A leaf rust resistance gene, different from Lr34, associated with leaf tip necrosis in wheat

The gene Lr34 has contributed to durable resistance to leaf rust caused by Puccinia triticina in wheat worldwide. The closely associated leaf tip necrosis is generally used as the gene's marker. Lr34 has been postulated in many Indian bread wheat cultivars including ‘C 306’, based on the associated leaf tip necrosis and a few other field and glasshouse observations. The present study showed monogenic control of adult‐plant resistance in ‘C 306’ to leaf rust pathotype 77‐5 (121R63‐1). The F₂ segregation in the crosses between ‘C 306’ and the two known carriers of Lr34, ‘Line 897’ and ‘Jupateco 73’‘R’ fitted a digenic ratio. The F₃ families derived from the susceptible F₂ segregants were true breeding for susceptibility, proving the absence of Lr34 in ‘C 306’. The cross between ‘Line 897’ and ‘Jupateco 73’‘R’ did not segregate for susceptibility. Resistance in the cross ‘Agra Local’ (susceptible) × ‘C 306’ was associated with leaf tip necrosis, showing that the leaf rust resistance gene in ‘C 306’ was associated with leaf tip necrosis, but was different from Lr34. This gene is being temporarily designated as Lr‘C 306’. Hence, leaf tip necrosis cannot be considered as an exclusive marker for selecting Lr34 in wheat improvement.     

Genotypic difference for the susceptibility of Japanese, Chinese and European pears to Venturia nashicola, the cause of scab on Asian pears

Venturia nashicola, the cause of scab on Asian pears, is distinct from Venturia pirina, a causal fungus of European pear scab. Although scab caused by V. nashicola is one of the most serious diseases in the Japanese pear (Pyrus pyrifolia Nakai var. culta Nakai), information available regarding resistant breeding against V. nashicola is limited. In this study, 12 genotypes of Japanese pear, seven genotypes of Chinese pear (Pyrus ussuriensis Maxim.) and four genotypes of European pear (Pyrus communis L. var. sativa DC.) and/or their offspring were evaluated for susceptibility to V. nashicola with leaf and fruit inoculation tests. At 30–40 days after full bloom in their developmental stage, unfolded young leaves and fruit were inoculated with conidial suspensions of V. nashicola for each genotype, and the responses were rated at 30 days postinoculation for the inoculated leaves and at 42 days postinoculation for the inoculated fruits. No visible symptoms were found in European pear ‘Bartlett’ and ‘La France’ and their respective offspring ‘290‐36’ and ‘282‐12’, in the Japanese pear ‘Kinchaku’ and in the Chinese pears ‘Cangxili’ and ‘Hongli’; these genotypes were evaluated as highly resistant to V. nashicola. Necrotic lesions without sporulation were observed in the Chinese pears ‘Qiubaili’, ‘Manyuanxiang’, ‘Yuanbali’ and ‘Xiangyali’, which were regarded as resistant. Sporulating lesions were formed on the other genotypes, such as the major Japanese pear cultivars ‘Kosui’ and ‘Nijisseiki’, which were regarded as susceptible. The response of inoculated leaves coincided well with that of inoculated fruit for each genotype. When the severity of scab symptoms on scab‐susceptible genotypes was further rated with disease severity (DS) values, a genotypic difference was observed for overall DS values in a successive 2‐year measurement among the susceptible genotypes. Based on the DS values of leaf and fruit scabs, the Japanese pears ‘Niitaka’, ‘Shinko’, ‘Nijisseiki’, ‘Gold Nijisseiki’, ‘Osa Nijisseiki’ and ‘Shinsui’ were considered to be less susceptible to V. nashicola than the typical susceptible cultivar ‘Kosui’.     

Genetic basis of seedling-resistance to leaf rust in bread wheat 'Thatcher'

The bread wheat cultivar ‘Thatcher’ is documented to carry the gene Lr22b for adult‐plant resistance to leaf rust. Seedling‐resistance to leaf rust caused by Puccinia triticina in the bread wheat cultivar ‘Thatcher’, the background parent of the near‐isogenic lines for leaf rust resistance genes in wheat, is rare and no published information could be found on its genetic basis. The F₂ and F₃ analysis of the cross ‘Agra Local’ (susceptible) × ‘Thatcher’ showed that an apparently incompletely dominant gene conditioned seedling‐resistance in ‘Thatcher’ to the three ‘Thatcher’‐avirulent Indian leaf rust pathotypes – 0R8, 0R8‐1 and 0R9. Test of allelism revealed that this gene (temporarily designated LrKr1) was derived from ‘Kanred’, one of the parents of ‘Thatcher’. Absence of any susceptible F₂ segregants in a ‘Thatcher’ × ‘Marquis’ cross confirmed that an additional gene (temporarily designated LrMq1) derived from ‘Marquis’, another parent of ‘Thatcher’, was effective against pathotype 0R9 alone. These two genes as well as a second gene in ‘Kanred’ (temporarily designated LrKr2), which was effective against all the three pathotypes, but has not been inherited by ‘Thatcher’, seem to be novel, undocumented leaf rust resistance genes.     

Nature's Concept. The ‘New Agriculture’ amidst Ecology,Economy and the Demythologization of the Gene

From worldwide discussions about the limits of agriculture has arisen a powerful vision of sustainable development. Phrases like ‘limitation’, ‘sustainability’, ‘sufficient supply’, ‘fair distribution’ and ‘productivity of resources’ are no longer hindrances but guidelines for a fairer and safer world. ‘Nature's Concept' focuses on biological and ecological principles. On this basis, criteria of action have to be defined in order to determine long‐term economic consequences of agri‐production. The costs of destruction of natural resources, such as reduction of genetic resources, changes to the world climate and soil degradation, are inestimably large. The long‐term effects show the real substance of the agri‐shift and the demands on research. The solution for sustainable agriculture is more than ever a scientific development of ‘tools’ for a sensible management of resources. Gene technology may be an option to reduce the ecological risks of agriculture, especially those of devastating land use. For this purpose, new education programmes with international links and interventions by states are crucial in order to solve conflicts when short‐term interests interfere with long‐term ecological values. The international agri‐centres could have a further impact to guarantee access to new techniques for all countries. Thus agriculture could finally become a major pillar in a fair world order.     

'Francolí', a late flowering almond cultivar re-classified as self-compatible

To verify the compatibility behaviour of the almond cultivar ‘Francolí’ and to clarify its S genotype a combination of pollination tests, stylar ribonuclease and allele specific PCR analysis was used. ‘Francolí’ was released from IRTA's breeding programme in 1994, having been putatively raised from the cross ‘Cristomorto’ (S₁S₂) × ‘Gabaix’ (S₁₀S₂₅). This cultivar was also reported to be self‐incompatible but revealing only one S band in the zymograms after S‐RNases analysis. ‘Francolí’ sets nuts after test crossing with two S₁S₂₅ cultivars, having a different genotype from that earlier reported. ‘Francolí’ was also observed to be self‐compatible after selfing flowers in the field and in the laboratory. ‘Francolí’ was re‐assigned the S₁S_f genotype after test crossing, stylar ribonuclease and PCR data analysis. After microsatellite analysis, the self‐compatible ‘Tuono’ (S₁S_f) cultivar is suggested as the male parent of ‘Francolí’ instead of the earlier reported ‘Gabaix’.     

Abiotic stresses,constraints and improvement strategies in chickpea

Chickpea (Cicer arietinum L.) is cultivated mostly in the arid and semi‐arid regions of the world. Climate change will bring new production scenarios as the entire growing area in Indo–Pak subcontinent, major producing area of chickpea, is expected to undergo ecological change, warranting strategic planning for crop breeding and husbandry. Conventional breeding has produced several high‐yielding chickpea genotypes without exploiting its potential yield owing to a number of constraints. Among these, abiotic stresses include drought, salinity, water logging, high temperature and chilling frequently limit growth and productivity of chickpea. The genetic complexity of these abiotic stresses and lack of proper screening techniques and phenotyping techniques and genotype‐by‐environment interaction have further jeopardized the breeding programme of chickpea. Therefore, considering all dispiriting aspects of abiotic stresses, the scientists have to understand the knowledge gap involving the physiological, biochemical and molecular complex network of abiotic stresses mechanism. Above all emerging ‘omics’ approaches will lead the breeders to mine the ‘treasuring genes’ from wild donors and tailor a genotype harbouring ‘climate resilient’ genes to mitigate the challenges in chickpea production.     

Genetic analysis of resistance to green leafhopper, Nephotettix virescens (Distant), in three varieties of rice

The genetics of resistance to green leafhopper, Nephotettix virescens (Distant), in rice varieties ‘IR36’ and ‘Maddai Karuppan’ and breeding line ‘IR20965‐11‐3‐3’ was studied. The reactions of F₁ hybrids, F₂ populations and F₃ lines from the crosses of test varieties with the susceptible variety ‘TN1’ revealed that resistance in ‘IR36’ and ‘Maddai Karuppan’, is governed by single recessive genes while resistance in ‘IR20965‐11‐3‐3’ is controlled by a single dominant gene. Allele tests with the known genes for resistance to green leafhopper revealed that the recessive gene of ‘IR36’ is different from and inherited independently of Glh1, Glh2, Glh3, Glh4, Glh5, Glh8 and Glh9t. This gene is designated as glh10t. The recessive gene of ‘Maddai Karuppan’ and the dominant gene of ‘IR20965‐11‐3‐3’ are also non‐allelic to Glh1, Glh2, Glh3, Glh4, Glh5 and Glh8t. Thus, the dominant gene of IR20965‐11‐3‐3 is designated as Glh11t. The allelic relationships of the recessive gene of ‘Maddai Karuppan’ with glh8 and glh10t should be investigated.     

The linkage between the stem rust resistance gene Sr2 and pseudo-black chaff in wheat can be broken

Recessively inherited gene Sr2 has provided the basis of durable resistance to stem rust (caused by Puccinia graminis tritici) in wheat (Triticum aestivum L.) worldwide. The associated earhead and stem melanism or ‘pseudo‐black chaff’ is generally used as a marker for this gene. Sr2 has been postulated in many wheat cultivars of India including ‘Lok 1’, based on associated pseudo‐black chaff in adult plants, and leaf chlorosis in seedlings. However, dominant inheritance of the resistance factor operating in ‘Lok 1’, and a 13 : 3 (resistant : susceptible) F₂ segregation in the ‘Sr2‐line’ (‘Chinese Spring’⁶ × ‘Hope’ 3B) × ‘Lok 1’ cross confirmed that Sr2 was absent in ‘Lok 1’. Susceptible plants with a pseudo‐black chaff phenotype were observed in F₂ populations of ‘Agra Local’ (susceptible) × ‘Lok 1’, and the ‘Sr2‐line’ × ‘Lok 1’ crosses. Most of the F₃ families derived from the susceptible F₂ segregants with pseudo‐black chaff phenotypes were true breeding for the expression of pseudo‐black chaff with susceptibility to stem rust. Thus, linkage of pseudo‐black chaff with Sr2 in wheat can be broken, and hence, caution may be exercised in using pseudo‐black chaff as a marker for selecting Sr2 in breeding programmes.     

Genotype analysis of the wheat semidwarf Rht‐B1b and Rht‐D1b ancestral lineage

In wheat, semidwarfism resulting from reduced height (Rht)‐B1b and Rht‐D1b was integral to the ‘green revolution’. The principal donors of these alleles are ‘Norin 10’, ‘Seu Seun 27’ and ‘Suwon 92’ that, according to historical records, inherited semidwarfism from the Japanese landrace ‘Daruma’. The objective of this study was to examine the origins of Rht‐B1b and Rht‐D1b by growing multiple seed bank sources of cultivars comprising the historical pedigrees of the principal donor lines and scoring Rht‐1 genotype and plant height. This revealed that ‘Norin 10’ and ‘Suwon 92’ sources contained Rht‐B1b and Rht‐D1b, but the ‘Seu Seun 27’ source did not contain a semidwarf allele. Neither Rht‐B1b nor Rht‐D1b could be definitively traced back to ‘Daruma’, and both ‘Daruma’ sources contained only Rht‐B1b. However, ‘Daruma’ remains the most likely donor of Rht‐B1b and Rht‐D1b. We suggest that the disparity between historical pedigrees and Rht‐1 genotypes occurs because the genetic make‐up of seed bank sources differs from that of the cultivars actually used in the pedigrees. Some evidence also suggests that an alternative Rht‐D1b donor may exist.     

Fine mapping of qSS‐9, a major and stable quantitative trait locus,for seed storability in rice (Oryza sativa L.)

Seed storability in rice (Oryza sativa L.) is an important agronomic trait. We previously showed a quantitative trait locus of seed storability, qSS‐9, on chromosome 9 in a backcross population of ‘Koshihikari’ (japonica) / ‘Kasalath’ (indica) // ‘Koshihikari’. In this study, fine mapping of the chromosomal location of qSS‐9 was performed. Effect of ‘Kasalath’ allele of qSS‐9 was validated using a chromosome segment substitution line, SL36, which harboured the target quantitative trait loci (QTL) from ‘Kasalath’ in the genetic background of ‘Nipponbare’ under different ageing treatments in different environments. Subsequently, an F₂ population from a cross between ‘Nipponbare’ and SL36 was used for fine mapping of qSS‐9. Simultaneously, four subnear isogenic lines (sub‐NILs) that represented different recombination breakpoints across the qSS‐9 region were developed from F₃ progeny. Finally, the qSS‐9 locus was located between the Indel markers Y10 and Y13, which delimit a region of 147 kb in the ‘Nipponbare’ genome. These results provide a springboard for map‐based cloning of qSS‐9 and possibilities for breeding rice varieties with strong seed storability.     

Evaluation of resistance to sharka (Plum pox virus) of several Prunus rootstocks

Sharka (Plum pox virus, PPV) severely affects the production of most Prunus species in the areas affected by the disease. In this study, the resistance of 15 Prunus rootstocks to a Dideron type isolate of PPV was evaluated under controlled conditions in an insect‐proof greenhouse. After four cycles of study,‘GF677’ almond x peach hybrid,‘Myrobolan 29C plum and ‘L2’ cherry did not show any symptoms and were ELISA‐DASI and RT‐PCR negative. These were considered resistant to PPV. The rest of the rootstocks assayed showed symptoms of sharka (confirmed by ELISA‐DASI or RT‐PCR), although the level of susceptibility was different for each rootstock.‘GF305’ peach, ‘Puebla de Soto’ plum and ‘Real Fino’ apricot, were highly susceptible to PPV, showing strong sharka symptoms and being ELISA and RT‐PCR positive. ‘Marianna 2624’ plum,‘AC 9921‐07’ hybrid and ‘CP‐2’ plum showed susceptibility to PPV confirmed by ELISA‐DASI and RT‐PCR positives.‘Nemaguard’ and ‘Nemared’ hybrids, ‘Torinel’ plum and ‘STN2’ hybrid showed an intermediate susceptibility to PPV with slight sharka symptoms and were ELISA‐DASI and RT‐PCR positive. Whereas, ‘Montclar’ peach and ‘Evrica’ hybrid showed moderate resistance to PPV with slight sharka symptoms and were ELISA positive but RT‐PCR negative. The results open new possibilities in the search for different sources of resistance to PPV within Prunus.     

Evaluation of cold hardiness in two sets of near-isogenic lines of wheat (Triticum aestivum) with polymorphic vernalization alleles

In wheat, variation at the orthologus Vrn‐1 loci, located on each of the three genomes, A, B and D, is responsible for vernalization response. A dominant Vrn‐1a allele on any of the three wheat genomes results in spring habit and the presence of recessive Vrn‐1b alleles on all three genomes results in winter habit. Two sets of near‐isogenic lines (NILs) were evaluated for DNA polymorphisms at their Vrn‐A1, B1 and D1 loci and for cold hardiness. Two winter wheat cultivars, ‘Daws’ and ‘Wanser’ were used as recurrent parents and ‘Triple Dirk’ NILs were used as donor parents for orthologous Vrn‐1 alleles. The NILs were analysed using molecular markers specific for each allele. Only 26 of 32 ‘Daws’ NILs and 23 of 32 ‘Wanser’ NILs had a plant growth habit that corresponded to the marker genotype for the markers used. Freezing tests were conducted in growth chambers programmed to cool to ?21.5°C. Relative area under the death progress curve (AUDPC), with a maximum value of 100 was used as a measure of death due to freezing. The average relative AUDPC of the spring habit ‘Daws’Vrn‐A1a NILs was 86.15; significantly greater than the corresponding winter habit ‘Daws’Vrn‐A1b NILs (42.98). In contrast, all the ‘Daws’Vrn‐A1bVrn‐B1aVrn‐D1b and Vrn‐A1bVrn‐B1bVrn‐D1a NILs (spring habit) had relative AUDPC values equal to those of their ‘Daws’ sister genotypes with Vrn‐A1bVrn‐B1bVrn‐D1b NILs (winter habit). The average AUDPC of spring and winter habit ‘Wanser’ NILs differed at all three Vrn‐A1, Vrn‐B1 and Vrn‐D1 locus comparisons. We conclude that ‘Daws’ and ‘Wanser’ have different background genetic interactions with the Vrn‐1 loci influencing cold hardiness. The marker for Vrn‐A1 is diagnostic for growth habit and cold hardiness but there is no relationship between the Vrn‐B1 and Vrn‐D1 markers and the cold tolerance of the NILs used in this study.     

Inheritance of resistance to the 'Kanpur' race of Phytophthora drechsleri in pigeonpea

Phytophthora drechsleri causes stem blight, which is one of the most serious diseases of pigeonpea. Eight races of this fungus have been identified, but the inheritance of resistance to all these races is not clear except for race P2. This study examined the inheritance of resistance to race ‘Kanpur’ (KPR) of P. drechsleri in eight crosses involving four resistant parents, viz.‘KPBR 80‐2‐1′, ‘KPBR 80‐2‐2′, ‘Hy 3C and ‘BDN 1′, and two susceptible parents, viz.‘Bahar’ and ‘PDA 10′. The reactions of the parental lines, and their F₁, F₂ and backcross generations were studied in an infected plot. In the F₁ generation of all crosses, a susceptible reaction was observed that indicated dominance of susceptibility over resistance. The segregation pattern in F₂ indicated that two homozygous recessive genes (pdr₁pdr₁pdr₂pdr₂) were responsible for imparting resistance in the parents, ‘KPBR 80‐2‐1’ and ‘KPBR 80‐2‐2′, and that a single homozygous recessive gene (pdrpdr) was responsible for resistance in the parents ‘Hy 3C and ‘BDN 1′. Therefore, ‘KPBR 80‐2‐1’ and ‘KPBR 80‐2‐2’ with two genes for resistance are better donors because the resistance transferred from them will be more durable compared with ‘Hy3C and ‘BDN1’ with only one gene for resistance.     

The inheritance of resistance to the blossom weevil, Anthonomus rubi, in the cultivated strawberry, Fragaria×ananassa

The objective of this research was to determine which strawberry germplasm could be used to combine late flowering with reduced susceptibility to the strawberry blossom weevil, Anthonomus rubi. Seven cultivars and three breeding lines were compared for their susceptibility to A. rubi, by introducing adult weevils onto detached inflorescences. No consistent differences were detected but this contradicted observations from field trials. Five late‐flowering strawberry genotypes were crossed in a half‐diallel programme and progeny were tested for their susceptibility to A. rubi by using detached inflorescences and in a field trial where plants were exposed to a natural infestation. There was good correspondence between the results from the two methods and heritable differences were detected in both experiments, with the additive genetic variance being the more important. The cultivars ‘Idea’ and ‘Alice’ were identified as promising parents for reduced susceptibility while progeny from ‘Sophie’ were most likely to be susceptible.     

Genetic control of crossability of triticale with rye

Limited genetic knowledge is available regarding crossability between hexaploid triticale (2n= 6x= 42, 21″, AABBRR, amphiploid Triticum turgidum L.‐Secale cereale L.) and rye (2n= 14, 7″, RR). Our objectives were to determine (1) the crossability between triticales and rye and (2) the inheritance of crossability between F₂ progeny from intertriticale crosses and rye. First, ‘8F/Corgo’, a hexaploid triticale, was crossed as a female with two landrace ryes, ‘Gimonde’ and, ‘Vila Pouca’ and two derived north European cultivars, ‘Pluto’ and ‘Breno’. These crosses produced 21.7, 20.9, 5.9, and 5.6%, seed‐set or crossability, respectively, showing that the landrace ryes produced higher seed‐set than the cultivars. Second, ‘Gimonde’ rye was crossed as a male with four triticales for 3 years. The control cross, ‘Chinese Spring’ wheat × rye, produced 80‐90% seed‐set. Of the four triticales, ‘Beagle’ produced 35.7‐56.8% seed‐set. The other three triticales produced less than 20% seed‐set, showing that the triticales differ in crossability with ‘Gimonde’ rye. Third, six FiS from intertriticale crosses (‘8F/Corgo’בBeagle’, ‘Beagle’בCachirulo’, ‘Lasko’בBeagle’, ‘8F/Corgo’בCachirulo’, ‘Lasko’בCachirulo’, ‘Lasko’ב8F/Corgo’) were crossed to ‘Gimonde’ rye. Results indicated that lower crossability trait was partially dominant in the two F₁S from crosses involving ‘Beagle’(high crossability) with‘8F/Corgo’ and ‘Cachirulo’(low crossability) and completely dominant in the ‘Beagle’בLasko’ cross, as it happens in wheat. Fourth, segregants in four F₂ populations (‘Lasko’בBeagle’, ‘8F/Corgo’בBeagle’, ‘Lasko’ב8F/Corgo’, and‘8F/Corgo’בCachirulo’) were crossed with rye. Segregation for crossability was observed, although distinct segregation classes were blurred by environmental and perhaps other factors, such as self‐incompatibility alleles in rye. Segregation patterns showed that ‘Beagle’, with high crossability to rye, carries either Kr1 or Kr2. The three triticales with low crossability with rye were most likely homozygous for Kr1 and Kr2. Therefore, it is likely that the Kr loci from A and B genomes acting in wheat also play a role in triticale × rye crosses.     

A contribution to the systematics of a piedmontese plum ecotype

Prunus domestica L., P. insititia L., P. salicina Lindl. and P. cerasifera Ehrh. are the most important species included in the plum group. Many ‘cultivars’ have an undefined origin and share very similar morpho‐phenological characteristics that make their identification difficult. This is the case of ‘Ramasin’, a group of Piedmontese genotypes whose fruits are small, ellipsoidal and very tasty. They are commonly considered as P. domestica varieties, even though on the basis of some morphological characteristics they are similar to other species such as P. insititia. In order to study the origin of this group, the DNA of 25 genotypes of ‘Ramasin’, and that of some ‘cultivars’ of P. domestica, P. insititia, P. cerasifera, P. salicina and two selections of P. spinosa L. was examined. The PCR‐RAPDs method (Random Amplified Polymorphic DNA amplified by Polymerase Chain Reaction) was used and all 69 primers that were tested generated more or less polymorphic bands. From the results of these analyses it can be supposed that the ‘Ramasin’ plums are a single genetically heterogeneous group. Moreover it can probably be assumed that ‘Ramasin’ arose from crosses between P. domestica and P. insititia.     

Arsenic Stress in Plants

Being a toxic metalloid and group I carcinogen, Arsenic (As) poses a threat to plants, especially to crops which are consumed by human beings, and sooner or later results in hyper/hypopigmentation and skin cancer. It is a well‐known fact that South‐East Asia is suffering from groundwater As contamination, and according to a recent report, the contamination has been found also in Hungary, Mexico, Argentina, Australia, United States, etc. Thus, As contamination has become a global problem. As is toxic even at low concentration because it has no known function as nutrients. Arsenite (III) and arsenate (V) are the main phytoavailable forms of inorganic arsenic. Being analogous to phosphate, As(V) is transported by a phosphate‐cotransport system in plants, whereas As(III) is transported through ‘OsNIP2.1’ (member of aquaporin superfamily) in rice. Besides, ‘AsSe1’ (As‐accumulation gene), ‘AsTol’ (As‐tolerance gene) and ‘OsACR2.1’ (an arsenate reductase gene) have also been identified. The production of phytochelatins (PCs), a metal‐binding thiol peptide, in response to As stress may hold a way of proper As tolerance in plants but still needs a thorough study. However, with the proper knowledge of arsenic speciation, transportation, accumulation, overexpression in crop plants may result in ways to develop arsenic tolerant transgenics.