AUTHOR=Kaur Ajinder , Sharma Urvashi , Singh Sarvjeet , Singh Ravinder , Vikal Yogesh , Singh Satnam , Malik Palvi , Kaur Khushpreet , Singh Inderjit , Bindra Shayla , Sarmah Bidyut Kumar , Sandhu Jagdeep Singh 

TITLE=Introgressing cry1Ac for Pod Borer Resistance in Chickpea Through Marker-Assisted Backcross Breeding

JOURNAL=Frontiers in Genetics

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2022.847647

DOI=10.3389/fgene.2022.847647

ISSN=1664-8021

ABSTRACT=<p>The gram pod borer <italic>Helicoverpa armigera</italic> is a major constraint to chickpea (<italic>Cicer arietinum</italic> L.) production worldwide, reducing crop yield by up to 90%. The constraint is difficult to overcome as chickpea germplasm including wild species either lacks pod borer resistance or if possessing resistance is cross-incompatible. This study describes conversion of elite but pod borer-susceptible commercial chickpea cultivars into resistant cultivars through introgression of cry1Ac using marker-assisted backcross breeding. The chickpea cultivars (PBG7 and L552) were crossed with pod borer-resistant transgenic lines (BS 100B and BS 100E) carrying cry1Ac that led to the development of BC<sub>1</sub>F<sub>1</sub>, BC<sub>1</sub>F<sub>2</sub>, BC<sub>1</sub>F<sub>3</sub>, BC<sub>2</sub>F<sub>1</sub>, BC<sub>2</sub>F<sub>2</sub>, and BC<sub>2</sub>F<sub>3</sub> populations from three cross combinations. The foreground selection revealed that 35.38% BC<sub>1</sub>F<sub>1</sub> and 8.4% BC<sub>1</sub>F<sub>2</sub> plants obtained from Cross A (PBG7 × BS 100B), 50% BC<sub>1</sub>F<sub>1</sub> and 76.5% BC<sub>1</sub>F<sub>2</sub> plants from Cross B (L552 × BS 100E), and 12.05% BC<sub>2</sub>F<sub>2</sub> and 82.81% (average) BC<sub>2</sub>F<sub>3</sub> plants derived from Cross C (PBG7 × BS 100E) carried the cry1Ac gene. The bioassay of backcross populations for toxicity to <italic>H</italic>. <italic>armigera</italic> displayed up to 100% larval mortality. BC<sub>1</sub>F<sub>1</sub> and BC<sub>1</sub>F<sub>2</sub> populations derived from Cross B and BC<sub>2</sub>F<sub>3</sub> population from Cross C segregated in the Mendelian ratio for cry1Ac confirmed inheritance of a single copy of transgene, whereas BC<sub>1</sub>F<sub>1</sub> and BC<sub>1</sub>F<sub>2</sub> populations obtained from Cross A and BC<sub>2</sub>F<sub>2</sub> population from Cross C exhibited distorted segregation ratios. BC<sub>1</sub>F<sub>1</sub> plants of Cross A and Cross B accumulated Cry1Ac protein ranging from 11.03 to 11.71 µgg<sup>−1</sup> in leaf tissue. Cry1Ac-positive BC<sub>2</sub>F<sub>2</sub> plants from Cross C demonstrated high recurrent parent genome recovery (91.3%) through background selection using SSR markers and phenome recovery of 90.94%, amongst these 30% plants, were homozygous for transgene. The performance of BC<sub>2</sub>F<sub>3</sub> progenies derived from homozygous plants was similar to that of the recurrent parent for main agronomic traits, such as number of pods and seed yield per plant. These progenies are a valuable source for <italic>H</italic>. <italic>armigera</italic> resistance in chickpea breeding programs.</p>