Evaluating heat and drought resilience in ancient Indian Dwarf wheat Triticum sphaerococcum Percival using stress tolerance indices

Abstract

This study is the first to characterize the ancient wheat landrace Triticum sphaerococcum for drought and heat tolerance indices. A total of 116 T. sphaerococcum accessions and 6 bread wheat cultivars were evaluated under terminal heat (late sowing) and drought (restricted irrigation) stress during the 2021-22 (CS1) and 2022-23 (CS2) cropping seasons. Significant genotypic variation for stress indices was observed. T. sphaerococcum exhibited smaller yield declines under stress compared to bread wheat. In CS1, 57% of the accessions showed drought tolerance, and 63% exhibited heat tolerance. In CS2, 30 out of 45 accessions displayed tolerance to drought (SSI_D: 0.29-0.99), and 24 accessions showed tolerance to heat (SSI_H: 0.50-0.99). Correlation analysis revealed a negative correlation between the stress susceptibility indices (SSI, SSPI) and grain yield under stress, while yield index (YI), mean productivity (MP), geometric mean (GMP), harmonic mean (HM), and mean relative performance (MRP) showed a positive correlation. Using principal component, biplot, and cluster analyses, it was found that accessions TS49 and TS27 did best in drought stress and TS49, TS61, and PAUTS16 did best in heat stress. These ancient wheat accessions represent valuable genetic resources for breeding stress-tolerant wheat cultivars and enhancing genetic diversity.

Keywords: Triticum sphaerococcum; Drought and heat tolerance; Indian Dwarf wheat; Stress tolerance indices.

Fig. 1

Weekly weather parameter data of 2021-2022 wheat growing season of IARI, New Delhi.

Fig. 2

Weekly weather parameter data of 2022-23 wheat growing season of IARI, New Delhi.

Fig. 3

Weather parameter data from second fortnight of March 2022 to first fortnight of April 2022.

Fig. 4

Weather parameter data for the month of April 2023.

Fig. 5

Boxplot illustrates the variation among accessions of T. sphaerococcum and T. aestivum (check) cultivars for grain yield and stress indices under drought stress conditions. T. sphaerococcum accessions showed lesser susceptibility to drought against T. aestivum accessions when compared in terms of SSI, SSPI, RSI and PYR.

Fig. 6

Boxplot shows variation among accessions of T. sphaerococcum and T. aestivum (check) cultivars for grain yield and stress indices under heat stress conditions. T. sphaerococcum accessions showed higher yield stability as indicated by higher value for YSI and lower values for SSI, SSPI, RSI and PYR.

Fig. 7

Correlation among grain yield and stress indices under drought stress conditions.

Fig. 8

Correlation among grain yield and stress indices under heat stress conditions.

Fig. 9

Principal component analysis (PCA) based biplot showing correlation among the grain yield and stress indices under drought condition.

Fig. 10

Principal component analysis (PCA) based biplot showing correlation among the grain yield and stress indices under terminal heat stress conditions.

Fig. 11

K means clustering pattern among T. sphaerococcum accessions and checks based on grain yield and drought tolerance indices.

Fig. 12

K means clustering pattern among T. sphaerococcum accessions and checks based on grain yield and heat tolerance indices.

Fig. 13

Ridgeline plot showing variation among selected accessions of T. sphaerococcum and T. aestivum (check) varieties for grain yield and stress indices under drought and heat stress conditions. The vertical black lines indicate the mean trait value in the respective production environment. TA_N, T. aestivum under normal condition; TA_D, T. aestivum under drought condition; TA_H, T. aestivum under heat condition; TS_N, T. sphaerococcum under normal condition; TS_D, T. sphaerococcum under drought condition; TS_H, T. sphaerococcum under heat condition.