Navegando por Autor "Shareef, Muhammad"

Agora exibindo 1 - 2 de 2

Impact of drought on assimilates partitioning associated fruiting physiognomies and yield quality attributes of desert grown cotton
(Acta Physiologiae Plantarum, 2018-03-19) Fiaz, Muhammad; Shareef, Muhammad; Gu, Dongwei; Zeng, Fanjiang; Ahmed, Zeeshan; Waqas, Muhammad; Zhang, Bo; Iqbal, Hassan
Deficit irrigation has great significance for sustainable cultivation of cotton in water scarce arid regions, but this technique creates drought situation that induces stress adaptive changes in cotton plants due to indeterminate growth habit. In the present experiment, the impact of drought stress on assimilates partitioning associated vegetative and reproductive development, and yield quality attributes of cotton were examined under desert conditions. Four levels of drip irrigation including 100, 80, 60, and 40% replenishment of depleted water from field capacity were applied to develop drought stress regimes during two growing seasons (2015 and 2016). Results revealed that under limited water supplies, plant’s preference for allocation of photo-assimilates was roots > leaves > fruits that substantially increased root–shoot ratio and hampered reproductive growth. Consequently, boll density (m−2), fresh boll weight and lint yield (kg ha−1) were significantly reduced. An obvious change in partitioning of assimilates inside stressed bolls was observed that indicated relatively more accumulation in seeds than fiber, thus reducing the fiber quality. In addition, decreased starch, oil, and protein contents in seeds of stressed plants markedly reduced 100 seeds weight and also the vigor. Later, seed quality confirmatory tests of subsequent years (2016 and 2017) showed significant reduction in emergence counts (m−2) and seedling biomasses of seeds harvested from deficit drip irrigated cotton. These results suggest that deficit irrigation could necessarily be an appropriate yield optimization and water saving technique for cotton in desert environment but, for the best quality fiber and cottonseeds, full irrigation should be preferred.
Toxicological and morphological effects of tebufenozide on Anticarsia gemmatalis (Lepidoptera: Noctuidae) larvae
(Chemosphere, 2018-12) Fiaz, Muhammad; Martínez, Luis Carlos; Plata-Rueda, Angelica; Gonçalves, Wagner Gonzaga; Shareef, Muhammad; Zanuncio, José Cola; Serrão, José Eduardo
The velvetbean caterpillar, Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae), is an important soybean pest in the Americas. Tebufenozide, a novel nonsteroidal ecdysone agonist is used to control this pest. Bioassays were conducted to assess tebufenozide toxicity and their ultrastructural effects on midgut of A. gemmatalis. The toxicity, survivorship, behavior response, and respiration rate for A. gemmatalis larvae after exposure to tebufenozide were evaluated. Also, A. gemmatalis larvae were treated with LC50 obtained from tebufenozide and changes were observed on their midgut cells after 24, 48 and 96 h. Tebufenozide was toxic to A. gemmatalis (LC50 = 3.86 mg mL−1 and LC90 = 12.16 mg mL−1) and survivorship was 95% for adults that had not been exposed to tebufenozide, decreasing to 52% with LC50 and 27% with LC90 estimated value. Damage to midgut cells was increased with exposure time. These cells show damaged striated border with release of protrusions to the midgut lumen, damaged nuclear membrane and nucleus with condensed chromatin and increase in amount of autophagic vacuoles. Mitochondria were modified into nanotunnels which might be an evidence that tebufenozide induces damage to cells, resulting in cell death, proved by immunofluorescence analyses. This insecticide also caused paralysis movement with change in homeostasis and compromised larval respiration. Thus, sublethal exposure to tebufenozide is sufficient to disturb the ultrastructure of A. gemmatalis midgut, which might compromise insect fitness, confirming tebufenozide a possible controlling insecticide.