Transcriptional profile of AvrRpt2EA-mediated resistance and susceptibility response to Erwinia amylovora in apple

Most of the commercial apple cultivars are highly susceptible to fire blight, which is the most devastating bacterial disease affecting pome fruits. Resistance to fire blight is described especially in wild Malus accessions such as M. × robusta 5 (Mr5), but the molecular basis of host resistance response to the pathogen Erwinia amylovora is still largely unknown. The bacterial effector protein AvrRpt2EA was found to be the key determinant of resistance response in Mr5. A wild type E. amylovora strain and the corresponding avrRpt2EA deletion mutant were used for inoculation of Mr5 to induce resistance or susceptible response, respectively. By comparison of the transcriptome of both responses, 211 differentially expressed genes (DEGs) were identified. We found that heat-shock response including heat-shock proteins (HSPs) and heat-shock transcription factors (HSFs) are activated in apple specifically in the susceptible response, independent of AvrRpt2EA. Further analysis on the expression progress of 81 DEGs by high-throughput real-time qPCR resulted in the identification of genes that were activated after inoculation with E. amylovora. Hence, a potential role of these genes in the resistance to the pathogen is postulated, including genes coding for enzymes involved in formation of flavonoids and terpenoids, ribosome-inactivating enzymes (RIPs) and a squamosa promoter binding-like (SPL) transcription factor.

The Causal Agent of Fusarium Disease Infested Shallots in Java Islands of Indonesia

The success of disease control is largely determined by the validity of information about the type of causal-pathogen. Fusarium oxysporum f. sp. cepae (FOC) was reported to attack shallots and cause leaf twisting disease in Indonesia. We have conducted researches to investigate the causal agent of Fusarium disease and carried out growth tests on nine genotypes of shallots to determine the disease severity and disease indexes, and the correlation between diseases several agronomic traits. Thirty-five strains of Fusarium spp were isolated from wilted shallots tree and bulbs. Based on morphological characterization and rapid test to the isolates, they were identified as F oxysporum, F verticillioides, F solani and F proliferatum. The shallot genotypes that showed a tolerant response to FOC isolates tested were only Sumenep variety. Mentes, Tajuk, Batu Ijo, and Bima Brebes varieties show susceptible response.

Studies on Biology and Antibiosis Resistance in Mango (Mangiferae indica) Varieties Against Mango Mealy Bug, Drosicha mangiferae Green (Hemiptera: Margarodidae)

Mango is known as king of fruits. Among mango pests, mango mealy bug, Drosicha mangiferae (MMB), is considered one of the most destructive pests of mango orchards and other plantations. Whenever it enters in any orchards it is difficult to eradicate it from those orchards. The experiment was conducted at Entomological Research Sub Station, Multan-Punjab, Pakistan, during 2009 and 2010, to evaluate fitness of mango mealy bug on different varieties of mango and biology on ‘Chaunsa’ variety. Mango mealy bug, Drosicha mangiferae Green (Hemiptera: Coccoidea: Margarodidae), is matter of concern, as it is widespread pest of woody plants even in urban areas. A study was conducted on cultivar resistance and fecundity of mango mealy bug. The ‘Chaunsa’ cultivar of mango proved highly susceptible to mango mealy bug with maximum number of eggs laid, i.e. 335.90, and maximum weight, i.e. 0.239 g of the female, was recorded on the cultivar ‘Chaunsa’. The maximum length, i.e. 1.63 cm, and width, i.e. 0.80 cm of female, was observed on ‘Chaunsa’, which showed a susceptible response and did not differ significantly with the width of female on ‘Black Chaunsa’. Regarding biology, the 1st instar male and female duration on an average is 56.3 days, whereas the 2nd instar has 26 days. In case of the 3rd instar, female has duration 19.5 days and male has three days. Male has pupal stage, while it is absent in female. On an average two study years, the ranking of susceptibility of mango cultivars was as under: ‘Chaunsa’ > ‘Black Chaunsa’ > ‘Malda’ > ‘Fajri’ > ‘Retaul-12’ > ‘Langra’ > ‘Sensation’ > ‘Sindhri’ > ‘Dusehri’ > ‘Sufaid Chaunsa’ > ‘Anwar Reutul’ and > ‘Tukhmi’.

EVALUATION OF VARIOUS LINES OF WHEAT AND EPIDEMIOLOGY AGAINST LOOSE SMUT (USTILAGO TRITICI)

Fungal diseases pose a potential threat to successful cereal production in wheat particularly in Pakistan. Loose smut caused by Ustilago tritici is an important disease of wheat. During the current research various lines of wheat were screened against the deadly disease, results showed no line was resistant against the disease in the wheat genetic resources, mostly varieties showed susceptible to highly susceptible response. All the environmental variables were found conducive for the development of the disease. The disease is a serious concern for wheat production and potential breeding programs are the need of time to cater the losses due to this disease.

SUSCEPTIBILITY OF CHILLI LINES / VARIETIES TOWARDS CHILLI LEAF CURL VIRUS AND ITS MANAGEMENT THROUGH VECTOR CONTROL

Chilli leaf curl virus (ChiLCV) is a serious problem for chilli production in Pakistan and India. In this study, fourteen different chilli lines / varieties were screened for their resistance/susceptibility towards ChiLCV in open field trials. Data of disease severity and disease incidence was recorded on weekly basis. Out of all varieties screened, Tatapuri Chilli and CH111 showed high susceptibility towards the chilli leaf curl disease. Talhari, CH 99, CH103, CH 106, CH107, CH108, CH109, GSL111 showed susceptible response whereas CBS1292 showed moderately susceptible response towards the disease. Only two cultivars Hybrid-46 and Hot Queen were found as moderately resistant. The screening experiment showed that most of the chilli varieties are susceptible to chilli leaf curl disease and resistance is lacking in local germplasm. Furthermore, three insecticides: Imidacloprid, Polo and Emamectin were tested for their efficacy for the management of disease and whitefly vector in field conditions at weekly intervals. Out of three insecticides, Polo gave best results as compared to Emamectin and Imidacloprid against chilli leaf curl disease and whitefly vector.

EVALUATION OF GROUND NUT MATERIAL AGAINST TIKKA LEAF SPOT DISEASE UNDER NATURAL FIELD CONDITIONS AT NARC

The ground nut material, (including germplasm, candidate line etc) was planted at NARC in a previously sick field with the objective to check material for resistance against tikka leaf spot disease caused by Cercospora personata. A total of 44 entries were evaluated under four different sets of experiments whereas BARD-479 was included as the check. Among four candidate entries one entry exhibited 1R reaction two were 3MR compared to check which showed 7S reaction. Among the 13 entries of the International Confectionery ground nut trail 5 entries showed 1R and 5 were showing 3MR reactions whereas two entries exhibited 5MS. Among fifteen entries of NUGYT, six entries were found resistant(R), seven were moderate resistant (MR) while one entry was moderately susceptible (MS). Among thirteen entries of advance medium maturity ground nut yield trail, seven were found resistant (R), four were MR while one entry exhibited MS compared to check which exhibited S reaction. Based on this evaluation it is concluded that 18 entries have exhibited the resistance against Tikka disease whereas BARD-479 (Check) showed susceptible response under natural conditions. The lines showing 1R reaction can be used in the varietal development.

EVALUATION OF AVAILABLE GENETIC RESOURCE AGAINST BACTERIAL BLIGHT OF COTTON IN PAKISTAN

Bacterial leaf Blight of cotton a major seed borne foliar disease that attacks the crop at all growth stages leading to cause severe losses in conducive environment. To find out best source of resistance against pathogen this research was conducted in the field area Department of Plant Pathology, University of Agriculture Faisalabad. Incidence of bacterial blight of cotton was determined on twenty eight varieties/advanced lines sown in field to determine the resistance resource against the disease. Two years data showed that seventeen varieties (BT-Z-33, BT-S-78, BT-786, BT-A-ONE, BT -282, BT-886, BT-3701, BT-SPECIAL, BT-802, Non Bt-FH 901, BT-92, BT-131, BT-905, BT-SUPPER, Non Bt-MNH 496, Non Bt-FH 1000, and BT-121) expressed moderately resistant response with 21-50 % disease incidence (rating 4). Five varieties viz. Non Bt-FH 207, Non BT-N 112, Non BT-FH 942, Non BT-MNH 6070 and Non Bt-FH 941exhibited moderately susceptible response with 51-70% disease incidence under rating 5. Four varieties namely Non BT-N 814, Non Bt-FH 900, Non BT-ANMOL and Non Bt-FH 2015 showed susceptible response with 71-80% disease incidence (rating 6) while Non BT-REDACOLA and Non BT-C 26 expressed highly susceptible response with disease incidence 81-100% rating 7 against bacterial blight disease of cotton. Results indicate that a wide range of resistant resource is present in Pakistan against the disease. The selection of diverse germplasm/resistant varieties through screening is the most efficient, environment friendly and economical management strategy for farmers against this disease.

Multiple Phytohormone Signals Control the Transcriptional Response to Soybean Aphid Infestation in Susceptible and Resistant Soybean Plants

The soybean aphid (Aphis glycines) is a major phloem-feeding pest of soybean (Glycine max). A. glycines feeding can cause the diversion of photosynthates and transmission of plant viruses, resulting in significant yield losses. In this study, we used oligonucleotide microarrays to characterize the long-term transcriptional response to soybean aphid colonization of two related soybean cultivars, one with the Rag1 aphid-resistance gene and one aphid-susceptible cultivar (without Rag1). Transcriptome profiles were determined after 1 and 7 days of aphid infestation. Our results revealed a susceptible response involving hundreds of transcripts, whereas only one transcript changed in the resistant response to aphids. This nonexistent resistance response might be explained by the fact that many defense-related transcripts are constitutively expressed in resistant plants, whereas these same genes are activated in susceptible plants only during aphid infestation. Analysis of phytohormone-related transcripts in the susceptible response showed different hormone profiles for the two time points, and suggest that aphids are able to suppress hormone signals in susceptible plants. A significant activation of abscissic acid, normally associated with abiotic stress responses, at day 7, might be a decoy strategy implemented by the aphid to suppress effective salicylic acid- and jasmonate-related defenses.

Molecular basis of resistance in wheat varieties against spot blotch disease

During present investigation, among the six wheat genotypes tested against six isolates of Bipolaris sorokiniana, the genotype BOW‘S’ showed resistance response against three isolates, namely, BS-D-1, BS-DWRK-2 and BS-K-4, whereas moderately resistance response against remaining 3 isolates i.e. BS-F-3, BS-P-5 and BS-V-6.The genotype A-9-30-1 showed almost highly susceptible response against each isolate except BS-D-1 which exhibited susceptible reaction on this genotype. Thus, it is clear that genotype BOW ‘S’ has broad genetic base for resistance, whereas genotype A-9-30-1 has no gene for resistance against these six isolates tested. Remaining five genotypes showed varying response, ranging from highly susceptible, susceptible, moderately susceptible, moderately resistant and resistant against various isolates of B. sorokiniana tested.

Plant-Parasitic Nematodes Infecting Grapevine in Southern Spain and Susceptible Reaction to Root-Knot Nematodes of Rootstocks Reported as Moderately Resistant

Incidence and nematode population densities of plant-parasitic nematodes were determined in 64 samples of soil and grapevine roots collected from commercial vineyards in southern Spain between October 2003 and May 2005. In addition, a histopathological study was done of root-stock roots naturally infected by root-knot nematodes (Meloidogyne spp.). Nematodes infecting the rootstocks were identified according to conventional procedures, and the Meloidogyne spp. were furthermore identified by sequence characterized amplified region-polymerase chain reaction (SCAR-PCR) and isozyme esterase analyses. The most important plant-parasitic nematodes detected, in order of decreasing frequency of total soil infestation and root infection (percentage of samples), were Mesocriconema xenoplax (34.4%), Meloidogyne incognita (26.6%), Meloidogyne javanica (14.1%), Xiphinema index (12.5%), Xiphinema italiae (10.9%), Pratylenchus vulnus (6.3%), and Meloidogyne arenaria (1.6%). No disease symptoms were observed on aboveground plant parts of the infected grapevines, except for plants in some fields where soil was infested with the virus-vector nematodes X. index and X. italiae. Those grapevines showed a yellow mosaic pattern in leaves early in the growing season and the internode shortening characteristic of infections by Grapevine fanleaf virus. Rootstocks infected by root-knot nematodes (Meloidogyne spp.) showed distorted feeder roots and large- to moderate-sized root galls, present either singly or in clusters. Histopathology of galled roots showed a typical susceptible response to infection by root-knot nematodes: cellular alterations were induced in the cortex, endodermis, pericycle, and vascular system, including giant-cell formation and severe distortion of vascular tissues. Most Meloidogyne egg masses ocurred on the surface of the galled root tissues, a position that could facilitate dispersion of the nematode eggs and juveniles and the occurrence of secondary infections. Some of the grapevine rootstocks surveyed in this study (Paulsen 1103, Richter 110, Rupestris du Lot, and SO4) had previously been reported to be resistant to Meloidogyne spp.; however, the population densities of these nematodes found in soil and roots sampled in the present study, as well as the compatible host-parasite relationship revealed by histopathology, indicate a susceptible response to Meloidogyne spp. from southern Spain.