A null allele of granule bound starch synthase (Wx-B1) may be one of the major genes controlling chapatti softness

Abstract

Chapatti (unleavened flatbread) is a staple food in northern India and neighboring countries but the genetics behind its processing quality are poorly understood. To understand the genes determining chapatti quality, differentially expressed genes were selected from microarray data of contrasting chapatti cultivars. From the gene and trait association studies, a null allele of granule bound starch synthase (GBSS; Wx-B1) was found to be associated with low amylose content and good chapatti quality. For validation, near-isogenic lines (NILs) of this allele were created by marker assisted backcross (MAB) breeding. Background screening indicated 88.2 to 96.7% background recovery in 16 selected BC3F5 NILs. Processing quality and sensory evaluation of selected NILs indicated improvement in chapatti making quality. Traits that showed improvement were mouthfeel, tearing strength and softness indicating that the Wx-B1 may be one of the major genes controlling chapatti softness.

Fig 1. Schematic representation of the crossing program for the generation of NILs for null allele of GBSS-4A gene.

Solid box indicates crossing and the dotted box indicates selfing. FGS- Foreground selection; BGS- Background screening.

Fig 2

A. Good chapatti with small uniform spots and good puffiness. B Screening of Indian germplasm with codominant PCR markers to understand the variation of GBSS-4A allele. The 668 bp fragment indicates null allele while 778 bp fragment indicates functional allele. 1. C306; 2. Sonalika; 3. K8027; 4. LOK1; 5. HI1563; 6. PBW343; 7. PBW621; 8. Negative control.