance genes for marker assistant selection based on elite germplasms.An elite resistance inbred line,BT-1,with tropical germplasm and two susceptible inbred lines,N6 and xi502 with Huangzaosi germplasm,respectively,were screened in our lab.Based on the above elite inbreds,four group near-isogenic lines were established.The resistance QTL primarily mapped on chromosome 4 bin 4.04-4.05 by artificial inoculation with multiple years and environments.Based on the result,we analysed the major resistance QTL and studied the mechanism of resisitance to fusarium verticillioides ear rot in maize.The results are as follows:1.The genetic background recovery rates of the four kinds of NTLs which were constructed previously were detected on generation BC₃F₃ and BC₄F₅.Based on the result,the NIL with highergenerations were developed in 2012.The NILs were developed from the generation BC₃F₃ and BC₄F₅ of the forward and reverse NIL of N6 to BC4F3,BC5F2 generation.For the forward and reverse NIL of xi502,the generations were developed from BC₄F₅ to BC5F2 generation.The genetic background recovery rates on BC4F3,BC5F2 generation were detected.The results showed that the genetic background recovery rates of different populations all have reached above 96%.2.The NILs with target segment for QTL were planted in four different environments in summer,2012.Genetic analysis on QTL of resistance to fusarium verticillioides ear rot in maize was carried out using different overlapping segments.The result showed that the QTL validated in bin 4.04-4.05,within marker internal umcl652-umcl969 was disintegrated two QTLs,temporarily named as qRjvl and qRjv2,located bin 4.04-4.05 and bin 4.06,within marker internal umcl652-umcl969 and bnlgl 137,respectively.We verified and corrected the results.3.To further understand the mechanism of resistance to fusarium verticillioides ear rot in maize,we inoculated the fusarium verticillioides in our laboratory by using the two inbred lines,BT-1 and N6,completely resistant and significantly susceptible to FV,respectively.The changes of morphological and histological were observed and the enzyme activity was assayed.We found that the volume and length of bacterium from the surface of BT-1 less than that of N6 in different infection-time after inoculation by observing the morphological.We did not find the hypha between the two inbred lines three days after inoculation by observing the histological.With the time of infection lengthen the hypha invaded from the band of the seed on seventh day after inoculation and the hypha in embryo of BT-1 less than that of N6.We found a large number of hypha in embryo and the embryo was eaten by fungus to empty,while the hypha did not be found in endosperm between the two inbred lines.These results showed that the difference of two parents mainly focus on that morphological and the embryo of histological after inoculation.To further investigate the processes of enzyme activity involved in maize ear rot upon infection by FM we assayed the enzyme activity of CAT and POD.The result showed that the enzyme of CAT may be related to disease-resistant,but the enzyme of POD may be uncorrelated with maize ear rot from the change rule.We need forther study to verity whether the two enzymes are related to disease-resistant.4.In this study,the QTL analysis of resistance to fusarium verticillioides ear rot in maize was carried out using multiple repeated and multiple environments.The QTL validated was disintegrated two QTLs,and temporarily named qRfvl and qRJv2.At the same time,the Mechanism research was carried out using the materials with different resistance,mainly from the morphological and histological changes in embr>o of resistant and susceptible reaction materials.The CAT enzyme may be related to disease-resistant by testing its activity.It can by used as the physiological index to identify the resistance of different materials;This study provides a theoretical basic for map based cloning of disease resistance by genetic analysis and the morphological observation and physiology testing.