Validation of stay-green and stem reserve mobilisation QTLs: Physiological and Gene expression approach

Sukumar Taria ¹ Ajay Arora ^1* Sudhir Kumar ¹ Hari Krishna ^1* Biswabiplab Singh ¹ Shashi Meena ¹ Animireddy China Malakondaiah ¹ Kousalya S ¹ Jasdeep Chatrath Padaria ² Pradeep Kumar Singh ¹ BADRE ALAM ³ Sushil Kumar ³ Ayyanadar Arunachalam ³

• ¹ Indian Agricultural Research Institute (ICAR), New Delhi, India
• ² National Institute for Plant Biotechnology, Indian Council of Agricultural Research, New Delhi, Delhi, India
• ³ Central Agroforestry Research Institute (CAFRI), Jhansi, Uttar Pradesh, India

Using physiological and gene expression approach, QTLs for stay-green (SG) and stem reserve mobilisation (SRM) were validated in a pot experiment study by using contrasting recombinant inbred lines including its parental lines (HD3086/HI1500) in wheat. The experiment was laid down in completely randomized design under normal (control, drought) and late sown (heat and combined stress) conditions during rabi season 2022-23. Drought stress was imposed by withholding of irrigation at anthesis stage, whereas heat stress was imposed by one-month late sowing to normal sowing condition. Combined stress was imposed by onemonth late sowing along with restricted irrigation at flowering stage. Superior lines (HDHI113 and HDHI87) have both SG and SRM traits, whereas inferior lines (HDHI185 and HDHI80) have contrasting traits i.e. lower SG and SRM traits. HD3086 and HI1500 have SG and SRM traits respectively. The potential candidate genes were identified based on the flanking markers of mapped QTLs using BioMart tool in Ensembl Plant database to validate the identified QTLs.Real-time gene expression was conducted with SG-linked genes in the flag leaf and SRMlinked genes in the peduncle. From this study, HDHI113 and HDHI87 showed higher expression of SG-related genes in flag leaf under stress conditions. Furthermore, HDHI113 and HDHI87 maintained higher chlorophyll a content of 7.08 and 6.62 mg/gDW and higher net photosynthetic rate (PN) of 17.18 and 16.48 µmol CO2/m 2 /s respectively under combined stress condition. However, these lines showed higher expression of SRM-linked genes in peduncle under drought stress, indicating drought stress aggravates SRM in wheat. HDHI113 and HDHI87 recorded higher 1000 grain weight and spike weight difference under combined stress, further validated the identified QTLs linked to SG and SRM traits. Henceforth, identified QTLs can be transferred to developed wheat varieties through efficient breeding strategies for yield improvement during harsh climate conditions.