Maize Inbred Line B96 Is the Source of Large-Effect Loci for Resistance to Generalist but Not Specialist Spider Mites

Abstract

Maize (Zea mays subsp. mays) yield loss from arthropod herbivory is substantial. While the basis of resistance to major insect herbivores has been comparatively well-studied in maize, less is known about resistance to spider mite herbivores, which are distantly related to insects and feed by a different mechanism. Two spider mites, the generalist Tetranychus urticae, and the grass-specialist Oligonychus pratensis, are notable pests of maize, especially during drought conditions. We assessed resistance (antibiosis) to both mites of 38 highly diverse maize lines, including several previously reported to be resistant to one or the other mite species. We found that line B96, as well as its derivatives B49 and B75, were highly resistant to T. urticae. In contrast, neither these three lines, nor any others included in our study, were notably resistant to the specialist O. pratensis. Quantitative trait locus (QTL) mapping with replicate populations from crosses of B49, B75, and B96 to susceptible B73 identified a QTL in the same genomic interval on chromosome 6 for T. urticae resistance in each of the three resistant lines, and an additional resistance QTL on chromosome 1 was unique to B96. Single-locus genotyping with a marker coincident with the chromosome 6 QTL in crosses of both B49 and B75 to B73 revealed that the respective QTL was large-effect; it explained ∼70% of the variance in resistance, and resistance alleles from B49 and B75 acted recessively as compared to B73. Finally, a genome-wide haplotype analysis using genome sequence data generated for B49, B75, and B96 identified an identical haplotype, likely of initial origin from B96, as the source of T. urticae resistance on chromosome 6 in each of the B49, B75, and B96 lines. Our findings uncover the relationship between intraspecific variation in maize defenses and resistance to its major generalist and specialist spider mite herbivores, and we identified loci for use in breeding programs and for genetic studies of resistance to T. urticae, the most widespread spider mite pest of maize.

Evaluation of Resistance of Eleven Maize Races (Zea mays L.) to the Red Spider Mite (Tetranychus merganser, Boudreaux)

“…They concluded that there is a direct resistance induction of Z. mays to T. urticae . Bui et al [ 7 ] evaluated the resistance of 38 inbred maize lines to T. urticae and O. pratensis . They found that T. urticae (median ~8–50) exhibited greater variation than O. pratensis (median ~30–50) when compared with progeny per female (eggs and viable mites, all stages) in six days of evaluation under greenhouse conditions; meanwhile, Bui et al [ 12 ] evaluated inbred maize W22, from which Ds transposon insertions were recovered in three genes responsible for DIMBOA-Glc synthesis—BX1, BX2, and BX6.…”

“…Bynum et al [ 14 ] reported that T. urticae caused different feeding damage rates in 12 maize inbred lines. Besides, Bui et al [ 7 ] documented that T. urticae causes the highest feeding damage rate on maize inbred line B73 than O. pratensis . Treviño-Barbosa [ 25 ] reported a higher feeding damage of T. merganser in C. papaya (47.00 ± 0.73%) than to P. vulgaris (40.67 ± 1.76%), M. oleifera (32.33 ± 1.76%), C. annuum var.…”

“…Corn production is affected between 6% and 19% due to herbivore by arthropod pests [ 5 ]. However, climate change has increased the metabolic rates and winter survival of arthropods, which coupled with a global average surface temperature increase of 2 °C may cause maize yield losses of up to 30% of damaged crops caused by insects and mite pests [ 6 , 7 ]. Corn cultivation is susceptible to attack by different insect pests, such as Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), Spodoptera frugiperda Smith (Lepidoptera: Noctuidae), Mythimna separata Walker (Lepidoptera: Noctuidae), and Rhopalosiphum maidis Fictch (Hemiptera: Aphididae) [ 8 , 9 , 10 ].…”

“…[ 11 ]. Tetranychus urticae Koch and Oligonychus pratensis Banks are considered important pests in corn crops because the feeding damage of these mites causes large grain yield losses in corn [ 7 , 12 ]. In California, USA, Bacon et al [ 13 ] reported a reduction in corn yield of up to 32% due to damage caused by T. urticae .…”

“…The resistance of different maize inbred lines to T. urticae [ 20 , 21 ], T. cinnabarinus [ 22 , 23 ], and O. pratensis [ 7 , 12 ] have been evaluated. However, there are few studies on the resistance of plants to T. merganser [ 24 , 25 ].…”