Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

Investigation into chromosome morphology of sugar beet and related wild species

Summary In the genusBeta, chromosomes at pachytene are about 10 times longer than in mitotic metaphase and show a conspicuous differentiation of chromomeres along their arms. It is shown that in sugar beet (Beta vulgaris) these chromomeres are mainly restricted to well defined blocks adjacent to the centromere regions. In the wild speciesB. procumbens, the chromomeres are found not only in the centromere regions, but also occur intercalary. In both species, conspicuous telomeres have not been observed. TentativeFeulgen-DNA measurements revealed that the difference in chromomere distribution between these species is probably not caused by significant differences in DNA amounts. As the patterns observed in sugar beet also occur in other members of the sectionVulgares and those observed inB. procumbens in the other two members of the sectionPatellares, it is hypothesized that the heterochromatin distributions are representative for the sections mentioned.

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Untersuchung zur Chromosomenmorphologie der Zuckerrübe und verwandter Wildarten

Zusammenfassung In der GattungBeta sind die Chromosomen im Pachytän etwa 10mal so lang wie in der mitotischen Metaphase und zeigen eine deutliche Differenzierung der Chromomeren entlang ihrer Arme. Es wird gezeigt, daß diese Chromomeren bei der Zuckerrübe (Beta vulgaris) hauptsächlich auf gut definierte, den Centromerregionen benachbarte Regionen beschränkt sind. Bei der WildartB. procumbens werden die Chromomeren nicht nur in den Centromerregionen gefunden, sondern sie kommen auch interkalar vor. Bei beiden Arten sind deutliche Telomeren nicht beobachtet worden. Probemessungen vonFeulgen-DNA ergaben, daß der Unterschied in der Chromomerenverteilung zwischen diesen Arten wahrscheinlich nicht durch signifikante Unterschiede im DNA-Gehalt verursacht wird. Da die bei der Zuckerrübe beobachteten Muster auch bei anderen Vertretern der SektionVulgares und die beiB. procumbens beobachteten bei den anderen beiden Vertretern der SektionPatellares auftreten, wird angenommen, daß die Heterochromatinverteilungen typisch für die erwähnten Sektionen sind.

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Beta 10 , ë . , ë (Beta vulgaris) , , , . . procumbens , . ë . , , , . , ë, Vulgares, , . procumbens — Patellares, , .

     

Genetic diversity of Fagopyrum homotropicum, a wild species related to common buckwheat

Nineteen natural populations of Fagopyrum homotropicum, a self-fertilizing close relative of common buckwheat, from the Yunnan and Sichuan provinces of China were investigated for their chromosome number and allozyme variation at 16 loci of 11 enzymes. Three populations, 'Deqin', 'Zhongdian', and 'Xiancheng', were revealed to be allotetraploid. Judging from allozyme constitution of the tetraploid and their possible progenitors, diploid progenitors are probably the diploid population of F. homotropicum from Lijiang and a natural population of F. esculentum ssp. ancestralis. Diploid populations of F. homotropicum are fixed for a given allele at almost all isozyme loci. Allozyme variation has been maintained in natural populations mainly by fixing different alleles in different populations, as they are highly differentiated among the populations (G_st = 0.969). The position of populations in the phylogenetic tree constructed from genetic distance nearly corresponded with the geographical position of the populations.     

Analysis of genetic diversity in Tunisian durum wheat cultivars and related wild species by SSR and AFLP markers

Thirty-four durum wheat cultivars representing the Tunisian durum (Triticum durum Desf.) wheat collection and seven wild species of wheat relatives (Triticum turgidum L., T. dicoccon Schrank., T. dicoccoides (Körn) Schweinf., T. araraticum Jakubz., T. monococcum L., Aegilops geniculata Roth, and Aegilops ventricosa Tausch) were analysed with amplified fragment length polymorphism (AFLP) and microsatellite (SSR) markers. Both marker systems used were able to differentiate durum wheat cultivars from the wild relatives and to specifically fingerprint each of the genotypes studied. However, the two marker systems differed in the amount of detected polymorphisms. The 15 SSR markers were highly polymorphic across all the genotypes. The total number of amplified fragments was 156 and the number of alleles per locus ranged from 3 to 24 with an average of 10.4. Two SSR markers alone, Xwms47 and Xwms268, were sufficient to distinguish all 34 durum wheat genotypes. The five AFLP primer pair combinations analysed yielded a total of 293 bands, of which 31% were polymorphic. The highest polymorphic information content (PIC) value was observed for SSRs (0.68) while the highest marker index (MI) value was for AFLPs (7.16) reflecting the hypervariability of the first and the distinctive nature of the second system. For durum wheat cultivars, the genetic similarity values varied between 31.3 and 81% for AFLPs (with an average of 54.2%), and between 3.6 and 72.7% for SSRs (with an average of 19.9%). The rank correlation between the two marker systems was moderate, with r = 0.57, but highly significant. Based on SSR markers, highest genetic similarity (GS) values were observed within the modern cultivars (37.3%), while the old cultivars showed a low level of GS (19.9%). Moreover, the modern cultivars showed low PIC and MI values. UPGMA Cluster analysis based on the combined AFLP and SSR data separated the wild wheat species from the durum wheat cultivars. The modern cultivars were separated from the old cultivars and form a distinct group.     

Conservation of wild Lilium species

This review considers the question of whether nature reserves are of practical value to horticulture, using the case of lily culture. In both agriculture and horticulture there is a constant readjustment with Nature to conquer diseases, create new plant forms, or adapt the existing cultivated forms to special conditions of soil, climate, and environment. Among the 80–90 species of Lilium the great variety in their respective flowers stands out immediately, and, with their different physiological characteristics, crossing the species leads to a wide range of different hybrids. To be able to keep up a great variety of healthy hybrids, it is necessary to maintain the original species, as they supply new genes and sometimes carry appropriate resistance-factors. Hybrids and species are complementary and not supplementary, however useful the hybrids may be. The distribution and conservation status of lily species show that they should have more protection—not only in the interest of science, education, and recreation, but also of horticulture and aesthetics.     

Resistance to Meloidogyne javanica in wild Arachis species*

The root-knot nematode, Meloidogyne javanica Race 3 is an important nematode parasite of groundnut. Greenhouse evaluation of 184 accessions of 33 wild Arachis spp. five interspecific derivatives, 18 groundnut cultivars for root damage (galls formed by nematode) and nematode reproduction demonstrated that resistance to the nematode is available in the genepool of wild Arachis spp. Seven accessions, ICG 8952 (Arachis helodes), ICC 13211 (A. sylvestris), ICG 13224 (A. kretscmeri), ICG 13231 (Arachis sp.), ICG 14862 (A. kuhlmannii), ICG 14868 (A. stenosperma), and ICG 14915 (A. sylvestris) were highly resistant to nematode reproduction and root damage. There was no gall and eggmass formation on any plant of these accessions. Thirty-three accessions were resistant and 14 were moderately resistant. All the tested accessions of A. monticola, A. benensis, A. ipaensis, A. hoehnei, A. kempff-mercadoi, A. valida, A. chiquitana, A. rigonii, A. vallsii, A. dardani, A. paraguariensis, A. triseminata, interspecific derivatives, and groundnut cultivars were susceptible. The possible use of resistance sources in the breeding program is discussed.     

Identifying unique populations in long-dispersal marine species: Gulfs as priority conservation areas

Identification of areas which should be a subject of protection is crucial for safeguarding the marine ecosystems. Amongst the reasons for protecting a region or location, the existence of unique populations or evolutionary significant units for one or more key species is a priority. The North American silver hake, Merluccius bilinearis, is currently managed as two stocks (northern and southern) without considering gulf areas separately. Employing microsatellite and mitochondrial markers we have detected significant F_ST values between hake individuals inhabiting gulfs and those distributed in the open sea, and asymmetric gene flow, higher from the gulf to the open sea than in the opposite direction. These differences can be interpreted as signals of separate populations in gulfs which may act as sources of variability for hake species. Occurrence of similar phenomena in Atlantic waters in both the northern and the southern Hemisphere, for these two pelagic–demersal hake species, suggests that gulfs may constitute a target for designing marine protected areas and confirms the adequacy of gulf-specific management already employed in Argentina.     

The extent of embryo and endosperm growth following interspecific hybridization between Cicer arietinum L. and related annual wild species

In vivo interspecific pollinations were performed and immature seed development investigated by histological methods in order to study crossability barrier(s) in Cicer L. species wide hybridization. Seven of the eight wild annual Cicer species, belonging to the secondary and tertiary gene pools, were used in reciprocal crosses with the cultivated chickpea. It was confirmed that the zygote was formed in all interspecific crosses. The embryos showed continued and retarded growth at different rate in various crosses, but eventually aborted at an early pro-embryo stage in all crosses except C. arietinum L. ×C. echinospermum Dav. Reciprocal cross differences were observed in early embryo growth rate and could have implications in obtaining hybrids. This study further emphasizes the necessity for developing appropriate and efficient in vitro procedures for rescuing immature globular hybrid pro-embryos, which will make the wild Cicer gene resources amenable to chickpea improvement.     

Sources of resistance to cyst nematode in cultivated and wild Cicer species

Summary Among the nematodes infesting chickpea (Cicer arietinum L.) plants in Syria, cyst nematode (Heterodera ciceri Vovlas, Greco et Di Vito) is the most important. It is uneconomical to grow chickpea in fields infested with cyst nematode and to control this nematode with nematicide. Therefore, investigations were conducted at ICARDA, Syria from 1987 to 1991 to identify sources of resistance to cyst nematode in 7258 lines of C. arietinum and 102 lines of eight annual Cicer species including C. bijugum K.R. Rech. (13 lines), C. chorassanicum (Bge) M. Pop. (3 lines), C. cuneatum Hochst. ex Rich. (3 lines), C. echinospermum P.H. Davis (8 lines), C. judaicum Boiss. (18 lines), C. pinnatifidum Jaub. & Sp. (18 lines), C. reticulatum Ladiz. (36 lines), and C. yamashitae Kitamura (3 lines). All lines were grown in a greenhouse at 15–25°C in pots containing soil infested with 20 eggs of the nematode g^-1 soil. Nematode infestation was evaluated on a 0 to 5 scale based on number of females and cysts on roots. Resistance was found in one line of C. bijugum, six lines of C. pinnatifidum, and one line of C. reticulatum. No lines of C. arietinum, C. chorassanicum, C. cuneatum, C. echinospermum, C. judaicum, or C. yamashitae was resistant to cyst nematode. Plants with resistance have been recovered in the F₃ generation from crosses between the cultigen and C. reticulatum, indicating the possibility of transfer of gene(s) for resistance to cyst nematode from wild to cultivated Cicer species.Joint contribution from Istituto di Nematologia Agraria, ICARDA and ICRISAT (International Crops Research Institute for the Semi-Arid Tropics), Patancheru P.O., A.P. 502 324, India.     

Regional priority setting for rare species based on a method combining three criteria

We propose a method to establish regional-level priorities for plant species that is based on three criteria. These involve two main criteria associated with species rarity, (a) small range size and thus regional responsibility and (b) low population numbers and thus local rarity, and a third criteria associated with habitat vulnerability to distinguish species currently threatened by human activities. Application of the method shows how the three criteria can be objectively and readily quantified (using a system of equal numbers of ranks) and combined into a hierarchy of priorities. We show how this can be done by using regional responsibility as a first order priority followed successively by local rarity and habitat vulnerability. Since the criteria are closely associated with rarity, this method is easily understandable for decision makers. We illustrate the application of the method to plants (a species rich group) at two regional scales where the objectives are different. If adapted to the availability of different types of data, the three criteria could be used to produce comparable lists in different countries and regions.     

Deconstructing molecular phylogenetic relationship among cultivated and wild Brassica species

Genetic Resources and Crop Evolution - Brassica represents an agriculturally important and diverse group of oilseed crops with a long evolutionary history. Molecular markers played an important...     

Characterization of resveratrol content in ten wild species of section Arachis, genus Arachis

Peanut is one of the few plants that synthesizes resveratrol, a phenolic compound of the stilbene class, which has been associated with reduced risk of developing chronic diseases, such as cancer, cardiovascular diseases, skin diseases, pulmonary diseases, diabetes and neurological diseases. Resveratrol was detected in different parts of the peanut plant, including roots, leaves, seeds and their derivatives. The wild species of the Arachis section are also strong candidates to synthesize resveratrol because they are phylogenetically closely related to cultivated peanut. Our objective was to characterize the resveratrol content in ten wild species of Arachis with three different genomes (A, B and K). The plant material was composed of leaves of the ten species treated (test) and not treated (control) with ultraviolet (UV) radiation. The test and control samples were extracted and the identification and quantification of resveratrol was performed using high performance liquid chromatography (HPLC). All species studied synthesized resveratrol and the concentrations ranged from 299.5 μg/g in A. kempff-mercadoi to 819.9 μg/g in A. cardenasii. DPPH antioxidant activity varied between 18.7 % for A. duranensis and 48.2 % in A. simpsonii. The results showed that wild Arachis species are a potential source of alleles for improvement of cultivated peanut, with the aim of achieving higher resveratrol content in leaves.     

Detection of adult-plant resistance to Puccinia triticina in a collection of wild Triticum species

Three hundred and fifty three Triticum accessions, several also classified as Aegilops and comprising 13 diploid, tetraploid or hexaploid species, were screened for seedling and adult-plant resistance to Puccinia triticina Eriks. using a mixture of pathotypes UVPrt2, 3, 9 and 13. Seedlings were spray-inoculated with a suspension of freshly collected urediospores in distilled water containing Tween 20^® seven days after planting. Infection types (ITs) were scored 10 days post-inoculation (d.p.i.). Fully expanded flag leaves were inoculated and ITs and leaf rust severity were scored 16 d.p.i. One hundred and eighty two of the accessions were resistant to moderately resistant in the adult stage, whereas 126 were resistant or moderately resistant as seedlings to the pathotype mixture. Hypersensitive adult-plant resistance was particularly apparent in lines of T. timopheevii, T. sharonense, T. longissimum, T. searsii and T. turgidum. In T. turgidum, which comprised 272 accessions, approximately 44% of the adult plants were resistant to moderately resistant compared to 28% of the seedlings. The expression of these adult-plant resistances varied between hypersensitive flecking of flag leaves, and small pustules commonly associated with chlorosis and/or necrosis of leaf tissue. Partial resistance, expressed by small pustules without any apparent chlorosis, was observed in species such as T. tauschii, T. turgidum ssp. durum and T. turgidum ssp. pyramidale.     

Morphological variability in cultivated and wild species of Luffa (Cucurbitaceae) from India

Immature fruits of cultivated species of Luffa are commonly used as summer vegetable in India. Rich morphological variability occurs in cultivated species of Luffa in different growing regions of the country. To study morphological variability in cultivated and wild Luffa from different agro-ecological regions of India, a total of seventy accessions were assembled. Morphological variations in leaf, fruit and seed characters were found to delimit cultivated and wild Luffa species. Cluster analysis revealed two major clusters, one comprising of 36 accessions of Luffa acutangula and the other of 30 accessions belonging to L. aegyptiaca. A local cultivar “Satputia” (L. hermaphrodita) was classified along with cultivated L. acutangula and wild L. acutangula var. amara. Wild species namely L. graveolens and L. echinata were clustered closer to the L. acutangula.     

Diversity for abiotic and biotic stress resistance in the wild annual Cicer species

Data on 228 accessions of eight annual wild Cicer species and 20 cultivated chickpea check lines were evaluated for diversity in response to six of the most serious biotic and abiotic stresses which reduce crop yield and production stability of chickpea, i.e., ascochyta blight, fusarium wilt, leaf miner, bruchid, cyst nematode, and cold. Relative frequencies of score reactions to the above six stresses were recorded from all the annual wild Cicer species and the cultivated taxon. Patterns of distribution and amount of variation of the resistance reactions differed between stresses and species. C. bijugum, C. pinnatifidum and C. echinospermum showed accessions with at least one source of resistance (1 to 4 score reactions) to each stress. Overall, C. bijugum showed the highest frequencies of the highest categories of resistance. Next in performance was C. pinnatifidum followed by C. judaicum, C. reticulatum and C. echinospermum. Furthermore, C. bijugum had the highest number of accessions with multiple resistance to the six stresses; two accessions were resistant to five stresses and 16 to four. According to the Shannon-Weaver diversity indices (H), five species showed discrete mean diversity indices which varied from 0.649 in C. pinnatifidum to 0.526 in C. judaicum, whereas C. chorassanicum, C. cuneatum and C. yamashitae showed the lowest Hs, which were respectively 0.119, 0.174 and 0.216. Pair-wise correlations among the six biotic and abiotic stresses showed the possibility of combining these resistances. Interestingly, multiple resistant accessions were predominantly of Turkish origin.     

Geographical variation of solanidane aglycone glycoalkaloids in the wild potato species Solanum chacoense Bitter

The Colorado Potato Beetle is a serious pest of the cultivated potato. Natural resistance has been found in a few wild species, including Solanum chacoense Bitter, in which the resistance is attributed to the presence of leptine glycoalkaloids. Production and accumulation of these compounds within S. chacoense varies widely and appears to be inherited in a quantitative fashion, but high leptine-producing clones occur rarely. In the present study, 15 different accessions from various locations and altitudes of origin within central to northern Argentina and Paraguay were analyzed for foliar glycoalkaloid (leptine, leptinine, solanine, chaconine) content. The objective was to infer the frequency of leptine production in ecogeographically distinct S. chacoense accessions, and to ascertain any possible association between leptine levels/concentrations and ecogeographical location. Leptines were detected in 8 of the 15 accessions, and the amounts within each accession varied widely. Most of the leptine-containing accessions originated from western Argentina except two in province Córdoba in central Argentina. There was no relationship between elevational level and leptine, but there was a negative trend with total glycoalkaloids (TGA) and elevation, due to solanine and chaconine levels which decreased with increasing elevation. In addition, nine unidentified, putative glycoalkaloids were detected, in very high proportions in some individuals and accessions. This study raises interesting questions about glycoalkaloid distribution, helps provide direction for new avenues of leptine and glycoalkaloid research, and proposes a systematic, ecogeographically based method for bioprospecting genes controlling rare plant secondary compounds.     

Carbon-nitrogen interaction related to P,K, Ca,and Mg nutrients in field crops

Carbon (dry matter)-nitrogen relationship was expressed as DM_t = DM₀ × exp(CNI × N_t) in Gramineae crops (including root crops), and DM_t = DM₀ + CNF × N_t in Leguminosae crops, where DM_t is the amount of dry matter at various growth stages, N_t is the amount of nitrogen absorbed at various growth stages, DM₀ is the initial value, and CNI and CNI′ are coefficients. Thus, since the carbon-nitrogen relationship was different between Gramineae and Leguminosae crops, it is expected that the accumulation processes of other minerals such as phosphorus (P), potassium (K), calcium (Ca), or magnesium (Mg) during growth would be different between Gramineae and Leguminosae crops if these nutrients are closely related to the carbon and nitrogen metabolism. As nitrogen is the most important nutrient for plant growth, the relationship between N_t and the amount of other minerals such as phosphorus (P_t), potassium (K_t), calcium (Ca_t), or magnesium (Mg_t) absorbed in plants at various growth stages was examined in field crops.

In Gramineae crops, the P_t-N_t, K_t-N_t, and Mg_t-N_t relationships during growth were described as follows:

where P₀ and Mg₀ are initial values, and PNI, KNI, K_max, and MgNI are coefficients. Since the P_t-N_t and K_t-N_t relationships changed according to the growing conditions, the values of PNI and KNI were statistically estimated from the data of various growth stages at each treatment. As PNI showed a linear regression with CNI, P_t and also K_t was expressed by the equation which included CNI. Thus both phosphorus and potassium accumulation were closely related to the carbon-nitrogen interaction. While the Mg_t-N_t relationship was less affected by various growing conditions, MgNI was estimated from the data including all treatments, indicating that Mg accumulation was regulated only by nitrogen nutrient. Ca_t was not related to N_t.

In Leguminosae crops, the P_t-N_t, K_t-N_t, and Mg_t-N_t relationships were described as follows:

where P_0, K₀, and Mg₀ are initial values, and PNI′ and KNI′ are coefficients. Since the P_t-N_t, K_t-N_t, and Mg_t-N_t relationships were less affected by various growing conditions as in the case of DM_t-N_t, the values of PNI′ and KNI′, and MgNI were estimated from the data including all treatments. Thus, P, K, and Mg accumulation was closely regulated by N nutrient. Ca_t was not related to N_t.

Consequently, in Gramineae crops, P and K accumulation was assumed to be related to the carbon-nitrogen interaction, while in Leguminosae crops, P and K accumulation was assumed to be related to only nitrogen nutrient, indicating that the role of P and K nutrients differed according to differences in the balance of the carbon-nitrogen metabolism. Since MgNI was estimated from the same form of Mg_t-N_t regression regardless of Gramineae and Leguminosae crops, Mg accumulation was assumed to be closely regulated by only nitrogen nutrient. Ca accumulation was neither related to N nutrient nor carbon-nitrogen interaction.     

Boron deficiency and toxicity symptoms for several crops as related to tissue boron levels

Boron deficiency symptoms in snap beans (Phaseolus vulgaris L.) showed as general yellowing of tops with slow flowering and pod formation, while toxicity caused reduced growth and burned dark brown older leaves especially on the edges. In radish (Raphanus sativus L.)_f B deficiency resulted in roots which were brown upon cutting and had thick periderm. Even at 4 ppm applied B, no visible B toxicity was noted in radish. The plant tissue B levels of less than 9 to 12 ppm were associated with B deficiency in radish and beans; and greater than 125 ppm with B toxicity in beans. In tomatoes (Lycopersicon esculentum, Mill) B deficiency resulted in reduced growth while B toxicity at 4 ppm applied B caused poor and slow germination. Boron deficiency and toxlcity in tomatoes were related to < 12 and > 172 ppm B, respectively, in tissue. No B deficiency was noted in corn (Zea mays L.) and timothy (Phleum pratense L.). The B toxicity in these two crops appeared as marginal burning and dark brown tips of older leaves and was related to greater than 98 and 176 ppm tissue B in corn and timothy, respectively.