Potato variety improvement through marker assisted selection
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Late blight (LB), caused by Phytophthora infestans (Mont.) de Bary, is the most destructive for potato. The main objective of this study was to evaluate 72 potato lines, derived from cross products of the recipient cv. ACI Pakri-1 and a LB resistant donor variety, against late blight. The experiment was conducted with three levels of inoculums pressure (i) LB inoculation & no fungicide, (ii) No LB inoculation & no fungicide and (iii) No LB inoculation & fungicide. LB infection was assessed at 10 days interval by scoring the percentage of foliage destruction. Three categories of potato lines were selected considering level of LB infection and tuber appearance - (a) LB resistant - 8 lines, (b) LB tolerant - 14 lines, and (c) LB susceptible - 14 lines. The foliage destruction of selected LB resistant lines was considered to be between 1 to 25%, in LB tolerant lines between 25 to 50 %, and in LB susceptible lines between 51 to 90% at 85 DAP. The recipient ACI Pakri-1 had 100% foliage destruction at 63-65 DAP. On the other hand, lowest foliage destruction 1-2% was recorded in Line 8. In LB resistant lines low AUDPC, rAUDPC and susceptible scale value were found. The highest susceptible scale value 9 was recorded mostly in LB susceptible cv. ACI Pakri-1 and BARI Alu-40; where the range of susceptible scale value 0.1 was calculated in line. However, LB resistant gene Rpi-abpt and Rpi-blb1, amplified using marker R2-F1/R2-R3 and 1521/518 respectively, were identified through marker assisted selection (MAS) in the donor variety and crossed LB resistant line 8, 13, 41, 61, 72 and 54 but absent in recipient ACI Pakri-1. Round tubers, mostly of uniform size, deep to light red and white skin, red and deep eye were found in resistant lines. The highest number of tubers/ hill (20) was recorded in line 8 under natural inoculums pressure, and the highest weight of tuber/hill (460g) was found in line 8 and yield was 38.3 Mt/ha, which was higher than the donor variety (31.5 Mt/ha) and the recipient ACI Pakri-1 (29.0 Mt/ha) under fungicide application treatment. Finally, based on the potentiality against LB and yield performance, Line 8 was registered as potato variety namely ACI LBR Pakri-1 by Seed Wing, Ministry of Agriculture, Bangladesh.