Reaction of resistant and susceptible rice genotypes against brown planthopper (<Emphasis Type="Italic">Nilaparvata lugens</Emphasis>)

The study was carried out to assess the reaction of different rice genotypes in response to brown planthopper (BPH)Nilaparvata lugens (Stål.) attack and the possible use of these genotypes in BPH management. The resistant genotypes PTB 33, ADT 45 and ASD 7 and the moderately resistant genotypes CO 43 and KAU 1661 recorded the lowest nymphal preference, fecundity, feeding rate, survival, growth index, population buildup and plant dry weight loss per mg of insect dry weight produced, and more unhatched eggs, longer nymphal development period, days to wilt and higher Functional Plant Loss Index compared with the susceptible genotype TN1. In resistant and moderately resistant genotypes, a greater accumulation of defense enzymes such as peroxidase and polyphenol oxidase in response toN. lugens infestation was recorded one day after infestation, and more pathogenesis-related protein and chitinase activity was noted 3 days after infestation. The activity was sustained for more than a week after infestation compared with the susceptible genotype TN1.     

Host plant resistance through physico-chemical characters against major insect pests of okra occurring in the Gangetic plains of eastern India

Okra production in the tropics is threatened by attack of insect-pests, fruit and shoot borer (FSB), jassid and whitefly causing severe loss in marketable yield particularly in the Gangetic plains of eastern India. No developed varieties/hybrids are free from attack of these pests. However, improved lines of okra have potential to broaden the genetic variability may improve resistance to these pests. Therefore, the population dynamics of these pests were recorded from 24 advance breeding lines/varieties of okra during peak infestation period over two consecutive years. Morphological leaf traits and biochemical parameters were assessed as potential mediators of resistance. The population of these pests reached above economic threshold levels during the month of September. Significant genotypic differences in terms of infestation of these pests were observed. Negatively correlated physico-chemical characters might be considered as important indices for selection of genotype tolerant to these pests. As indicated by the low infestations, the tolerance of BCO-1 to FSB, whitefly and that of Arka Anamika to jassid is based on both antixenotic properties of the genotypes. The donor parents BCO-1 and Arka Anamika should, therefore, be introduced into okra breeding programs to enhance tolerance against these pests.     

Identification of allele specific AFLP markers linked with bacterial wilt [Ralstonia solanacearum (Smith) Yabuuchi et al.] resistance in hot peppers (Capsicum annuum L.)

Even though the bacterial wilt is identified as the most destructive disease in hot peppers world-wide, robust molecular markers that facilitate marker assisted selection are absent till date. Kerala Agricultural University (India) has released two hot peppers named Ujwala and Anugraha which show high level field resistance to this pathogen. The variety Anugraha was developed through backcross breeding between a high yielding but highly susceptible variety Pusa Jwala with the highly resistant Ujwala, using Pusa Jwala as a recurrent parent. Thus, Pusa Jwala and Anugraha are near isogenic lines (NILs) differing for the resistance to bacterial wilt only and the resistance is governed by a homozygous recessive (rr) gene action. The F₁s of Anugraha × Pusa Jwala were selfed to generate the segregating F₂ population. The F₂ population has been field screened, 10 highly susceptible and 10 most resistant plants were identified and DNA from these plants were bulked separately. Bulked segregant analysis with AFLP primer combination EcoACT + MseCAC was done using the DNA from donor parent Ujwala, susceptible parent Pusa Jwala, resistant parent Anugraha, bulked susceptible F₂ and bulked resistant F₂ plants. On resolution using capillary electrophoresis system in genetic analyzer, the AFLP products have yielded three polymorphic bands (103, 117, and 161 bp) which were linked with the resistant recessive allele and three polymorphic bands (183, 296, 319 bp) linked with the dominant susceptible allele of the bacterial wilt resistance gene. The results were confirmed through co-segregation analysis in most resistant and susceptible plants of F₂ segregating population.     

Varietal resistance in eggplant (Brinjal)(Solanum melongena) to the cotton jassid(Amrasca biguttula biguttula)

Twenty-nine varieties of brinjal (Solanum melongena Linn.) were screened in the field for resistance to the cotton jassid,Amrasca biguttula biguttula (Ishida). Vars. Junagadh Sel-1, Aushey, R-34, H-4 and T-3 were considered resistant, as they either harbored a small jassid population or suffered less injury than the other varieties tested. The jassid population per unit leaf area was considered a good criterion for ascertaining the varietal differences. Screen-house tests with two resistant and three susceptible varieties at the cotyledonary and flowering stages showed that five or ten nymphs of the 3rd and 4th instar per seedling, and ten nymphs per leaf at the flowering stage, constituted the optimum population level for resistance screening of brinjal germplasm. Susceptible varieties developed hopper-burn faster, and with fewer jassids, than the resistant varieties. A prolonged nymphal stage and reduced nymphal survival and fecundity-cum-fertility, showed the presence of antibiosis in Junagadh Sel-1, R-34 and Aushey, followed by H-4; it was lacking in T-3. A low rate of development of hopper-burn despite a large jassid population per unit leaf area, suggested that the nature of jassid resistance in T-3 was tolerance. However, Junagadh Sel-1 and Aushey exhibited a very high level of resistance to the cotton jassid. Biophysical resistance to the cotton jassid was imparted in brinjal by the following morphological characteristics (in decreasing order of importance): long hair on mid-rib, high density of hair on leaf lamina, long hair on lamina, more erect hair on mid-rib, more hair per bunch, high density of hair on mid0rib, thin leaf lamina, and high density of hair on side-veins.     

Characterization of culturable gut bacterial isolates from wild population of melon fruit fly (<Emphasis Type="Italic">Bactrocera cucurbitae</Emphasis>) and assessing their attractancy potential for sustainable pest management

The melon fruit fly, Bactrocera cucurbitae (Coquillett) poses a serious threat to cucurbit production worldwide. Its management by conventional means remains difficult due to their proclivity to oviposite in fruit. In view of the increasing environmental safety concerns, use of biocontrol agents for sustainable pest control holds immense potential. Given this, the study intended to identify the cultivable bacteria inhabiting the intestinal tract of adult male and female melon fruit flies (Bactrocera cucurbitae) separately from field-collected population, and to assess the attractiveness of these bacteria to the fly. All selected bacterial isolates were identified and characterized based on morphological, biochemical and 16S rRNA gene sequence. Bacterial community identified in the gut of B. cucurbitae predominantly composed of Enterobacteriaceae followed by Staphylococcaceae, Enterococcaceae, Bacillaceae and Brucellaceae. Further, the laboratory bioassay was employed to examine the attractiveness of the supernatant as well as whole culture broth of 10 different species of bacteria to B. cucurbitae adults. Among these, Klebsiella oxytoca and Citrobacter freundii followed by Bacillus cereus were found highly attractive to fruit flies. The field experiment using supernatant of two bacteria demonstrated that the K. oxytoca was significantly more attractive to female flies followed by C. freundii.     

Effect of host genotype on leaf rust (Puccinia triticina) lesion development and urediniospore production in wheat seedlings

Experiments were performed in controlled conditions to compare several aggressiveness components of an isolate of Puccinia triticina on different wheat ( Triticum aestivum ) genotypes. Latency period, urediniospore production per lesion and per unit of sporulating surface, lesion size, and nitrogen and carbon content of the spores were measured on four host genotypes. Three of the host cultivars (Soissons, Altria and Isengrain) were susceptible and the fourth (Trémie) was resistant to the isolate used in the experiments, producing a mesothetic infection type. In all the analyses, lesion density was used as a covariable. The latent period was identical on the susceptible host cultivars, and there were no marked differences in the urediniospore production capacity when related to the sporulating surface area. In cv. Isengrain, differences in lesion size relative to the other susceptible cultivars resulted in lower urediniospore production per lesion. Urediniospore production per lesion and lesion size were density dependent and decreased exponentially with increasing lesion density. Urediniospore production per unit of sporulating surface was either independent of lesion density or marginally dependent (decreased linearly with a limited rate). On the resistant cultivar, Trémie, the latent period was longer and of a much greater variance compared with the susceptible cultivars. Urediniospore production per lesion was considerably reduced, but this reduction was fully accounted for by a reduction in lesion size, the urediniospore production capacity of the diseased tissue remaining equivalent to that observed in the susceptible cultivars. In all cultivars the C and N contents of the urediniospores were considered unchanged, even if minor differences were detected.     

棉花品种抗黄萎病性与体内生化成分相关分析

对棉花不同抗感黄萎病性品种生化成分分析结果表明:棉花品种在无菌土中体内可溶性还原糖含量相应地高于接菌土中的含量。蕾期抗耐品种平均含量为2.276％,高于感性品种的1.417％,而铃期趋势相反。叶片单宁含量高于根部。在无菌土中,抗耐品种叶片单宁含量平均为3.58％,高于感病品种的3.28％;而在接菌条件下趋势相反。根部棉酚含量显著高于叶部,但两者极显著相关。在无菌土和接菌土中,抗性品种棉酚含量均高于耐性品种,而耐性品种又高于感性品种。棉株体内棉酚含量与棉花品种抗黄萎病性显著正相关。同工酶谱测定显示,过氧化物酶在抗感品种的无病症叶片中,酶带特征基本一致,叶片显症后表现主酶带区加宽,主酶带数增多,变化趋势与症状严重度正相关。在显症条件下,抗性品种酯酶同工酶活性略强于感性品种;与无症叶相比,显症叶的SOD酶带数由原来的4—6条减少至3—4条,抗性品种的酶带数少于感性品种1—2条。     

Pathological and biochemical changes in Brassica juncea (mustard) infected with Albugo candida (white rust)

Components of disease reaction, including incubation period, pustule types, inoculum production and disease index (DI); and contents of protein, phenols, soluble sugars and reducing and non-reducing sugars were investigated in cotyledonary and true leaves of six genotypes of Brassica juncea : Varuna, Kranti, EC-399296, EC-399299, EC-399313 and EC-399301, inoculated with Albugo candida . Cotyledonary leaves were examined 14 days after inoculation (d.a.i.), whereas true leaves were scored 14 and 21 d.a.i. Disease indices were assessed on a 0% (resistant) to 100% (susceptible) scale. DIs at the cotyledonary leaf stage in the above six genotypes were 67, 65, 32, 31, 31 and 38%, respectively, whereas at the true-leaf stage they were 21, 28, 12, 17, 9 and 4%, respectively at 14 d.a.i., and 35, 45, 17, 19, 20 and 6%, respectively at 21 d.a.i. Protein contents were highest in the genotypes with the highest DIs, such as Varuna at the cotyledonary leaf stage and Kranti at the true-leaf stage, and lowest in the genotypes with the lowest DIs, such as EC-399299 at the cotyledonary stage and EC-399301 at the true-leaf stage. Total phenols, total sugars, reducing sugars and non-reducing sugars were generally negatively correlated with DI, but were not always consistent, particularly when differences in DI were small. The results indicated that factors conditioning the response of host genotypes to A. candida may differ or operate in different ways at different growth stages.     

茶树对茶橙瘿螨抗性机制的研究

作者分析了对茶橙瘿螨抗性和感性的两组无性系茶树新梢叶片下表面形态特征、叶片组织结构和新梢内含物含量。结果表明,抗性品种的叶片下表面茸毛密度、新梢咖啡碱和氨基酸的含量显著高于感性品种;叶片下表面气孔密度和新梢还原糖含量则相反。叶片组织结构、新梢茶多酚和可溶蛋白的含量抗、感品种间无显著差异。在氨基酸的组份中,以茶树特有氨基酸茶氨酸的含量差异最显著,其次是谷氨酸、丙氨酸、甘氨酸、天门冬氨酸、缬氨酸和丝氨酸。采用反渗叶盘法测定了多种氨基酸、咖啡碱、葡萄糖对该螨生物学的影响,明确了咖啡碱和多种氨基酸具有增加该螨活动时间、抑制其取食,从而影响其生长、繁殖的生理效应;葡萄糖有助于该螨的取食和繁殖。据此表明,茶树新梢叶片下表面多茸毛、低气孔密度的形态学抗螨机制和新梢高氨基酸、咖啡碱含量和低还原糖含量的生化抗螨机制。     

Effects of host plant genotype and seedbank density on Striga reproduction

Prevention of seed input to the seedbank of Striga hermonthica‐infested fields is an important objective of Striga management. In three consecutive years of field experimentation in Mali, Striga reproduction was studied for 10 sorghum genotypes at infestation levels ranging from 30 000 to 200 000 seeds m^?2. Host resistance was identified as an important determinant of Striga reproduction, with the most resistant genotypes (N13, IS9830 and SRN39) reducing Striga reproduction by 70–93% compared with the most susceptible genotype (CK60‐B). Seedbank density had a significant effect on Striga seed production. Higher seedbank density resulted in more Striga plants, which led to increased intra‐specific competition and consequently a reduced level of reproduction per plant. For the most susceptible sorghum genotypes, density dependence also occurred in the earlier belowground stages. Striga reproduction continued beyond harvest. At the high infestation level just 8% of the total reproduction was realised after harvest, whereas at the low infestation level 39% was attained after harvest. Even though host‐plant genotype plays a significant role in Striga reproduction, calculations indicated that only at very low infestation levels the use of the most resistant genotype was able to lower the Striga seedbank.     

新疆棉花品种次生代谢酶活性与诱导抗蚜性的关系

为了明确不同棉花品种次生代谢酶活性与诱导抗蚜性的关系,研究了不同类型棉花品种在棉蚜为害胁迫下,苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)和多酚氧化酶(PPO)活性的变化及其对抗蚜性的影响。结果表明,未受蚜害时不同品种同一酶活性存在显著差异;受蚜害诱导后,抗蚜品种和感蚜品种3种酶活性均有不同程度的上升,抗蚜品种酶活性显著高于感蚜品种,诱导抗蚜性的强弱在不同品种间差异显著。     

Screening Lactuca for resistance to Myzus persicae

A macrotest was developed to screen rapidly many genotypes ofLactuca in the greenhouse for resistance toMyzus persicae. In this test the estimated number of aphids on certain leaves of plants artificially exposed to aphid infestation was representative for the total number of aphids per plant. Significant differences in resistance between genotypes were observed and several partially resistant PIVT numbers were found among 645 accessions tested in 1973 and 1974. Also a microtest with leaf cages was developed in which biomass after seven to eight days of larval development and net larvae production during four to seven days functioned as criteria of resistance. Besides differences between genotypes, also within plants and between plants of the same genotype significant differences were found to occur. After testing nineteen genotypes with different levels of resistance it appeared that there was a clear relationship between results from both types of tests.     

Susceptibility of eight Algerian olive cultivars to <Emphasis Type="Italic">Bactrocera oleae</Emphasis> infestation – a pomological and nutritional quality perspective

The olive fruit fly, Bactrocera oleae (Rossi), is the major olive pest in the Mediterranean Basin, being responsible for high losses in olive production. The objective of this work was to study the influence of B. oleae infestation on the pomological parameters and nutritive value (lipids, proteins, carbohydrates and ash) of eight olive cultivars (Abani, Aellah, Blanquette de Guelma, Chemlal, Ferkani, Limli, Rougette de Mitidja and Souidi) from Algeria. The results displayed different degrees of susceptibility of the studied cultivars to this pest. Fruit size (weight) and the Fruit weight / stone weight ratio are significantly correlated with the attack. The statistical treatment of the results (PCA and HAC) highlighted different behaviors from the cultivars, concerning the attack. There are some cultivars more susceptible, being the nutritional value also affected. The lipid and protein contents were positively correlated with the attack and the carbohydrates negatively, suggesting a careful choice by the B. oleae. Ovipositional preference of olive fruit fly females and the success of larval development in different olive cultivars are crucial to establishing new approaches in Integrated Pest Management (IPM) against this pest.     

Biochemical changes in the <Emphasis Type="Italic">Brassica juncea-fruticulosa</Emphasis> introgression lines after <Emphasis Type="Italic">Lipaphis erysimi</Emphasis> (Kaltenbach) infestation

Insect damage leads to changes in biochemical profile of plants. Response of three Brassica juncea-fruticulosa introgression lines (already reported resistant to Lipaphis erysimi) in terms of changes in biochemical constituents after aphid infestation was studied along with B. fruticulosa (resistant parent), B. juncea var. PBR ?210 (susceptible parent) and B. rapa ecotype brown sarson BSH-1 (susceptible check). These six genotypes were grown under aphid infested and uninfested conditions and were sampled at peak aphid infestation to analyze the biochemical changes caused by aphid feeding from top 10 cm central twig of plant. A significant reduction in glucosinolates content in aphid infested plants of three introgression lines (I₈, I₇₉ and I₈₂) was observed while opposite was observed in B. fruticulosa, PBR-210 and BSH-1. Exactly opposite trend was observed for total phenols where aphid infestation resulted in significant increase in phenols content in the three introgression lines while a decrease was observed in B. fruticulosa, PBR-210 and BSH-1. A general trend of decline in flavonols, total sugars and free amino acids content was observed after aphid infestation in all the genotypes. Glucosinolates and total phenols served as biochemical bases of resistance in the three introgression lines since there was downregulation of glucosinolates and upregulation of total phenols as against opposite trend observed in BSH-1 and PBR-210.     

棉花抗蚜性与可溶性糖含量的关系

为探讨可溶性糖含量与棉花抗蚜性的关系,在室内人工接蚜为害和田间自然蚜群两种条件下,测定不同抗蚜性棉花品种受棉蚜为害后叶片中可溶性糖含量及其对棉蚜生长发育和繁殖的影响。结果表明:未受棉蚜为害时,抗性品种中可溶性糖含量高于感性品种,棉蚜为害胁迫后,抗蚜棉花品种可溶性糖含量升高,感蚜品种的可溶性糖含量降低。棉蚜的生长发育和繁殖与棉花叶片中可溶性糖含量呈显著的相关,可溶性糖与棉蚜若蚜历期呈正相关,与内禀增长率呈负相关。本研究说明可溶性糖含量对棉花的抗蚜性有一定的影响,转基因棉可溶性糖含量低于常规棉品种可能是导致非目标害虫棉蚜猖獗的原因之一。     

Diversity of the cultivable gut bacterial communities associated with the fruit flies <Emphasis Type="Italic">Bactrocera dorsalis</Emphasis> and <Emphasis Type="Italic">Bactrocera cucurbitae</Emphasis> (Diptera: Tephritidae)

Gut microbes play an important role in insect morphogenesis, nutrition, development of resistance against parasitoids and detoxification of toxic compounds. A culture-based approach is therefore an useful tool for the characterization of cultivable microbial communities associated with the insect gut. In the present study an attempt was made to decipher the gender specificity of gut bacterial communities of two major fruit fly species of India viz., Bactrocera dorsalis (Hendel) and Bactrocera cucurbitae (Conquillett) (Diptera: Tephritidae). Based on molecular identification, B. dorsalis females were found to predominantly harbor the bacterial species Enterobacter cloacae, Enterobacter asburiae and Citrobacter freundii, while B. dorsalis males were found to harbor Providencia rettgerii, Klebsiella oxytoca, Enterococcus faecalis and Pseudomonas aeruginosa The cultivable diversity from females of B. cucurbitae comprised mainly of Morganella morganii and Bacillus pumilis while B.cucurbitae males were predominantly colonized by aerobic endospore formers viz., Bacillus cereus, B. licheniformis and B. subtilis. The above findings have thrown light on a distinct pattern of gender specific gut bacterial colonization in fruit flies, which have to be factored in for the formulation of fruit fly management strategies.     

Preference and infestation level of Anastrepha fraterculus (Wiedemann, 1830) on fruits of some Psidium guajava L. cultivars and relation to their physicochemical parameters

This study aimed to verify the preference and infestation level of Anastrepha fraterculus (Diptera: Tephritidae) [South American fruit fly] in fruits of guava cultivars and to correlate them to variables such as peel coloration, soluble solids and pH of fruit cultivars. The following cultivars were used: Pedro Sato, Paluma, Cascão and Século XXI. The infestation was evaluated in cages, considering two scenarios: no-choice and multiple choice. In both tests, evaluations of the fruit attraction to insects were conducted for a period of 1′, 3′, 5′, 10′, 20′, 30′, 1 h, 2 h, 6 h, 12 h and 24 h. The visit of A. fraterculus on the assayed cultivars in relation to the time was studied by logistic regression. After 10 days, the number of larvae in each fruit was recorded. In the multiple choice test, the visit proportions were significantly higher in the fruits of cvs. Século XXI and Pedro Sato than in those of cvs. Paluma and Cascão. In the no-choice test, the visit proportions were significantly lower in the Paluma fruits. In both tests, the rate of fruit infestation by A. fraterculus did not differ among cvs. Pedro Sato, Paluma and Cascão, whereas the fruits of cv. Século XXI were more infested. The indexes of pH did not interfere with the infestation of A. fraterculus, whereas a high rate of soluble solids and low color angle appear to be crucial for discriminating the fruits of the most susceptible cultivars. Infestation rate of Século XXI fruits displayed significant correlations with: °Brix (r= 0.7078) and color angle (h) (r= –0.9499) of guava fruits under the multiple choice conditions.     

Virulence and inoculum density‐dependent interactions between clubroot resistant canola (Brassica napus) and Plasmodiophora brassicae

To mitigate the impact and dissemination of clubroot in western Canada, canola (Brassica napus) producers have relied on clubroot resistance traits. However, in 2013 and 2014, new strains of the clubroot pathogen, Plasmodiophora brassicae, emerged that are virulent on most clubroot‐resistant (CR) canola genotypes. Novel strains of the pathogen were inoculated onto two susceptible canola cultivars, one resistant line and six CR cultivars. Although all cultivars/lines showed a susceptible response to inoculation with the new strains of P. brassicae, the severity of disease reaction, root hair infection rates and the amount of P. brassicae DNA present in each canola genotype varied depending on the strain. In addition, the effect of inoculum density on disease severity and gall formation was recorded for one of these new strains on a universally susceptible Chinese cabbage cultivar and one susceptible and 10 resistant canola genotypes. Although root galls were observed at an inoculum density of 10³ spores per mL of soil, clear differentiation of susceptible and resistant reactions among canola cultivars/lines was not observed until the inoculum density reached 10⁵ spores mL^?1. At a spore density of 10⁶ spores mL^?1 and above, all cultivars/lines developed susceptible reactions, although there was some differentiation in the degree of reaction. This study shows the potential to develop a unique disease profile for emergent clubroot pathotypes and shows a useful range of spore densities at which to study new P. brassicae strains.     

甘薯品种对疮痂病的抗性及其机理分析

为查明我国南方甘薯主栽品种抗疮痂病的能力,用疮痂菌孢子悬液对16份品种作苗期接种与田间病情系统观察.结果表明,广薯79-15、潮薯1号等8份表现感病-中感;福薯26、广薯88-70等8份表现中抗-高抗;不同抗、感品种在田间表现长短不一的感病期.对6份品种藤蔓不同的部位和株龄的组织结构作显微测量与计数、接种试验以及糖含量测定显示,不同品种皮层组织结构差异决定对疮痂病的抗、感性;抗病品种藤蔓具有较厚的角质层,叶片气孔和幼嫩组织的腺鳞数目都较少,表现潜育期长,病斑少.且同一品种不同株龄皮层结构差异与感病程度间有密切关系,但其藤蔓糖含量与品种抗性之间不相关.     

Metabolic profiling in the roots of coffee plants exposed to the coffee root-knot nematode, Meloidogyne exigua

To understand the effect of nematode Meloidogyne exigua infestation on coffee plants, resistant and susceptible coffee seedlings were inoculated with second-stage juveniles of M. exigua, and root metabolites were studied for four time intervals at 0, 24, 48 and 96 h. During this important period for parasite establishment, the concentrations of phenols, carbohydrates, amino acids and alkaloids in the roots were measured, and hydrogen nuclear magnetic resonance spectra of the root extracts were used to identify and quantify other metabolites. One of the most striking changes was the concentration of fumaric acid on resistant plants, which varied from 59 μg g(of root)^?1 to 138 μg g(of root)^?1 during the first 24 h of the nematode inoculation. The same level of variation was observed much later (96 h) in susceptible plants. Similarly, formic and quinic acid concentrations increased more rapidly in the resistant plants compared to the susceptibles. Sucrose concentrations increased to 370 % in the first 48 h in the resistant plants but showed no significant variation in the susceptible plant. Besides, the concentration of alkaloids was much higher at 24 and 48 h in the susceptibles compared to the resistant plants. These results suggest that the higher production of sucrose as well as formic, fumaric and quinic acids, and the lower production of alkaloids by the resistant cultivar in the first 48 h after the nematode inoculation are associated with the resistance of coffee plants to M. exigua.