Additional sources of resistance to groundnut rosette disease in groundnut germplasm and breeding lines

Groundnut rosette, a virus disease of groundnut (Arachis hypogaea) transmitted by the aphid, Aphis craccivora Koch, reduces yield in susceptible cultivars by 30–100%. Additional sources were sought in germplasm accessions involving 2301 lines from different sources and from 252 advanced breeding lines derived from crosses involving earlier identified sources of resistance to rosette. The lines were evaluated in field screening trials using an infector row technique during 1996 and 1997 growing seasons. Among the germplasm lines, 65 accessions showed high levels of resistance while 134 breeding lines were resistant. All rosette disease resistant lines were susceptible to groundnut rosette assistor virus. This work identified germplasm and breeding lines that will contribute to an integrated management of groundnut rosette disease. These new sources also provide an opportunity to eliminate yield losses due to the rosette disease.     

Resistance to groundnut rosette disease in wild Arachis species

One hundred and sixteen accessions representing 28 species in the genus Arachis were evaluated for resistance to groundnut rosette disease using an infector row technique during the 1996/97, 1997/98, 1998/99 and 1999/2000 growing seasons at Chitedze, Malawi. Of these, a total of 25 accessions belonging to Arachis diogoi (1 accession), A. hoehnei (2), A. kretschmeri (2), A. cardenasii (2), A. villosa (1), A. pintoi (5), A. kuhlmannii (2), A. appressipila (3), A. stenosperma (5), A. decora (1), and A. triseminata (1) showed resistance to the groundnut rosette disease. No visible disease symptoms were observed in several accessions belonging to A. appressipila, A. cardenasii, A. hoehnei, A. kretschmeri, A. villosa, A. pintoi, A. kuhlmannii, and A. stenosperma. Some accessions in A. appressipila, A. diogoi, A. stenosperma, A. decora, A. triseminata, A. kretschmeri, A. kuhlmannii, and A. pintoi were resistant to all three components of rosette, Groundnut rosette ass is tor virus (GRAV), Groundnut rosette virus (GRV) and its satellite RNA (sat. RNA). Two accessions in A. stenosperma and one accession in A. kuhlmannii showed the presence of all three components of the rosette disease. Several wild Arachis accessions were resistant to GRAV. All the accessions of A. batizocoi (4), A. benensis (2), A. duranensis (46), A. dardani (1), A. ipaensis (1), A. magna (1), A. monticola (3), A. oteroi (1), A. pusilla (4), and A. valida (2) were susceptible to rosette disease. In all these accessions, infected plants were chlorotic and severely stunted. The value of exploitation of the resistance in wild Arachis species in rosette resistance breeding programmes is discussed.     

The nature of the resistance in groundnut to rosette disease

Groundnut rosette disease is caused by a complex of three agents, groundnut rosette virus (GRV) and its satellite RNA, and groundnut rosette assistor virus (GRAV); the satellite RNA is mainly responsible for the disease symptoms. Groundnut genotypes possessing resistance to rosette disease were shown to be highly resistant (though not immune) to GRV and therefore to its satellite RNA, but were fully susceptible to GRAV.     

Different variants of the satellite RNA of groundnut rosette virus are responsible for the chlorotic and green forms of groundnut rosette disease*

Groundnut plants with symptoms of rosette disease contain groundnut rosette virus (GRV), but GRV is transmitted by Aphis craccivora only from plants that also contain groundnut rosette assistor virus (GRAV). Two main forms of rosette disease are recognised, ‘chlorotic rosette’ and ‘green rosette’. GRV cultures invariably possess a satellite RNA and this is the major cause of rosette symptoms: satellite-free isolates derived from GRV cultures from Nigerian plants with chlorotic or green rosette, or from Malawian plants with chlorotic rosette, induced no symptoms, or only transient mild mottle or interveinal yellowing, in groundnut. When the satellite RNA species from GRV cultures from Nigerian green or Malawian chlorotic rosette were reintroduced into the three satellite-free isolates in homologous and heterologous combinations, the ability to induce rosette symptoms was restored and the type of rosette induced was that of the cultures from which the satellite RNA was derived. Thus different forms of the satellite are responsible for the different forms of rosette disease. Other forms of the satellite induce only mild chlorosis or mottle symptoms in groundnut. Individual plants may contain more than one form of the satellite, and variations in their relative predominance are suggested to account for the variable symptoms (ranging from overall yellowing to mosaic) seen in some plants graft-inoculated with chlorotic rosette.     

Inheritance of resistance to groundnut rosette virus in groundnut (Arachis hypogaea L.)

A method of field screening groundnut seedlings for resistance to groundnut rosette virus (GRV), by means of which over 97% incidence was induced in rows of susceptible test plants, was developed at Chitedze Research Station in Malawi. Two GRV-resistant Virginia cultivars (RG 1 and RMP 40) were crossed with three susceptible cultivars, one from each of the Spanish (JL 24), Valencia (ICGM 48) and Virginia (Mani Pintar) botanical groups. Twelve F₁ reciprocal crosses and their F₂ and backcross generations were produced and the material screened in nurseries in 1985/86 and 1986/87. Seedlings raised from plants which did not become infected in the field were inoculated in the glasshouse in order to eliminate susceptible escapees. The numbers of diseased and healthy individuals in each population were subjected to χ² tests. In the majority of the F₂ populations a good fit was obtained for a ratio of one resistant to 15 susceptible plants, a ratio to be expected if resistance to GRV were determined by a pair of independent complementary recessive genes. This was further supported by data from backcross generations.     

A variant of the satellite RNA of groundnut rosette virus that induces brilliant yellow blotch mosaic symptoms in Nicotiana benthamiana

Some Malawian cultures of groundnut rosette virus (GRV) give rise to variants that, although still causing symptoms of the chlorotic type of rosette in groundnut, induce brilliant yellow blotch mosaic symptoms, instead of the usual veinal chlorosis and mild mottle, in Nicotiana benthamiana. One such isolate (YB) induced the formation in infected plants of a 0.9 kbp dsRNA having extensive sequence homology with molecules of similar size in other naturally occurring isolates of GRV. These dsRNA molecules were shown to be double-stranded forms of single-stranded satellite RNA molecules. Experiments in which the satellite was removed from and restored to isolate YB, or exchanged with those from other GRV isolates, showed that it carries the determinant for yellow blotch mosaic symptoms. Plants inoculated with the 0.9 kbp dsRNA (denatured or undenatured) developed yellow blotch mosaic even when the satellite-free GRV helper was not inoculated until 11 days later. The satellite RNA is therefore a very stable molecule. Prior infection of N. benthamiana with a GRV isolate containing a normal form of the satellite protected against expression of yellow blotch mosaic symptoms when the plants were later inoculated with isolate YB, whereas prior infection with satellite-free isolates did not. This provides a simple method of determining whether a GRV isolate has an associated satellite RNA. The YB satellite seems to be a newly recognised variant additional to those known to cause the chlorotic, green and other forms of groundnut rosette disease.     

The Effect of Groundnut rosette assistor virus on the Agronomic Performance of Four Groundnut (Arachis hypogaea L.) Genotypes

The effect of Groundnut rosette assistor virus (GRAV), in the absence of the other two agents (Groundnut rosette virus and its satellite RNA) of the groundnut rosette disease virus complex, was evaluated on the agronomic performance of four groundnut (=peanut) genotypes (CG‐7, ICGV‐SM‐90704, JL‐24 and ICG‐12991) with different botanical characteristics. All genotypes infected with GRAV showed mild yellowing/chlorosis of leaves and the symptoms persisted throughout their growth period. ELISA absorbance values indicated lower amounts of GRAV antigen in ICGV‐SM‐90704 than in the other genotypes. The reduction in leaf area due to GRAV infection varied between 15.5% and 21.7%, whereas the plant height was decreased between 11.3% and 13.4% among the four genotypes. GRAV infection caused 28.4%, 16.9%, 21.7% and 25.5% reduction in the dry weight of haulms in CG‐7, ICGV‐SM‐90704, JL‐24 and ICG‐12991 respectively. Plants infected with GRAV showed greater reduction in seed weight in CG‐7 (52.2%), followed by JL‐24 (46.1%), ICG‐12991 (40.7%) and ICGV‐SM‐90704 (25.7%). These results provide evidence for the first time that GRAV infection, without GRV and sat RNA, affect plant growth and contribute to yield losses in groundnut.     

Detection of groundnut rosette umbravirus infections with radioactive and non-radioactive probes to its satellite RNA

A cloned cDNA copy of the satellite RNA of groundnut rosette virus (GRV), labelled with either ³²P or digoxigenin, was used as a probe to detect the satellite RNA in infected leaves. The test was successfully applied to N. benthamiana and to groundnuts, infected with isolates of GRV from East and West Africa and with isolates which cause different types of symptom in groundnuts, including one which is almost symptomless. Although the probe did not react with extracts from plants infected with GRV isolates from which the satellite RNA had been artificially eliminated, all naturally occurring GRV isolates contain the satellite RNA. The test therefore provides a reliable indicator of infection by GRV.     

Impact of groundnut rosette disease on nutritive value and elemental composition of four varieties of peanut (Arachis hypogaea)

Proximate and elemental composition of four peanut genotypes infected with groundnut rosette disease (GRD) was examined. Moisture and ash content generally decreased while fat and energy content increased in seeds from diseased plants. Protein and carbohydrate varied between seeds of diseased and healthy plants of the different varieties with no consistent pattern. Instrumental neutron activation analysis of 10 elements within leaves, stems and seeds showed elevated levels of K, Al and Cl in leaves, stems and seeds in at least three of the four varieties infected with GRD while Na was decreased in stems but increased in seeds. While significant differences were found, Mg, Mn, Ca and Zn did not show any consistent change with respect to plant part or genotype, between diseased and healthy plants. V and Fe were found at low levels in leaves and stems and not detected in seeds. This represents the first report on the effect of GRD on the nutritive quality of peanuts.     

Resistant sources in groundnut germplasm lines against peanut bud necrosis tospovirus disease

Of the 242 groundnut genotypes, tested both in epiphytotic field and laboratory conditions, the genotypes viz., ICGV 90009, ICGV 86699, ICGV 86329, 91177, 91234, ICGV‐94252 and TG 26 were found promising both with low incidence of PBND besides longer incubation periods, DFSA, DLSA and IP 50%. Further, significant positive correlation was found between IP 50% vs DLSA, DFSA and final PBND (%) was negatively correlated with IP 50% and DFSA.     

Comparison of the coat protein of groundnut rosette assistor virus with those of other luteoviruses

The coat protein gene of groundnut rosette assistor virus (GRAV) was cloned and sequenced. The deduced amino acid sequences of the coat protein and of another protein encoded in a different, overlapping, reading frame resemble those of other luteoviruses. Four monoclonal antibodies against GRAV, prepared using denatured coat protein as immunogen, also reacted with some other luteoviruses in ELISA. Nevertheless, they will be useful as reagents for the identification of GRAV infections in groundnut.     

Epidemiology of groundnut rosette virus disease: current status and future research needs@

Rosette is the most destructive virus disease of groundnut in sub-Saharan Africa. It is caused by a complex of three agents, namely groundnut rosette assistor virus, groundnut rosette virus and its satellite RNA. The disease appears to be indigenous to Africa as it has not been recorded elsewhere. Thus rosette represents a new-encounter situation as the disease is thought to have spread to the introduced groundnut from indigenous host plants. Rosette has been known since 1907 and much information has been obtained on the main features of the disease, viz. its biology, transmission, viral aetiology and diagnosis, and the impact of chemical control of the aphid vector, cultural practices and virus-resistant varieties on disease management. However, there are still many gaps in the available knowledge, especially the reasons for the large and unpredictable fluctuations in the incidence and severity of rosette disease throughout sub-Saharan Africa. Three unresolved issues of particular importance concern the nature of the primary source(s) of inoculum, the means of survival of virus and vector during unfavourable periods, and the distances over which the aphid vector can disperse and disseminate virus. Now that the aetiology of the disease is understood and diagnostic tools have been developed, the time is opportune for new initiatives in understanding the ecology and epidemiology of rosette. Substantial progress can be made by developing a co-ordinated multi-disciplinary research programme and making full use of the latest techniques, approaches and experience gained elsewhere with other insect-borne viruses. This information would help to explain the sporadic disease epidemics that cause serious crop losses and sometimes total crop failure, and would also facilitate the development of disease forecasting methods and sustainable integrated disease management strategies.     

Screening of chilli germplasm for resistance to Alternaria leaf spot disease

Chilli is one of the spices used to enhance the flavour and taste of cooked food. Fungal diseases are the main biological constraints in chilli production, and Alternaria leaf spot disease caused by Alternaria alternata is one of the most devastating diseases of chilli. One of the effective and environmentally friendly ways to control this disease is introgress resistance from wild relative/varieties to the cultivated one. The first step towards introgression of resistance genes is to screen the chill germplasm for leaf spot resistance. In the current study, we screened the chilly germplasm and identified the sources of leaf spot resistance, which can be harnessed in resistance breeding programmes.     

优异大麦种质资源的抗性鉴定和评价

1998～1999年,将1997年筛选出的191个农艺性状表现优良的大麦品种进行大麦黄花叶病、大麦白粉病、大麦赤霉病、大麦条纹病及耐盐等抗性的鉴定评价,结果表明,抗及高抗大麦黄花叶病品种60份,抗大麦赤霉病品种59份,高抗大麦条纹病品种89份,抗大麦白粉病品种19份,芽期耐盐品种17份,苗期耐盐品种2份.     

黄瓜资源对黄瓜绿斑驳病毒广东分离物的抗性水平鉴定

【背景】黄瓜绿斑驳花叶病毒(Cucumber green mottle mosaic virus,CGMMV)是严重威胁葫芦科作物生产的毁灭性病原之一,该病毒已入侵我国十多个省份,危害西瓜、黄瓜等作物并造成严重的经济损失。早在2009年广东即发现CGMMV为害西瓜和黄瓜,但黄瓜等葫芦科作物对其抗性情况尚不清楚。【方法】采用人工机械摩擦接种方法,测定了14份黄瓜种质资源对CGMMV广东分离物的抗性水平。【结果】从广东葫芦病样中分离获得CGMMV,该病毒分离物MP基因序列与国内报道的各分离物同源率均在99%以上;14份黄瓜种质资源对该病毒分离物均表现为感病。【结论与意义】广东主要黄瓜资源对CGMMV均表现为感病,这为我省防控该病毒病提供了科学依据,也为黄瓜抗病育种提供了指导。     

Effect of jasmonic acid and salicylic acid induced resistance in groundnut on Helicoverpa armigera

Induced resistance in plants affects insect growth and development as a result of the up‐regulation of defence‐related secondary metabolites or enzyme‐binding proteins. In the present study, the effects of jasmonic acid (JA) and salicylic acid (SA) induced resistance in groundnut on Helicoverpa armigera (Hübner) are examined. Larval survival, larval weights and the activities of digestive enzymes (total serine protease and trypsin) and of detoxifying enzymes [glutathione S‐transferase (GST) and esterase (EST)] are studied in insects fed on four groundnut genotypes with moderate levels of resistance to H. armigera (ICGV 86699, ICGV 86031, ICG 2271 and ICG 1697) and a susceptible genotype (JL 24). The plants are pre‐ and/or simultaneously treated with JA and SA, and then infested with H. armigera, which are allowed to feed for 6 days. Significantly lower serine protease and trypsin activities are observed in H. armigera fed on plants treated with JA. Greater GST activity is recorded in insects fed on JA and SA treated plants, whereas EST activity is low in H. armigera larvae fed on plants treated with JA and SA. Serine proteases, trypsin and GST activities and larval weights (r = 0.74–0.95) and larval survival (r = 0.77–0.93) are positively correlated, whereas EST activity and larval weight (r = ?0.55) and larval survival (r = ?0.65) are negatively correlated. The results suggest that midgut digestive and detoxifying enzymes can be used as indicators of the adverse effects of constitutive and/or induced resistance in crop plants on the insect pests and the role of JA and SA in insect pest management.     

Metabolic profiling for dissection of late leaf spot disease resistance mechanism in groundnut

Late leaf spot (LLS) caused by fungi Passalora personata is generally more destructive and difficult to control than early leaf spot. The aim of this study was to decipher biochemical defense mechanism in groundnut genotypes against P. personata by identifying resistance specific biomarkers and metabolic pathways induced during host–pathogen interaction. Metabolomics of non-infected and infected leaves of moderately resistant (GPBD4 and ICGV86590), resistant (KDG128 and RHRG06083) and susceptible (GG20, JL24 and TMV2) genotypes was carried out at 5 days after infection (65 days after sowing). Non-targeted metabolite analysis using GC–MS revealed total 77 metabolites including carbohydrates, sugar alcohols, amino acids, fatty acids, polyamines, phenolics, terpenes and sterols. Variable importance in projection (VIP) measure of partial least squares-discriminant analysis (PLS-DA) showed that resistant and moderately resistant genotypes possessed higher intensities of ribonic acid, cinnamic acid, malic acid, squalene, xylulose, galactose, fructose, glucose, β-amyrin and hydroquinone while susceptible genotypes had higher amount of gluconic acid 2-methoxime, ribo-hexose-3-ulose and gluconic acid. Heat map analysis showed that resistant genotypes had higher intensities of β-amyrin, hydroquinone in non-infected and malic acid, squalene, putrescine and 2,3,4-trihydroxybutyric acid in infected leaves. Dendrogram analysis further separated resistant genotypes in the same cluster along with infected moderately resistant genotypes. The most significant pathways identified are: linoleic acid metabolism, flavone and flavonol biosynthesis, cutin, suberin and wax biosynthesis, pentose and glucuronate interconversions, starch and sucrose metabolism, stilbenoid biosynthesis and ascorbate and aldarate metabolism. Targeted metabolite analysis further confirmed that resistant genotypes possessed higher content of primary metabolites sucrose, glucose, fructose, malic acid and citric acid. Moreover, resistant genotypes possessed higher content of salicylic, coumaric, ferulic, cinnamic, gallic acid (phenolic acids) and kaempferol, quercetin and catechin (flavonols). Thus metabolites having higher accumulation in resistant genotypes can be used as biomarkers for screening of LSS resistant germplasm. These results unravel that higher amount of primary metabolites leads to stimulate the accumulation of more amounts of secondary metabolites such as phenolic acid, flavanols, stilbenes and terpenoids (squalene and β-amyrin) biosynthesis which are ultimately involved in defense mechanism against LLS pathogen.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-00985-5.     

国际水稻白叶枯病圃种质资源在华南的抗性评价和利用

在华南生态稻区鉴定评价2270份国际水稻品种资源对白叶枯病的抗性,结果表明参试材料对华南优势致病菌系Ⅳ型菌的抗性,高抗（1级）500个占22.03%,抗（3级）617个占27.18%,中感（5级）355个占15.64%,感（7级）373个占16.43%,高感（9级）425个占18.72%;对华南强毒菌系Ⅴ型菌的抗性,高抗（1级）131个占8.23%,抗（3级）322个占20.23%,中感（5级）292个占18.34%,感（7级）422个占26.50%,高感（9级）425个占26.70%;对Ⅳ和Ⅴ型菌双抗的有411份,占25.82%。 筛选出BG1222、IRBB5、IRBB7、IRBB203等一批抗病兼有较好农艺性状的水稻品种资源抗性遗传分析,发现BG1222携带抗病新基因,并定位于第1染色体上;抗源创新利用,育成一批优质抗病新品系,其中利用IRBB5（xa5）育成华南首个抗白叶枯病强毒菌系Ⅴ型菌优质水稻新品种白香占。     

Resistance in groundnut (Arachis hypogaea L.) to Aphis craccivora (Koch).

The behaviour, development and reproductive capacity of Aphis craccivora, vector of a number of groundnut viruses, are compared on a range of susceptible and resistant genotypes. Field trials demonstrated no significant difference between genotypes in the rate of arrival of alates, but population development was slower, and subsequent population decline faster, on the genotype EC 36892 (ICG 5240). Behavioural studies in the screenhouse, likewise showed no inhibition to alighting onto EC 36892 though choice tests demonstrated a significant redistribution of the population in favour of the susceptible genotype TMV 2 (ICG 221) over the following 10 h. In clip cage experiments, development was faster and nymphal numbers were higher on the genotype TMV 2 compared to EC 36892.     

小麦抗旱种质资源的遗传多样性

在雨养和灌水条件下,田间栽培小麦抗旱材料。根据结实器官建成与物候期、生育期的对应关系,通过供试材料产量构成因素的旱、水表现,分析在各因素形成时期的抗旱性。分别以抗旱系数和抗旱指数作为评价抗旱性的指标,通过聚类分析供试材料的遗传多样性。结果发现有些材料表现为全生育期抗旱,而有些材料只在苗期、拔节期、开花期和灌浆期等一个或几个生育时期表现抗旱;有的材料表现为抗旱高产,但有的材料产量水平较低;同时还发现部分抗旱种质资源在灌水条件下有较大的增产潜力。