Identification and Evaluation of Drought Tolerance and Screening of Drought-Tolerant Germplasm for Core Germplasms in Proso Millet at Adult Stage

Drought is one of the major constraints influencing on the growth, development, and yield of proso millet. To screen excellent drought-tolerant accessions and identification indicators will promote the drought-tolerant varieties breeding and drought tolerance molecular mechanisms analysis of proso millet.

In this study, 200 core germplasm accessions of proso millet were used to identify field drought tolerance at adult stage in 2021-2022 at Dunhuang, Gansu province, with two treatments of normal irrigation and drought stress. Eleven morphological indicators, such as leaf area (LA), main stem diameter (MSD), number of main stem nodes (NMSN), main panicle length (MPL), peduncle length (PL), plant height (PH), straw weight per plant (SWPP), panicle weight per plant (PWPP), grain weight per plant (GWPP), thousand grain weight (TGW), and yield per plot (YPP) were determined. Comprehensive drought tolerance coefficient (CDTC value), drought resistance index (DRI value), and drought resistance comprehensive evaluation value (D value) were combined to identify the drought tolerance of proso millet at adult stage.

There were significant differences in all eleven indexes among different accessions under different water treatments, including leaf area, main stem diameter, number of main stem nodes, main panicle length, peduncle length, plant height, straw weight per plant, panicle weight per plant, grain weight per plant, thousand grain weight, and yield per plot. The growth of proso millet was inhibited under drought stress treatments. Compared with the normal irrigation treatments, all the eleven indexes under drought treatments were significantly reduced, and yield per plot was more sensitive to drought treatments. The correlation analysis found that certain degrees of correlation existed among the drought tolerance coefficients of all traits, the correlation between panicle weight per plant and grain weight per plant was strongest, with a correlation coefficient of 0.943. Eleven evaluation indexes were converted into six comprehensive indexes by principal component analysis, with a cumulative variance contribution of 80.667%. The drought tolerance ranking of proso millet accessions based on CDTC value, DRI value and D value was generally consistent. The 200 proso millet accessions were classified into four categories according to D value cluster analysis, 10 of cluster Ⅰ were highly drought tolerant, 70 of cluster Ⅱ were drought tolerant, 81 of cluster Ⅲ were drought sensitive, and 39 of cluster Ⅳ were highly drought sensitive. Plant height, grain weight per plant, panicle weight per plant and main panicle length were highly correlated with D value, with correlation coefficients of 0.756, 0.697, 0.696 and 0.679, respectively. The regression equation for the drought tolerance evaluation was constructed by stepwise regression analysis: Y=-1.509+0.362X₁+0.174X₂+0.349X₃+0.389X₄+0.307X₅+ 0.251X₆+0.218X₇.

The drought resistance comprehensive evaluation value method could be suitable for evaluating the drought resistance of proso millet at adult stage. Ten accessions with highly drought tolerance, such as Balinzuogedashu (00000525), Gaotaiwumizi (00002677) and Minlehongmizi (00002687). Plant height, panicle weight per plant and main panicle length could be used as primary evaluation indexes for drought tolerance of proso millet at adult stage.