Studi efek introgresi PUP1 (P Uptake1) untuk meningkatkan toleransi padi terhadap defisiensi fosfor

Abstract

Phosphorus is one of the major nutrient for plant. P-deficiency occurs in most of soil, mostly due to the bounding of P to minerals, such as Ca, Fe, and Al, therefore, P is not available for plants. Rice plant having tolerance to Pdeficiency is very important, because it can decrease the input of P fertilizer, lime, and organic matter. Genes related to P uptake had been mapped (Pup1/P Uptake 1) and some molecular markers for selection purposes have already been developed. Activities for introgression of Pup1 into Indonesian modern rice varieties were conducted to increase the yield and to observe effect of Pup in the Indonesian varieties. Pup1 from Kasalath and NIL-443 was introgressed into Situ Bagendit and Batur, through conventional breeding (backcross method). They are Situ Bagendit x Kasalath, Situ Bagendit x NIL-C443, Batur x Kasalath, and Batur x NIL-C443. Their progenies were selected using molecular markers (spesific markers for Pup1 and SSR markers). This experiments were conducted in Indonesia and IRRI (Philippines) since August 2006 up to June 2009. Development of Pup1 lines were conducted using foreground, recombinant, dan background markers up to BC2F3 lines for each crossing. Based on molecular analysis, genotype condition of Pup1 locus indicated homozygote locus for all of BC2F2 selected lines, and this result was also found in the subsequent generation. Small part of donor segment (Kasalath or NIL-C443) still remaining in the BC2F3 lines in different location, so it will influence plant performance. These donor parent segment were 1.6 – 2.6 % of genome total lenght of rice genome. Testing on BC2F3 lines were performed using 3 methods : nutrient solution (0.5 ppm P and 10 ppm P under 0 ppm Al and 45 ppm Al), Ultisol soil from Kentrong Village (2 kg P/ha and 25 kg P/ha), and field experiment at Taman Bogo, Lampung (no P fertilizer and add P fertilizer). The results showed that many variation of agronomic characters at each BC2F3 lines occurs for each experiment, but effect of Pup1 on agronomic characters can be clearly detected on less P compared with adequate P. Pup1 on BC2F3 lines influenced on the increasing of plant dry weight compared the parent, but tend to decrease on generative phase (especially weight of filled grain/plant), eventhough some lines showed better performance than their parent on both, dry weight and the weight of filled grain/plant. For further experiment, the BC2F3 lines had been selected at Taman Bogo field experiment, Lampung, by individual plant.