Evolution of maize landraces in southwest China: Evidence from the globulin1 gene

• We cloned and sequenced fifty-two DNA sequences of Glb1 genes from maize landraces from southwest China.
• A higher level of sequence variation was found in maize landraces.
• The maize landrace and parviglumis had no fixed differences and many shared polymorphisms.
• It is deduced that the maize landrace in southwestern China is domesticated from parviglumis and first introduced to Sichuan.

To explore the evolution of maize landraces from southwest China, we conducted a population genetic analysis of DNA sequence variation in globulin1 (Glb1) gene from 71 individuals representing the maize landrace, common maize, parviglumis, Zea luxurians, and Tripsacum dactyloides. We tested 477 variable, 800 conserved, and 253 informative sites in the Glb1   gene sequences. On the basis of πˆ per base pair and θˆ per base pair, the highest level of sequence variation was detected in parviglumis, followed by maize landraces and common maize. Z. luxurians and T. dactyloides retained a low level of variation. For Glb1 gene, negative or almost zero estimates for Tajima's D and Fu and Li's statistics in the 8 taxa, show that neutral evolution can be accepted. A large number of shared polymorphisms existed with no fixed differences between parviglumis and both the maize landrace and common maize. Maximum Likelihood (ML) analysis showed that sequences from maize landraces, common maize, parviglumis, and Z. luxurians were separated into two well-supported clades, and sequences from T. dactyloides constituted a distinct group. Excluding T. dactyloides and Z. luxurians, median-joining (MJ) network analysis clustered the remaining taxa into five haplotypes, revealing a higher level of haplotype diversity in the landrace. The findings suggest that the maize landrace in southwest China was domesticated from parviglumis and first introduced to Sichuan from India via Tibet.