Comparative Analysis of Water Stress Regimes in Avocado Plants during the Early Development Stage

Abstract

The avocado cv. Hass requires a suitable rootstock for optimal development under water stress. This study evaluated the performance of two avocado rootstocks (ANRR88 and ANGI52) grafted onto cv. Hass under four water stress conditions, 50% and 25% deficit, and 50% and 25% excess during the nursery stage. Plant height, leaf area (LA), dry matter (DM), and Carbon (OC) content in the roots, stems, and leaves were measured. Root traits were evaluated using digital imaging, and three vegetation indices (NDVI, CI_RE, and MTCI) were used to quantify stress. The results showed that genotype significantly influenced the response to water stress. ANRR88 exhibited adaptation to moderate to high water deficits. ANGI52 adapted better to both water deficit and excess, and showed greater root exploration. LA and DM reductions of up to 60% were observed in ANRR88, suggesting a higher sensitivity to extreme changes in water availability. More than 90% of the total OC accumulation was observed in the stem and roots. The NDVI and the MTCI quantified the presence and levels of stress applied, and the 720 nm band provided high precision and speed for detecting stress. These insights are crucial for selecting rootstocks that ensure optimal performance under varying water availability, enhancing productivity and sustainability.

Keywords: avocado seedling; phenotyping; spectral images; vegetation index; water stress.

Figure 1

Average plant height (cm) for the different treatments evaluated: water restriction of (T1) 50% and (T2) 25%, water excess of (T3) 25% and (T4) 50%, and (T5) control. Values represent the mean of the two rootstocks evaluated. Both rootstocks were combined with a common cv. Hass scion. Different letters indicate statistical differences at a significance of p ≤ 0.05 according to the Tukey test.

Figure 2

Leaf area (cm²) of the avocado plants using rootstock (A) ANRR88 and (B) ANGI52 for the different treatments evaluated: water restriction of (T1) 50% and (T2) 25%, water excess of (T3) 25% and (T4) 50%, and (T5) control. Both rootstocks were combined with a common cv. Hass scion. Different letters indicate statistical differences at a significance of p ≤ 0.05 according to the Tukey test.

Figure 3

Dry matter (g m^–2) partitioning per plant organ: leaves (light blue), stem (medium blue), and roots (dark blue) for ANRR88 (A) and ANGI52 (B). Treatments: water restriction of (T1) 50% and (T2) 25%, water excess of (T3) 25% and (T4) 50%, and (T5) control. Both rootstocks were combined with a common cv. Hass scion. Different letters indicate statistical differences at a significance of p ≤ 0.05 according to the Tukey test.

Figure 4

Organic Carbon (mg OC g^–1 DT) partitioning per plant organ: leaves (light blue), stem (medium blue), and roots (dark blue) for ANRR88 (A) and ANGI52 (B). Treatments: water restriction of (T1) 50% and (T2) 25%, water excess of (T3) 25% and (T4) 50%, and (T5) control. Both rootstocks were combined with a common cv. Hass scion. Different letters indicate statistical differences at a significance at the p ≤ 0.05 according to the Tukey test.

Figure 5

Mean values per treatment for (A) NDVI, (B) MTCI, and (C) CI_RE. Treatments: water restriction of (T1) 50% and (T2) 25%, water excess of (T3) 25% and (T4) 50%, and (T5) control. Both rootstocks were combined with a common cv. Hass scion. Different letters indicate statistical differences at a significance of 0.05 level, according to the Tukey test.

Figure 6

Process of avocado root conditioning for imaging: (A) washing, (B) sample before imaging, (C) angle opening data calculated by the software, and (D) density area occupied estimated by the software.