Number Of Resistant Plants Research Articles

Parent-offspring regression and intergeneration correlation analysis in powdery mildew resistance derived F4 and F5 generations of oat

The present investigation was undertaken to determine the intergeneration correlation and parent-offspring regression in F4 and F5 generations of seven different oat crosses which were grown during Rabi 2019-20 and 2020-21, respectively, at Experimental Farm of Fodder Section, CSKHPKV, Palampur. Correlation studies revealed a negative correlation between crude protein yield per plant with grain yield per plant in F5 generation and a positive correlation between fresh fodder yield per plant and dry matter yield per plant in both generations, revealing crude protein yield as major forage yield component. F4 generation progenies showed highly significant and positive values of intergeneration correlation and regression with F5 generation progenies for grain yield per plant, crude protein yield per plant, harvest index and number of tillers per plant in most of the crosses, which indicated that the performance of plants on the basis of these traits is a reliable indicator of their performance in subsequent generations. Narrow sense heritability increased with the advancement of generation from F4 to F5, indicating the additivity of gene effects for the traits such as grain yield per plant, 100-grain weight, harvest index and crude protein yield per plant. Two progenies P4-5-2 -5 and P4-5-2-8 of the cross HJ-8 × JPO-46 were resistant to powdery mildew disease in F5 generation and the number of resistant plants was more in F5 generation over F4 generation which showed the efficiency of selection for resistance to powdery mildew.

Resistance of Eucalyptus pellita to rust (Puccinia psidii)

Eucalypts rust (Puccinia psidii) is currently one of the major diseases in commercial eucalypt plantations in Brazil. The primary method of disease control is the use of resistant genotypes, and, among the different species of Eucalyptus, E. pellita is indicated as a promising source of resistance. In this work, the genetic control of rust resistance in E. pellita through inoculations under controlled conditions of 441 plants from four full-sibling families was studied. Inoculations were performed using the monopostular isolate UFV-2, race 1. All families tested segregated for rust resistance, and the number of resistant plants was higher than susceptible in all crosses. Inheritance models based on few genes did not fully explain the observed segregation patterns, and the narrow-sense heritability of rust resistance was estimated between 32.7% and 37.3%. The results suggested that rust resistance in E. pellita is complex and is controlled by major- and minor-effect genes.

INHERITANCE OF RESISTANCE TO PStV IN TRANSGENIC PEANUTS CONTAINING cp PStV GENE

Inheritance of Resistance to PStV in Transgenic Peanuts Containing cp PStV Gene. We have obtained transgenic peanut lines containing coat protein gene of PStV. To get maximal use of the transgenic character in a breeding program, it is necessary that the transgene is also stably inherited and expressed. This experiment was conducted from June 2002 – January 2005 at Plant Molecular Biology Laboratory, Bogor Agricultural University, and Queensland Agricultural Biotechnology Center, The University of Queensland, Australia. The research aimed (1) to test whether PStV cp transgene was functional in progenies derived from crosses between transgenic peaanut plants containing PStV cp gene and non-transgenic ones and (2) to determine pattern of inheritance of resistance to PStV as a result of PStV cp gene action. Several crosses were made between trangenic peanut cv.Gajah resistant to PStV (T4 generation) and non-transgenic peanut line WS susceptible to PStV. The F1 and F2 populations were mechanically inoculated with PStV two weeks after planting. The experiment showed that all plants in the F1 population were less susceptible to PStV, suggesting that the transgene was partially dominant. Phenotipic segregation in F2 population was not Mendelian with the appearance of quick and slow recovery plants and the number of resistant plants being more than expected. However, the proportion of transgenic and non-transgenic plants followed 3:1 ratio, which was Mendelian.

Influence of Coat Protein Transgene Copy Number on Resistance in Transgenic Line 63-1 against Papaya Ringspot Virus Isolates

Line 63-1 is a `Sunset'-derived transgenic papaya expressing the coat protein (CP) gene from a mild mutant of a Hawaiian isolate of Papaya ringspot virus (PRSV). Previous work showed that line 63-1 R1 plants exhibited a range of resistance to severe PRSV isolates from Hawaii (HA), Jamaica (JA), Thailand (TH), and Brazil (BR). Genetic and molecular data obtained in this study confirm that line 63-1 has two CP transgene insertion sites; segregation analysis shows that the CP and the npt II genes are present at both loci. To study the potential effect of gene dosage on resistance, various populations of R1, R2, and R3 seedlings were challenged by PRSV HA, BR, and TH. A R1 population obtained by self-pollination of line 63-1 hermaphrodite R0 plant exhibited resistance to all three isolates. The percentage of plants resistant to all three PRSV isolates increased in 63-1-derived populations as a result of recurrent selection. Additional genetic studies demonstrate that the number of resistant plants in a 63-1-derived population is directly correlated with the number of plants with multiple transgene copies. We conclude that transgene dosage plays a major role in affecting the resistance of 63-1 to PRSV isolates from various geographical locations.

Field Reactions of Segregating Populations of Interspecific Hybrids of Lycopersicon Species to Natural Infection by Xanthomonas campestris pv. vesicatoria (Doidge) Dye

The progenies arising from crosses between cultivated tomatoes and a wild relative were screened with their parents for resistance to bacterial leaf spot disease. The aim is to develop a tolerant variety that is well adapted to humid forest ecology where the disease is endemic. The results obtained showed that the cultivated varieties, Roma and Nsukka local, were highly susceptible with disease incidence of 100 per cent. The wild relative on the other hand showed a high level of resistance with a reduced disease incidence. The reactions of the backcrosses and F2 offspring were not impressive as negligible percentage of resistant plants were identified in the F2 . Plants with resistance were recovered in the F3 generation from crosses between the wild and L. esculentum indicating the possibility of transfer of gene(s) for resistance of leaf spot from the wild to the cultivated tomatoes. The increase in the number of resistant plants in this generation is an indication that genes for resistance to leaf spot can be accumulated over generations thereby increasing the selection potentials for resistance to the pathogen in higher generations.

In vitro techniques for selecting wheat (Triticum aestivum L.) for Fusarium-resistance. II. Culture filtrate technique and inheritance of Fusarium-resistance in the somaclones

Calli of resistant, intermediary and susceptible wheat (Triticum aestivum L.) varieties were selected using culture filtrates of Fusarium graminearum and F. culmorum and the regenerants were evaluated for resistance up to R3. Czapek-Dox broth medium was inoculated with mycelia of Fusarium isolates and incubated for 2–6 weeks. Filtrates were added to MS callus growing medium, then 5 weeks-old calli were transferred onto this medium (MST) for 4–5 weeks. MST containing 30% filtrate was found to be suitable for selection. Resistant calli were transferred again to fresh MST for further two selection cycles. The surviving calli produced less fertile regenerated lines (R0) than the non-selected ones. Among 18 R1 lines tested for Fusarium-resistance in the seedling stage by artificial inoculation in the greenhouse, two (11.1%) were significantly more resistant, one (5.6%) was more susceptible than the original cultivar and the rest (83.3%) behaved similarly to the donor plants. Among unselected R3 lines of three varieties, practically the same number of resistant plants were found as among the related selected ones. When the R3 selfed generations obtained through double-layer and culture filtrate selection techniques were tested for Fusarium-resistance, 35.7% of the lines were found to be more resistant than the original cultivars, none was more susceptible and 64.3% had a reaction similar to that of the source materials. Thus, inheritance of the disease reaction was not stable in all cases. Success of in vitro selection for Fusarium-resistance depended also on the genotype, and toxin analysis showed that although being effective, the selective media contained deoxynivalenol only exceptionally. In selecting wheat for Fusarium-resistance in vitro, the culture filtrate technique proved better than the double-layer procedure.

Monosomic analysis of stem rust resistance in the wheat cultivar Almus

Monosomic analysis of resistance to stem rust, race 11 (isolate G 425) was carried out in the cultivar Almus (GDR) possessing a 1B/1R translocation. F2 progenies of monosomic and disomic F1 plants of Almus crossed with 21 monosomic lines of Chinese Spring were tested. Two lines (1B and 6B) differed significantly from the disomic segregation ratio by a higher number of resistant plants and two other lines (1D and 6A) by a lower number of resistant plants. The results fitted a hypothesis comprising the interaction of two genes for resistance and two inhibitors.

Influence of Soil pH and Calcium Nutrition on Resistance of Alfalfa to Bacterial and Verticillium Wilt

Alfalfa plants of a resistant, a susceptible and a highly susceptible strains were grown in unlimed soil at pH 5.8 and in limed one at pH 6.9 and inoculated by the pathogens of vascular wilt, Corynebacterium insidiosum and Verticillium albo-atrum. Two types of liming were performed: 1) before inoculation and 2) after inoculation. Liming of the soil led to an increase in number of resistant plants. In susceptible plants the external symptoms of disease on the plant tops were delayed or alleviated. This phenomen was more conspicuous with Verticillium wilt than with bacterial wilt. The favourable effect of liming was less distinct in resistant strains than in susceptible ones. For an increase in resistance, post-infection liming of the soil was more effective in the case of bacterial wilt, while pre-infection liming provided the best results in the Verticillium wilt. The nitrogen content in the dry matter of roots from plants grown in limed soil was higher by more than a quarter as compared to roots from plants growing in unlimed soil.