Phenotypic Screening of F4 Breeding Lines against Bacterial Blight Disease in Rice

Biotic stresses are major threat to rice production. Among biotic stresses, bacterial leaf blight is one of the major diseases affecting rice grain production in rice growing areas. Present investigation was conducted to evaluate phenotypic effect of 50 breeding lines from a cross (Pranahitha//ISM/MTU1010) in glass house at Regional Agricultural Research Station, Jagtial by inoculating Bacterial leaf blight culture (DX-020) by leaf clipping method. Out of these 50 F4 lines evaluated, twenty nine breeding lines showed resistant reaction with disease score of 1. Eleven lines showed moderately resistant reaction with disease score 3. Twenty nine breeding lines that were resistant with disease score 1, had excellent grain yield. Hence, these lines can be advanced to further generations. Thus the present study has demonstrated that phenotypic selection is successful in the glass house and these breeding lines with higher yield levels are expected to perform better in the field trials and further in the farmers fields with the good level of bacterial blight resistance.

Response of cotton genotypes against the incidence of Alternaria leaf blight of cotton under field conditions

Aim: To identify the resistant source present in the breeding materials against Alternaria leaf blight disease of cotton (Gossypium spp.). Methodology: Breeding entries were sown in a randomized complete block design in the experimental site. Disease intensity on each genotype at 45, 90, 135 and 180 days after sowing (DAS) were recorded from leaves of lower, middle and upper parts of plants and graded. According to 0 - 4 disease scoring scale, per cent disease index (PDI) was calculated and genotypes were categorized into different categories based on disease reaction Results: Development of Alternaria disease was noticed at early days of crop growth in few genotypes and the disease increased upto 135 days after sowing. The maximum mean per cent disease index of 41.17 and 40.06 were recorded in Br.14a (ZT)1333 and Br.14a (ZT)1332 respectively. The least PDI of 0.58 was recorded in Br.03a (ZT)1303. Disease incidence of <11.00% of was reported in 37 entries at 45 days after sowing. None of the genotypes showed apparently immune reaction, twenty-one genotypes showed resistant reaction, eleven genotypes were moderately resistant and five showed moderately susceptible reaction. Interpretation: Twenty-one breeding lines showed resistant reaction against Alternaria leaf blight disease under field conditions, however, further utilization of these lines may be carried out in breeding programmes for the development of resistant source against this disease.

Screening of vegetables crop genotype against root-knot nematode (Meloidogyne incognita) under polyhouse conditions

Root-knot nematode, Meloidogyne incognita is an economically important plant-parasitic nematode of vegetable crops grown under open as well as protected cultivation. Use of resistant cultivar is an important measure for managing root-knot nematode as compared to the other management strategies. Despite the potential importance of this nematode, sources of resistance to M. incognita are not yet available for breeding purposes. Present studies were conducted to evaluate the resistant reaction of crop genotype (cucumber japanes long green, tomato shu, cherry tomato P. cherry tomato-1, bitter gourd pusa aushadhi and capsicum yalo wonder) against M. incognita under polyhouse conditions (2018-20). Sixty days after sowing, observations were recorded on number of galls/plant and final nematode population. All the crop genotypes of vegetables were showed varying degree of response against M. incognita. Out of five crop genotypes of vegetables, four (cucumber japanes long green, tomato shu, cherry tomato P. cherry tomato-1 and bitter gourd Pusa aushadhi) were susceptible/highly susceptible while capsicum yalo wonder showed moderately resistant reaction against M. incognita in both the years (2018-2020) and this genotype can be used as a source of resistance.

Genetic Divergence of Rice Genotypes Revealed by Bacterial Blight Disease and Morphological Traits

Bacterial blight is a perilous impediment for rice production. Resistant variety is a sustainable approach to fend off the loss of rice due to bacterial blight disease. In this study, 94 genotypes were screened against bacterial blight disease and its morphological diversity was assessed to find out the resistant donor with desirable morphological characters. Bacterial blight pathogen was inoculated following leaf clipping method for disease scoring. Out of 94 genotypes, 12 showed a resistant reaction, 13 showed moderately resistant reaction and 69 genotypes showed a susceptible reaction. Positive correlation was recorded between yield and most of the morphological characters. Yield hill─1 was significantly correlated with the number of tiller hill─1 (0.503**), number of effective tiller hill─1 (0.538**), total number of spikelets panicle─1 (0.595**), number of filled grain panicle─1 (0.595**), number of unfilled spikelet panicle─1 (0.239*) and 1000 grain weight hill─1 (0.843**). Eleven quantitative characters grouped 94 rice genotypes in 16 clusters at coefficient 3.38 and it indicated the presence of great amount diversity among the genotypes. Principal component analysis (PCA) supported the cluster analysis and the first four principal components explained around 70.99% of total divergence for all morphological characters. Principal coordinate analysis (PCoA) demonstrated that the genotypes BR8862-29-1-5-1-3, SVIN301, SVIN321, BR9207-45-2-2, SVIN018, lRBB5, SVIN038, BRRI dhan28 and BRRI dhan29 were placed in distant position from the centroid and it indicated that they were more diverse than the genotypes near the centroid. However, based on disease reaction and genetic diversity analysis crossing could be made between, resistant genotypes such as SVIN317, SVIN017, SVIN316, SVIN313, SVIN315, SVIN314, SVIN038, SVIN307, SVIN302, SVIN304 with the susceptible variety more specifically with BRRI dhan28, BRRI dhan29, BRRI dhan50, BRRI dhan58, BRRI dhan63, BRRI dhan74, BRRI dhan81 and BRRI dhan84 to develop bacterial blight resistant variety. Bangladesh Rice J. 24 (1): 73-84, 2020

Genome-wide transcriptome reveals mechanisms underlying Rlm1-mediated blackleg resistance on canola

Genetic resistance to blackleg (Leptosphaeria maculans, Lm) of canola (Brassica napus, Bn) has been extensively studied, but the mechanisms underlying the host–pathogen interaction are still not well understood. Here, a comparative transcriptome analysis was performed on a resistant doubled haploid Bn line carrying the resistance gene Rlm1 following inoculation with a virulent (avrLm1) or avirulent (AvrLm1) Lm isolate on cotyledons. A total of 6999 and 3015 differentially expressed genes (DEGs) were identified, respectively, in inoculated local tissues with compatible (susceptible) and incompatible (resistant) interactions. Functional enrichment analysis found several biological processes, including protein targeting to membrane, ribosome and negative regulation of programmed cell death, were over-represented exclusively among up-regulated DEGs in the resistant reaction, whereas significant enrichment of salicylic acid (SA) and jasmonic acid (JA) pathways observed for down-regulated DEGs occurred only in the susceptible reaction. A heat-map analysis showed that both biosynthesis and signaling of SA and JA were induced more significantly in the resistant reaction, implying that a threshold level of SA and JA signaling is required for the activation of Rlm1-mediated resistance. Co-expression network analysis revealed close correlation of a gene module with the resistance, involving DEGs regulating pathogen-associated molecular pattern recognition, JA signaling and transcriptional reprogramming. Substantially fewer DEGs were identified in mock-inoculated (control) cotyledons, relative to those in inoculated local tissues, including those involved in SA pathways potentially contributing to systemic acquired resistance (SAR). Pre-inoculation of cotyledon with either an avirulent or virulent Lm isolate, however, failed to induce SAR on remote tissues of same plant despite elevated SA and PR1 protein. This study provides insights into the molecular mechanism of Rlm1-mediated resistance to blackleg.

RESISTANCE IN COMMON BEAN TO UROMYCES APPENDICULATUS UNDER FIELD AND GREENHOUSE CONDITIONS

Bean rust, caused by Uromyces appendiculatus, is a major disease in common bean which occurs annually in The Rhodope Mountains and sporadic in the plains of Bulgaria. The present study aims to find sources of resistance in common bean to the pathogen for using in a breeding program. The reaction of fifty-five Phaseolus vulgaris accessions to the pathogen was monitored under field condition. Infection type, disease intensity and area under the disease progress curve were calculated. Twelve common bean cultivars were inoculated with eight pathotypes of races 20-2, 20-16, and 20-18 in the greenhouse, and infection type was estimated. Twelve accessions had an immune reaction, eight accessions had resistant a reaction, two accessions had a middle resistant reaction, and seven accessions had a susceptible reaction to U. appendiculatus population in both field estimations. Five cultivars showed resistant phenotype to the eight pathotypes in the greenhouse, four of which were resistant in the field (Abritus, Beslet, Trakiya, and Prelom). Five cultivars had a susceptible or resistant reaction to the pathotypes of the same race, resulting from different interaction between resistant genes in the host and virulent genes in the pathogen. Nine accessions showed race-nonspecific resistance in the field expressed in low disease intensity and susceptible/resistant phenotype.

Screening, confirmation and field evaluation of promising resistant germplasm of different pulses against root knot nematode, Meloidogyne javanica

Aim: Experiment conducted in the microplots infested with the root knot nematode, Meloidogyne javanica against the germpalms of thechickpea, pigeon pea, mungbean and urdbean. Methodology: In this study, 71 genotypes of chickpea, 30 genotypes of pigeon pea, 14 genotypes of mungbean and 12 genotypes of urdbean were screened for their reaction to root-knot nematode, M. javanica in infested microplots. Initial nematode population was recorded. Various germplasms of pulses was sown in microplots. The plants were maintained as per the standard agronomic practices. All the germplasm were assessed to determine gall index. Results: Seventy one genotypes of chickpea were screened against M. javanica, among them 19 were highly resistant, 8 resistant and 12 were found to be moderately resistant. Out of 30 genotypes of pigeonpea, 19 were highly resistant, 2 were resistant and 3 were moderately resistant to the root-knot nematode. Fourteen genotypes of mungbean screened against M. javanica, none of the germplasm was found resistant, however, four genotypes showed moderately resistant reaction. Interpretation: It may be concluded that several types of reaction were observed in screened germplasm of pulse viz., highly susceptible, susceptible, moderately resistant and resistant. These types of reaction may be due to different genotypic content of the germplasms.

Evaluation of Promising Sugarcane Clones in Plant Cane against Natural Infection of Pokkah Boeng Disease

Pokkah boeng caused by Fusarium sp is becoming a serious fungal disease on basis of its rapid spread during last few years, posing new threat to sugarcane cultivation. Earlier Pokkah boeng disease was of minor importance but now it has become matter of concern as it is spreading rapidly in sugarcane growing areas having monoculture of single variety. The present investigation entitled “Evaluation of promising sugarcane clones in plant cane against natural infection of pokkah boeng disease” was carried out at Regional Sugarcane and Rice Research station, Rudrur, Nizamabad, Telangana (India) to identify the source of resistance with single series design. Among the ten promising sugarcane clones evaluated in plant cane against Pokkah boeng disease three clones viz., 2014R11, 2010R854 and 83R23 showed resistant reaction.

Identification of novel resistance source in traditional varieties against major diseases of rice

Traditional rice varieties maintained and cultivated by farmers are the potential sources of resistant donors that can be used for breeding rice varieties with durable resistance. They possess traits potentially adaptable to a wide range of abiotic and biotic stresses. Characterization of these germplasm is essential in rice breeding varieties and provides valued information for developing new rice. In this study, a large-scale screening of 167 traditional rice varieties was carried out to identify resistance sources against blast, sheath blight and brown spot diseases of rice. The mean location severity index (LSI) of leaf blast, sheath blight and brown spot was 6.91,7.14 and 7.84, respectively. Among the varieties screened, five varieties viz., Malgudi sanna, Putta batta, Selamsanna, Sadaholga and Mysuru sanna showed resistant reaction against blast, while only one variety Putta batta showed resistant reaction against brown spot, none of the varieties showed resistant reaction against sheath blight. However, only one variety Bangara sanna-4 showed moderate resistance to the sheath blight disease. The identified resistant varieties can be used as potential source for breeding durable resistant varieties in the future crop improvement programmes.

Characterization of seedling and adult plant resistance to stripe rust in recombinant inbred lines derived from wheat landrace PI388222 × Avocet cross

Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating fungal disease of wheat (Triticum aestivum L.). The best economical technique for disease control is breeding for genetic resistance to stripe rust. To find resistance genes in landrace PI388222 from Pakistan, a segregating population was developed by a cross between PI388222 and susceptible Australian spring wheat line Avocet ‘S’. The F2:4 seeds were harvested and seeds were planted in the greenhouse of Washington State University Pullman, to grow F4:5 recombinant inbred lines (RIL). A variable set of seedling reactions were noted when a set of 136 F5 and parental lines were screened with four Puccinia striiformis f. sp. tritici races (PSTv-37, PSTv-40, PSTv-4 and PSTv-51). The great proportion of RILs showed resistant reaction displayed by the RILs was against PSTv-40, for which 85% of the RILs showed resistant reaction, while less resistance to the race PSTv-37 was detected against which the resistance was for only 49% of the RILs. The RIL population was further evaluated at two locations; Palouse Conservation Field Station (PCFS) and Mount Vernon (MV). In MV field, 76% of RILs displayed resistant reaction while 15% of RILs exhibited moderate reaction. About 53% of RILs exhibited resistant reaction to four P. tritici races that were used in glasshouse screening and they were also resistant in field environments at PCFS and MV. This study demonstrates that landrace comprises partial resistance in the range of resistant to moderately resistant lines.