Development of Improved Ciherang-Sub1 Having Tolerance to Anaerobic Germination Conditions

Abstract

The increased severity and frequency of flooding is causing greater yield reductions in most rice-growing areas. To address this, popular cultivars were improved through introgression of SUB1, an FR13A-derived QTL conferring submergence tolerance at the vegetative stage, using marker-assisted backcrossing (MABC). Ciherang-Sub1, one of these improved near isogenic lines (NILs), showed significantly higher tolerance compared to the original cultivar while retaining its desirable agronomic qualities. However, due to the current shift to direct seeding, seed germination may also be adversely affected by flooding; thus the addition of major QTLs which can confer anaerobic germination (AG) tolerance will be highly beneficial. The AG tolerance QTL, qAG-9-2, also referred to as AG1, derived from Khao Hlan On, a Myanmar landrace, has been introgressed into the elite cultivar IR64 to produce IR64-AG1. This research focused on the transfer of AG1 to Ciherang-Sub1 via MABC, using IR64-AG1, a closely-related donor. Introgression of AG1 and recovery of the Ciherang genome was done in two backcross generations followed by one generation of selfing. The use of a closely-related donor shortened the development period to two years which could have been further reduced if a larger BC1F1 population had been used. Phenotypic evaluation showed that introgression of AG1 significantly increased AG tolerance compared to Ciherang-Sub1, and that the newly developed Ciherang-Sub1+AG1 retained the submergence tolerance from SUB1. The approach is very promising for faster development of improved lines using closely-related cultivars or improved lines as donors for introducing key traits.

Diagnostic kit for rice blight resistance

“…This is of particular relevance because breeding efforts are more extensive in this context, owing to the recessive nature of SWEET-based resistance. CRISPR-Cas9 was used to edit five of the six EBE sites in the three SWEET promoters in widely used indica rice mega variety IR64 and in Ciherang-Sub1, a new flooding-tolerant elite line 24,33,34 . We generated edited lines with alterations in single or multiple EBEs.…”

Submergence Tolerance in Rice: Review of Mechanism, Breeding and, Future Prospects

“…Through standardized methods of screening at the IRRI, landraces tolerant to flooding at the germination stage were identified, which include Ma-Zhan Red, Nanhi, Khao Hlan On, and Khaiyan [17]. These rice germplasms have been used in physiological studies and genetic mapping for the development of improved rice lines with high levels of tolerance to aerobic germination stress using molecular and conventional breeding methods [41]. In India, rice varieties such as Sabita, Ambika, Saraswati, and Hangseswari are recommended by the Indian Council of Agricultural Research for deep-water rice farmers.…”

“…The gene encoding a trehalose-6-phosphate phosphatase (OsTPP) confers stress tolerance has been cloned and functionally validated [60]. This QTL has also been transferred to popular high-yielding rice varieties [41].…”

Pyramiding QTLs controlling tolerance against drought, salinity, and submergence in rice through marker assisted breeding

“…Shoot Na + and K + concentration (mg/g) and Na + /K + ratios of BILs and parents under control and salt stress (100 mM) conditions using hydroponic solution. to develop submergence-tolerant versions of popular rice varieties [17,24,43,44]. Similarly, efforts towards mapping of drought tolerance traits in rice at IRRI, Philippines identified several major effect QTLs in different mapping populations [11][12][13]45].…”