Assessment of Triticosecale-Derived Wheat Introgressions for Karnal Bunt (Tilletia Indica Mitra) Resistance

Triticosecale-Derived wheat Introgressions for Karnal Bunt Resistance

Abstract

Karnal bunt (KB) caused by Tilletia indica is a quarantine disease of wheat that reduces grain quality and hinders international trade. Rye (Secale cereale) has long been harnessed as a valuable source of  resistance to diverse biotic and abiotic stresses. Its transfer into bread wheat is facilitated through triticale (Triticosecale), which often carries KB resistance. The present study involves evaluation of 337 introgression lines for KB under artificially created epiphytotic conditions during two consecutive crop seasons (2020-21 and 2021-22). The lines were developed by introgressing KB resistant triticale accessions (TL 2908, TL 2065, TL 3021 and TL 3048) into elite wheat cultivars (PBW 343, PBW 550 and DBW 17) serving as recipient backgrounds. Screening for KB resistance revealed that 26 lines were highly resistant (HR) and 151 lines were resistant (R). The highest proportion of highly resistant (HR) lines was observed among the introgression lines derived from the cross TL 3048/2*CS(S)//PBW 343 (15.05%), followed by TL 3021/2*CS(S)//PBW 550 (13.11%). In contrast, the maximum proportion of resistant (R) lines was recorded in introgressions derived from TL 2908/2*CS(S)//DBW 17 (83.33%) and TL 3048/2*CS(S)//PBW 550 (70.00%). To determine the chromosomal basis of resistance, the 177 lines identified as highly resistant (HR) and resistant (R) were further analyzed using expressed sequence tag (EST)-based markers specific to rye chromosomal regions. Marker analysis resulted in identification of 4 lines carrying both 4RL and 4RS chromosome arms, while 53 lines possessing introgressed segments of 4RL. These results indicate that the rye chromosome arms 4RL and 4RS may contribute to KB resistance in the evaluated material. The findings therefore suggest that 4RL and 4RS are potential carriers of KB resistance loci. These rye chromosomal regions could be further validated and fine-mapped to identify the genetic determinants underlying KB resistance. Moreover, the identified KB resistant introgression lines will be a valuable pre-breeding material and potential donor sources for the development of KB resistant wheat cultivars in future breeding programs.