Carotenoid Cleavage Dioxygenase 8 Enhances Interspecific Facilitation in Maize‐Soybean Intercropping via Arbuscular Mycorrhiza Symbiosis Under Phosphate Limitation

ABSTRACT

Carotenoid Cleavage Dioxygenase 8 ( CCD8 ) regulates strigolactone (SL) biosynthesis, which mediates the establishment of arbuscular mycorrhiza fungal (AMF) symbiosis. This symbiosis makes a major contribution in nutrient uptake, thereby improving crop productivity, mostly without the need for specific inoculation. Quantifying the extent of this contribution in typical intercropping systems remains challenging. A pot experiment was conducted using ZmCCD8 knockout ( zmccd8 ), overexpression ( ZmCCD8 ‐OE), and wild type (WT) maize lines, grown in sole cropping or intercropping with soybean under low phosphate (LP) and control conditions. Intercropped ZmCCD8 ‐OE and soybean showed a 61.9% higher overyielding effect, partially attributed to a 72.7% greater AMF colonisation rate in ZmCCD8 ‐OE than WT counterparts under LP. Together with the greater root, AMF promoted P accumulation by 58% and 35% in the ZmCCD8 ‐OE shoot and root, respectively. Conversely, intercropped zmccd8 conferred negative impacts under LP, corresponding to 47.6% and 63.4% less overyielding and AMF colonisation, respectively. Consistent with these results was differential expression of genes ( CCD8, D14, CCaMK , CYCLOPS , RAM1 , PT6 / PT8 ) regulating AMF symbiosis and P uptake in maize and soybean. Collectively, ZmCCD8 enhances interspecific facilitation by stimulating root growth and AMF symbiosis, providing a genetic approach for higher crop productivity in intercropping systems without inoculation.