ABSTRACT

Sorghum [Sorghum bicolor L. Moench] is vital cereal crop for semi-arid regions like India, grown in both rainy (kharif) and post-rainy (rabi) seasons. Rabi sorghum often faces terminal drought due to reliance on stored soil moisture, greatly affecting productivity. In the present study evaluated 96 rabi sorghum genotypes during rabi 2019 and 2020 seasons at ICAR-IIMR Hyderabad to assess genetic variability, heritability and identified promising candidates for breeding programs aimed at improving drought tolerance and yield. Efforts included enhancing drought resilience in the rabi varieties M35-1 and CSV-29R by introducing stay-green QTLs (Stg3a and Stg3b) from the drought-tolerant parent B35 through marker-assisted introgression.
The evaluation revealed significant genotypic differences and considerable genetic diversity among the landraces. Notably, IS18512 exhibited early flowering, while PR3047 was late flowering. Plant height varied significantly, with PR3167 being the tallest, and B35 the shortest. At maturity, genotypes RSLG2386 had the highest number of green leaves. SPAD readings were highest in IS22152 and B35 at the boot leaf stage, with B35 maintaining the highest readings at maturity. Panicle weight was highest in IC420956 during rabi 2019 and IC345199 in the following season, these genotypes also recorded the highest grain yield per plant in their respective seasons. Genotypes like IS18512, PR3167, TSLC-3 and IC420956 displayed promising traits, making them potential candidates for further breeding.
Genetic variability analysis revealed that the PCV was higher than the GCV, indicating significant environmental effects. High heritability was noted for panicle length, grain yield per plant, and panicle weight, suggesting strong genetic control. Path analysis showed positive direct effects of panicle weight, SPAD readings, and the number of green leaves at maturity on grain yield. Mahalanobis D² statistics indicated significant genetic diversity, with Clusters V (B35) and VI (IC420956, RSLG2241), displaying high mean values for grain yield and panicle weight, making them valuable for breeding.
In the study's second phase, stay-green QTLs Stg3a and Stg3b were introduced into elite rabi varieties M35-1 and CSV-29R through marker-assisted introgression. The M35-1 x B35 cross advanced to the BC2F3 generation, and CSV-29R x B35 to the BC1F3 generation. Homozygous plants carrying both QTLs were identified across backcross generations, resulting in lines with enhanced drought tolerance and potentially improved yields. This marks a significant advancement in developing drought-tolerant sorghum varieties for semi-arid regions.
Further evaluation of backcross progenies at ICAR-IIMR, Hyderabad and ICAR-CRS, Solapur showed significant variation MAB M35-1, BC2F3 lines with stay-green QTLs demonstrated a range of flowering times and plant height, with progeny like 13-13-37 showing the highest grain yield per plant (g). MAB CSV-29R, BC1F3 progenies exhibited diverse performance, while B35 reported early flowering but lower yields, whereas genotypes C3-8-69 excelled in grain yield and 100-seed weight. The high genetic variability and notable heritability for traits like plant height and panicle weight suggested that these traits are favorable for genetic improvement in sorghum. The MGIDI index analysis identified proginies Notably, 13-13-44 and C3-8-69 was identified as a top genotype in both locations, indicating its consistent performance across environments. Introducing stay-green QTLs into elite varieties boosts drought resilience and yield. Key genotypes identified highlight the importance of genetics in improving sorghum productivity in semi-arid regions.