Evaluation of cotton germplasm for morphological and biochemical host plant UPdates resistance traits against sucking insect pests complex

Background:Sucking insect pests cause severe damage to cotton crop production.The development of insect resistant cotton cultivars is one of the most effective measures in curtailing the yield losses.Considering the role of morphological and biochemical host plant resista nee(HPR)traits in plant defense,12 cotton genotypes/varieties were evaluated for leaf area,leaf glanding,total soluble sugars,total soluble proteins,total phenolics,tannin and total flavonoids against fluctuating populations of whitefly,thrips and jassid under field conditions.Results:The population of these insects fluctuated during the growing seas on and remained above threshold level(whitefly>5,thrips>(8-10)f or jassid>1 per leaf)during late June and early July.Strong and negative association of whitefly(r=-0.825)and jassid(r=-0.929)with seed cotton yield was observed.Mean population of insects were the highest in Glandless-1 followed by NIA-82 and NIA-M30.NIAB-Kiran followed by NI AB-878 and Sadori were the most resistant,with the mean population of 1.41,1.60,1.66(whitefly);2.24,232,2.53(thrips)and 037,0.31,036(jassid),respectively.The resistant variety NIAB-Kiran showed less soluble sugars(8.54 mg.g^(-1)),soluble proteins(27.11 mg.g^(-1))and more phenolic(36.56 mg.g^(-1))and flavonoids(13.10mg.g^(-1))as compared with the susceptible check Glandless-1.Moreover,all insect populations were positively correlated with total soluble sugars and proteins.Whitefly populations exhibited negative response to leaf gossypol glands,total phenolics,tannins and flavonoids.The thrips and jassid populations had a significant and negative correlation with these four biochemical HPR traits.Conclusion:The ide ntified resistant resources and HPR traits can be deployed against sucking in sect pests'complex in future breeding programs of developing insect resistant cotton varieties.

Challenges and Progress in Evaluating Apple Root Resistance Responses to Pythium ultimum Infection

Due to the hidden nature of roots in the soils, it is more challenging to investigate their resistance traits and defense responses as compared to those of the aerial organs. At the same time, it is self-evident that root health is fundamental to a plant’s entire life and productivity. It is also easily conceivable that root function, physiology, morphology, and architecture are constantly impacted by the complex soil environment including both biotic and abiotic factors. This report summarizes and updates the challenges and progress in evaluating resistance responses of apple root to infection from a necrotrophic oomycete pathogen, Pythium ultimum. Several obstacles impede the progress of investigating apple root resistance traits including the difficulties of direct and real-time evaluation and the lack of a continuous supply of apple plants for repeated infection assays. Systematic and detailed analyses were made possible by implementing a micropropagation procedure for continuously generating uniform apple plants for repeated infection assays. As a result, an elite panel of apple rootstock germplasm with distinct resistance levels was identified. These apple rootstock genotypes with well-defined resistance levels are the much-needed plant materials for subsequent genomics and transgenics analyses to define the functional roles of specific candidate genes. Careful microscopic examination revealed contrasting necrosis progression patterns between resistant and susceptible genotypes, which shed light on the potential mechanisms underlying resistance traits. Our continuing research will provide a clearer view regarding the genetic elements regulating resistance traits in apple roots to P. ultimum infection.

No trade-off between trichome production and tolerance to leaf and inflorescence damage in a natural population of Arabidopsis lyrata

Aims Early models of plant defense conceived resistance and tolerance to herbivore damage as mutually exclusive strategies.support for this idea has been equivocal and studies on these two strategies are still needed to understand the evolution of defenses in natural populations.In Arabidopsis lyrata,the production of trichomes,a documented resistance trait,has been associated with a fitness cost in the absence of herbivores.We examined whether trichome production is also associated with reduced tolerance to simulated herbivore damage.Methods We conducted a field experiment in a natural swedish population of A.lyrata where we inflicted leaf(0 vs.50%of the area of each leaf removed)and inflorescence damage(0 vs.50%of inflores-cences removed)to trichome-producing and glabrous plants in a factorial design.We examined the response(survival,growth and reproduction)of the plants to the imposed damage over 2 years.Important Findingstrichome-producing plants were not less tolerant than glabrous plants to simulated herbivore damage(no significant morph×leaf damage or morph×inflorescence damage interactions).Inflorescence and leaf damage had independent negative effects on the performance of damaged plants.leaf damage reduced rosette size the year of damage,but effects on reproductive output in the year of damage,and on survival and reproductive performance the following year were weak and not statistically significant.Inflorescence damage significantly reduced the number of flowers,fruits and seeds the year of damage,but not in the following year.Irrespective of morph,the study population was more tolerant to leaf than to inflorescence damage.the results indicated no trade-off between trichome production and tolerance,suggesting that these two defense mechanisms have the potential to evolve indepen-dently in this A.lyrata population.