Evaluation of Adapted Wheat Cultivars for Tolerance to Pythium Root Rot

Abstract

Genetic resistance in wheat (Triticum aestivum) against Pythium species would be an efficient means of control of this major root fungal pathogen, but so far no source has been identified. In addition, no long-term, sustainable options for controlling Pythium root rot are available; therefore, identifying and then incorporating genetic resistance into wheat cultivars would create an ideal method of control for this disease. The objective of this study was to examine the level of tolerance to Pythium root rot among a diverse set of wheat germ plasm collected from all major wheat production regions in the United States. Pythium debaryanum isolate 90136 and P. ultimum isolate 90038, previously identified as the most virulent Pythium isolates on wheat, were used to infest pasteurized soil, which was seeded with wheat genotypes and placed in a growth chamber maintained at a constant 16°C with a 12-h photoperiod and ambient humidity. Length of the first leaf and plant height measurements were recorded, and roots were digitally scanned to create computer files that were analyzed using WinRhizo software for length and number of tips. Significant (P < 0.05) differences in plant variables were detected among wheat genotypes in the presence of both Pythium species, and a significant (P < 0.0001) correlation between plant stunting and root loss was detected. Based on both shoot and root measurements, Caledonia, Chinese Spring, MN97695, and OR942504 appear to be highly susceptible to Pythium root rot, whereas genotypes KS93U161, OH708, and Sunco were the most tolerant to this disease.

Influence of glyphosate, crop volunteer and root pathogens on glyphosate‐resistant wheat under controlled environmental conditions

“…Genetic resistance in wheat is not available for Rhizoctonia solani ,18, 19 G. graminis var. tritici or Pythium spp 23. The present authors did not see any increased susceptibility in the absence of glyphosate.…”

“…Tillage breaks apart hyphal networks in the soil, accelerates the decomposition of crop residues that contain pathogen inoculum and results in an increase in microbial activity that may inhibit pathogens. There is no genetic resistance to these pathogens in adapted cultivars,18–21 although some cultivars are more tolerant than others,22, 23 and genetic tolerance to Rhizoctonia has been identified in a mutagenized spring wheat line (Okubara PA et al , unpublished). The current best management recommendation for growers is to apply herbicide to weeds at least 3 weeks prior to planting to allow pathogen inoculum to decline as a result of microbial activity 24.…”

Impact of cover crop in pre-plant of apple orchards: relationship between crop health, root inhabiting fungi and rhizospheric bacteria

“…On the other hand, the preliminary test on cereals as cover crops was performed on the basis of grain cereal tolerance variability to Pythium spp. based on the germoplasm reaction as reported by Higginbotham et al (2004). In addition to this, rye was excluded from the outset of this study because of its high susceptibility to Pythium spp.…”

Large root systems: are they useful in adapting wheat to dry environments?

“…In light of these results, comparisons between relatively contemporary cultivars may not capture the full genetic variation available within the species. The problem is compounded by environmental factors affecting root growth, such as acid subsoils, compaction layers, root diseases and predation (Tang et al 2003;Higginbotham et al 2004;Botwright Acuña et al 2007). These factors can either limit the expression of root system size or differentially effect genotypes, compromising the capacity to assess the value of potentially different root systems.…”