Hello everyone, I am currently extracting plant DNA using the 2% CTAB method. The procedure is as follows:

• Add 0.05g of fresh or dried leaf sample + 1.2 mL of 2% CTAB (containing 1% PVP) + 60 µL of 10% SDS + 2% β-mercaptoethanol (v/v) to the CTAB extraction buffer just before use.
• Incubate at 65°C for 40 minutes, inverting the tubes a few times every 20 minutes. Cool the mixture to room temperature. Centrifuge at 12,000 rpm for 15 minutes. Collect the supernatant.
• Add an equal volume of P:C:I (25:24:1), repeat twice. Centrifuge at 12,000 rpm for 5 minutes. Then add C:I (24:1) at a 1:1 ratio. Mix gently and collect the supernatant.
• Add 3M sodium acetate (CH₃COONa) at a 1:2 ratio. Centrifuge at 12,000 rpm for 5 minutes. Collect the supernatant.
• Add 2 volumes of 70% ethanol to the supernatant. Mix gently by inverting the tubes. Incubate at -20°C overnight. Centrifuge at 12,000 rpm for 5 minutes.
• Discard the supernatant. Add 500 µL of 70% ethanol to wash the pellet. Centrifuge at 6,500 rpm for 5 minutes. Discard the ethanol and let the pellet air-dry at room temperature (do not over-dry). Repeat this step twice.
• Add 50 µL of DEPC-treated water and store at -20°C.

However, the result is as shown in the picture — still dirty and highly degraded. I don’t know what the cause is, as I’ve ruled out factors such as non-refrigerated centrifugation and vortexing (since I did not use a vortex at all). The grinding step was also not very fine, so I’m feeling quite stuck and would really appreciate any help or suggestions.

(When I used this DNA for PCR, the PCR products were actually quite good.)