Ancient Aus Rice Lineages Hold the Key to Stable Yields in Drought-Hit Rainfed Fields

Rice feeds more people than any other cereal, yet a large share of the world’s rice paddies depend on rain rather than irrigation, leaving harvests hostage to the whims of the monsoon. For the millions of smallholder farmers who cultivate these rainfed fields, the difference between a good season and a bad one often comes down to how well a variety tolerates drought, poor soils and unpredictable weather. A new study from India now shines a spotlight on an underexploited group of traditional rice varieties, the aus gene pool, and identifies several genotypes that deliver consistently high yields across radically different growing conditions. The findings, published in the Indian Journal of Genetics and Plant Breeding, offer plant breeders a ready-made set of donor lines for developing rice that stays productive even when the environment turns hostile.

The research, led by Puranjoy Sar and Somnath Roy of the ICAR-Central Rice Research Institute’s Central Rainfed Upland Rice Research Station in Hazaribag, together with colleagues at the ICAR Research Complex for NEH Region in Manipur and the Crop Physiology and Biochemistry Division in Cuttack, set out to answer a deceptively simple question: which aus rice varieties can be trusted to perform well no matter what the season throws at them? The aus group, one of the three major varietal groups of Asian cultivated rice alongside indica and japonica, is prized among geneticists for its early maturity and remarkable tolerance of drought and nutrient-poor soils. Yet, as the authors note, the contribution of this adaptive diversity to yield stability across contrasting production systems has remained poorly quantified until now.

To fill that gap, the team evaluated 47 aus genotypes across four distinct field environments at Hazaribag in the eastern Indian state of Jharkhand, a region where rainfed rice cultivation dominates. The four environments were deliberately chosen to represent the major management systems faced by rainfed farmers: direct-seeded conditions under rainfed cultivation, low-phosphorus soils, conventional transplanted paddies, and aerobic systems in which the crop is grown in unsaturated soil much like wheat or maize. The trials ran across three growing seasons, from 2022 to 2024, giving the researchers enough environmental variation to test each genotype’s mettle under genuinely contrasting conditions rather than a single lucky or unlucky year.

The statistical machinery brought to bear on the data was as important as the fieldwork itself. Grain yield from each plot was dissected using three complementary analytical frameworks: the additive main effects and multiplicative interaction model, better known as AMMI; the classic Eberhart-Russell regression approach, which estimates how sensitively a genotype responds to improving or deteriorating environments; and a suite of multivariate stability methods. This multi-pronged design matters because no single stability statistic is perfect. AMMI models excel at visualizing and quantifying genotype-by-environment interaction, while regression-based parameters capture a genotype’s responsiveness to environmental change. When independent methods converge on the same set of winners, breeders can be far more confident that the selection reflects real biology rather than statistical artifact.

The results revealed just how dominant the environment is in shaping rainfed rice yields. Environmental effects accounted for 36.0 percent of the total variation in grain yield, while the interaction between genotype and environment, the statistical term describing how varieties rank differently from one field or season to the next, explained another 34.1 percent. In contrast, the genotypes’ own main effects contributed only 18.8 percent of the variation. In practical terms, this means that where and how a rice plant is grown matters nearly as much as the genes it carries, and that a variety performing brilliantly in a transplanted paddy may flop in an aerobic or phosphorus-starved field. For breeders, ignoring this interaction is a recipe for releasing varieties that disappoint farmers the moment they leave the research station.

Across the four environments, mean grain yields of the 47 genotypes spanned an impressive range, from 197 to 484 grams per square meter, a more than twofold difference that underscores the untapped productive potential sitting within this germplasm. Stability parameters varied just as widely, with some genotypes swinging dramatically between good and bad environments while others held their yields remarkably steady. The critical outcome of the study, however, was the discovery that the same small group of genotypes emerged at the top of every analytical framework applied. Named varieties and accessions including Kalia, ARC 11959, ARC 12021, ARC 12079, Devarasi and Sada aus consistently combined above-average grain yield with reduced sensitivity to environmental fluctuation.

What makes this convergence especially valuable is that these top performers were not merely stable in a statistical sense; they were also robust under the two stresses that matter most in rainfed systems, water limitation and phosphorus deficiency. The genotypes showed favourable performance under drought and in phosphorus-poor soils, supporting their classification as broadly adapted rather than specialists tuned to a single niche. The ARC-prefixed accessions trace back to the traditional rice collections assembled by Indian agricultural research programs, and landraces such as Kalia and Sada aus represent farmer-selected material refined over generations of cultivation in marginal environments. Their ability to buffer yield across direct-seeded, transplanted, aerobic and low-phosphorus conditions suggests they carry combinations of adaptive traits, likely spanning root architecture, nutrient-use efficiency and drought-response physiology, that modern high-yielding varieties have often lost.

Earlier work by some of the same authors lends mechanistic plausibility to these field observations. Recent genome-wide association studies in aus rice have identified quantitative trait loci underlying early seedling vigour, a trait crucial for direct-seeded systems where seedlings must establish quickly in unpredictable soil moisture. Other research has documented phosphorus starvation tolerance in aus material, including the effect of the well-known PSTOL1 gene, and independent international studies have linked variation in aus root architecture, particularly nodal root diameter, to grain yield maintenance under drought. The new stability analysis complements this genetic work by pinpointing exactly which accessions deserve priority as donors in crossing programs, effectively narrowing the search space for breeders seeking to combine multiple stress-adaptive traits in a single variety.

The implications extend well beyond a single research station in Jharkhand. Rainfed rice accounts for a substantial share of production across South Asia and sub-Saharan Africa, and climate projections suggest that rainfall variability will only intensify, making yield stability, rather than peak yield alone, an increasingly central breeding objective. Genotypes that maintain output across drought, nutrient limitation and shifting management systems are precisely the kind of insurance that vulnerable farming systems need. By quantifying how much of yield variation is driven by genotype-by-environment interaction and by delivering a validated shortlist of broadly adapted donors, the study provides a practical foundation for dissecting the genetic architecture of multi-stress adaptation. If the stability of Kalia, Devarasi and their fellow aus lines can be traced to specific genes and introgressed into elite backgrounds, the ancient diversity preserved in this overlooked rice group could help secure harvests for the farmers who need it most.

Subject of Research: Yield stability evaluation of aus rice genotypes across contrasting rainfed agro-ecologies for identifying donor lines for rainfed rice breeding

Article Title: Yield Stability of aus Rice Genotypes Across Contrasting Rainfed Agro-Ecologies: Identifying Potential Donors for Rainfed Rice Improvement

Article References: Yield Stability of aus Rice Genotypes Across Contrasting Rainfed Agro-Ecologies: Identifying Potential Donors for Rainfed Rice Improvement. (n.d.). https://doi.org/10.1007/s44489-026-00022-3

Image Credits: AI Generated

DOI: 10.1007/s44489-026-00022-3

Keywords: aus rice, yield stability, rainfed rice, genotype-by-environment interaction, AMMI analysis, drought tolerance, low phosphorus tolerance, plant breeding, germplasm, Hazaribag, direct-seeded rice, landrace