Marker-assisted backcross breeding for enhancing β-carotene of QPM inbreds

Maize possesses natural variations for crtRB1 (β-carotene hydroxylase) and lcyE (lycopene-e-cyclase) which significantly enhances provitamin A (proA) concentration. Enhancement of kernel proA carotenoids in QPM genetic background is of greater value. In this study, allelic variability for proA carotenoids was analyzed to identify promising β-carotene donor to introgress into QPM inbreds employing molecular breeding. Maize inbred MGU23379 (6.31 μg/g of β-carotene) was used as β-carotene donor to cross with recurrent parents (RPs), CB6-36 (CBML6) and CB7-28 (CBML7). In conversion program, F1, BC1F1, BC2F1, BC2F2, BC2F3, and BC2F4 materials were generated. In each generation, foreground selection was carried out with crtRB1-3′TE and umc1066. The crtRB1-3′TE segregated as per the expectation. Selection for modifiers, recombinants, and background genome of RPs was carried out in BC populations. The individuals with high recovery of recurrent parent genome were retained. Tryptophan/lysine content in introgressed progenies was on par, but β-carotene content was significantly high (6.25and 6.80 μg/g) compared to original inbreds (0.71 and 1.29 μg/g). Phenotypic data recorded for different traits in the BC2F3 populations did not show any significant difference between the converted BC2F3 families and their RPs. Also, grain yield of converted inbreds (PVCBML6 and PVCBML7) was on par with their original lines. In PVCBML6, stem anthocyanin pigmentation was reduced and silk color was changed to dark pink; whereas in PVCBML7, tassel was more erect and sparer; and silk color was changed to light pink compared to original inbreds. Converted inbreds provides an ideal platform for stacking number of nutritionally important traits.