Evaluation of rice accessions for resistance to the whitebacked planthopper Sogatella furcifera (Horváth) (Homoptera: Delphacidae)

Rice, Oryza sativa L., and wild rice accessions from the world collection were evaluated for resistance to the whitebacked planthopper, Sogatella furcifera (Horváth). Of 48554 O. sativa accessions from 96 countries, 401 (0·8%) were selected for resistance and 351 (88%) of these were from Nepal, India, and Pakistan where S. furcifera is a serious pest. However, some resistant accessions originated from regions beyond the distribution of S. furcifera. Many of the wild rice accessions, consisting of 28 species primarily from the O. minuta Presl., O. nivara Sharma et Shastry and O. officinalis Wall groups, were resistant. Although no S. furcifera-resistant commercial cultivars have been released, advanced breeding lines with resistance to S. furcifera and other major insect pests have been developed.     

Varietal resistance in rice against Sogatella furcifera (Horváth)

The whitebacked planthopper, Sogatella furcifera (Horváth) (Homoptera: Delphacidae), is emerging as a serious pest of rice in many countries. Because of the increased economic importance of the insect and the difficulty of controlling it with insecticides, incorporation of natural resistance to S. furcifera has become a major objective of the rice improvement programme at the International Rice Research Institute. Several research centres in national rice improvement programmes in India, Indonesia and Korea are also currently screening germplasm for resistance to S. furcifera. Literature documenting the status of research on varietal resistance and the current strategy in germplasm evaluation and breeding programme is reviewed. Rice varieties resistant in various countries and sources of resistance used in breeding are listed. Varieties with multiple resistance to different leafhopper and planthopper pests are also listed. The mechanism and the inheritance of resistance in rice varieties are reviewed. The possibility of biotype development is discussed and future strategies in such an eventuality are pointed out.     

Greenhouse techniques to identify field resistance to the brown planthopper,Nilaparvata lugens (Stål) (Homoptera: Delphacidae), in rice cultivars

Two seedbox screening techniques were compared to determine levels of resistance of rice cultivars to three brown planthopper, Nilaparvata lugens (Stål), biotypes. The commonly used standard seedbox screening test (SSST) where eight second-instar nymphs were infested on 7-day-old seedlings was compared with a modification (MSST) where four second-instar nymphs were infested on each of 20-day-old plants. In the SSST, the initial infestation killed the susceptible cultivars whereas in the MSST the F₁ progeny killed the susceptible cultivars. The cultivars ASD 11, Wagwag, Utri Rajapan, IR46 and Kencana were susceptible in the SSST but moderately resistant or resistant in the MSST, indicating an increase in the level of resistance with plant age. Feeding rate and population growth of N. lugens were the factors involved in the resistance of 30-day-old plants. The MSST provides a rapid method for identifying field-resistant cultivars in the greenhouse and can be used to identify field-resistant lines in a rice-breeding programme for stable resistance to N. lugens.     

Protein changes in rice seedlings during the enhancement of chilling resistance by different stress pretreatment

The changes of proteins in the rice (Oryza sativa L. ) Tesanai 2 seedling under salt ( NaCl ,4 g/L), heat shock (42℃, 3h), and cold(14℃, 3d) pretreatments were compared toexplore the mechanism of the cross adaptationto different environmental stresses.     

Field evolution of insecticide resistance in the brown planthopper (Nilaparvata lugens Stål) in China

The brown planthopper (Nilaparvata lugens Stål) is one of the most destructive pests of rice crops in Asian countries including China, Vietnam, Thailand, etc. Evolution of resistance in this pest insect to isoprocarb, buprofezin, pymetrozine, imidacloprid and other neonicotinoid insecticides has been reported. In order to investigate the current status of resistance to commonly used insecticides, nine field populations of N. lugens were collected from Central China, East China and South China, and resistance to insecticides was monitored from 2009 to 2012. All the 9 field populations collected in 2012 had developed extremely high resistance to imidacloprid, with resistance ratios (RR) ranging from 209.3 to 616.6. Resistance to imidacloprid was much higher in 2012 than in 2009. The RR of thiamethoxam varied from 17.4 to 47.1, and the RR of nitenpyram varied from 1.4 to 3.7 in 2012. Of the 9 field populations, six populations showed higher resistance to nitenpyram in 2012 than in 2011. RR for buprofezin varied from 110.1 to 221.6 in 2012 whereas resistance was at a medium level (RR 20.4 ∼ 39.4-fold) in 2009. RR for pymetrozine ranged from 34.9 to 46.8 in 2012. As for isoprocarb, RR ranged from 21.7 to 38.1 in 2012. The obvious increase in resistance to widely applied insecticides indicates that insecticide resistance management strategies are urgently needed to prevent or delay further increase of insecticide resistance in N. lugens.     

Effects of the insecticide triazophos on the ultrastructure of the flight muscle of the brown planthopper Nilaparvata lugens Stål (Hemiptera: Delphacidae)

The brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), is a long-distance migratory insect pest in temperate eastern Asia and is a classical resurgent rice pest that is induced by insecticides. Knowledge of the effect of insecticides on the flight capacity of insects is needed to understand their migration, which may help to improve the management of insect pests. Our previous study demonstrated that some insecticides enhance the flight capacity of BPH. However, the effect of insecticides on the flight muscle of BPH is not well understood. Thus, the present study examined the effect of triazophos, a classical insecticide that induces the resurgence of BPH, on the ultrastructure of macropterous females using transmission electron microscopy. The results showed that the diameter of myofibrils one and two days after adult female emergence (DAE) following treatment with 40 ppm triazophos was significantly greater than that of the control, increasing by 31.4 and 21.5%, respectively. In addition, the length of the sarcomeres at two and three DAE was significantly greater than that of the control, increasing by 73.8 and 50.8%, respectively. The percentage of mitochondrial volume in the muscle fibres at one and two DAE was 146.2 and 67.7% greater than that of the control, respectively. These findings show that the mechanisms of triazophos-induced enhancement of the flight capacity of BPH involve changes in the ultrastructure of the flight muscle.     

Mechanism of rice variety resistance to the yellow stem borer,Scirpophaga incertulas (Walker)

Yellow stem borer (YSB) , Scir-pophaga incertulas (Walker) has become the main rice insect pest once again along the Changjiang River since 1990s. Unfortunately, no rice variety with resistance to YSB has been reported so far. Japonica Zhen-dao 2 with moderate resistance to YSB was found. In 10 rice varieties with different resistance levels, YSB individuals showed distinct developmental rates, and the asynchronous development even occurred in the same rice variety. In this     

Studies on the relationship between the changes of the endogenous scavengers of active oxygen and resistance in hybrid rice under temperature stress

The seedlings of indica hybrid rice Weiyou 49 and Weiyou 28 were exposed to 1℃ and 40℃ .and the changes of activity (content) of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbic acid (ASA), glutathione (GSH),malondialdehyde (MDA) and leakage of electrolytes (%) were measured.     

Mapping of a New Gene Wbph6（t） Resistant to the Whitebacked Planthopper, Sogatella furcifera, in Rice

A rice population consisting of 90 TN1/Guiyigu F3 lines was employed to analyze the linkage between DNA markers and a new gene Wbph6(t) conferring resistance to whitebacked planthopper, Sogatella furcifera By using the mapping approach of bulked extremes and recessive class, Wbph6(t) was mapped onto the short arm of chromosome 11 with a genetic distance of 21.2 cM to SSLP marker RM167.     

Can resistance in Bemisia tabaci (Homoptera: Aleyrodidae) be overcome with mixtures of neonicotinoids and insect growth regulators?

Tobacco whitefly, Bemisia tabaci is an important polyphagous insect pest which has developed resistance to various insecticides worldwide. Mixtures of insecticides with different modes of action may delay the onset of resistance. Bioassays were performed to investigate the effects of various mixtures of neonicotinoid and insect growth regulator (IGR) insecticides against a susceptible and a resistant strain. The results of the study showed that potentiation ratio (PR) of all neonicotinoids + buprofezin or pyriproxyfen mixtures at 1:1, 10:1 and 20:1 ratios was greater than 1 suggesting synergistic interactions between insecticides. Maximum potentiation occurred at the 1:1 ratio (PR = 1.69–7.56). The PRs for mixture of acetamiprid, thiamethoxam, thiacloprid or nitenpyram with buprofezin or pyriproxyfen at 1:10 and 1:20 ratios were less than 1 indicating antagonistic interactions. Addition of synergists, S, S, S, tri-butyl phosphorotrithioate (DEF) or piperonyl butoxide (PBO) in the insecticide solutions largely overcame the resistance to all tested neonicotinoids, indicating that the resistance was associated with esterases or mono-oxygenases, respectively. Likewise, addition of both DEF and PBO in mixture with neonicotinoids and IGRs also suggested a similar mechanism of resistance in B. tabaci to the tested insecticide groups. The mechanism of synergism between neonicotinoids and IGRs is unclear. Implications of using mixtures to counteract pesticide resistance are discussed. Mixtures of neonicotinoids with buprofezin or pyriproxyfen at a 1:1 ratio could be used to restore the efficacy of these neonicotinoids against B. tabaci.     

Effect of intermittent irrigation following the system of rice intensification (SRI) on rice yield in a farmer’s paddy fields in Indonesia

System of rice intensification (SRI) has been disseminated in many countries because of its high yield, although the mechanism of yield increase has yet to be fully understood. The aims of this study were to clarify the actual water management of a skilled SRI farmer in irrigated paddy field of Indonesia and to examine the effect of intermittent water management on rice growth and yield. Yield and yield components were compared in the field experiments in the farmer’s fields under intermittent (SRI) or flooded (FL) irrigation for 4 years from 2013 to 2016. The daily mean water depth of SRI plots during 0–40 days after transplanting showed very shallow (ca. 2 cm) or little lower than soil surface and continued to be lower than soil surface during reproductive stage when panicles were formed. The yield of SRI significantly exceeded that of FL for 4 years by 13% (P?=?0.0004), so did the panicle numbers per area (P?=?0.036). The yield increase in SRI was associated with the increased number of panicles, which should have resulted from enhanced tiller development under shallow water level during the vegetative stage. The increased number of panicles was, however, counteracted by the reduced number of spikelets per panicle and resulted in nonsignificant increase in the spikelet density, defined as number of spikelets per unit area of crop. This dampening change in spikelet number per panicle could have been caused by limited supply of either nitrogen or carbohydrate during the panicle development stage under the intermittent water supply. A greater yield increase by SRI could be expected by improving nutrient or water management during the reproductive stage.     

Utilization of nuclear magnetic resonance (NMR) in the determination of water status on rice seeds

The relation between seed viability and waterstatus in seed was studied. The experimentwas carried out at Zhongshan University.Seeds of hybrid rice Shanyou 63 were collectedfrom Guangdong Academy of Agriculture Sci-ences in 1993 and then stored for one year inopen air or with silica gel. Before and afterstorage, the relative content of free water and     

From science to application: field demonstrations to enhance sustainable rice production in the north of Vietnam—lessons from the LEGATO project

Two major human-made problems in rice production systems in the north of Vietnam concern the low plant-available silicon content of soils and the low biodiversity. The results of the LEGATO project suggest a change to an environmentally friendly rice production system that will help to recover biodiversity. We propose here a framework for a demonstration and dissemination model that will be exemplary for the farmers once it has been successfully realized. We advocate local-option models in different districts to demonstrate to farmers. The methods should be adapted to local and ecoregional differences in climate and land-use tradition, and they explicitly take into account soil care, organic fertilizer, manual weeding, native nectar-rich plant bunds, manual pest snail collection, hymenopteran nesting aids, and biodiversity and yield monitoring.     

Geographic Variation of Diapause and Sensitive Stages of Photoperiodic Response in Laodelphax striatellus Fallén (Hemiptera: Delphacidae)

Large numbers of the small brown planthopper Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae) occur in temperate regions, causing severe losses in rice, wheat, and other economically important crops. The planthoppers enter diapause in the third- or fourth-instar nymph stage, induced by short photoperiods and low temperatures. To investigate the geographic variation in L. striatellus diapause, we compared the incidence of nymphal diapause under various constant temperature (20 and 27°C) and a photoperiod of 4:20, 8:16, 10:14, 12:12, 14:10, and 16:8 (L:D) h regimes among three populations collected from Hanoi (21.02° N, 105.85° E, northern Vietnam), Jiangyan (32.51° N, 120.15° E, eastern China), and Changchun (43.89° N, 125.32° E, north-eastern China). Our results indicated that there were significant geographic variations in the diapause of L. striatellus. When the original latitude of the populations increased, higher diapause incidence and longer critical photoperiod (CP) were exhibited. The CPs of the Jiangyan and Changchun populations were ∼12 hr 30 min and 13 hr at 20°C, and 11 hr and 11 hr 20 min at 27°C, respectively. The second- and third-instar nymphs were at the stage most sensitive to the photoperiod. However, when the fourth- and fifth-instar nymphs were transferred to a long photoperiod, the diapause-inducing effect of the short photoperiod on young instars was almost reversed. The considerable geographic variations in the nymphal diapause of L. striatellus reflect their adaptation in response to a variable environment and provide insights to develop effective pest management strategies.     

Erratum to: Woody habitats promote pollinators and complexity of plant–pollinator interactions in homegardens located in rice terraces of the Philippine Cordilleras

Paddy and Water Environment -     

Effect of day length and temperature on the pollen fertility in photo(thermo)-sensitive genic male-sterile rice

The effect of day length and temperature on the pollen fertility of five photoperiod-sensitive genic male-sterile japonica rice lines (PGMSR) and three temperature-sensitive genic malesterile indica rice lines (TGMSR) were investigated in phytotron. The light source used for illumination was xenon lamp, and the light intensity which plant accepted on the leaf surface was 300—350μmol photons m~(-2)s~(-1). The results indicated that pollens of PGMSR 7001S and E47S aborted completely whereas a little part of 31116S pollens appeared normal under long day photoperiod (LD,25℃,15h) (Table 1). High temperature (HT, 30℃, 12h) and lower temperature (LT,     

Genetic expression and effects of the rolled leaf gene Rl(t) in hybrid rice (Oryza sativa L.)

We constructed a nearisogenic line of rolled leaf gene Rl(t), which ex-pressed incompletely dondnance for the character of rolled leaf(RL), with ge-netic background of Zhenshan 97B. Using RL Zhenshan 97B and the originalZhenshan 97B as the female parents, and Minghui 63 and Yanhui 559 as themale parents, crosses of RL Shanyu 63 (RS63) and Shanyu 63(S63), RLShanyou 559 (RS559) and Shanyou 559 (S559) were made. Inheritance andeffects of Rl(t) in hybrid rice were studied at the flowering and at the 20 d afterflowering, respectively. Results were as follow:     

Ultrastructure and AcPase ultracytochemical localization of the abortive functional megaspores in intersubspecific F_1 hybrid rice(Oryza sativa)

Exploitation of the high yield potential intersubspecific heterosis has so far been hampered due to primarily the existence of high femalesterility. We have offered a cytological explanation for this abortion, such as the absence of embryo sacs or the occurrence of empty embryo sacs. Here we report the ultrastructural changes and ultracytochemical localization of acid phosphatase(AcPase) in the abortive functional megaspores. The F_1 hybrid was derived from a cross, Liaoqiu 5 (japonica)×Zhenjinzhen (indica), which showed high seed sterility in F_1 plants. The tissue prepared for enzyme ultracytochemicl study was fixed in 2.5% glutaraldehyde and 4% paraformaldehyde, incubated at 20℃ in the complete reaction medium of Barka-Anderson for 2h, post-fixed in 1% OsO_4 before ethanol-dehydration, infiltration and embedding in Epon 812. The sections, cut on. LKB-2088V ultramicrotome, were viewed and photographed, either unstained (in the case of AcPase localization) or double-stained with urayl acetate and lea