GA-sensitive Rht13 gene improves root architecture and osmotic stress tolerance in bread wheat

Abstract

The root architecture, more seminal roots, and Deeper roots help the plants to uptake the resources from the deeper soil layer to ensure better growth. The Gibberellic acid-sensitive (GA-sensitive) Rht genes are well known for increasing drought tolerance in wheat. Much work has been performed on the effect of these genes on the plant agronomic traits and little work has been done on the effect of Rht genes on seminal roots and root architecture. This study was designed to evaluate 200 wheat genotypes under normal and osmotic stress. The genotypes were sown in the solution culture and laid under CRD factorial arrangement with three replications and two factors i.e., genotypes and treatments viz. normal and osmotic stress (20% PEG-6000) applied one week after germination. The data was recorded for the root traits. Results demonstrated that out of 200 genotypes, the GA-sensitive Rht13 gene was amplified in 21 genotypes with a fragment length of 1089 bp. In comparison, the GA-insensitive Rht1 gene was amplified in 24 genotypes with a band size of 228 bp. From 200 wheat genotypes, 122 genotypes produced 5 seminal roots, 4 genotypes 4 seminal roots, and 74 genotypes 3 seminal roots. The genotypes G-3 (EBW11TALL#1/WESTONIA-Rht5//QUAIU#1), G-6 (EBW01TALL#1/SILVERSTAR-Rht13B//ROLF07) and G-8 (EBW01TALL#1/SILVERSTAR-Rht13B//NAVJ07) produced 5 seminal roots and have longer coleoptile (> 4.0 cm), root (> 11.0 cm) and shoot (> 17 cm) under normal and osmotic stress. Furthermore, Ujala 16, Galaxy-13, and Fareed-06 produced 3 seminal roots and have short coleoptile (< 3 cm), root (< 9.0 cm) and shoot (< 10.0 cm). These results showed that the genotypes showing the presence of GA-sensitive Rht genes produced a greater number of seminal roots, increased root/shoot growth, and osmotic stress tolerance compared to the genotypes having GA-insensitive Rht genes. Thus, the Rht13 gene improved the root architecture which will help to uptake the nutrients from deeper soil layers. Utilization of Rht13 in wheat breeding has the potential to improve osmotic stress tolerance in wheat.

Keywords: Breeding; Drought; Dwarfing genes; Grain yield; Osmotic stress; Root architecture.

Fig. 1

Phylogenetic analysis of Rht genes in Wheat (Ta), Soybean (Glymax) and unicellular organism Nostoc punctiforme (WP) to find the evolutionary history of Rht genes

Fig. 2

Gene structure analysis of Rht gene(s) in wheat showing the arrangements of introns, CDS and upstream and downstream

Fig. 3

Motif analysis of Rht gene(s) in wheat shows that the Rht genes are involved in various functions including Regulatory, ABA Responsiveness, Light Responsiveness, Cis-acting element in promotor and enhancer, Meristem expression, Anoxic specific inducibility, Low-temperature responsiveness, Drought inducibility, Auxin responsive element. The gene names are added on the vertical side and the different colors of the motif represent different functions involved

Fig. 4

PCR amplicons (a) P-1 = Rht1 at 228 bp (b) P2 = Rht13 at above 1 Kb. M1 and M2 show the ladder 50 bp and 1 Kb, respectively, while the number shows the PCR product of genotypes DNA. Figure that the genotypes 1, 3, 4, 5 and 7 Rht13 gene above 250 bp. 8, 9, 11, and 12 showed the presence of Rht13 gene at 1Kb

Fig. 5

Biplot display of seedling traits viz. coleoptile length (CL), seminal roots (SR), root length (RL) and shoot length (SL) of 200 wheat genotypes under normal (N) and osmotic stress (D) conditions. The Circle shows the theoretical highest extent of arrows, added by 68% of default confidence interval. Arrows depicts the correlation among these traits

Fig. 6

The genotypes showing 3 seminal roots (Ujala-16) vs. 5 seminal roots (G-6 = EBW01 TALL#1/SILVERSTAR-Rht13B//ROLF07) grown in Hoagland nutrient medium

Fig. 7

Correlation estimates of seedling traits viz. coleoptile length (CL), seminal roots (SR), root length (RL) and shoot length (SL) of 200 wheat genotypes sown under the solution culture (Hoagland solution) in a) normal condition (no stress) and b) osmotic stress (20% PEG). Blue shade shows positive association, and the light pink shade depicts the negative correlation. The start on these shades shows the significance (p ≤ 0.05) of correlation. The circle size showed the degree of association among the traits. More the size more will be the strong association