Enhancing the efficiency of disease resistance breeding in cotton using marker technology
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Enhancing the efficiency of disease resistance breeding in cotton using marker technology

 

Project Leader: Iain Wilson

Key Researchers: Iain Wilson and Qian-Hao Zhu

Brief Summary of Project Objectives: 

This disease marker project aims to find molecular markers linked to resistance for three important diseases affecting the cotton industry in Australia, Black Root Rot (BRR), Verticillium Wilt (VW), and Fusarium Wilt (FW) that will be used by the Core Breeding and Core Biotech projects for marker assisted selection to more rapidly produce resistant varieties.

Market/end user: Cotton growers through the Core Breeding and Core Biotech Projects as the primary end user of the research

Estimated year to uptake by end user: 

A Cotton Bunchy Top (CBT) resistant variety (Sicot 620) developed using DNA markers was commercially released in 2018, but the aim is to incorporate CBT resistance into all new cotton varieties.New molecular markers for okra leaf and Bacterial Blight (BB) resistance have been used in early generation breeding from 2016.Resistance against the non-defoliating VW pathotype derived from Sicot F-1 and BRR from diploid cotton is progressing well, but will require further selection cycles to achieve elite yield and fibre characteristics.Novel disease resistant varieties derived from diploid cotton for FW and VW resistance will be much longer term depending on the nature of the resistance and the difficulties in fixing traits in elite cultivar backgrounds. Markers will accelerate breeding from this point.

Executive Summary

The disease marker group, in close cooperation with our Cotton breeders made good progress on this project, despite the fallout from the 2020 hailstorm in Canberra, and the ongoing coronavirus pandemic. The research and germplasm developed moves us closer to improved disease resistant elite germplasm for several important diseases.For Black Root Rot (BBR), elite varieties with strong levels of resistance can occur via two possible routes and which one we follow will depend on both the level of BRR resistance observed in the field and agronomic performance. A resistance locus obtained from the D-genome donor (G. trilobum) has good resistance to BRR in the Narrabri bioassay but requires further testing on the level of resistance it provides in the field before it is pursued. The second route involves two A-genome loci, which confer good field BRR resistance, but current lines containing the loci have yield and fibre quality penalties, so are unsuitable for commercial release.

Figure 2: Agronomic trials of BRR material.  Note: this material is still seven to ten years away from being released in a commercial variety.

Verticillium Wilt (VW) field trials performed as part of the CBA host plant resistance project over several years have demonstrated that lines selected with the assistance of molecular markers linked to non-defoliating (ND) VW resistance from Sicot F-1, have good field ND VW resistance. Results from the 2021/22 season again indicated lines selected with markers performed well for survival and symptoms compared to existing elite lines. However, this season was conducive to severe VW disease (wet and cool), resulting in most lines becoming significantly infected, as indicated by vascular browning. One line with good VW resistance and acceptable yield and fibre quality is being incorporated into the single plant selection phase of the core breeding cycle.

Plants selected for increased defoliating (D) VW resistance derived from Synthetic and G. barbadense resistant sources were tested in the field for the first time in 2021/22. Although the field predominately contained the non-defoliating (ND) VW pathotype, some promising lines were identified for possible future trials, although these lines will require trials in a predominately D VW pathotype field for thorough validation.

The Fusarium Wilt (FW) nursery results in the 2021/2022 season have been delayed due to the wet finish of the season. However, the 2020/21 season results allowed us to identify novel genomic regions from synthetic derived and race cotton lines associated with FW resistance. These regions will require validation in future seasons.

Molecular marker technology combined with classical backcrossing is delivering cotton germplasm with enhanced resistance to BRR, FW and VW. Delivery of lines with increased disease resistance and elite fibre quality and yields is expected within the life of the next project, with the identification of potential causal genes allowing further marker selection to reduce any deleterious linkage drag.