Abstract
Wheat (Triticum aestivum L.) production is constantly affected by weeds in the farming system. Chemical-based weed management is widely practiced; broad-spectrum herbicides such as metribuzin have been successfully used to control weeds in Australia and elsewhere of the world. Breeding metribuzin-resistant wheat through genetic improvement is needed for effective control of weeds. Quantitative trait loci (QTLs) mapping efforts identified a major QTL on wheat chromosome 4A, explaining up to 20% of the phenotypic variance for metribuzin resistance. The quantitative nature of inheritance of this QTL signifies the importance of near-isogenic lines (NILs), which can convert a quantitative trait into a Mendelian factor for better resolution of the QTL. In the current study, NILs were developed using a heterogeneous inbred family method combined with a fast generation-cycling system in a population of Chuan Mai 25 (resistant) and Ritchie (susceptible). Seven pairs of NILs targeting the 4A QTL for metribuzin resistance were confirmed with a molecular marker and phenotyping. The resistant allele from the resistant parent increased metribuzin resistance by 63–85% (average 69%) compared with the susceptible allele from the susceptible parent. Segregation analysis in the NIL pairs for thousand grain weight (TGW) (g), biomass per plant (kg), tillers per plant, plant height (cm), yield per plant, and powdery mildew visual score (0–9) indicated that these traits were linked with metribuzin resistance. Similarly, TGW was observed to co-segregate with metribuzin resistance in most confirmed NILs, signifying that the two traits are controlled by closely linked genes. The most contrasting NILs can be further characterised by transcriptomic and proteomic analyses to identify the candidate genes responsible for metribuzin resistance.
Highlights
Wheat is a major food source in the world
Of the 18 pairs, seven were confirmed near-isogenic lines (NILs) pairs against metribuzin, and others were confirmed as recombination types (Figure 1A–D and Figure 2)
The confirmed NIL pairs were analysed for other morphological traits to study the traits that might link to the metribuzin resistance locus; for example, the leaf chlorophyll content may be controlled by photosystem-related genes, which can contribute to photosynthate partitioning for yield-related traits in crops [22]
Summary
Wheat is a major food source in the world. Weeds constantly affect wheat production, competing for moisture, nutrient, and light resources, resulting in plant height reduction, nutrient starvation, and wilting [1]. Weed infestation may reduce wheat yields, sometimes by 50% [2]. Weeds cost Australian agriculture an estimated $2.5 billion to. Controlling weeds is a prerequisite for safe agricultural production. Controlling weeds with herbicides is one of the most common and effective weed control measures [4]. Metribuzin is a broad-spectrum herbicide used extensively in dryland farming systems in Australia [5]. It is a triazine herbicide that interferes with photosystem II (PSII) electron transport in plant chloroplasts [6]. Metribuzin can harm valuable crops, such as wheat in the field
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