Banoth Madhu: Marker Assisted Selection for Disease Resistance in Rice. The use of DNA markers in plant breeding is called marker assisted selection (MAS). Bacterial leaf blight (BLB) is a major disease of rice, limiting production throughout the world. Xanthomonas oryzaepv. oryzae is highly virulent pathogen, causing major losses in Rice. Present scenario needs development of disease resistant variety through marker assisted selection is the most promising way to improve their performance.

1. Markers-Assisted Selection for Disease Resistance
Banoth Madhu
Ph.D Research Scholar
Genetics and Plant Breeding
Tamil Nadu Agricultural University, Coimbatore

2. Plant materials
 The donor line was a NIL in the genetic background of PR 106 (SS1113), possessing three
BB resistance genes, Xa21, xa13 and xa5 (Singh et al. 2001).
 The recurrent parent was a BB susceptible cultivar, Samba Mahsuri (BPT 5204).
 BB susceptible check was Taichung Native 1 (TN 1).

3. Amount of recurrent parent genome contribution ‘G’
Marker assisted selection

5. Results

6. Generation Number of
plantsscored
Number of plants that are
triple heterozygotes
Estimated maximum %
contribution of recurrent
parent genome to selectedBC
plant
Expected % contribution of
recurrent parent genome
to selected BC pant
BC1F1 145 11 72 75
BC2F1 126 10 80 87.5
BC3F1 120 8 89 93.754
BC4F1 80 6 96 96.875
Number of triple ‘R’ gene heterozygotes identified and estimation of recurrent parent genome
contribution
S.No. Gene combinations SS1113 X BPT 5204 BC4 F2 Line numbers
1 Xa21/Xa21 xa13/xa13 xa5/xa5 5 B-170, 189, 197, 210, 226
2 Xa21/Xa21 xa13/xa13 Xa5/Xa5 5 B-24, 29, 60, 69, 277
3 Xa21/Xa21 Xa13/Xa13 xa5/xa5 4 B-159, 199, 261, 266
4 xa21/xa21 xa13/xa13 xa5/xa5 2 B-48, 173
5 Xa21/Xa21 Xa13/Xa13 Xa5/Xa5 4 B-142, 249, 270, 276
6 xa21/xa21 xa13/xa13 Xa5/Xa5 4 B-9, 32, 182, 187
7 xa21/xa21 Xa13/Xa13 xa5/xa5 2 B-136, 184
Number of lines with multiple ‘R’ gene combinations

7. Evaluation of bacterial blight resistance in gene pyramid lines. Rice plants that
were forty days old were inoculated with saturated cultures of the BXO1 strain of
X. oryzae pv. oryzae as described in Materials and Methods. Lesion lengths were
measured 15 days after inoculation.

9. Conclusion;
• Four homozygous lines possessing high BB resistance, yield and grain quality similar to Samba Mahsuri
were nominated for AICRIP trials - IET 19026 - IET 19045 - IET 19046 - IET 19590

10. Improved Samba Mahsuri (IET 19046) - A first variety from MAS in India