Major Foliar Disease Research Articles

Major Foliar Fungal Diseases of Annual and Perennial Crops: Challenging National Food and Nutritional Security

India’s food grain production, which was 82 million tones in 1960-61, reached to about 271.37 million tones in 2018-19. The population, which was 439 million in 1960, rose to 1369 million in 2019. In India, more than 250 million people do not have adequate food despite comfortable food and foreign exchange reserves and high growth in GDP. The problems of declining land, water and labour force engaged in agriculture have impacts on projected food demands for growing population. Cereals, pulses, tubers, vegetables and fruits are important that provide food and nutritional requirements. All these crop plants are susceptible to diseases both in field and post-harvest. Globally, these diseases are responsible for loss of 10% of global food production. Every year, 30% of crops are lost in India due to pests and diseases. The crop loss due to pest and diseases is estimated to be Rs. 90, 000 crores annually. Among these, fungal foliar diseases are economically important.

Identification of novel sources for resistance against ascochyta blight and botrytis grey mould of chickpea

Ascochyta blight (Ab) and botrytis grey mould (bGM) are the major foliar diseases of chickpea that can cause severe yield losses. Thus, to identify stable sources, a set of 388 lines including 288 lines from Reference Set of chickpea and 100 advanced breeding lines were screened at PAU, Ludhiana for two years against Ab and bGM. One accession, ICC 1915, from the Reference Set and 24 advanced breeding lines were found resistant against Ab. None of the lines was found resistant against bGM, however, some lines were found moderately resistant. The identified lines can be used as sources of resistance in the disease resistance breeding programmes.

SCREENING OF MAIZE INBRED LINES UNDER ARTIFICIAL EPIPHYTOTIC CONDITION FOR THEIR REACTION TO TURCICUM LEAF BLIGHT AND COMMON LEAF RUST.

Common leaf rust (Puccinia sorghi Schw) and Turcicum leaf blight (Exserohilum trurcicum) is the major foliar fungal diseases of maize in Ethiopia causing yield losses in the range of 12% to 61% rely up on the genotypes. Screening was done on 178 (106 quality protein maize and 72 normal maize lines )maize inbred lines against Common leaf rust (CLR) and Turcicum leaf blight (TLB) diseases in order to know the reaction of those maize lines for two consecutive years. The experiment was conducted at Ambo plant protection research center (TLB and CLR) and Bako agricultural research center (TLB only), on station experimental fields. Out of 178 maize inbred line, 105 (53 quality protein maize and 52 normal maize lines) were evaluated for CLR; and 73 (53 quality protein maize and 20 normal maize lines) were evaluated for TLB. A randomized complete block design was used. Artificial inoculation was made twice a week for three continuous weeks, when plants were 30-45cm high (4-5 leaf stages). Among 73(53 quality protein maize and 20 normal maize lines) maize lines, resistant and susceptible responses were recorded on 42 (33 quality protein maize and 9 normal maize lines) and 3 (1 quality protein maize and 2 normal maize lines) lines for TLB disease, respectively. Out of 105 (53 quality protein maize and 52 normal maize lines) maize lines, resistant and susceptible responses were recorded on 33 (11 quality protein maize and 22 normal maize lines) and 4 (quality protein maize only) lines for CLR disease, in that order. Those selected resistance maize lines from this screening will be used in breeding program and finding of resistant maize lines for both diseases should be continued using modern screening tools as well as techniques in addition to this conventional method. 

Process of infection and colonization of Pseudocercospora kaki in persimmon leaves

AbstractCercosporiosis, caused by Pseudocercospora kaki, is the major foliar disease in persimmon crops. Despite the importance of the disease, we have little information about the interaction of this pathogen with persimmon leaf tissues. Therefore, to elucidate the infection and colonization process in these pathosystem, we investigated this interaction using light and scanning electron microscopy. Forty‐eight hours after inoculation, the germ tubes produced from conidia and entered the leaf tissue only through the stomata. The lesions formed were limited to the areolas of leaf venation. The accumulation of phenolic and lipophilic compounds, and parietal thickening by increased pectin content in the cells of the bundle sheath, restricted the advance of the fungus. During the colonization process, hyphae produced vesicles in the intercellular spaces of the mesophyll. These vesicles in contact with the cell wall of the chlorophyll parenchyma caused parietal changes. Pathogen sporulation occurred only on the adaxial surface of the leaves and produced sporodochium exposed on the outer leaf surface. This study showed how P. kaki penetrates in the persimmon leaves, and the process of colonization, with epidermal alterations and the lysis and collapse of mesophyll cells in the lesioned area, and finally, the formation of reproduction structures of the pathogen.

Identification and diversity of tropical maize inbred lines with resistance to common rust (Puccinia sorghi Schwein).

Common rust (CR) caused by Puccinia sorghi Schwein is one of the major foliar diseases of maize (Zea mays L.) in Eastern and Southern Africa. This study was conducted to (i) evaluate the response of elite tropical adapted maize inbred lines to Puccinia sorghi and identify resistant lines (ii) examine associations between CR disease parameters and agronomic traits, and (iii) assess the genetic diversity of the inbred lines. Fifty inbred lines were evaluated in field trials for three seasons (2017–2019) in Uganda under artificial inoculation. Disease severity was rated on a 1–9 scale at 21 (Rust 1), 28 (Rust 2), and 35 (Rust 3) days after inoculation. Area under disease progress curve (AUDPC) was calculated. The genetic diversity of the lines was assessed using 44,975 single nucleotide polymorphism markers. Combined ANOVA across seasons showed significant (P < .001) line mean squares for the three rust scores and AUDPC. Heritability was high for Rust 2 (0.90), Rust 3 (0.83), and AUDPC (0.93). Of the 50 lines, 12 were highly resistant to CR. Inbred lines CKL1522, CKL05010, and CKL05017 had significantly lower Rust 3 scores and AUDPC compared to the resistant check CML444 and are potential donors of CR resistance alleles. The genetic correlations between CR disease resistance parameters were positive and strong. A neighbor‐joining (NJ) tree and STRUCTURE suggested the presence of three major groups among the lines, with lines highly resistant to CR spread across the three groups. The genetic diversity among the highly resistant lines can be exploited by recycling genetically distant lines to develop new multiple disease resistant inbred lines for hybrid development and deployment.

Screening of linseed (Linum usitatissimum L.) germplasm under epiphytotic conditions against major foliar diseases

A set of 258 linseed germplasmaccessions were evaluated for major foliar diseases under epiphytotic conditions at AICRP linseed experimental block, Main Agricultural Research Station, Raichur during rabi 2019-20. Amongthe tested germplasm none of the lines were completely free from powdery mildew and Alternaria blight infection. The germplasm accession 20204 showed resistance for powdery mildew but no resistant source is recorded against Alternaria blight. Under moderately resistant group, 19801 and 20216 showed resistance to both Alternaria blight and powdery mildew. Twenty germplasm lines were identified against powdery mildew disease. The rest of the germplasm were moderately susceptible, susceptible or highly susceptible to powdery mildew and Alternaria blight infection.

Identification of candidate genes for quantitative downy mildew resistance in cucumber – a review

Cucurbit downy mildew (DM), caused by the obligate biotrophic oomycete Pseudoperonospora cubensis, is a major foliar disease of cucumber. Cucumber accession PI197088 was previously shown to be one of the most promising donors for DM resistance. The resistance in PI197088 is controlled by multiple quantitative trait loci (QTL), each with a relatively small effect. We developed a cucumber line with a 12 Mb introgression from PI197088 in a susceptible background. This introgression line was partially resistant to DM. Subsequently, we combined fine mapping data with RNAseq and whole genome resequencing to identify candidate genes for the resistance conferred by this introgression. Interestingly, fine-mapping data suggested that the partial resistance is caused by a combination of multiple genetically linked genes, leading to three subQTL, each with a different effect on the disease phenotype. In one of these subQTL we identified several Receptor Like Kinase genes (RLK). A novel RLK gene appeared to be present in resistant genotypes. In susceptible genotypes, including the reference genotype “Chinese Long 9930”, this novel gene has a 551 base pair deletion, and was therefore not correctly predicted during the annotation of the cucumber genome. In another subQTL, we found a loss-of-function mutation in the novel susceptibility gene (S-gene) CsAAP2A, encoding an amino acid transporter. In the resistant genotype a non-functional allele of this gene is present due to integration of a transposable element in its coding sequence.

Distribution and Importance of Maize Grey Leaf Spot in West Oromia, Ethiopia

Maize (Zea mays) is one of the most widely cultivated crops in the world. In Ethiopia, it’s a major staple food with an average productivity of 3.94 t ha -1 , which is below the world average of 5.78 tones ha -1 . A significant portion of this yield gap is attributed to biotic and abiotic stresses. Of diseases, grey leaf spot is one of the major foliar diseases threatening maize production in Ethiopia. Loss caused due to grey leaf spot reached 49.5% in Ethiopia. The objective was to assess the distribution and importance of Grey Leaf Spot. The assessments were done by sampling 81 maize fields in 9 districts from 3 zones during 2017. Purposive multistage sampling method was used. Data were analyzed using three-stage nested design. The survey result showed the highest disease prevalence 62.96 % was recorded in East Wollega and the lowest (22.22%) in West-Wollega zone. The highest mean incidence 35.06 % was recorded in East Wollega whilst the lowest 9.51% in West-Shewa. The maximum Severity index of 31.43% was in East Wollega whereas the minimum in West-Wollega (10.05%) zones. At a district level, the highest prevalence was recorded in Leka-Dulecha followed by Gobu-Seyo with disease prevalence of 88.9% and 66.7%, respectively. The highest mean incidence 48.15% was at Gobu-Seyo whereas the lowest was recorded in Gimbi 1.1%. The highest mean severity index was in Leka-Dulecha 46.11% whilst the lowest in Gimbi 1.78%. Thus, there is a need to develop management strategies like crop rotation with non-host, use of tolerant varieties to reduce the impact of the disease on maize production. Keywords: Maize disease, Incidence, Severity Index DOI: 10.7176/JNSR/11-17-03 Publication date: September 30 th 2020

Tar Spot: An Understudied Disease Threatening Corn Production in the Americas.

Tar spot of corn has been a major foliar disease in several Latin American countries since 1904. In 2015, tar spot was first documented in the United States and has led to significant yield losses of approximately 4.5 million t. Tar spot is caused by an obligate pathogen, Phyllachora maydis, and thus requires a living host to grow and reproduce. Due to its obligate nature, biological and epidemiological studies are limited and impact of disease in corn production has been understudied. Here we present the current literature and gaps in knowledge of tar spot of corn in the Americas, its etiology, distribution, impact and known management strategies as a resource for understanding the pathosystem. This will in tern guide current and future research and aid in the development of effective management strategies for this disease.

Assessment of Disease Resistance and High Yielding Traits of Common Buckwheat Genotypes in Subtropical Climate of Nepal

Twelve common buckwheat (Fagopyrum esculentum Moench) genotypes received from Hill Crops Research Program, Kabre, Dolakha were evaluated for resistance against major foliar fungal diseases and high yielding traits at the research field of National Maize Research Program, Rampur, Chitwan during winter seasons of two consecutive years 2017 and 2018. The design of the experiment was Randomized Complete Block having three replications. The unit plot size was 3m x 2m with 25cm row to row spacing and continues plant to plant spacing was maintained and net harvested plot was 6 sq meters. The experiment was planted at last week of October in both years. The recommended dose of fertilizer was 30:30:0 for N:P:K kg ha-1 respectively and seed rate 50 kg ha-1. Disease data were recorded for downy mildew (Perenospora fagopyri), powdery mildew (Erysiphepolygoni) and botrytis leaf blight (Botrytis cinerea) severity on 20 randomly tagged plants/plot. The yield and yield attributing traits were recorded. Buckwheat genotypes differed significantly (p&lt;0.05) on disease severity, grain yield and yield attributing traits. Genotypes CBBP-01, KIF-72-22-520, GF5283, ACC#2234 and ACC#2213 were resistant to powdery mildew, downy mildew and botrytis leaf blight and also resulted in higher grain yield. Grain yield had found strong negative correlation with the fungal disease severity of buckwheat. These genotypes might be useful for the development of major foliar fungal disease resistant high yielding common buckwheat variety in inner terai region of Nepal.&#x0D; SAARC J. Agri., 18(1): 143-152 (2020)

Isoflucypram, the first representative of a new succinate dehydrogenase inhibitor fungicide subclass: Its chemical discovery and unusual binding mode.

Succinate dehydrogenase inhibitors (SDHIs) have played a crucial role in disease control to protect cereals as well as fruit and vegetables for more than a decade. Isoflucypram, the first representative of a newly installed subclass of SDHIs inside the Fungicide Resistance Action Committee (FRAC) family of complex II inhibitors, offers unparalleled long‐lasting efficacy against major foliar diseases in cereals. Herein we report the chemical optimization from early discovery towards isoflucypram and the first hypothesis of its altered binding mode in the ubiquinone binding site of succinate dehydrogenase. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Characterization of Colletotrichum ocimi Population Associated with Black Spot of Sweet Basil (Ocimum basilicum) in Northern Italy.

Black spot is a major foliar disease of sweet basil (Ocimum basilicum) present in a typical cultivation area of northern Italy, including the Liguria and southern Piedmont regions, where this aromatic herb is an economically important crop. In this study, 15 Colletotrichum isolates obtained from sweet basil plants with symptoms of black spot sampled in this area were characterized morphologically and by nuclear DNA analysis using internal transcribed spacers (ITS) and intervening 5.8S nrDNA as well as part of the β-tubulin gene (TUB2) regions as barcode markers. Analysis revealed all but one isolate belonged to the recently described species C. ocimi of the C. destructivum species complex. Only one isolate was identified as C. destructivum sensu stricto (s.s.). In pathogenicity tests on sweet basil, both C. ocimi and C. destructivum s.s. isolates incited typical symptoms of black spot, showing that although C. ocimi prevails in this basil production area, it is not the sole causal agent of black spot in northern Italy. While no other hosts of C. ocimi are known worldwide, the close related species C. destructivum has a broad host range, suggesting a speciation process of C. ocimi within this species complex driven by adaptation to the host.

Meta-QTL analysis of tan spot resistance in wheat.

A total of 19 meta-QTL conferring resistance to tan spot were identified from 104 initial QTL detected in 15 previous QTL mapping studies. Tan spot, caused by the fungal pathogen Pyrenophora tritici-repentis (Ptr), is a major foliar disease worldwide in both bread wheat and durum wheat and can reduce grain yield due to reduction in photosynthetic area of leaves. Developing and growing resistant cultivars is a cost-effective and environmentally friendly approach to mitigate negative effects of the disease. Understanding the genetic basis of tan spot resistance can enhance the development of resistant cultivars. With that goal, over 100 QTL associated with resistance to tan spot induced by a variety of Ptr races and isolates have been identified from previous QTL mapping studies. Meta-QTL analysis can identify redundant QTL among various studies and reveal major QTL for targeting in marker-assisted selection applications. In this study, we performed a meta-QTL analysis of tan spot resistance using the reported QTL from 15 previous QTL mapping studies. An integrated linkage map with a total length of 4080.5cM containing 47,309 markers was assembled from 21 individual linkage maps and three previously published consensus maps. Nineteen meta-QTL were clustered from 104 initial QTL projected on the integrated map. Three of the 19 meta-QTL located on chromosomes 2A, 3B, and 5A show large genetic effects and confer resistance to multiple races in multiple bread wheat and durum wheat mapping populations. The integration of those race-nonspecific QTL is a promising strategy to provide high and stable resistance to tan spot in wheat.

Genome-wide association mapping of tan spot resistance in a worldwide collection of durum wheat.

Resistance to tan spot in durum wheat involves race-nonspecific QTL and necrotrophic insensitivity gene. Tan spot, caused bythe necrotrophic fungus Pyrenophoratritici-repentis, is a major foliar disease on all cultivated wheat crops worldwide. Compared to common wheat, much less work has been done to investigate the genetic basis of tan spot resistance in durum. Here, we conducted disease evaluations, necrotrophic effector (NE) sensitivity assays and a genome-wide association study using a collection of durum accessions. The durum panel segregated for the reaction to disease inoculations and NE infiltrations with eighteen accessions being highly resistant to all races and most of them insensitive to both PtrToxA and PtrToxB. Over 65,000SNP markers were developed from genotyping-by-sequencing for the association mapping. As expected, sensitivity to PtrToxA and PtrToxB was mapped to the chromosome arms 5BL and 2BS, respectively. For the fungal inoculations, a quantitative trait locus (QTL) on chromosome 3B was associated with resistance to all races and likely corresponds to the race-nonspecific resistance QTL previously identified in common wheat. The Tsn1locus was not significantly associated with tan spot caused by the PtrToxA-producing isolates Pti2 and 86-124, but the Tsc2 locus was significantly associated with tan spot caused by the PtrToxB-producing isolate DW5. Another QTL on chromosome arm 1AS was associated with tan spot caused by the PtrToxC-producing isolate Pti2 and likely corresponds to the Tsc1 locus. Additional QTL for specific races was identified on chromosome 1B and 3B. Our work highlights the complexity of genetic resistance to tan spot and further confirms that the Ptr ToxA-Tsn1 interaction plays no significant role in disease development in tetraploid wheat.

Population structure of Alternaria species causing leaf blight of sunflower (Helianthus annuus L.) in India

Leaf blight disease of sunflower caused by Alternaria species is one of the major foliar diseases occurring in sunflower cultivated areas of India. Leaf blight samples collected from sunflower growing areas during rainy season were colonized by Alternariaster helianthi while samples collected during spring season incited by Alternaria alternata. Among two Alternaria species, A. helianthi was the predominant pathogen among the isolates. A total of 220 A. helianthi isolates; 30 A. alternata isolates collected during 2009–10 to 2011–12 from infected sunflower leaves in nine states of India were characterized based on phenotypic, molecular and pathogenic aggressiveness. Molecular identification based on phylogenic analysis using partial internal transcribed spacer regions showed that A. helianthi and A. alternata isolates separated into 11 phylogenetic groups. The pathogenicity on sunflower cultivars KBSH-1, KBSH-44, DRSF-108, PI-535890, TX-16R, Morden revealed that some A. helianthi isolates were highly aggressive with blighting on Morden and DRSF-108. Based on aggressiveness on sunflower cultivars, four groups identified in A. helianthi isolates; three groups in A. alternata isolates. There was no association between phylogenetic group, disease severity and geography of collection among the isolates. Isolates Ah-15, 38, 47, 48, 49, 50, 97, 98, 99, 100, 107, 108, 109, 110, 111, 112, 125 and 126 in A. helianthi; Aa-3, 7, 4 and 9 in A. alternata were aggressive on sunflower cultivars which would be utilized in future disease screening programmes. This is the first report on population structure of Alternaria species and also highlights that A. helianthi is the predominant pathogen associated with sunflower leaf blight in India.

Farmers&amp;apos; Knowledge, Perceptions and Management of Black Sigatoka in Small Plantain-Based Farms in Southern Benin

Plantain (Musa paradisiaca) is a key crop, relevant to achieve food security and improve the livelihoods of many households in Africa, particularly in West Africa, where it has become a major staple food. But along with its production, farmers are facing a major foliar disease, the Black Sigatoka that limits the productivity. The yield losses incurred by farmers due to this disease can reach 50%. Knowledge regarding this disease is crucial for effective management of the disease. This paper aims at diagnosing the differences in perceptions and knowledge between farmers and scientists with regard to strategies of managing black Sigatoka on plantain. A survey was conducted on 446 randomly selected farmers using a semi-structured questionnaire in five major plantain growing municipalities (Athiémé, Adja-Ouèrè, Tori-Bossito, Ouinhi, Zè) in Benin. This study came up with knowledge and perceptions of farmers on the symptoms, causes, conducive conditions for disease development, and means of dissemination and strategies for managing black Sigatoka. It appeared that most farmers recognized the disease lesions on the leaves, but failed to associate these symptoms with the targeted disease. In addition, farmers had very limited knowledge of the causal agent, disseminating mechanism and effective management methods. The majority of farmers that are aware of the symptoms (92.7%) associated the yield loss on plantain field with the occurrence of this disease. This appreciation varied from a significant yield loss (54.2%) to a moderate yield loss (45.8%). Most farmers (69%) did not adopt any disease control measures. Deleafing was the most common control method used by 30.2% of the farmers. Apart from this technique, very few farmers reported using synthetic pesticides and biopesticides based on neem leaves (Azadirachta indica). Agricultural research institutes and farmers’ advisory systems were poorly involved in building and managing knowledge related to black Sigatoka in southern Benin. This study has the merit to bring out key information that will help design appropriate programme that would make it possible to manage this disease successfully in short and medium terms with smallholder farmers.

Utilization of Advanced Backcross Population Derived from Synthetic Amphidiploid for Dissecting Resistance to Late Leaf Spot in Peanut (Arachis hypogaea L.)

Late leaf spot (LLS) is the major foliar disease, which often occur with rust and cause severe yield losses worldwide in peanut (Arachis hypogaea L.). In order to map and introgress the resistance alleles for LLS into an elite cultivar ICGS 76, the advanced backcross approach was used for identification of quantitative trait locus (QTL). The synthetic amphidiploid ISATGR 278–18 (A. duranensis ICG 8138 × A. batizocoi ICG 13160) which is known to harbor resistance alleles for foliar diseases was used as donor parent to generate AB-QTL population comprising of 164 introgression lines (ILs). A linkage map with 114 microsatellite markers was developed spanning 746.15 cM distance with an average inter-marker distance of 6.55 cM. QTL analysis yielded 14 main-effect QTLs (mQTLs) (explaining up to 38.58% PVE) for LLS and 10 mQTLs (up to 10.99% PVE) for rust. In addition, four epistatic QTLs (eQTLs) (explaining up to 4.97% PVE) were observed for foliar diseases. Furthermore, seven mQTLs and 16 eQTLs were observed for agronomic traits. Several ILs showed high resistance to LLS with agronomic attributes from recurrent parent. This study reports the utilization of the untapped resistance source for LLS from A. batizocoi that was not extensively used earlier in peanut crop improvement.

QTL mapping of resistance to tan spot induced by race 2 of Pyrenophora tritici-repentis in tetraploid wheat.

A total of 12 QTL conferring resistance to tan spot induced by a race 2 isolate, 86-124, were identified in three tetraploid wheat mapping populations. Durum is a tetraploid species of wheat and an important food crop. Tan spot, caused by the necrotrophic fungal pathogen Pyrenophora tritici-repentis (Ptr), is a major foliar disease of both tetraploid durum wheat and hexaploid bread wheat. Understanding the Ptr-wheat interaction and identifying major QTL can facilitate the development of resistant cultivars and effectively mitigate the negative effect of this disease. Over 100 QTL have already been discovered in hexaploid bread wheat, whereas few mapping studies have been conducted in durum wheat. Utilizing resistant resources and identifying novel resistant loci in tetraploid wheat will be beneficial for the development of tan spot-resistant durum varieties. In this study, we evaluated four interconnected tetraploid wheat populations for their reactions to the race 2 isolate 86-124, which produces Ptr ToxA. Tsn1, the wheat gene that confers sensitivity to Ptr ToxA, was not associated with tan spot severity in any of the four populations. We found a total of 12 tan spot-resistant QTL among the three mapping populations. The QTL located on chromosomes 3A and 5A were detected in multiple populations and co-localized with race-nonspecific QTL identified in other mapping studies. Together, these QTL can confer high levels of resistance and can be used for the improvement in tan spot resistance in both hexaploid bread and durum wheat breeding. Two QTL on chromosomes 1B and 7A, respectively, were found in one population when inoculated with a ToxA knockout strain 86-124ΔToxA only, indicating that their association with tan spot was induced by other unidentified necrotrophic effectors, but under the absence of Ptr ToxA. In addition to removal of the known dominant susceptibility genes, integrating major race-nonspecific resistance loci like the QTL identified on chromosome 3A and 5A in this study could confer high and stable tan spot resistance in durum wheat.

Performance of popcorn introductions for agronomic characters, grain yield and popping qualities in the forest and derived savannah agro-ecologies of Nigeria

The study focus on the evaluation of popcorn lines for their yield and agronomic potentials. Genetic materials were evaluated under irrigation in a three-replicate in a Randomized Complete Block Design (RCBD) with a commercial variety as check. Two seeds were planted per hole using two- row plots of 5 m long with inter and intra-row spacing of 0.75 m x 0.5 m, respectively in two locations viz: Ibadan and Ikenne representing the forest and savannah agro-ecologies of Nigeria respectively. Genotypes (G) differed significantly (ρ ≤ 0.01) for almost all the characters measured except for ear aspect. Location (L) as well as G x L interaction effects were also well pronounced on all agronomic characters measured except for days to silking and ears per plant. Popcorn 33-1-Y, large pearl shaped, Popcorn 40-Y and Popcorn 34-Y were high yielding with a potential of above 2.0 t ha−1. These materials were found to be fairly resistant to major foliar diseases of the tropical humid ecologies. They are recommended for further evaluation across different agro-environments for possible propagation by popcorn farmers in Nigeria to boost production.

Mapping quantitative trait loci associated with southern leaf blight resistance in maize (Zea mays L.)

AbstractSouthern leaf blight (SLB) caused by the fungus Cochliobolus heterostrophus (Drechs.) Drechs. is a major foliar disease of maize worldwide. Our objectives were to identify quantitative trait loci (QTL) for resistance to SLB and flowering traits in recombinant inbred line (RIL) population derived from the cross of inbred lines LM5 (resistant) and CM140 (susceptible). A set of 207 RILs were phenotyped for resistance to SLB at three time intervals for two consecutive years. Four putative QTL for SLB resistance were detected on chromosomes 3, 8 and 9 that accounted for 54% of the total phenotypic variation. Days to silking and anthesis–silking interval (ASI) QTL were located on chromosomes 6, 7 and 9. A comparison of the obtained results with the published SLB resistance QTL studies suggested that the detected bins 9.03/02 and 8.03/8.02 are the hot spots for SLB resistance whereas novel QTL were identified in bins 3.08 and 8.01/8.04. The linked markers are being utilized for marker‐assisted mobilization of QTL conferring resistance to SLB in elite maize backgrounds. Fine mapping of identified QTL will facilitate identification of candidate genes underlying SLB resistance.