MOLECULAR CHARACTERIZATION OF BROWN PLANTHOPPER Nilaparvata lugens (Stål) POPULATIONS IN TELANGANA STATE AND IDENTIFICATION OF GENES FOR BPH RESISTANCE

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Date
2022-01-03
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PROFFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Abstract
The present studies were conducted at ICAR-Indian Institute of Rice Research, Rajendranagar and Central Instrumentation Cell, College of Agriculture, Rajendranagar to study the spectrum of virulence, morphometrics, molecular characterization and clustering of brown planthopper (BPH) Nilaparvata lugens (Stål) (Delphacidae: Hemiptera) populations collected from Telangana state. Resistance sources were identified and characterization of resistance gene (s) for BPH in germplasm accessions was carried out. Mechanisms of resistance were studied in the selected rice gene differentials and germplasm accessions. A total of thirty two rice gene differentials with known and unknown genetics were evaluated for their resistance to nine brown planthopper populations collected from different districts of Telangana i.e., Adilabad, Khammam, Karimnagar, Mahbubnagar, Medak, Nalgonda, Nizamabad, Rangareddy, Warangal along with IIRR glasshouse population by adopting internationally accepted Standard Seedbox Screening Test (SSST) and scored on 0-9 scale by following the IRRI method of Standard Evaluation System (SES) for rice. Among thirty two rice gene differentials tested, 3 gene differentials viz., PTB 33, RP 2068-18-3-5 and RPBio4918-230S were categorized as resistant (DS 1.0 to 3.0), 13 as moderately susceptible (DS 5.1 to 7.0), 15 as susceptible (DS 7.1 to 8.9) and 1 gene differential as highly susceptible (DS 9.0) to brown planthopper populations. Among all the BPH populations, Medak BPH population was found highly virulent (DS 7.46) and least virulent was Mahbubnagar population (DS 6.34). In the resistant gene differentials, PTB 33 and RP 2068-18-3-5 the feeding was less in terms of low honeydew excretion and more number of probing marks suggesting antixenosis mechanism of resistance for feeding. Brown planthopper adults probed more number of times and fed more and excreted more honeydew compared to nymphs. The resistant gene differentials viz., RP 2068-18-3-5, RP BIO 4918-230S showed less nymphal survival (%), low growth index, highest proportion of males (%) indicating antibiosis mechanism of resistance. The sex ratio in most of the BPH populations was in favour of females. The proportion of macropterous adults was more than brachypterous adults in the BPH populations. The macropterous females emerged in more numbers compared to brachypterous females, macropterous males and brachypterous males. In general, the brachypterous females weighed more compared to macropterous females, macropterous males and brachypterous males. The gene differential, RP BIO 4918-230S revealed longest nymphal duration and more number of days to wilt indicating the antibiosis and tolerance mechanisms of resistance. The damage score has a positive correlation with fecundity, honeydew excretion and adult body weights. The damage score is negatively correlated with probing marks, days to wilting, nymphal duration, percent males and macropterous adults. Growth index has positive and significant correlation with nymphal survival. The measurements such as total length of the body, width of the body, length of wings, width of the wing, interocular distance, antennal length and tibial spur length of adult Brachypterous and macropterous forms of females and males were recorded. On an average Nalgonda BPH population showed highest body length, wing length, antennal length, interocular distance, length of tibial spur and highest rostrum length. Other morphological parameters i.e., body length and width, wing length and width, antennal length, interocular distance and length of tibial spur differed among different brown planthopper populations. When both genotypic and phenotypic clusters were compared, Adilabad & Warangal populations, Nalgonda & Khammam populations and Mahbubnagar & Nizamabad populations were found to be similar, whereas, Ranga Reddy & Medak and Karimnagar & IIRR glasshouse populations differed phenotypically and genotypically. Out of thousand germplasm accessions screened, one germplasm accession IC 518805 was highly resistant (DS 0.9), eleven germplasm accessions were resistant to brown planthopper with a damage score of 1.1-3.0. The brown planthopper adults fed less and excreted less honeydew on the germplasm accession i.e., IC 515974 (22.66 mm2 ). Nymphal honeydew was low 21.33 mm2 to 49 mm2 ) on resistant and moderately resistant entries viz., PTB 33, IC 576798, IC 519101, IC 517008 and IC 518849 compared to susceptible check. Fecundity and nymphal duration were less on resistant germplasm accessions compared to susceptible ones. In general, the sex ratio was in favour of females (1.22Females:1.0Males). In the germplasm accessions, the winged females were maximum in proportion (24.57%) followed by winged males (28.50%), wingless females (26.29%) and wingless males (20.63%). In general, the macropterous females weighed more (2.95 mg) compared to brachypterous females (2.89 mg), macropterous males (1.09 mg) and brachypterous males (1.05 mg). The number of days to wilt were more in the entries IC 519101, PTB 33, IC 75778 and IC 540340(A). Molecular profiling by using 17 SSR markers for detecting 9 BPH genes revealed that the germplasm accessions viz., IC 75883, IC 75887, IC 75778, IC 75886, IC 515880, IC 517008 and IC 515974 were observed to have Bph2 gene. The germplasm accessions viz., IC 575211, IC 75778, IC 75886, IC 75883, IC 515159, IC 515880, IC 540340(A), IC 200940, IC 517008 and IC 444008 were observed to have Bph3 gene. The germplasm accessions viz., IC 519101, IC 75883, IC 575211, IC 75887, IC 75778, IC 75886, IC 515159, IC 540340(A), IC 200940, IC 517008 and IC 515974 were observed to have Bph6 gene. The germplasm accessions viz., IC 75885, IC 515159 and IC 540340(A) have Bph17 gene. IC 519101 and IC 540340(A) were found to be have Bph20 gene. Among the germplasm accessions with different genes/gene combinations, Bph6+Bph20 (IC 519101), Bph2+Bph6 (IC 515974, IC 517008 and IC 75883), Bph2+Bph6+Bph17 (RP 2068-18-3-5 and RP 4918-230-S) and Bph32+Bph17 (PTB33) showed resistant reaction. The genes/gene combinations viz., Bph3+Bph6 (200940), Bph3+Bph17 (IC 75885) and Bph2+Bph3+Bph6 (IC 75886) showed moderately resistant reaction. The identified gene differentials and germplasm accessions can be used in the breeding programmes to develop brown planthopper resistant varieties.
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