Selection for Phytophthora Root Rot Resistance in Chickpea Crosses Affects Yield Potential of Chickpea × Cicer echinospermum Backcross Derivatives

Abstract

Phytophthora root rot (PRR) of chickpea (Cicer arietinum) caused by Phytophthora medicaginis is an important disease. Partial resistance to PRR is sourced from Cicer echinospermum. In this study, we evaluated if lines with low levels of PRR foliage symptoms in two contrasting recombinant inbred line (RIL) populations parented by chickpea cultivars (Yorker and Rupali) and 04067-81-2-1-1 (C. echinospermum, interspecific breeding line) had a significant drag on yield parameters. For the Yorker × 04067-81-2-1-1 population with the highest level of PRR resistance, in the absence of PRR, low foliage symptom RIL had significantly later flowering and podding, lower grain yields, and lighter seed and shorter plant phenotypes than high foliage symptom RIL. A quantitative trait locus analysis identified significant QTL for flowering, height, 100-seed weight, and yield, and there was a significantly higher frequency of alleles for the negative agronomic traits (i.e., drag) from the 04067-81-2-1-1 parent in low foliage symptom RIL than in high foliage symptom RIL. For the Rupali × 04067-81-2-1-1 population with lower levels of PRR resistance, in the absence of PRR, low foliage symptom RIL had significantly lighter seed and shorter plants than high foliage symptom RIL. Significant QTL were detected, the majority were for the timing of flowering and podding (n = 18), others were for plant height, yield, and 100-seed weight. For this second population, the frequency of alleles for the negative agronomic traits from the 04067-81-2-1-1 parent did not differ between low and high foliage symptom RIL. The 100 seed weight of RIL under moderate PRR disease pressure showed some promise as a yield component trait to identify phenotypes with both high levels of PRR resistance and grain yield potential for further seed number evaluations. We identified that large population sizes are required to enable selection among chickpea × C. echinospermum crosses for high levels of PRR resistance without a significant drag on yield.

Keywords: 100 seed weight; agronomic traits; partial resistance; resistance drag; root disease; wild relative.

Figure 1

Rupali × C. echinospermum backcross RIL population, the proportion of dead seedlings and podded plants from the Hermitage 2015 Phytophthora medicaginis inoculated irrigated experiment on x axis versus the results of the Tamworth 2017 non-diseased grain production experiment, y axis results, for the parameters (a) whole population seed yield, (b) 100-seed weight, and (c) plant height. The 2014 6 RIL and 2015 20 RIL foliage symptom phenotype groups (high foliage symptom, HFS; low foliage symptom, LFS) are presented for plot a. For plots b and c only, the 2015 20 RIL foliage symptom phenotype groups are presented and include group means and least significant difference (LSD) values for the main effects and foliage symptom group by RIL interaction.

Figure 2

Yorker × C. echinospermum backcross RIL population, the proportion of dead seedlings and podded plants from Hermitage 2015 Phytophthora medicaginis inoculated irrigated experiment on x axis versus the results of the Tamworth 2017 non-diseased grain production experiment y axis results, for the parameters (a) seed yield, (b) 100-seed weight, (c) 50% flowering day, (d) 50% podding day, and (e) plant height. The 2014 6 RIL and 2015 20 RIL foliage symptom phenotype groups (high foliage symptom, HFS; low foliage symptom, LFS) are presented for plot a. For plots b to e only, the 2015 20 RIL foliage symptom phenotype groups are presented and include group means and least significant difference (LSD) values for the main effects and foliage symptom group by RIL interaction.

Figure 3

Position of quantitative trait loci (QTL) detected in Rupali × C. echinospermum backcross recombinant inbred line (RIL) population (black bars) for the Tamworth 2017 non-diseased grain production experiment. The vertical QTL bars represent the physical position (two LOD drops from the QTL maximum likelihood value). The colored bars represent the QTL identified in previous studies. Growth habit qGH-C1 [20], qGH-C4 [22], phytophthora root rot resistance q1PRR-C3, q2PRR-C3, q3PRR-C3, qPRR-C5, qPRR-C6, q1PRR-C8, q2PRR-C8 [11], 50% flowering q50F-C3 [23], 100-seed weight qHSW-C3, q3HSW-C4, qHSW-C7 [24], q1HSW-C4 [22], q2HSW-C4 [25], and plant height qPHT-C4 [24].

Figure 4

Position of quantitative trait loci (QTL) detected in the Yorker × C. echinospermum backcross recombinant inbred line (RIL) population (black bars) for the Tamworth 2017 non-diseased grain production experiment. The vertical QTL bars represent the physical position (two LOD drops from the QTL maximum likelihood value). The colored bars represent the QTL identified in previous studies. Growth habit q1GH-C1 [20], q1GH-C6 [26], q2GH-C6 [20], phytophthora root rot resistance qPRR-C3, qPRR-C6, qPRR-C8 [11], 100-seed weight q1HSW-C4 [20], q2HSW-C4 [25], and q3HSW-C4 [24].

Figure 5

Foliage symptom (FS) and 100-seed weight comparisons. Symptom comparisons for selection group 1 (a) recombinant inbred line (RIL) from the cv. Rupali × C. echinospermum backcross (RB) for the proportion (Prop.) of dead seedlings, (b) Yorker × C. echinospermum backcross (YB) RIL comparing the proportion of non-symptomatic plants in the Tamworth 2016 natural inoculum experiment (NI16) and the Hermitage 2015 (HM15) Phytophthora medicaginis inoculated irrigated experiments, linear regression with red fitted regression lines with blue 95% confidence intervals. Hundred-seed weight comparisons of selection group 1 of the Tamworth 2017 non-diseased grain production experiment and the Hermitage 2015 P. medicaginis inoculated dryland experiments for the (c) RB RIL, correlation 0.693, p = 0.018 and the (d) YB RIL, correlation 0.321, p = 0.308, correlation with the high FS RIL C019 excluded 0.826, p = 0.0017.