Resistance to rust (Puccinia arachidis Speg.) identified in nascent allotetraploids cross-compatible with cultivated peanut (Arachis hypogaea L.)

Peanut rust, caused by Puccinia arachidis Speg., is a foliar disease that plagues peanut production along with early and late leaf spots, Passalora arachidicola (Hori) U. Braun and Nothopassalora personata (Berk. & M.A. Curtis) U. Braun, C. Nakash, Videira & Crous, respectively. Rust can cause up to 80% yield losses without control and is widespread in tropical countries but is also a sporadic problem in the United States. An integrative plant management strategy with rust resistant peanut cultivars is needed to decrease dependence on costly fungicides and increase yields for farmers who cannot afford or do not have access to fungicides. Only moderate levels of rust resistance have been found in cultivated peanut germplasm, but fortunately, high resistance to rust has been identified in wild Arachis species that can be introgressed into peanut cultivars. In this study, 16 diploid, wild Arachis species, five diploid, interspecific hybrids, 11 unique, allotetraploid interspecific hybrids, and two cultivated peanut controls were tested for resistance to rust. Resistance was evaluated in vitro by incubation time, susceptibility index (calculated based on the number of lesions of different diameters)/ leaf area, total number of lesions/ leaf area, and total number of sporulating lesions/ leaf area. All wild Arachis species tested were very highly resistant to rust, except for A. ipaënsis , the B-genome progenitor of cultivated peanut. Additionally, all interspecific hybrids and synthetic allotetraploids not produced with A. ipaënsis as a parent did not show symptoms for rust. Any of these nine synthetic allotetraploids, BatCor , BatDur 1, BatDur 2, BatSten 1, GregSten , MagCard , MagDio , MagDur , and ValSten 1 are recommended for progression to QTL mapping of rust resistance. These resistance QTLs can be pyramided into peanut cultivars to protect yields in the United States and to increase yields in tropical, developing countries for farmers that cannot afford, or do not have access to, costly fungicides.

RESEARCHES ON REPORTING THE ATTACK OF SOME PEANUTS DISEASES CULTIVATED ON SANDY SOILS

Peanuts (Arachis hypogaea L.) are widely grown as a food and oleaginous species. Cultivation of peanuts offers important economic benefits, but one of the most important challenges that growers confront is the fight against destructive diseases. Culture is susceptible to a variety of pathogens, such as bacteria, fungi, viruses, and nematodes, resulting in low yields and degradation of grain quality. Among the most devastating fungal diseases of peanuts are Cercospora arachidicola, Puccinia arachidis, Sclerotium rolfsii which cause substantial loss of production. Loss of yields due to the incidence of peanut disease may be up to 50%. Fungicides can be used to combat fungal diseases, but there are alternative disease control options, such as cultural practices, cultivation of resistant varieties, which can be useful in combating diseases by reducing the frequency of application of fungicides.

Ketahanan Beberapa Genotipe Kacang Tanah terhadap Penyakit Karat (Puccinia arachidis) dan Bercak Daun (Cercosporidium personatum)

<p>Pertumbuhan tanaman kacang tanah seringkali menghadapi kendala biotik antara lain infeksi karat dan bercak daun akhir yang disebabkan oleh jamur Puccinia arachidis dan Cercosporidium personatum. Penelitian ini bertujuan mengevaluasi ketahanan 24 genotipe kacang tanah terhadap penyakit karat dan bercak daun dengan cara inokulasi kedua patogen tersebut. Penelitian disusun berdasar rancangan acak kelompok, tiga ulangan. Pengamatan dilakukan terhadap pertumbuhan dan hasil tanaman, perkembangan penyakit, jumlah pustul, jumlah dan diameter uredospora. Hasil penelitian menunjukkan bahwa gejala penyakit karat ditemukan pada minggu pertama setelah inokulasi, sedangkan gejala bercak daun pada minggu ke enam setelah inokulasi. Satu genotipe bereaksi agak tahan dan genotipe lainnya agak rentan hingga rentan terhadap karat daun, sedangkan terhadap bercak daun, semua genotipe bereaksi agak tahan dan tahan pada 10 minggu setelah inokulasi (MSI). Jumlah pustul dan bercak tertinggi terdapat pada kelompok genotipe agak rentan hingga rentan dan jumlah daun berkurang sejalan dengan peningkatan intensitas penyakit. Genotipe LG5/BK10)-89-68 memiliki respons agak tahan terhadap infeksi karat dan bercak daun, sedangkan varietas Takar 1 dan Hypoma 3 memiliki respons agak rentan, dan agak tahan terhadap karat daun pada 10 MSI. Oleh karena itu, genotipe LG5/BK10)-89-68, varietas Takar 1 dan Hypoma 3 dapat digunakan menjadi tetua untuk perakitan varietas tahan karat dan bercak daun.</p>

Evaluation of Improved Valencia Peanut Varieties for Production in Haiti

ABSTRACT Late leaf spot (Cercosporidium personatum) and peanut rust (Puccinia arachidis) are the most important diseases of peanut (Arachis hypogaea L.) in Haiti. Traditional Haitian peanut varieties are not only susceptible to these diseases but are also typically grown without benefit of a fungicide program. Five trials were conducted from 2015 to 2017 to evaluate the performance of six Valencia varieties in Quartier-Morin, Haiti (with an additional trial in 2017 at the Central Plateau) with respect to yield, resistance to rust and leaf spot diseases, and response to a fungicide program. A split-plot design with four or six replications was used in these studies. In each, “variety” was the whole plot and presence or absence of a fungicide program was the subplot. Valencia market types 309 Red, 309 Tan, M2, M3, SGV0801 and a local landrace were compared with and without Muscle ADV (tebuconazole + chlorothalonil, Sipcam) (2.3 L/ha) applied at 45, 60 and 75 days after planting (DAP). Final disease ratings (late leaf spot and peanut rust) were assessed approximately 94 DAP and plots were harvested the day following. In all trials, 309 Tan variety had the least amount of leaf spot and rust, but resulted in the lowest yield in four out of five trials, averaging 1727 kg/ha across fungicide treatments. M3, M2 and 309 Red were generally the numerically highest-yielding varieties, averaging 2906, 2864 and 2541 kg/ha across fungicide treatments, respectively, but were not statistically higher than the local Haitian Valencia, averaging 2374 kg/ha. Three fungicide applications during the season significantly increased yields in most trials for all varieties except 309 Tan. The highest and lowest average increase in yield from fungicide was for 309 Red (1126 kg/ha) and 309 Tan (103 kg/ha), respectively. The results from this study conducted over 2 years and 4 seasons document that while resistance to late leaf spot and rust is available in Valencia varieties, yield potential is not directly associated with that resistance. Also, use of fungicide improves yield potential in more susceptible varieties.

New Mycodiplosis gall midge (Diptera: Cecidomyiidae) feeding on fungal rusts (Fungi: Pucciniomycetes) that are pathogenic on cultured plants

Larvae of a gall midge were found feeding on the fungal rust Maravalia pterocarpi (Pucciniomycetes: Pucciniales: Chaconiaceae) infesting the economically important sua tree Dalbergia tonkinensis (Fabaceae) on Hainan Island, China. The adults, pupae and larvae were collected, their morphology was studied and a segment of the Cytochrome Oxidase unit I (COI) mitochondrial gene was sequenced. The gall midge proved to be a species new to science that belongs to the genus Mycodiplosis (Diptera: Cecdiomyiidae). Comparison of the sequence to published Cecdiomyiidae sequences revealed that, despite being undescribed and unnamed, it was previously found in east and south-east Asia to feed on several rust species: Puccinia coronata (Pucciniomycetes: Pucciniales: Pucciniaceae) that develops on Lolium multiflorum (Poaceae), Puccinia sp. on Zea mays (Poaceae), Puccinia arachidis on Arachis hypogaea (Fabaceae) and Puccinia allii on Allium fistulosum (Amaryllidaceae). The new species is described and named here Mycodiplosis puccinivora Jiao, Bu & Kolesik. It occurs in China, Japan, Thailand, Bangladesh and possibly Malaysia and Australia. In Hainan it has four to five generations per year.

Efikasi Agensia Hayati Trichoderma sp. Terhadap Karat Daun (Puccinia arachidis) Pada Kacang Tanah

Kacang tanah (Arachis hypogeae) merupakan bahan pangan yang diminati oleh masyarakat. Kontribusi produksi kacang tanah dari Provinsi Jawa Timur terhadap produksi Nasional mengalami penurunan pada tahun 2016. Faktor penyebab rendahnya hasil panen kacang tanah di Indonesia yaitu penyakit karat daun (Puccinia arachidis). Dalam penelitian ini, pengendalian karat daun pada tanaman kacang tanah dengan jamur antagonis Trichoderma sp. Penelitian ini memiliki tujuan untuk mengetahui bagaimana pengaruh agensia hayati Trichoderma sp. terhadap intensitas serangan penyakit karat daun, jumlah polong dan berat basah polong kacang tanah. Penelitian ini dilaksanakan pada bulan Juli 2017 hingga Maret 2018 di Laboratorium Perlindungan Tanaman Politeknik Negeri Jember dan lahan di Desa Antirogo, Kecamatan Sumbersari, Kabupaten Jember. Penelitian ini menggunakan Rancangan Acak Kelompok non faktorial terdiri dari 4 perlakuan di antaranya A0 (Tebukonazol 0,3 ml/l), A1 (Trichoderma sp. 105cfu/ml), A2 (Trichoderma sp. 106cfu/ml), A3 (Trichoderma sp. 107 cfu/ml) dengan 6 ulangan. Uji data menggunakan ANOVA (Analyze of Varians) dan uji lanjut dengan BNT 5%. Hasil dari penelitian adalah bahwa dari 4 perlakuan tersebut tidak berpengaruh nyata terhadap tingkat intensitas serangan karat daun, jumlah polong serta berat polong kacang tanah. Intensitas serangan Puccinia arachidis berkorelasi negatif terhadap jumlah polong dan berat basah polong.