Impact of Water Stress on the Productivity and Quality Parameters of Wheat and Their Potential Use in the Breeding Program ^†

Abstract

Wheat occupies a prominent place at the national and international levels. This food crop is considered a main source of human and animal nutrition. Water stress is one of the main causes of the decline in bread wheat production in Morocco. Therefore, breeding for resilient varieties is of great importance to overcome this challenge. In this context, the main objective of this study is to assess the impact of drought on the productivity of bread wheat and to determine the key selection criteria for drought tolerance in a Mediterranean environment. To do this, 31 varieties and lines of bread wheat were evaluated at two contrasted INRA experimental stations during the 2020–2021 cropping season. Five productivity and quality parameters were assessed: grain yield, biomass, number of fertile spikes, thousand grain weight, and protein content. The results demonstrate the negative impact of water stress on the various parameters studied, except for the protein content which was higher in arid conditions compared to the favourable ones. Based on correlation analysis, the number of fertile spikes and the biomass could constitute the potential selection criteria for drought resistance. These trials will be repeated for several years under the effect of other intensities of stress and agro-ecosystems and by incorporating other parameters to confirm the results obtained. The line “BT19I5” showed great yield potential under both conditions and can be of great interest for farmers and for potential release at the national program.

1. Introduction

The cereal sector occupies a decisive place in the Moroccan agriculture. Cereal crops are considered a main source of human and animal nutrition. In Morocco, bread wheat (Triticum aestivum L.) is the most consumed cereal, estimated at 258 kg/year/person. About 3 million hectares of wheat are grown annually, with a global production of 48.2 million quintals in 2021.

This cereal crop has been given special attention, particularly in breeding programs in Mediterranean countries, because of its adaptation to semi-arid environments and its unique technological quality, compared to other cereals [1]. Bread wheat production is affected by several abiotic stresses, mainly drought and heat and biotic stresses via attacks by parasites and pests [2], which hinders the achievement of good economic yields of good quality.

The sensitivity of bread wheat to water stress is one of the main causes of the decline in national production over years and even decades. Thus, the orientation of research in the identification of new agricultural techniques and the dissemination of resilient varieties, are part of the adaptation strategies for reducing the effects of climate change and increasing cereal yield in the long term. Grain yield has low heritability (<20%) over variable stress intensities and unpredictable environmental conditions [2]. Thus, the identification of reliable secondary indirect selection criteria can improve the efficiency of selection for drought tolerance [3].

In this perspective, the main objective of this study is to (1) evaluate the impact of drought on the productivity of bread wheat; (2) deduce the key selection criteria for drought tolerance in the Moroccan environment; and (3) determine the best promising lines that are resilient to stress and of interest to farmers in the Mediterranean and arid regions in general.

2. Materials and Methods

The genetic material consists of 31 varieties and lines of bread wheat from the national breeding program at the National Institute for Agronomic Research (INRA). The trials were carried out in two contrasting cereal regions in terms of rainfall at two INRA experimental sites. The first station is located in the region of Rabat “Marchouch” known by humid and relatively favorable climatic conditions (>500 mm). The second station “Jemaat Shaim” is part of the arid agroecosystem in Safi region with an average annual rainfall of less than 300 mm.

The experimental design is a complete randomized block design with three repetitions. Each elementary plot consists of 6 lines of 5 m in length and a spacing of 0.20 m. Five parameters of productivity and quality were analyzed: grain yield, biomass (BM), number of fertile spikes (NFS), thousand grain weight (TGW) and protein content. Statistical analyzes were performed using Genstat 18 software to perform analysis of variance for each site and between sites in addition to Pearson correlation between the various parameters studied.

3. Results and Discussion

The cropping season 2021–2022 has been generally favorable. The national cumulative rainfall amounted to 271.9 mm with a good temporal and spatial distribution against 286.9 mm for the average of the last 30 years, with a slight decrease of 5%. The favorable station of Marchouch (MCH) recorded 367 mm, while the arid station of Jemmat Shaim (JS) accumulated 201 mm.

The average yield at Marchouch was 57.3 qx/ha and 10.7 qx/ha at Jemaat Shaim. The genotypes gave better yields in the Marchouch station (MCH) than in Jemaat Shaim (JS). Indeed, the MCH station represents the favorable environment for the production of cereals where rainfall generally exceeds 400 mm annually. However, the JS station is located towards the south in arid zones where annual rainfall does not exceed 200 mm/year. The genotypes evaluated showed different performances from one station to another (

Table 1. Mean grain yield of the different genotypes at the two stations JS: Jemaat Shaim, MCH: Marchouch.

Genotype/Line	Yield at JS (qx/ha)	Yield at MCH (qx/ha)	Genotype/Line	Yield at JS (qx/ha)	Yield at MCH (qx/ha)
Achtar	8.56	50.14	T3BT	8.89	50.85
T1BT	8.34	47.08	T4BT	12.89	59.44
T2BT	5.78	49.98	T5BT	11.56	45.03
Arrehane	12.89	62.11	CCBT144	10.22	54.53
Bandera	9.78	60.64	T6BT	12.00	49.00
BT19A04	13.00	59.89	T7BT	10.34	49.25
BT19A21	13.67	62.92	T8BT	9.89	60.11
BT19I5	15.56	70.25	T9BT	10.56	59.00
BT20A217	11.11	64.67	PVT3	10.34	57.61
CCBG	11.78	62.07	Radia	11.00	65.31
CCBT108	10.44	62.53	INRA-10	7.22	50.36
CCBT155	9.67	50.36	PVT4	9.00	53.83
CCBT175	14.56	55.72	Resulton	7.56	65.43
CCBT65	11.56	60.61	BT15-42	14.22	57.5
PVT1	12.44	62.50	INRA-11	7.11	54.22
PVT2	9.33	64.22

). The lines “BT19I5”, “BT19A21”, “CCBT175” and “CCBG” genotypes presented the best results in terms of yield in the Jemaat Shaim station with an average yield of 14.2 qx/ha; while “BT19I5”, “BT20A217”, in addition to the varieties Resulton and Radia, are the most productive in Marchouch with an average yield of 57.1 qx/ha. The line “BT19I5” remains the most promising as it shows the best performance in both water conditions.

The results demonstrate the negative impact of water stress on the various parameters studied (

Table 2. Descriptive statistics of the different parameters studied in the two experimental stations.

Criteria	Favourable Station (Marchouch)	Arid Station (Jemaat Shaim)
Yield (qx/ha)	57.33	10.68
BM (g)	275.5	106.2
NEF	77.48	44.60
TGW (mg)	36.13	28.01
Proteins (%)	13.65	17.09

BM: Biomass; NEF: Number of fertile spikes; TGW: Thousand grain weight.

), as demonstrated by other previous studies [2,4]. The most influenced traits by water stress were biomass (−61%) and number of fertile spikes (−42%); while the protein content was higher in arid conditions compared to the favourable ones. The analysis of variance showed significant differences for all the parameters studied between the two contrasting stations in terms of rainfall (p < 0.001).

Correlation analysis (

Table 3. Pearson correlation between the characters studied in the arid site of Jemaat Shaim.

Traits	BM	NEF	TGW	Proteins	Yield
BM	1
NEF	0.24	-
TGW	0.01	−0.24	-
Proteins	−0.43 *	0.0007	−0.30	-
Yield	0.48 **	0.35 *	0.01	−0.15	-

BM: Biomass; NEF: Number of fertile spikes; TGW: Thousand grain weight. *, ** significant correlation at 0.5, 0.01 probabilities respectively.

and

Table 4. Pearson correlation between the traits studied in the semi-favourable site of Marchouch.

Traits	BM	NEF	TGW	Proteins	Yield
BM	-
NEF	0.52 **	-
TGW	−0.07	−0.002	-
Proteins	0.28	0.23	−0.19	-
Yield	0.17	−0.14	−0.04	−0.03	-

BM: Biomass; NEF: Number of fertile spikes; TGW: Thousand grain weight. ** significant correlation at 0.01 probabilities respectively.

) showed a strong association between yield, biomass and the number of fertile spikes in the arid conditions. Biomass is an important site of photosynthesis for the plant, allowing it to generate better productivity [5]. At the same time, the fertility of the spikes has a significant impact on the final yield, making it possible to generate a large number of grains. Therefore, preventing floret mortality at pre-flowering stage can hinder significant reductions in yield [6,7]. These two parameters could constitute potential selection criteria for drought tolerance in Mediterranean conditions. On the other hand, a negative association linked the biomass to the protein rate. This could be linked to the absence of rain during the March–April grain-filling period, which promotes competition between the different organs. At Marchouch, the only positive and significant correlation is that between the biomass and the number of fertile spikes under relatively favourable conditions.

4. Conclusions

The results obtained from this study demonstrate the significant impact of water stress on wheat productivity in Mediterranean and Moroccan conditions in particular. The number of fertile spikes and the biomass could constitute the potential selection criteria for drought resistance. These trials will be repeated for several years under the effect of other intensities of stress and agro-ecosystems and by incorporating other parameters to confirm the results obtained. The line “BT19I5” showed great yield potential under both conditions, can be of great interest for farmers, and therefore could be presented to the national catalogue for release after further evaluations.