This document summarizes genetic factors that affect abiotic stress tolerance in crops. It discusses genes and QTLs that confer tolerance to flooding, drought, salinity, ion toxicity, ion deficiency, low temperatures, and high temperatures. For each stress, specific genes are mentioned, such as SUB1 for submergence tolerance in rice, DRO1 for deeper rooting and drought tolerance in rice, and HKT1 genes for salt tolerance by regulating sodium transport in various crops. The document provides examples of genes from different crops that help tolerate the various abiotic stresses through mechanisms like ion transport, transcription factor regulation, or morphological adaptations.

1. GENETIC FACTORS AFFECTING
ABIOTIC STRESS TOLERANCE
Prepared by,
BHAVYASREE R K
2016800802
Dept. Of Genetics and Plant Breeding

2. Introduction
• Crop yield reduction and climatic change
• Beneficial loci for productivity : in challenging
environment
• Abiotic stress refers to suboptimal climatic
and/or edaphic conditions that adversely affect
cellular homeostasis and that ultimately impair
growth and fitness (Michelbart et al 2015)
• Tolerence or avoidance through acclimation and
adaptation :evolved through natural selection
• Gene and QTL mapping: genetic cause behind
biological mechanisms

3. Flooding
• Reduced energy owing to lower photosynthesis rate and/or
low O2 levels
• Rice
– SUBMERGENCE1 (SUB1)- Indian landrace Dhalputtia (FR13A)
– SNORKEL genes:SK1 and SK2- Thai deepwater accession
(Japonica) C9285
• survive more than 2 weeks of complete submergence
• The genes responsive for Ethylene responsive transcription
factors
– SUB1 :Ethylene-promoted inhibition of GA-mediated elongation
:energy conservation
– SK1 and SK2 : Ethylene- promoted, GA-mediated elongation of
stem internodes

5. Drought
• DRO1 : Rice from a tolerant genotype
– DRO1, DEEPER ROOTING1
– Unknown gene product
– Enhanced deep rooting; Auxin-regulated
asymmetric root growth

6. Salinity
• The genes codes for Na+ transporters
• HKT1;5-A at the Nax2 locus
– Triticum turgidum ssp. durum from Triticum monococcum
– Root Na+ exclusion from xylem vessels
• TaHKT1;5
– Triticum aestivum from T. aestivum D genome (origin
Aegilops tauschii
– Higher K+/Na+ in expanding and young leaves
• HKT1;5
– O. sativa ssp. japonica from Tolerant O. sativa ssp. indica
– Shoot K+/Na+ homeostasis

8. Ion toxicity
• High Al3+
– Root Al3+-activated transporter genes :
detoxification or compartmentalisation
– SbMATE at the AltSB locus : Sorghum
bicolor (Citrus chelation)
– MATE1 in Zea mays (Citrus chelation)
– ALMT in T. aestivum (Malate chelation)
– NRAT1 in O. sativa
(compartmentalization)

9. • High B
– Root B efflux transporter
– Restricts net B accumulation
– Bot1 in Hordeum vulgare
– Bot-B5b in Triticum aestivum
Ion toxicity

10. Ion deficiency
• Low Pi
– PSTOL1 at the Pup1 locus in O. sativa
– From African rice
– Protein kinase
– Enhanced crown root development
for improved Pi acquisition
• Low Fe3+ and Zn2+
– NAM-B1 in T. turgidum ssp. durum
• NAC Transcription factors
• Accelerates senescence and nutrient
remobilization to grain

11. Low and sub-freezing temperatures
• VRN1 at the FR1 locus
– T. aestivum & H. vulgare
– MADS box TF
– Regulation of vernalization; low-temperature-induced CBF
and regulation activation; freezing tolerance
• CBFs at the FR2 locus
– T. aestivum & H. vulgare
– CBFs (TFs)
– CBF copy number-dependent expression and regulon
activation; freezing tolerance
•

12. High temperature
• Rapid alterations in gene expression, increases in heat
shock protein (HSP) levels, modification of membranes,
alterations in the cytoskeleton and management of
oxidative stress
• Wheat
– Alien introgression from wild relative Leymus racemosus
provided heat tolerance
• Heat & drought tolerant rice :N22 (aus ssp.)
– QTLs : high levels of HSPs in anthers, spikelets and flag leaves
• Escape strategy :QTLs from Oryza officinalis
– avoid heat-induced spikelet sterility
– promoting dehiscence and fertilization in the cooler early
mornings

13. THANK YOU…