Genetic diversity and environmental associations of wild wheat, Triticum dicoccoides, in Israel.

Allozyme variation in the tetraploid wild progenitor of wheat, Triticum dicoccoides, was studied for the proteins encoded by about 50 gene loci in 457 individuals representing 12 populations from Israel. Six spikelet morphological traits were measured in the same populations. The results indicate that: (a) 16 loci (= 32%) were monomorphic in all 12 populations, 15 loci (= 30%) were locally polymorphic, and 19 loci (= 38%) were regionally polymorphic. All polymorphic loci (but one) displayed high levels of polymorphism (≧ 10%). In Israel, the proportion of polymorphic loci per population, P, in wild wheat averaged 0.25 (range, 0.16-0.38), and the genetic diversity index, He averaged 0.07, (range, 0.03 - 0.12). (b) Altogether there were 110 alleles at the 50 putative loci tested (c) Genetic differentiation of populations included regional and local patterns: (i) The coefficients of genetic distance between populations were high (mean D = 0.10 range, 0.02 - 0.25), and indicated sharp genetic differentiation over short distances, (ii) Common (≧ 10%) but sporadic and localized alleles were frequent (76%), and (iii) Rare alleles were few (only 5 alleles). (d) The patterns of allozyme and spikelet variation in the wild gene pool were significantly correlated with, and partly predictable by, water factors, including those of precipitation, evaporation, and relative humidity as well as of soil type, (e) All six spikelet characters showed statistically significant variation among localities and (f) Allozymic variation was correlated with spikelet variation.These results suggest in T. dicoccoides: (i) the operation of natural selection in population genetic structure, (ii) local adaptive genetic differentiation caused by diversifying selection through climate and soil, and (iii) the guidelines for sampling these resources for use in wheat breeding programs.

Beginnings of fruit growing in the old world.

The article reviews the available information on the start of fruit tree cultivation in the Old World. On the basis of (i) evaluation of the available archeological remains and (ii) examination of the wild relatives of the cultivated crops, it was concluded that olive, grape, date, and fig were the first important horticultural additions to the Mediterranean grain agriculture. They were most likely domesticated in the Near East in protohistoric time (fourth and third millennia B.C.) and they emerge as important food elements in the early Bronze Age. Domestication of all four fruit trees was based on a shift from sexual reproduction (in the wild) to vegetative propagation of clones (under domestication). Olive, grape, date, and fig can be vegetatively propagated by simple techniques (cuttings, basal knobs, suckers) and were thus preadapted for domestication early in the development of agriculture. The shift to clonal propagation placed serious limitations on selection and on fruit set under cultivation. We have examined the consequences of this shift in terms of the genetic makeup of the cultivars and traced the various countermeasures that evolved to ensure fruit set. Finally, it was pointed out that in each of these classic fruit trees we are confronted with a variable complex of genuinely wild types, secondary weedy derivatives and feral plants, and groups of the domesticated clones, which are all interfertile and interconnected by occasional hybridization. It was concluded that introgression from the diversified wild gene pool facilitated the rapid buildup of variation in the domesticated crops.

Cytogenetic studies of Trifolium spp. Related to berseem : IV. The relationships in the alexandrinum and vavilovi crossability groups, and the origin of the cultivated berseem.

The interspecific cytogenetic relationships among T. alexandrinum L., T. berytheum Boiss., T. salmoneum Mout., T. apertum Bobr., T. meironense Zoh. et Lern, and T. vavilovi Eig. were studied in several hundreds of intraspecific (WS) and interspecific (BS) F1 hybrids in all possible combinations, and in many of their progenies.Seed germination and development of F1 BS hybrids were normal, except in crosses involving T. vavilovi. Their pollen fertility and seed set was subnormal, with somewhat lower values in T. vavilovi progenies. No multivalents were observed in any F1 BS hybrid, but in some plants, four and also six chromosomes did not pair to form bivalents. B chromosomes were common in hybrids involving T. berytheum or T. salmoneum.Some BS F1 hybrids set ample seeds when selfed, and most of them originated from either one of two self-incompatible T. berytheum plants.The six taxa studied form three groups: (i) T. vavilovi, which is quite remote from the other five; (ii) T. meironense and T. apertum; and (iii) T. alexandrinum, T. berytheum and T. salmoneum. The two last species, especially T. salmoneum, seem to be the progenitors of the cultivated berseem.

Domestication of Pulses in the Old World: Legumes were companions of wheat and barley when agriculture began in the Near East.

This article reviews the available information on the place of origin and time of domestication of the cultivated pea (Pisum sativum), lentil (Lens culinaris), broad bean (Vicia faba), bitter vetch (V. ervilia), and chickpea (Cicer arietinum). On the basis of (i) an examination and evaluation of archeological remains and (ii) an identification of the wild progenitors and delimitation of their geographic distribution, it was concluded that pea and lentil should be regarded as founder crops of Old World Neolithic agriculture. Most probably they were domesticated, in the Near East, simultaneously with wheats and barley (certainly not later than the sixth millennium B.C.). Bitter vetch shows a similar mode of origin. The evidence on the broad bean and the chickpea is much more fragmentary and the wild progenitors of these legumes are yet not satisfactorily identified. But also these two pulses emerge as important food elements in Bronze Age cultures of the Near East and Europe.

Distribution of wild wheats and barley.

If we accept the evidence at face value, we are led to conclude that emmer was probably domesticated in the upper Jordan watershed and that einkorn was domesticated in southeast Turkey. Barley could have been domesticated almost anywhere within the arc bordering the fertile crescent. All three cereals may well have been harvested in the wild state throughout their regions of adaptation long before actual farming began. The primary habitats for barley, however, are not the same as those for the wheats. Wild barley is more xerophytic and extends farther downslope and into the steppes and deserts along the wadis. It seems likely that, while all three early cereals were domesticated within an are flanking the fertile crescent, each was domesticated in a different subregion of the zone. Lest anyone should be led to think the problem is solved, we wish to close with a caveat. Domestication may not have taken place where the wild cereals were most abundant. Why should anyone cultivate a cereal where natural stands are as dense as a cultivated field? If wild cereal grasses can be harvested in unlimited quantities, why should anyone bother to till the soil and plant the seed? We suspect that we shall find, when the full story is unfolded, that here and there harvesting of wild cereals lingered on long after some people had learned to farm, and that farming itself may have orig inated in areas adjacent to, rather than in, the regions of greatest abundance of wild cereals. We need far more specific information on the climate during incipient domestication and many more carefully conducted excavations of sites in the appropriate time range. The problem is far from solved, but some knowledge of the present distribution of the wild forms should be helpful.