A simple and efficient seed-based approach to induce callus production from B73 maize genotype

The wild type maize genotype, B73, is not amenable for callus production and an efficient protocol for B73 maize callus induction has never been reported up-to-date. Scientific efforts in producing B73 maize callus using all known callus inducible media have been unsatisfactory. Here we developed and described an efficient protocol for callus induction from B73 maize seedlings. The protocol is based on well known callus inducible media CM4C where we have sequentially subtracted some chemical compounds and added some new compounds mediating cell proliferations. This newly described protocol was able to induce callus production in a wide range of crop species including rice and soybean. We found that cell proliferation factors, NAA (auxin analog) and 2,4 D (auxin influx carrier) were not only very crucial but required for positive B73 maize callus induction. The absence of one or the other will lead to the failure of B73 maize callus production. The well known CM4C callus induction composition lacks NAA. Our findings will advance genetic studies of maize mutants generated from B73 genotype background.

Application of Wox2a in transformation of recalcitrant maizegenotypes

The genetic transformation plays an important role in plant gene functional analysis and its geneticimprovement. However, only a limited number of maize germplasms can be routinely transformed. Themaize gene Wuschel-like homeobox protein 2a (Wox2a) was shown to play a crucial role in promotingthe formation of embryonic cells and enhancing the efficiency of genetic transformation in maize. Thiscommentary discusses the mechanism by which the Wox2a gene contributes to the variation inembryogenic tissue culture response among different maize inbred lines. In addition, the frequency andintensity of Wox2a or Wus2/Bbm vector-induced somatic embryogenesis was also discussed. Theapplication of Wox2a in transformation of recalcitrant maize genotypes could well accelerate thedevelopment of maize genetic improvement.

Identification of maize(Zea mays L.)progeny genotypes based on two probabilistic approaches:Logistic regression and naïve Bayes

Weused two probabilisticmethods,Gaussian Naïve Bayes and Logistic Regression to predict the genotypes of the offspring of two maize strains,the BLC and the JNE genotypes,based on the phenotypic traits of the parents.We determined the prediction performance of the two models with the overall accuracy and the area under the receiver operating curve(AUC).The overall accuracy for both models ranged between 82%and 87%.The values of the area under the receiver operating curvewere 0.90 or higher for Logistic Regression models,and 0.85 or higher for Gaussian Naïve Bayesmodels.These statistics indicated that the two models were very effective in predicting the genotypes of the offspring.Furthermore,bothmodels predicted the BLC genotype with higher accuracy than they did the JNE genotype.The BLC genotype appeared more homogeneous and more predictable.A Chi-square test for the homogeneity of the confusionmatrices showed that in all cases the twomodels produced similar prediction results.That finding was in line with the assertion by Mitchell(2010)who theoretically showed that the twomodels are essentially the same.With logistic regression,each subset of the original data or its corresponding principal components produced exactly the same prediction results.The AUC value may be viewed as a criterion for parent-offspring resemblance for each set of phenotypic traits considered in the analysis.

Genetic dissection of maize seedling root system architecture traits using an ultra-high density bin-map and a recombinant inbred line population

Maize（Zea mays） root system architecture（RSA）mediates the key functions of plant anchorage and acquisition of nutrients and water. In this study,a set of 204 recombinant inbred lines（RILs） was derived from the widely adapted Chinese hybrid ZD958（Zheng58 Chang7-2）,genotyped by sequencing（GBS） and evaluated as seedlings for 24 RSA related traits divided into primary,seminal and total root classes. Signi ficant differences between the means of the parental phenotypes were detected for 18 traits,and extensive transgressive segregation in the RIL population was observed for all traits. Moderate to strong relationships among the traits were discovered. A total of 62 quantitative trait loci（QTL） were identi fied that individually explained from1.6% to 11.6%（total root dry weight/total seedling shoot dry weight） of the phenotypic variation. Eighteen,24 and 20 QTL were identi fied for primary,seminal and total root classes of traits,respectively. We found hotspots of 5,3,4 and 12 QTL in maize chromosome bins 2.06,3.02-03,9.02-04,and 9.05-06,respectively,implicating the presence of root gene clusters or pleiotropic effects. These results characterized the phenotypic variation and genetic architecture of seedling RSA in a population derived from a successful maize hybrid.