Breeding aluminum-tolerant maize germplasm using molecular marker-assisted selection

【Objective】The main-effect genes for aluminum(Al) tolerance were introgressed into common maize inbred lines, maize germplasms with Al tolerance were selected so as to provide reference for broadening Al-tolerant maize germplasms and breeding of Al-tolerant maize germplasms.【Method】Six backcross populations were constructed with Altolerant maize materials(CML530, CML532, CML533 and CML534) and common maize inbred lines(Xi1, 9058 and LX9801). Based on molecular marker-assisted selection(MAS), the targeted genes were selected using molecular markers(umc1468, ZmMATE1, ZmMATE2, MateF2 and ALMT93496) closely linked to Al-tolerant genes(ZmM1, ZmM2, ZmASL and ZmALMT2). The main-effect genes for Al tolerance were introgressed into common maize inbred lines, combined with the field performance, the stable lines were selected and Al-resistance was identified.【Result】In separated generation(BC₁F₁/S₁), 581 individuals were screened out from 6 populations at seedling stage using MAS, and a total of 69 individuals were selected. Combined with the field performance, 17 stable lines were finally obtained. The recovery rate of genetic background based on molecular markers was 73.9%-93.8%, with an average of 83.4%. Under the treatment of 0.2 mmol/L AlCl₃ solution, the growth of the roots of 17 stable lines was inhibited to varying degrees. The average net growth of the roots was 0.81 cm, which was extremely significantly lower(P<0.01, the same below) than that of the control(0.5 mmol/L CaCl₂ solution). The relative elongation of the roots of the stable lines showed extremely significant difference from that of the recurrent parent. The identification of Al tolerance at seedling stage showed that the relative root elongation rate of 17 selected lines ranged from 64.50%to 83.33%, with an average of 74.74%. All of them were medium or above Al-tolerant lines, NS1, NS9, NS10, NS14 and NS16 of which were highly Al-tolerant lines.【Conclusion】Molecular marker-assisted selection technique helps introgress the Al-tolerant major-effect genes into the normal maize inbred line. Moreover, the Al tolerance of inbred lines taking in more than one Al-tolerant genes is better than lines in the same population taking in a single Al-tolerant gene. Therefore, the accumulation of multiple Al-tolerant genes enhances the level of Al tolerance. The technology can serve as an effective method for the breeding of Al-tolerant maize germplasm.