Using Marker Assisted Selection to Hasten Screening of Cassava Cultivars Developed through Introgression of Cassava Mosaic Disease （CMD） Resistance into Cassava Landraces in Ghana

Cassava mosaic disease （CMD）, the most important disease of cassava （Manihot esculenta Crantz） is a potential threat to Africa＇s cassava production. The disease is embedded in most landraces resulting in low yields. Host plant resistance has been found to be the best control strategy. A breeding programme using genetic hybridisation and Marker Assisted Selection was initiated in 2007 to improve the resistance levels of farmer-preferred landraces and reduce the long breeding cycle for developing improved cassava varieties. Thirty farmer-preferred landraces were selected and crossed with a high yielding and mosaic resistant cultivar （TMEI l） from International Institute of Tropical Agriculture （IITA）. The resultant progenies found to have a reasonable level of resistance （score, 1-3） to the CMD were AW 18, 273 Nyamebekyere, NK 43, AW 3, NK 26, K 25, Dabodabo, Ahwengyankwa, 674 Debor, Degarti, Agric Bankye, and NK 57. These resultant progenies were backcrossed to the resistant cultivar. The backcross one （BC l） progenies totaling 224 were screened with molecular markers that are associated to the CMD 2 gene. De-oxyribonucleic Acid （DNA） was extracted from leaves of the 224 BC1 progenies and 13 parents. Two Simple Sequence Repeats （SSR） markers （SSY28 and NSl58） and one Sequenced Characterized Amplified Region （SCAR） marker RME1, were used to screen and select for the resistant BC l progenies. Marker Assisted Selection （MAS） revealed that 82% of the genotypes had at least a marker allele for the CMD2 gene, indicating resistance. The study further revealed that by using MAS, the breeding cycle of cassava in the generation of varieties could be reduced from 8 years to 2 years. The resistant genotypes identified will be evaluated for yield and starch cooking quality in future breeding work.

Farmer’s Perception of Cassava Mosaic Disease, Preferences and Constraints in Lupaula Province of Zambia

Cassava is the principal staple root crop, providing a major source of calories for rural and urban households in Luapula province of Zambia. However, the yields on smallholder farms are relatively low largely due to disease infections. The study was therefore conducted to establish farmers’ perceptions, knowledge and management of cassava mosaic disease (CMD), which is one of the major diseases of cassava, and to establish farmers’ preferred traits, constraints and assess sources of cassava cuttings for planting. Focus group discussions (FGD) and structured interviews involving 156 farmers in Mwense, Mansa and Samfya districts were conducted from December 2008 to March 2009. Knowledge of CMD was limited among the respondents. Only 2.4% of the respondents were aware of the disease despite high CMD incidence in farmers’ fields. The majority of the farmers were aware of the importance of insect pests;however, they could not differentiate between damages due to diseases or insect pests. High yield and early bulking traits were highly ranked. Most of the farmers planted local landraces on small-fields (<1 ha). It was evident that a local breeding programme aimed at developing locally adapted disease and pest resistant cassava cultivars was a pressing requirement.

Mapping of a Wheat Resistance Gene to Yellow Mosaic Disease by Amplified Fragment Length Polymorphism and Simple Sequence Repeat Markers

Wheat （Triticum aestivum L.） yellow mosaic virus （WYMV） is transmitted by a fungal vector through soil and causes serious wheat yield losses due to yellow mosaic disease, with yellow-streaked leaves and stunted plants. In the present study, the amplified fragment length polymorphisms （AFLP） and simple sequence repeat （SSR） were used to identify the molecular linkages with the resistance gene against WYMV. Bulked segregant analysis was performed with an F2 population derived from the cross of cultivar Ningmai 9 （resistant） × cultivar Yangmai 10 （susceptible）. By screening among the resistant or susceptible parents, the F2 pools and the individuals in the F2 population with 64 combined selective AFLP primers （EcoRI/MseI） or 290 reported SSR primers, a polymorphic DNA segment （approximately 120 bp） was amplified using the primer pair E2/M5, and an SSR marker （approximately 180 bp） was located on wheat chromosome 2A using the primer Xgwm328. Analysis with MAPMAKER/Exp Version 3.0b （Whitehead institute for Biomedical Research, Cambridge, MA, USA） indicated that these two markers were dominantly associated with the resistance gene at distances of 5.4 cM or 17.6 cM, respectively. The resistance gene to WYMV derived from Ningmai 9, is temporarily named YmNM, and was mapped to wheat chromosome 2A.

Screening Landraces for Additional Sources of Field Resistance to Cassava Mosaic Disease and Green Mite for Integration into the Cassava Improvement Program

Twelve cassava landraces were evaluated for sources of resistance genes to diseases and pests of major economic importance in Africa. The objective was to assess their levels of field resistance to mosaic disease （ACMD）, bacterial blight （CBB）, anthracnose （CAD）, and green mite （CGM）, compared to TMS30572, an elite cultivar widely adopted in Africa. Considerable genotypic variation was observed among cultivars for resistance to ACMD and CGM but not for CBB and CAD. The lowest mean incidence of 12% and severity of 1.8 on a scale of 1-5 for ACMD was recorded for Atu, a landrace with farmer acceptable qualities. In comparison, the improved cultivar, TMS 30572, had a mean disease incidence of 72% and a severity score of 2.8. Another landrace, MS-20 had the lowest CGM damage score （2.1） while TMS 30572 emerged as one of the susceptible cultivars with a damage score of 3. Additional sources of resistance to ACMD and CGM that may possibly be better than the popular improved cultivar, TMS 30572, were identified in this study. These could serve as novel sources of additional genes to complement existing resources for elite cassava breeding in Africa.

Estimating the severity of apple mosaic disease with hyperspectral images

Soil Plant Analysis Development(SPAD)Chlorophyll Meter reading was used to effectively characterize chlorophyll content,which is an important indicator of the health status of plant leaves.In this study,the hyperspectral images of apple leaves infected by apple mosaic virus(ApMV)were captured,and their SPAD values were measured.The spectral reflectance of leaves with varying degree infection of disease is significantly different.In particular,the reflectance in visible wavebands of leaves with a more serious infection was higher than that of leaves with a less severe infection.Several hyperspectral vegetation indices were highly correlated with the SPAD values of apple leaves(correlation coefficient>0.9).Models were established to estimate apple foliar SPAD values based on these vegetation indices.Among the models,the multivariate regression model with partial least square regression(PLSR)method achieved the highest accuracy.The SPAD value of a whole apple leaf was calculated from its SPAD distribution image and used as a quantitative index to represent the health status of an apple leaf.Furthermore,the SPAD value of a whole apple leaf could also be estimated rapidly and accurately by extracting the spectral average value of the whole leaf using a simple model.It can be used as a rapid detection method of SPAD values of apple leaves to monitor and describe the health conditions of apple leaves quantitatively.

Grading method of soybean mosaic disease based on hyperspectral imaging technology

Soybean is a crop with a long cultivation history that occupies an important position in agricultural production.Soybean mosaic virus disease(SMV)has caused a rapid decline in soybean yields,causing huge losses to the soybean industry,wherefrom its early detec-tion is particularly important.This study proposes a new classification method for the early SMV,dividing its severity into grades 0,1 and 2.In the case of a small number of experi-mental samples of soybeans,this study proposes a combined convolutional neural network and support vector machine(CNN-SVM)method for the early detection of SMV.Experimen-tal results showed that the accuracy of the training set of the CNN-SVM model reached 96.67%,and the accuracy rate of the test set reached 94.17%.The experiment proved the feasibility of using the proposed CNN-SVM model to classify early SMV under the new clas-sification method,and provided a new direction for early SMV detection based on hyper-spectral images.

Control Effects of Different Agents on Tobacco Mosaic Virus Disease

[Objectives] This study was conducted to screen out suitable agents for controlling tobacco mosaic virus disease and the best control period in Zhangzhou tobacco area, providing a theoretical basis for the control of virus diseases, thereby improving the quality of flue-cured tobacco and the income of tobacco farmers. [Methods] The effects on tobacco mosaic virus disease under the interaction between different agents and different application periods were investigated. The incidence of tobacco mosaic virus disease was investigated, and its control effect was analyzed. [Results] Different agents and different application periods had different control effects on tobacco mosaic virus disease. The incidence of tobacco mosaic virus disease: At 30 and 45 d after transplanting, the incidences of A2B1 treatment were the lowest, at 0.85%, 1.71%, respectively;and at 60 d after transplanting, the incidence of A3B1 treatment was the lowest, only 10.68%. The control effect: At 30 and 45 d after transplanting, A2B1 treatment had better control effects, reaching 79.39% and 73.06%, respectively. [Conclusions] 3% hypersensitive protein sprayed at 1 d before transplanting and 7 and 15 d after transplanting achieved the best effect, followed by 10% ningnanmycin sprayed at 1 d before transplanting and 7 and 15 d after transplanting. In tobacco production, it is recommended to apply 1 000 times dilution of 3% supersensitive protein microgranules for three times(at 1 d before transplanting and 7 and 15 d after transplanting), which can effectively prevent tobacco mosaic virus disease.

Adaptability and Phenotypic Stability of Resistance to Two Viral Diseases and Yield Traits in Cassava

Cassava productivity is hampered by pests and diseases including cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). The main objective of this study was to identify stable superior genotypes that combine disease resistance and high yield. Sixteen cassava genotypes were planted in a randomized complete block design with three replications for six planting seasons (years) at five sites in Tanzania. The genotypes were assessed using the additive main effect and multiplicative interaction (AMMI) analysis, and highly significant (P < 0.001) effects of genotype, environment, and genotype-by-environment (G*E) interactions were observed for all traits studied. Percent sum of squares (SS) due to environment (12.66% - 85.23%) was the highest followed by G*E (14.12% - 39.56%) for CMD foliar symptoms, root weight and dry matter. On the other hand, % SS due to genotype (52.14% - 69.14%) was highest followed by G*E (26.14% - 35.91%) for CBSD foliar and root symptoms indicating that the environment and G*E greatly influenced trait expression. The most stable genotypes which combined disease resistance and high yield were NDL 2003/31 and NDL 2003/111. The findings of this study will give impetus for the release of new cassava varieties that are not only high yielding but are also dually resistant to both CMD and CBSD in different locations and sites.

Occurrence of Major Diseases and Insect Pests in Medium-term Growth Period of Sugarcane and The Diseases Resistance Evaluation in Guangxi

To figure out major diseases and insect pests of sugarcane and sugarcane resistance to diseases,the occurrence of major diseases and insect pests on 11 main sugarcane varieties in eight sugarcane producing areas of Guangxi was investigated during the medium-term growth period of sugarcane in 2015,and field resistance to smut and mosaic diseases was evaluated. The results showed that the dead heart rate（ DHR） ranged from 0. 00% to 38. 55%; new-planting sugarcane of Guiliu 2 and ratoon sugarcane of Liucheng 05-136 suffered the most severe damage in Beihai city,and the DHR were 38. 55% and 37. 66%,respectively. The incidence rate of smut disease ranged from 0. 00% to 24. 89%. Ratoon sugarcane was more susceptible to smut than new-planting sugarcane among all investigated varieties. Variety ROC22 was most susceptible to smut,and performed moderate susceptibility. Guiliu 2 was the second susceptible and performed resistance,with the incidence rate of 7. 45%. The rest nine varieties had high resistance. Sugarcane mosaic disease occurred mildly in Guangxi,and the incidence rate ranged from 0. 39% to 7. 73%. ROC22,Guitang 42 and Guiliu 2 expressed moderate resistance and the rests exhibited resistance. Sugarcane in Nanning and Beihai suffered more severe damage than those in other producing areas. The field evaluation system of sugarcane resistance to borers was expected to be constructed. ROC22 was most susceptible to smut,compared with other main varieties. Mosaic diseases occurred lightly in Guangxi. Multi-location and multi-year observation are necessary for accurate evaluation of sugarcane resistance to smut and mosaic diseases.

Analysis of fig tree virus type and distribution in China

The common fig（Ficus carica L.）was one of the earliest horticultural crops to be domesticated.A number of different viruses can infect fig trees including Fig mosaic virus（FMV）that has been detected in several commercial fig trees in Xinjiang,China.However,the distribution of FMV and other fig-infecting viruses in China remains unknown.In the present study,a sample from an ancient fig tree growing in Xinjiang was investigated by electron microscopy（EM）followed by PCR/RT-PCR,and FMV,Fig badnavirus 1（FBV-1）and Fig leaf mottle-associated virus 1（FLMaV-1）were detected.Fig leaf samples（252）from commercial orchards across China were subjected to PCR/RT-PCR,and FMV,FBV-1 and Fig fleck-associated virus（FFka V）were relatively abundant（44.4,48.4 and 44%,respectively）,while FLMaV-1 and Fig mild mottle-associated virus（FMMa V）were much scarcer（5.6 and 0.4%,respectively）,and FLMaV-2,Fig cryptic virus（FCV）,and Fig latent virus（FLV）were not detected.The presence of disease-causing viruses in fig trees presents a significant challenge for fig producers in China.This study may help to promote actions aimed at controlling fig viruses,especially FMV.

Cryptic species composition and genetic diversity within Bemisia tabaci complex in soybean in India revealed by mtCOI DNA sequence

Bemisia tabaci is a cryptic species complex, causing signiifcant loss on many agricultural y important crops worldwide. Knowledge on species composition and diversity within B. tabaci complex is critical for evolving sustainable pest management strategies. Here we investigate the whitelfy species complex in soybean in major soybean growing states of India. The mitochondrial cytochrome oxidase gene subunit-1 (mtCOI) based phylogenetic relationships established using Bayesian methods indicated the existence of three cryptic species namely Asia I, Asia II 1, and Asia II 7. Al the haplotypes detected in the study could be assigned to these three cryptic species fol owing the species demarcation criteria of 3.5%divergence threshold. Of these, Asia II 1 was found to be predominant with wide spread distribution across the surveyed regions from cool temperate zones to hot and humid tropical plains. On the contrary, cryptic species Asia II 7 showed localized distribu-tion. The Asia II 1 exhibited the highest haplotype diversity and Asia I showed high level of nucleotide diversity. There was a signiifcantly high genetic differentiation among these three cryptic species. The MEAM 1, a dreadful invasive species was not detected in the specimens tested in the current study. The diversity and distribution of three cryptic species is discussed in the light of current knowledge on distribution of whitelfy species in India and yel ow mosaic disease observed during sampling survey.

华南三省(自治区)部分西番莲种植区花叶病病原检测及EAPV多聚蛋白基因序列分析

西番莲(Passiflora edulis Sims.)是热带亚热带地区重要经济作物,我国福建、广东、广西、海南等地广泛种植[1]。调查发现,我国南方多地西番莲花叶病为害严重,症状表现为叶片花叶、黄化、斑驳、畸形,甚至整株褪绿,严重影响西番莲的产量和品质。