A research paper entitled "Somatic variations in the meiosis-specific gene CrMER3 confer seedlessness in a citrus bud sport" authored by Professor Guo Wenwu and Professor Wu Xiaomeng's team from Huazhong Agricultural University was recently published online in the Journal of Integrative Plant Biology.

The study unveiled the molecular intricacies underpinning seedlessness in both male and female sterile citrus and the development of seedless fruit due to natural mutations in the meiosis gene CrMER3.

Aberrant meiosis results in sterility in both male and female seedless citrus. [Photo/news.hzau.edu.cn]

Using seeded citrus varieties (EG) as a control, the study observed that the floral organs of the somatic mutation variety seedless citrus (QS) displayed normal morphology, yet the mature pollen was inactive, resulting in seedless fruit. Even after pollination with active EG pollen, the fruit remained seedless, indicating sterility in both male and female components of QS. Further exploration pinpointed meiotic abnormalities as the root cause of sterility in QS and a specific 103 bp deletion in the CrMER3 gene region of QS.

Sanger sequencing indicated the presence of two CrMER3 allelic genes, CrMER3A and CrMER3a, in EG. Researchers confirmed the total absence of CrMER3 function in QS by dual immunofluorescence localization of CrMER3 and CrREC8.

Leveraging the CrMER3a mutation site, the team designed and developed KASP markers, validating their efficacy across different citrus types. This breakthrough provides a swift, efficient, and cost-effective molecular marker for selecting breeding parents for seedless citrus and early screening of hybrid offspring, culminating in the inception of a cohort of potential seedless germplasm.