The Role of Non-Coding RNA in Rice Immunity

Disease has been a major concern in the rice-growing sector, resulting in significant losses and compromised food security. To combat disease, plants have devised various defense strategies. Initial works in understanding plant–pathogen interactions were focused on discovering resistance and pathogenicity genes, as well as analyzing the functions of these genes in the host defense. Later, researchers discovered that regulatory elements, such as transcription factors, were essential players in modulating plant defenses. As the depth of research and knowledge in this field increased, non-coding RNA (ncRNA) were discovered to play key functions in plant immunity. In this review, we explore the contribution and interaction of microRNAs (miRNAs), long ncRNAs (lncRNAs), and small interfering RNAs (siRNAs) in controlling the rice immune response. The role and the interaction between ncRNAs and their targets have been discussed in detail. We believe that this information will be beneficial in disease resistance breeding of rice.

Evaluation of Pigeonpea Genotypes against Fusarium Wilt and Sterility Mosaic Disease in Gujarat

Background: Fusarium wilt (FW) and sterility mosaic disease (SMD) are two important biotic constraints to pigeonpea production worldwide that can cause loss up to 100 per cent. Host plant resistance is the most durable and economical way to manage these diseases. Methods: Thirty five pigeonpea genotypes comprises [mid early, mid late, dual and hybrid (mid early) group] were evaluated in a fusarium wilt and sterility-mosaic disease-screening nursery at three location viz., Sardarkrushinagar, Bharuch and Vadodara in Gujarat during kharif season 2015-16, to identify genotypes having resistance to both the diseases. Result: Five genotypes identified in each group of pigeonpea viz; mid early (SKNP1303, SKNP 1021, SKNP 0805, SKNP 0920, SKNP 1004), mid late (SKNP 1233, SKNP 10-34, AAUVT 07-10, AAUVT 09-24, GJP1207) and dual (SKNP-1119, BP 06-33, BP 08-06, BP 10-03, BP 10-04) and in hybrid (mid early) group only one hybrid i.e. SKNPCH 1211 were found combined resistance to Fusarium wilt and SMD ( less than 10% disease). These diverse genotypes that are resistant to Fusarium wilt and SMD may be useful in pigeonpea disease resistance breeding programme while hybrid identified as resistance to both the diseases may be recommended for commercial cultivation.

Genomics-Enabled Novel Insight Into the Pathovar-Specific Population Structure of the Bacterial Leaf Streak Pathogen Xanthomonas translucens in Small Grain Cereals

The Gram-negative bacterium Xanthomonas translucens infects a wide range of gramineous plants with a notable impact on small grain cereals. However, genomics-informed intra-species population structure and virulence repertories of the pathogen have rarely been investigated. In this study, the complete genome sequences of seven X. translucens strains representing an entire set of genetic diversity of two pathovars X. translucens pv. undulosa and X. translucens pv. translucens is provided and compared with those of seven publicly available complete genomes of the pathogen. Organization of the 25 type III secretion system genes in all the 14 X. translucens strains was exactly the same, while TAL effector genes localized singly or in clusters across four loci in X. translucens pv. translucens and five to six loci in X. translucens pv. undulosa. Beside two previously unreported endogenous plasmids in X. translucens pv. undulosa, and variations in repeat variable diresidue (RVD) of the 14 strains, tal1a of X. translucens pv. translucens strain XtKm8 encode the new RVDs HE and YI which have not previously been reported in xanthomonads. Further, a number of truncated tal genes were predicted among the 14 genomes lacking conserved BamHI site at N-terminus and SphI site at C-terminus. Our data have doubled the number of complete genomes of X. translucens clarifying the population structure and genomics of the pathogen to pave the way in the small grain cereals industry for disease resistance breeding in the 21st century’s agriculture.

Evaluation of the response of Turkey strains to Salmonella and Newcastle vaccines

This research work was carried out to evaluate the immune response of 3 turkey strains to salmonella and Newcastle vaccines measured via antibody titre. The study deployed a total of 120 poults (40 black, 40 white and 40 lavender) strains. To ascertain the initial antibody titre of all the birds, blood samples were obtained from their wing veins immediately after acclimatization for salmonella and Newcastle antibody titre. The test for salmonella and Newcastle antibody titre responses of the birds were performed using widal and haemagglutination inhibition (HI), respectively. The birds were divided into two broad groups tagged as A and B, which represented Salmonella and Newcastle vaccines, respectively. Each group had 3 sub-groups denoting the 3 strains of turkey used for the study. After vaccination, blood samples were collected from all the birds at 3 and 5 days for laboratory assessment of antibody titre response. The results showed that there was significant increase (p<0.05) in the antibody titre response of all the turkey strains after vaccination. Results obtained on the time of exposure of the birds to vaccine revealed that higher antibody titre values were obtained from the black and white turkey strains at 3 days than at 5 days after administration of Newcastle vaccine, except in the lavender strain, which had higher titre value at 5 days after Newcastle vaccination. Following administration of salmonella vaccine, black and lavender strains had statistically higher antibody titre response (2.03 and 2.10 mean loge widal, respectively) than white strain (1.86 mean loge widal). Similarly, the black strain also had higher antibody titre value when Newcastle vaccine was administered (2.35 mean loge HI) followed by lavender (1.99 mean loge HI) and white strain (1.71 mean loge HI). Black strains showed more antibody titre response and by implication, stronger immunity to Salmonella and Newcastle vaccines. More importantly, the differential response of the 3 turkey strains to vaccine could give turkey breeders the choice of selection of turkey breeds for disease resistance breeding.

Climate change will influence disease resistance breeding in wheat in Northwestern Europe

Wheat productivity is threatened by global climate change. In several parts of NW Europe it will get warmer and dryer during the main crop growing period. The resulting likely lower realized on-farm crop yields must be kept by breeding for resistance against already existing and emerging diseases among other measures. Multi-disease resistance will get especially crucial. In this review, we focus on disease resistance breeding approaches in wheat, especially related to rust diseases and Fusarium head blight, because simulation studies of potential future disease risk have shown that these diseases will be increasingly relevant in the future. The long-term changes in disease occurrence must inevitably lead to adjustments of future resistance breeding strategies, whereby stability and durability of disease resistance under heat and water stress will be important in the future. In general, it would be important to focus on non-temperature sensitive resistance genes/QTLs. To conclude, research on the effects of heat and drought stress on disease resistance reactions must be given special attention in the future.

Benefits of maize resistance breeding and chemical control against northern leaf blight in smallholder farms in South Africa

Maize underpins food security in South Africa. An annual production of more than 10 million tons is a combination of the output of large-scale commercial farms plus an estimated 250 000 ha cultivated by smallholder farmers. Maize leaves are a rich source of nutrients for fungal pathogens. Farmers must limit leaf blighting by fungi to prevent sugars captured by photosynthesis being ‘stolen’ instead of filling the grain. This study aimed to fill the knowledge gap on the prevalence and impact of fungal foliar diseases in local smallholder maize fields. A survey with 1124 plant observations from diverse maize hybrids was conducted over three seasons from 2015 to 2017 in five farming communities in KwaZulu-Natal Province (Hlanganani, Ntabamhlophe, KwaNxamalala) and Eastern Cape Province (Bizana, Tabankulu). Northern leaf blight (NLB), common rust, Phaeosphaeria leaf spot, and grey leaf spot had overall disease incidences of 75%, 77%, 68% and 56%, respectively, indicating high disease pressure in smallholder farming environments. NLB had the highest disease severity (LSD test, p<0.05). A yield trial focused on NLB in KwaZulu-Natal showed that this disease reduced yields in the three most susceptible maize hybrids by 36%, 71% and 72%, respectively. Eighteen other hybrids in this trial did not show significant yield reductions due to NLB, which illustrates the progress made by local maize breeders in disease resistance breeding. This work highlights the risk to smallholder farmers of planting disease-susceptible varieties, and makes recommendations on how to exploit the advances of hybrid maize disease resistance breeding to develop farmer-preferred varieties for smallholder production.

Whole genome analysis of the koa wilt pathogen (Fusarium oxysporum f. sp. koae) and the development of molecular tools for early detection and monitoring

Background Development and application of DNA-based methods to distinguish highly virulent isolates of Fusarium oxysporum f. sp. koae [Fo koae; cause of koa wilt disease on Acacia koa (koa)] will help disease management through early detection, enhanced monitoring, and improved disease resistance-breeding programs. Results This study presents whole genome analyses of one highly virulent Fo koae isolate and one non-pathogenic F. oxysporum (Fo) isolate. These analyses allowed for the identification of putative lineage-specific DNA and predicted genes necessary for disease development on koa. Using putative chromosomes and predicted gene comparisons, Fo koae-exclusive, virulence genes were identified. The putative lineage-specific DNA included identified genes encoding products secreted in xylem (e. g., SIX1 and SIX6) that may be necessary for disease development on koa. Unique genes from Fo koae were used to develop pathogen-specific PCR primers. These diagnostic primers allowed target amplification in the characterized highly virulent Fo koae isolates but did not allow product amplification in low-virulence or non-pathogenic isolates of Fo. Thus, primers developed in this study will be useful for early detection and monitoring of highly virulent strains of Fo koae. Isolate verification is also important for disease resistance-breeding programs that require a diverse set of highly virulent Fo koae isolates for their disease-screening assays to develop disease-resistant koa. Conclusions These results provide the framework for understanding the pathogen genes necessary for koa wilt disease and the genetic variation of Fo koae populations across the Hawaiian Islands.

Leptosphaeria maculans isolates reveal their allele frequency in western Canada

Blackleg, caused by Leptosphaeria maculans, is a major disease of canola in Canada, Australia, and Europe. For effective deployment of resistant varieties and disease management, it is crucial to understand the population structure of L. maculans. In this study, we analyze L. maculans isolates from commercial fields in western Canada from 2014 to 2016 for the presence and frequency of avirulence (Avr) genes. A total of 1, 584 isolates was examined for the presence of Avr genes AvrLm1, AvrLm2, AvrLm3, AvrLm4, AvrLm6, AvrLm7, AvrLm9, AvrLepR1, AvrLepR2, and AvrLmS using a set of differential host genotypes carrying known resistance genes and a PCR assay. Several Avr genes showed a higher frequency in the pathogen population, such as AvrLm6 and AvrLm7, which were present in >90% of isolates; while AvrLm3, AvrLm9 and AvrLepR2 showed frequencies of <10%. A total of 189 races (different combinations of Avr genes) were detected, with Avr-2-4-6-7-S, Avr-1-4-6-7 and Avr-2-4-6-7 as the three predominant races. When the effect of crop rotation was assessed, only a three-year rotation showed a significantly higher frequency of AvrLm2, relative to shorter rotations. This study provides the information for producers to select effective canola varieties for blackleg management, and for breeders to deploy new R genes in disease resistance breeding in the western Canada region.