Late Leaf Research Articles

Peanut (Arachis hypogaea) response to weed and disease management in northern Ghana

ABSTRACTWeeds and diseases can reduce peanut (Arachis hypogaea L.) yield or increase cost of production to maintain acceptable yield. While herbicides and fungicides have limited availability in many areas of Ghana and currently are too expensive for resource-poor farmers, control by these pesticides can have a major positive impact on peanut yield. Field experiments were conducted during the rainy seasons of 2009 and 2010 in northern Ghana to determine the effects of herbicide and hand weeding in combination with fungicides on pest management and peanut yield. Peanut pod yield was often more highly correlated with disease severity and canopy defoliation resulting from early leaf spot (caused by Cercospora arachidicola Hori) and late leaf spot (caused by Cercosporidium personatum (Berk. & M.A. Curtis) Deighton) than weed biomass. In some instances, less disease and canopy defoliation were observed when weeds were not controlled effectively compared with increased weed management through hand weeding or herbicide. Two hand weedings or applying pendimethalin preemergence with one hand weeding in combination with 4 applications of triadimefon and chlorothalonil resulted in the lowest weed density and canopy defoliation and often resulted in the highest peanut yield.

Differential gene expression in leaf tissues between mutant and wild-type genotypes response to late leaf spot in peanut (Arachis hypogaea L.).

Late leaf spot (LLS) is a major foliar disease in peanut (A. hypogaea L.) worldwide, causing significant losses of potential yield in the absence of fungicide applications. Mutants are important materials to study the function of disease-related genes. In this study, the mutant line M14 was derived from cultivar Yuanza 9102 treated with EMS. Yuanza 9102 was selected from an interspecific cross of cultivar Baisha 1016 with A. diogoi, and is resistant to several fungal diseases. By contrast, the M14 was highly susceptible to late leaf spot. RNA-Seq analysis in the leaf tissues of the M14 and its wild type Yuanza 9102 under pathogen challenge showed 2219 differentially expressed genes including1317 up-regulated genes and 902 down-regulated genes. Of these genes, 1541, 1988, 1344, 643 and 533 unigenes were obtained and annotated by public protein databases of SwissPort, TrEMBL, gene ontology (GO), KEGG and clusters of orthologous groups (COG), respectively. Differentially expressed genes (DEGs) showed that expression of inducible pathogenesis-related (PR) proteins was significantly up-regulated; in the meantime DEGs related to photosynthesis were down-regulated in the susceptible M14 in comparison to the resistant WT. Moreover, the up-regulated WRKY transcription factors and down-regulated plant hormones related to plant growth were detected in the M14. The results suggest that down-regulated chloroplast genes, up-regulated WRKY transcription factors, and depressed plant hormones related to plant growth in the M14 might coordinately render the susceptibility though there was a significant high level of PRs. Those negative effectors might be triggered in the susceptible plant by fungal infection and resulted in reduction of photosynthesis and phytohormones and led to symptom formation.

Aqueous plant extracts for control of groundnut leaf spot in Burkina Faso

Early and late leaf spots, the two fungal diseases of groundnut (Arachis hypogaea L.) caused by Cercospora arachidicola Hori. and Phaeoisariopsis personata (Berk and Curt), respectively, cause severe groundnut crop losses in arid zone of West Africa. The objective of this study was to evaluate efficacy of aqueous extracts of four native plants species of Burkina (Lippia multiflora Moldenke, Boscia senegalensis (Pers.) Lam, Ziziphus mucronata Willd. and Securidaca longepedonculata L) against these diseases, on a susceptible groundnut variety (TS32-1) in the field during the cropping seasons of 2010 to 2012, in Gampela district in Burkina Faso. The four extracts (50 g dry weight per liter of distilled water) were sprayed by using a manual sprayer (Solo). Disease incidence and severity, defoliation rate, necrotic leaf area, pod yield, and 100 seed weight were evaluated. Disease score which attests to the severity of parasitic attack was done following ICRISAT’s disease score scale, which ranges from 1 to 9. Treatments with aqueous extracts of L. multiflora and Z. mucronata recorded the best disease control. The disease scores of these treatments were less or equal to 4 (corresponding to a resistance of plants), and increased pod yield by 2676.889 kg ha-1 (L. multiflora) and 2976.926 kg ha-1 (Z. mucronata), respectively. This field trial has confirmed that plants tested significantly control leaf spot diseases of groundnut.Key Words: Arachis hypogaea, Cercospora arachidicola, Phaeoisariopsis personata

Late Leaf Spot Severity and Yield of New Peanut Breeding Lines and Cultivars Grown Without Fungicides.

Peanut (Arachis hypogaea) cultivars with resistance or tolerance to Cercospora arachidicola and/or Cercosporidium personatum, the causes of early and late leaf spot, respectively, are needed for organic production in the southeastern U.S. To determine the potential of new breeding lines for use in such production systems, field experiments were conducted in Tifton, GA, in 2014 and 2015 in which nine breeding lines and two cultivars, Georgia-06G and Georgia-12Y, were grown without foliar fungicide applications. In one set of trials, cultivar Georgia-12Y and most of the breeding lines evaluated had early season vigor ratings, early-season canopy width measurements, final plant populations, and pod yield that were greater than those of standard cultivar Georgia-06G. In those trials, final late leaf spot Florida scale ratings were lower and canopy reflectance measured as the normalized difference vegetation index (NDVI), was higher all the breeding lines than those of Georgia-06G. In another set of trials, two of those same breeding lines had final late leaf spot ratings similar to those of Georgia-12Y in 2014, whereas in 2015, six of those breeding lines had final leaf spot ratings that were lower than those of Georgia-12Y. Yields were similar for Georgia-12Y and all the breeding lines in the Gibbs Farm trials. Across years and breeding lines at the Lang Farm, the relationship between visual estimates of defoliation and NDVI was described by a two sector piecewise regression with NDVI decreasing more rapidly with increasing defoliation above approximately 89%. The utility of NDVI for spot comparisons among breeding lines appears to be limited to situations where there are differences in defoliation. Georgia-12Y and multiple breeding lines evaluated show potential for use in situations such as organic production where acceptable fungicides available for seed treatment and leaf spot control are limited.

Seasonal Variation in Mineral Nutrient Concentration of Primocane and Floricane Leaves in Trailing, Erect, and Semierect Blackberry Cultivars

Floricane-fruiting blackberry (Rubus L. subgenus Rubus, Watson) cultivars, ‘Marion’, ‘Black Diamond’, ‘Onyx’, ‘Columbia Star’ (early-season trailing types), ‘Ouachita’ (erect, midseason), and ‘Triple Crown’ and ‘Chester Thornless’ (semierect, late season) were studied for 2 years to determine whether these cultivars and types of blackberry should be sampled at a certain stage of development or time of season to best evaluate plant nutrient status. Leaf nutrient standards are based on primocane leaves in most countries, but there is interest in using floricane leaves. Primocane leaves were sampled every 2 weeks from late May through early October, whereas leaves on fruiting laterals (floricane) were sampled every 2 weeks from early May through fruit harvest. Leaves were analyzed to determine the concentration of macronutrients and micronutrients. The pattern of change in primocane leaf nutrient concentration varied between the trailing and the later-fruiting erect and semierect types, particularly for P, K, Ca, Mg, B, and Mn, where leaf levels were higher in the late season for the erect and semierect cultivars (except for P and K which were lower). Nutrient concentrations in floricane leaves decreased during growth and development of the lateral and fruiting season for N, P, K, and S, but increased for most other nutrients in all blackberry types. Floricane leaf N and K declined most rapidly during the fruit development period in all cultivars. Sampling of floricane leaves is not recommended, particularly for trailing types, as there are no sufficiency standards. In primocane leaves, the nutrients that did not show significant changes in concentration during the currently recommended sampling period of late July to early August were N, Mg, K, Ca, S, B, Mn, and Zn, but only in 2014. Leaf P, Fe, and Al were stable during this period in both years. In contrast, when sampling in mid to late August, leaf N, Mg, Fe, Mn, and Al were stable in both years and leaf K, Ca, S, B, Cu, and Zn were stable in one of the 2 years. We thus propose changing the recommended sampling time to mid to late August for these diverse blackberry cultivars. The current sufficiency standards for primocanes did not encompass the blackberry types and cultivars studied here, suggesting the standards may need to be revised for this region.

English

Groundnut is a highly self-pollinated crop, grown successfully in tropical and subtropical areas. The crop has narrow genetic base therefore, it is essential to create more variability in the segregating materials. Hence, in present investigation an attempt was made to assess the variability of important yield and yield contributing traits which will facilitate an understanding behind expression of character and also role of environment therein. High PCV and GCV values for kernel yield per plant, pod yield per plant, number of pods per plant, 100-pod weight, 100-kernel weight, shell weight and rust score in all backcross population revealed that the variation for these characters contributed markedly to the total variability and there was enough scope for selection based on these characters. Similarly, high values were noticed in all the backcross populations for kernel yield per plant, pod yield per plant, number of pods per plant, 100-pod weight, 100-kernel weight, shell weight, shelling percentage and late leaf spot score exhibited that these characters were mainly controlled by additive genes and selection of such traits might be effective for the improvement of groundnut. Thus, results clearly indicating that the presence of wide spectrum of genetic variation for the characters viz., kernel yield per plant, pod yield per plant, plant height, number of pods per plant, 100-pod weight, 100-kernel weight, shell weight, shelling percentage, late leaf spot and rust score suggesting that they respond to selection with greater efficiency for improvement of pod yield and kernel yield coupled with resistance to foliar diseases in groundnut.

Harnessing Genetic Diversity of WildArachisSpecies for Genetic Enhancement of Cultivated Peanut

Peanut (Arachis hypogaeaL.) is an important self‐pollinating tetraploid (AABB, 2n= 4x= 40) legume grown for the high‐quality edible oil and easily digestible protein in its seeds. Enormous genetic variability is present in the genusArachiscontaining 79 wild species and cultivated peanut. Wild species offer significant variability, particularly for biotic and abiotic stresses, and can be used to develop cultivars with enhanced levels of resistance to key stresses. However, utilization of these species requires use of ploidy manipulations, bridge crosses, and embryo or ovule rescue. For efficient use of diploid wild species from sectionArachis, several synthetics (amphidiploids and autotetraploids) have been developed using A‐ and B‐genome accessions with high levels of resistance to multiple stresses. These synthetics are used in crossing programs with cultigens to develop prebreeding populations and introgression lines (ILs) with high frequency of useful genes and alleles into good agronomic backgrounds. Evaluation of two such populations derived from ICGV 91114 × ISATGR 121250 (a synthetic derived fromA. duranensisKrapov. & W.C. Greg. ×A. ipaensisKrapov. & W.C. Greg.) and ICGV 87846 × ISATGR 265‐5 (A. kempf‐mercadoiW.C. Greg. & C.E. Simpson ×A. hoehneiKrapov. & W.C. Greg.) resulted in the identification of ILs with high levels of late leaf spot (LLS) and rust resistance and significant genetic variability for morphoagronomic traits. Genotyping of these ILs with markers linked to rust and LLS resistance provided evidence that introgression of possible novel alleles and resistance sources from different wild species other than the commonly usedA. cardenasiiKrapov. & W.C. Greg. will be beneficial for peanut improvement.

Agronomic evaluation of groundnut varieties under rainfed conditions of Dharmapuri District, Tamil Nadu

An experiment was conducted to assess the agronomic performance of groundnut varieties viz., CO-6, Kadiri-9, ICGV-91114 in comparison with farmer's preferred variety TMV-7 under rainfed condition in farmers' fields in Dharmapuri district, Tamil Nadu during kharif 2015. The result showed that the variety Kadiri-9 exhibited superiority in respect of higher dry matter production (40.3 g/plant), number of pods per plant (28.8) and pod yield (1632 kg/ha) and accrued higher net income (`.26670/ha) and benefit cost ratio (2.03). The varieties ICGV-91114, TMV-7 and Kadiri-9 were early in terms of days to 50 per cent flowering and maturity. The varieties CO-6 and Kadiri-9 were found tolerant to major pests and diseases like leaf miner, collar rot and late leaf spot.

Role of weather factors in development of late leaf spot (Phaeoisariopsis personata) on groundnut (Arachis hypogaea)

The field experiment was conducted during Kharif 2012 and 2013 to find out the influence of weather parameters viz., temperature, relative humidity, rainfall, rainy days and wind velocity on the intensity of late leaf spot disease and defoliation in four groundnut cultivars viz., JL-24, LGN-1, TAG-24 and TG-26. The prevailing weather condition viz., average temperatures of 30.92 °C (max.) and 22.31 °C (min.), average RH of 89.67 % (morning) and 64.25 % (evening), well distributed average rainfall of 50.33 mm, average rainy days of 2.67 and average wind velocity of 4.24 km/hr were found to be conducive for the initiation, development and spread of late leaf spot disease in susceptible groundnut Cv. JL-24, TAG-24 and tolerant Cv. LGN-1, TG-26. As a result, overall average maximum disease intensity of 33.97 (21.96 to 46.37 %) per cent and 29.06 (18.62 to 39.01 %) per cent, were recorded in JL-24 and TAG-24, respectively. Groundnut Cv. JL-24 and TAG-24 (susceptible) exhibited comparatively maximum average defoliation in the range of 6.65 to 14.05 (Av. 10.29 %) and 5.64 to 11.82 per cent (Av. 8.80 %), respectively. The correlation coefficient between weather variables and disease intensity in both the years indicated that maximum temperature had negative and non significant effect in all the groundnut cultivars; whereas, minimum temperature had positive and significant effect on the disease intensity in all the groundnut cultivars. Relative humidity (morning and evening) played significant positive role on the disease intensity in all the groundnut cultivars.

QTL‐seq approach identified genomic regions and diagnostic markers for rust and late leaf spot resistance in groundnut (Arachis hypogaea L.)

SummaryRust and late leaf spot (LLS) are the two major foliar fungal diseases in groundnut, and their co‐occurrence leads to significant yield loss in addition to the deterioration of fodder quality. To identify candidate genomic regions controlling resistance to rust and LLS, whole‐genome resequencing (WGRS)‐based approach referred as ‘QTL‐seq’ was deployed. A total of 231.67 Gb raw and 192.10 Gb of clean sequence data were generated through WGRS of resistant parent and the resistant and susceptible bulks for rust and LLS. Sequence analysis of bulks for rust and LLS with reference‐guided resistant parent assembly identified 3136 single‐nucleotide polymorphisms (SNPs) for rust and 66 SNPs for LLS with the read depth of ≥7 in the identified genomic region on pseudomolecule A03. Detailed analysis identified 30 nonsynonymous SNPs affecting 25 candidate genes for rust resistance, while 14 intronic and three synonymous SNPs affecting nine candidate genes for LLS resistance. Subsequently, allele‐specific diagnostic markers were identified for three SNPs for rust resistance and one SNP for LLS resistance. Genotyping of one RIL population (TAG 24 × GPBD 4) with these four diagnostic markers revealed higher phenotypic variation for these two diseases. These results suggest usefulness of QTL‐seq approach in precise and rapid identification of candidate genomic regions and development of diagnostic markers for breeding applications.

Genetic Dissection of Novel QTLs for Resistance to Leaf Spots and Tomato Spotted Wilt Virus in Peanut (Arachis hypogaea L.).

Peanut is an important crop, economically and nutritiously, but high production cost is a serious challenge to peanut farmers as exemplified by chemical spray to control foliar diseases such as leaf spots and thrips, the vectors of tomato spotted wilt virus (TSWV). The objective of this research was to map the quantitative trait loci (QTLs) for resistance to leaf spots and TSWV in one recombinant inbred line (RIL) mapping population of “Tifrunner × GT-C20” for identification of linked markers for marker-assisted breeding. Here, we report the improved genetic linkage map with 418 marker loci with a marker density of 5.3 cM/loci and QTLs associated with multi-year (2010–2013) field phenotypes of foliar disease traits, including early leaf spot (ELS), late leaf spot (LLS), and TSWV. A total of 42 QTLs were identified with phenotypic variation explained (PVE) from 6.36 to 15.6%. There were nine QTLs for resistance to ELS, 22 QTLs for LLS, and 11 QTLs for TSWV, including six, five, and one major QTLs with PVE higher than 10% for resistance to each disease, respectively. Of the total 42 QTLs, 34 were mapped on the A sub-genome and eight mapped on the B sub-genome suggesting that the A sub-genome harbors more resistance genes than the B sub-genome. This genetic linkage map was also compared with two diploid peanut physical maps, and the overall co-linearity was 48.4% with an average co-linearity of 51.7% for the A sub-genome and 46.4% for the B sub-genome. The identified QTLs associated markers and potential candidate genes will be studied further for possible application in molecular breeding in peanut genetic improvement for disease resistance.

Effects of elevated atmospheric O3 concentrations on early and late leaf growth and elemental contents of Acer truncatum Bung under mild drought

To investigate the possible interactive effects of elevated atmospheric ozone (O3) concentrations and periodic drought stress on physiology of Shantung maple (Acer truncatum Bung), an experiment was conducted from the growth season of 2012 to 2013 with open-top chambers (OTCs) in Changping district, a suburb of Beijing, China. Four treatments were administered with three replications in twelve OTCs which were NN (well watered+ambient air), NO (well watered+add 100nll−1 O3 above ambient air), DN (drought stress+ambient air) and DO (drought stress+add 100nll−1 O3 above ambient air). Leaf area (LA), leaf mass per area (LMA), individual leaf weight (ILW), carbon(C), nitrogen (N) and sulfur (S) contents in early and late leaves were measured at the end of the second year. The results showed: (1) Both elevated O3 concentration and drought treatments significantly reduced early leaf LMA, LA, ILW, leaf N and S contents, with a reduction of 28.7, 45.7, 61.3, 39.6, 16.1% by O3 stress and 12.5, 46.8, 53.5, 15.45 and 22% by drought stress, respectively, while only LMA of late leaf was reduced 12.1% by O3 treatments and LA and ILW were significantly reduced 23.3% and 30% by drought treatments. (2) Significant interactions of elevated atmospheric O3 concentration and mild drought were detected on LMA, LA, ILW, N and C contents in early leaves and LMA in late leaves. Except for LA, the decreases under interactive treatments were all less than independent O3 effects. In conclusion, late leaf had less responses to elevated O3 and drought stresses than early leaves which need to be considered separately. The interactive effects suggested drought had antagonistic effects with O3 on growth indicators except for LA, indicating drought could mitigate the adverse efforts from O3 effects.

Genetic analysis of foliar disease resistance, yield and nutritional quality traits in groundnut

A set of 340 diverse groundnut genotypes included in Genomic Selection Panel (GSP) was used to evaluate genetic parameters and trait associations for resistance to rust and late leaf spot (LLS) along with yield and nutritional quality traits. The findings revealed high genetic variability coupled with high heritability and genetic advance as percent of mean (GAM) for resistance to both the diseases and yield traits, whereas low variability for nutritional quality traits with high heritability and low GAM. Disease severity scores for rust and LLS at 90 days after sowing (DAS) were negatively associated with yield, indicating pod yield penalty, thus deploying host-resistance for rust and LLS is a good strategy to plug the pod yield losses and reduce the input cost. It is possible to simultaneously improve the number of pods per plant and hundred kernel mass that contribute to pod yield as no trade-offs were detected between them. The association of oil and protein content with pod yield showed no tradeoffs, suggesting the possibility of simultaneous improvement of pod yield either with high oil or protein content. In breeding programs that target development of groundnut varieties to meet two distinct end-uses, oil milling, and food and confectionery, selection for either high oil (for oil purpose) or high protein and low oil (food/confections) will be efficient, as an inverse association between oil and protein content was observed. The use of disease score at 90 DAS for rust and LLS is effective and optimizes resources to make selection decisions in breeding as positive association among disease severity scores at different periods (75, 90 and 105 DAS) was observed.

Biochemical Characterisation and Responses of Resistant and Susceptible Groundnut Genotypes to Late Leaf Spot (Phaeoisariopsis personata (Berk. and Curt.) Von Arx.)

Biochemical Characterisation and Responses of Resistant and Susceptible Groundnut Genotypes to Late Leaf Spot (Phaeoisariopsis personata (Berk. and Curt.) Von Arx.)

Character association and path coefficient analysis in groundnut (Arachis hypogaea L.)

In groundnut, correlation and path coefficient analysis was carried out to identify the suitable selection indices in F3 generation of four crosses viz., CO 7 × VRI Gn 6, TMV 2 × VRI Gn 6, TMV Gn 13 × VRI Gn 6 and VRI 2 × VRI Gn 6. Correlation analysis revealed that the traits viz., number of pods per plant, 100-pod weight (g), 100-kernel weight (g), shelling (%) and pod yield per plant (g) were positively associated with kernel yield per plant (g). Inter-correlation among these traits also recorded significantly positive association inmost ofthe crosses studied. Hence these characters may be considered as the important yield attributing characters and due importance should be given while breeding for high pod and kernel yield per plant (g) in groundnut. The association between sound mature kernel per cent, late leaf spot and rust scores with other yield component traits varies with the populations. Hence, these characters may also be considered as selection indices with caution. Moreover in path analysis, the trait pod yield per plant (g) exhibited high positive direct effect on kernel yield per plant (g). It also possessed significant and positive association with kernel yield per plant (g). Hence, pod yield per plant (g) plays a major role in determining the kernel yield per plant (g). The traits viz., number of pods per plant, 100-pod weight (g), 100-kernel weight (g) and shelling (%) recorded moderate to high indirect effect through pod yield per plant (g) on kernel yield per plant (g). Hence due emphasis should be placed on these traits for yield improvement in groundnut.

Response of groundnut (Arachis hypogaea L.) cultivars to late leaf spot disease (Passalora personata) under different sowing dates

Experiments were conducted to investigate the effect of date of sowing on groundnut cultivars against late leaf spot disease severity, defoliation, frequency and size of the leaf spot which revealed that all these aspects were significantly influenced by the date of sowing and crop varieties which directly affect the pod yield and test weight. The crop sown early on 25th June exhibited maximum mean late leaf spot disease severity (range 43.63 to 54.05%), defoliation (range, 17.22 to 22.30%), frequency (range, 1.32 to 1.78 / mm2) and size (range, 1.49 to 1.56 / mm2) and thereby gave reduced pod yield (range, 1225 to 1720 kg/ha) and test weight (28.66 to 32.97 g) followed by 10th July and 25th July. Among the groundnut cultivars, susceptible cv. JL 24 exhibited maximum mean disease severity (range, 35.94 to 54.05 %), defoliation (range, 11.61 to 22.30 %), frequency (range, 1.23 to 1.78 / mm2) and size (range, 1.26 to 1.56 / mm2), followed by TAG 24 and TG 26. However, LGN 1 exhibited least mean disease severity, defoliation, frequency and size with the highest pod yield (ranges, 1720 to 2332 kg/ha) and test weight (ranges, 32.97 to 38.59 g).

Quantitative Trait Locus Analysis of Late Leaf Spot Resistance and Plant-Type-Related Traits in Cultivated Peanut (Arachis hypogaea L.) under Multi-Environments.

Late leaf spot (LLS) is one of the most serious foliar diseases affecting peanut worldwide leading to huge yield loss. To understand the genetic basis of LLS and assist breeding in the future, we conducted quantitative trait locus (QTL) analysis for LLS and three plant-type-related traits including height of main stem (HMS), length of the longest branch (LLB) and total number of branches (TNB). Significant negative correlations were observed between LLS and the plant-type-related traits in multi-environments of a RIL population from the cross Zhonghua 5 and ICGV 86699. A total of 20 QTLs were identified for LLS, of which two QTLs were identified in multi-environments and six QTLs with phenotypic variation explained (PVE) more than 10%. Ten, seven, fifteen QTLs were identified for HMS, LLB and TNB, respectively. Of these, one, one, two consensus QTLs and three, two, three major QTLs were detected for HMS, LLB and TNB, respectively. Of all 52 unconditional QTLs for LLS and plant-type-related traits, 10 QTLs were clustered in five genetic regions, of which three clusters including five robust major QTLs overlapped between LLS and one of the plant-type-related traits, providing evidence that the correlation could be genetically constrained. On the other hand, conditional mapping revealed different numbers and different extent of additive effects of QTLs for LLS conditioned on three plant-type-related traits (HMS, LLB and TNB), which improved our understanding of interrelationship between LLS and plant-type-related traits at the QTL level. Furthermore, two QTLs, qLLSB6-7 and qLLSB1 for LLS resistance, were identified residing in two clusters of NB-LRR—encoding genes. This study not only provided new favorable QTLs for fine-mapping, but also suggested that the relationship between LLS and plant-type-related traits of HMS, LLB and TNB should be considered while breeding for improved LLS resistance in peanut.

The durable wheat disease resistance gene Lr34 confers common rust and northern corn leaf blight resistance in maize.

SummaryMaize (corn) is one of the most widely grown cereal crops globally. Fungal diseases of maize cause significant economic damage by reducing maize yields and by increasing input costs for disease management. The most sustainable control of maize diseases is through the release and planting of maize cultivars with durable disease resistance. The wheat gene Lr34 provides durable and partial field resistance against multiple fungal diseases of wheat, including three wheat rust pathogens and wheat powdery mildew. Because of its unique qualities, Lr34 became a cornerstone in many wheat disease resistance programmes. The Lr34 resistance is encoded by a rare variant of an ATP‐binding cassette (ABC) transporter that evolved after wheat domestication. An Lr34‐like disease resistance phenotype has not been reported in other cereal species, including maize. Here, we transformed the Lr34 resistance gene into the maize hybrid Hi‐II. Lr34‐expressing maize plants showed increased resistance against the biotrophic fungal disease common rust and the hemi‐biotrophic disease northern corn leaf blight. Furthermore, the Lr34‐expressing maize plants developed a late leaf tip necrosis phenotype, without negative impact on plant growth. With this and previous reports, it could be shown that Lr34 is effective against various biotrophic and hemi‐biotrophic diseases that collectively parasitize all major cereal crop species.

Correlation and path analysis studies in groundnut under different environment

In groundnut strong positive association was noticed between pod yield per plant and kernel yield per plant, oil yield per plant and significant and negative association with late leaf spot severity and rust incidence irrespective of the environments. Pod yield was also correlated with 100- kernel weight, plant height and oil content in environment III. The magnitude and direct association of pod yield with other characters varied from environment to environment. Inter correlation estimates for yield components revealed that plant height, 100-kernel weight, kernel yield per plant, oil yield per plant, late leaf spot severity, number of matured pods per plant, harvest index and plant height were significantly associated with one another and also with pod yield per plant which indicated that these characters were important components for improvement of pod yield in groundnut. This indicated that selection of genotypes based on oil yield per plant and kernel yield per plant is advantageous than the other characters.

Early sensing of peanut leaf spot using spectroscopy and thermal imaging

ABSTRACTEarly and late leaf spot are the most devastating, important fungal foliar diseases affecting peanut. The economic loss caused by peanut diseases justifies the necessity to develop more reliable detection methods. Point and image spectroscopy and thermal imaging were used in this study for the early detection of peanut leaf spot. The spectral reflectance factors differ significantly according to the health condition. The leaves of the healthy peanut showed a decreasing reflection in 1015 nm, whereas the heavily diseased leaves showed an increasing reflection. At the thermal infrared range, affected plants show a higher temperature than healthy ones. A presymptomatic decrease in leaf temperature using thermal imagery was found about 1.3°C lower than the healthy leaves. However, the diseased plant’s temperature was 2.2°C higher than that of the healthy one. The temperature difference allowed the discrimination between the infected and healthy leaves before the appearance of visible necrosis on leaves. Two simple indices, early leaf spot index (ELSI) and late leaf spot index (LLSI), were developed to allow early prediction of the peanut disease severity. The disease severity estimation using ELSI and LLSI has an overall accuracy of 78% and 89%, respectively. This demonstrates the efficiency of the proposed indices to estimate the peanut disease.