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The bird cherry-oat aphid, Rhopalosiphum padi (L.) (Heteroptera: Aphididae), causes heavy losses to wheat crops worldwide by direct damage and virus transmission. This study was conducted to identify putative resistance mechanisms in four wheat varieties (Bobtail, Ladd, Stephens, and Skiles) and one advanced line (YS434)where R. padi was subjected to choice and no-choice tests. Antixenosis, antibiosis and tolerance studies were conducted in controlled environmental conditions at temperature of 20±5°C, 50–65% RH, and a photoperiod of 14:10 (L:D) h. Based on the antixenosis test, the variety Skiles was found susceptible to R. padi, while the line YS434 showed a significant level of resistance; the varieties Bobtail, Ladd, and Stephens showed intermediate response. In the antibiosis experiment, R. padi produced less progeny on the variety Skiles as compared with other varieties, but the developmental time for nymphs was also significantly shorter on Skiles and recorded higher intrinsic rate of natural increase (r(m)) values as compared with the varieties YS434, Bobtail, and Ladd. In the tolerance tests, the variety Ladd showed significantly lower tolerance index value than YS434, followed by Skiles, Bobtail, and Stephens. The plant resistance index value was greater for the variety Ladd, followed by Stephens, YS434, and Bobtail. In conclusion, this study provides baseline information that will contribute to the identification of putative resistance factors for a future breeding program against this aphid.

Soybean aphids have become a serious pest of soybean, Glycine max L. (Merrill), since they were first detected in North America in 2000. Three soybean aphid biotypes have been documented in the United States in the last 10 yr, but few studies have been done on their feeding behavior in the United States The Electrical Penetration Graph is a convenient and successful tool to study the feeding behavior of piercing and sucking insects. This is the first attempt to study the feeding behavior differences between biotype 1 and biotype 2 on soybean genotypes using the Electrical Penetration Graph technique, and includes both resistant and susceptible soybean genotypes from Kansas and Michigan. The experiments were run for 9 h each for each genotype with a total of eight channels at a time. Results indicated that aphids feeding on susceptible genotypes had a significantly greater duration of sieve element phase than when feeding on resistant genotypes. Furthermore, the time taken to reach the first sieve element phase in resistant genotypes was significantly greater than in susceptible genotypes. Most of the aphids reached sieve element phase (> 90%) in susceptible genotypes, but only a few (< 30%) reached sieve element phase in resistant genotypes during the 9-h recording period; however, we found no differences in any other probing phases between resistant and susceptible genotypes except the number of potential drops in biotype 2. Thus, the resistance was largely associated with phloem tissues. Therefore, some biochemical, physical, or morphological factors could affect stylet penetration of aphids.

Canola (Brassica napus L.) is one of the economically important crops of Pakistan and mustard aphid, Lipaphis erysimi Kalt. (Hemiptera: Aphididae), is a serious threat to this crop. This experiment was conducted with an aim to screen out selected canola cultivars for their tolerance against L. erysimi infestation under glasshouse conditions. Experiment was carried out using completely randomized design with ten replications for each treatment during growing seasons of 2018 and 2019. Data were documented based on the tolerance indices (TI) and proportional plant dry weight change (DWT) to identify tolerance of canola crop. Results revealed that commercial cultivar 'Zahoor' comparatively performed well despite higher number of aphids found on itas compared its other counterparts "Abaseen, Omega and KS-75" and hence, was identified as tolerant to mustard aphid. This cultivar also exhibited strong vigor against mustard aphid and minimal symptoms of damages were observed. The yield losses based on DWT and TI in susceptible cultivar "Abaseen" was 40.79%, whereas it was 23.56% in Zahoor which confirmed the reduced percent yield losses in the later genotype. This study identified "Zahoor" as the most tolerant cultivar to mustard aphid followed by KS-75 and Omega hence, other susceptible cultivars should be replaced by Zahoor to attain higher and sustainable yield production in canola. [ABSTRACT FROM AUTHOR]

Potato (Solanum tuberosum L.) is an important vegetable food crop in Pakistan. Myzus persicae is an insect pest of potato, feeding on phloem tissues of leaves of potato plant and significantly reduces the yield of potato. Antixenosis experiments were performed to assess the resistance potential of eight different potato cultivars against M. persicae under glasshouse conditions for three different durations of time (12, 24 and 48 hours) during spring and autumn potato growing seasons of 2016. Both the experiments were conducted using a completely randomized design. Each experiment having eight treatments and each treatment was replicated 10 times. The replicated pots containing each of the eight potato cultivars were infested with 100 and 200 adult of M. persicae. Significant antixenosis effects among the tested potato cultivars were observed while the different durations of M. persicae infestation on potato cultivars also displayed significant antixenosis effects against M. persicae during the spring and autumn experiments in 2016. During both experiments, Sarpo Mira displayed the lowest number of adults per plant on release of 100 and 200 adults per plant. Sarpo Mira showed M. persicae infestation of 3.3 and 2.4 per plant per pot on release of 100 adults per plant during spring and autumn seasons, respectively while an infestation of 5.3 per plant 4.7 per plant on Sarpo Mira was observed on release of 200 adults of M. persicae during spring and autumn seasons, respectively. FD-70 had the highest number of M. persicae (13.7 per plant) in the pots released with 100 M. persicae during spring season while Asterix showed the highest number of M. persicae (13.8 per plant) in pots infested with 200 M. persicae during autumn season. Sarpo Mira also appeared to be the most resistant potato cultivar against M. persicae at 12, 24 and 48 hours post infestation of M. persicae. Overall, this study revealed the resistant potential of potato cultivar Sarpo Mira against M. persicae. [ABSTRACT FROM AUTHOR]