Identification And Gene Mapping Of A New Maize Tassel Stem Development Mutant

Maize （Zea mays L.） has the largest planting area in China among all the cereal crops. At the meantime, maize provides a useful model to study the genetic and molecular control of meristems. Maize tassel is an important reproductive organ, therefore its development occupies paramount importance throughout the life cycle. Many classical maize tassel mutants were described last century, providing important insights into the mechanism of developmental control on morphology and molecular level. During the previous studies, we isolated a natural, single recessive tassel stem meristem mutant tsb*-9LB090. As we know, tassel stem is not only the constituent part of male inflorescence, but also the extension of maize axis, furthermore reports on similar mutants have not been seen. So it is necessary to carry out a thorough research.This research consists of morphological identification, genetic analysis and gene mapping. Main results are as follows:1.the morphology of tsb*-9LB090 mutant:The structure above the first branch of tassel stem developed normally, neverthless the part beneath the first tassel branch growed crookedly,with regular bending. Furthermore the direction of bending and mazie tassel branch was in the same horizon. Anatomical observation results showed that tassle stem of mutant developed normally in tassel primordium formation stage tassel primordium Primordium stage^ spikelet meristem differentiation stage and floret meristem differentiation stage, so we predicted that bending appeared after tassel internode elongating period.2.Genetic analysis showed that the mutant tsb*-9LB090 was controlled by a recessive gene. The inflorescences of F1 were wild-type. In F2 generation, the proportion of mutant-type and wide-type was accord with 1:3, and in back crossing group the proportion was 1:1.3.Gene mapping was carried out with F2 generation.Results indicated that marker umcl357 on Chr.9 was linked with target gene, with 35.7 cM in distance. In order to narrow down the interval,40 SSRs has been designed and synthesized around umc1357,ultilizing the reference genome of maize, with a size of 1.59 Gb and the version number is ZmB73₅b, download link:http://ftp.maizesequence.org/current/.. Analysis manifested that there was three markers linked to the target gene more closely, moreover primer 40 and primer 14 was on the both side of target gene, with genetic distance of 3.8cM and 14.7cM respectively. The physical location of two markers were 127,811,140 and 130,355,129. As a result, the target gene was arched on the chromosome 9.4.Unlike maize inflorescence meristem mutant which has been descirbed, phenotypic expression of mutant has not been seen before. In addition,we has located the target gene on the ninth chromesome, and there has no other similar gene been reported in this area. So combining with its phenotypic characteristics,the gene was named TASSEL STEM BENDING（TSB）. In conclusion, we name the gene tassel stem bending（tsm）.