Seeds were germinated and plants established under quarantine conditions, then transferred to a nursery. Introduction orchards were established throughout the Negev desert (Fig. 1). Each of the introduction orchards has distinct climate and water quality characteristics (Table 2, 3, 4). To eliminate the effect of random local conditions each species was planted in three separate blocks at each site. Five to ten plants were used for each species per block.
All orchards are equipped with drip irrigation systems. Each tree is supplied with a 2-liter/hour dripper. When the canopy has developed either the dripper is replaced with one of larger capacity or additional drippers are added. Fertilization with NPK is given via the irrigation system. Sequestrene 134 is applied to correct iron deficiency symptoms. All irrigation and fertilization regimes were adapted from the recommendations of the Extension Service for mango trees grown in the Negev area (Frenkel and Zohar 1987). The following operations relevant for plant establishment are being carried out at all locations: growth measurements; phenological observations; climate, soil, water, and mineral analyses.
At the next stage, fruit and nut yields and quality will be determined, followed by clonal propagation of the selected clones and rootstocks.
This research was partially supported by the following agencies: US-AID CDR; GIARA-Germany-Israel Agriculture Research Agreement; PEF-Israel Endowment Fund; New-jersey Freedom From Hunger Campaign (Headed by Mr. Brach); and the Israeli Ministry of Agriculture.
Seeds germinated well, and seedlings grew under quarantine conditions and then in the nursery. Upon transfer to the various locations growth was inhibited, followed in many cases by death. With the exception of a few survivors at Qetura, the yehib plants did not become established in most of the orchards. Growth of the survivors occurred from May until October but was very slow both in the nursery and in the orchard (Fig. 2 and 3). Yellowing of leaves was common in many plants, generally followed by death. The survivors also showed some yellowing of leaves; this phenomenon was particularly marked in mid-summer, when temperatures can reach up to 48°C, but it was also observed in winter.
Seeds germinated after treatment with (2-chloroethyl) phosphonic acid (ethephon) (Keegan and Van Staden 1981). Seedlings were transplanted successfully in all orchards. At Neot Hakikar after a brief growth spurt in June the plants turned yellow, showed the typical leaf bum symptoms of NaCl damage, and subsequently died. At Qetura the main growth period occurred during the spring; in mid-summer growth slowed down. At the Besor location winter dormancy broke very late (in June), and growth continued until November (Fig. 4, 5). This location is much cooler than Qetura (Table 2). In all locations some of the trees showed signs of leaf yellowing, which was diagnosed as iron deficiency and corrected by applications of iron. The healthiest looking trees are those growing at the Besor plot (Fig. 5).
Seeds germinated after the operculum had been opened (Teichman et al. 1985). All plants were transferred successfully to the orchards. Breaking of winter dormancy occurred at Qetura first, then at Besor and Neot Hakikar. The slowest growth rate was recorded at Neot Hakikar. While growth was steady at Besor, at Qetura, rapid growth occurred from June to August followed by slower growth in September and October (Fig. 6, 7). Neot Hakikar is characterized by high salinity due mainly to NaCl, and many plant species failed to survive there. Marula did not show any signs of salinity leaf burns. At Qetura three-year-old male and female trees started to flower and fruit developed.
The seeds germinated rapidly; however, first development was very slow, and it took two years for seedlings to reach a size suitable for transplanting (a height of ca. 10-15 cm). The slowest growth rate was at Neot Hakikar. Cessation of growth occurred only during the mid-winter months (December, January, and February). At Qetura three-year-old plants reached a total shoot length of 160 cm (Fig. 8, 9).
The seeds germinated easily and seedlings transplanted well at all locations. At Neot Hakikar the plants turned yellow with severe symptoms of NaCl leaf burn; they survived for a while and then died. Fig. 10 shows plant growth at Besor and Qetura. At Qetura growth started in March/April and slowed down in the hottest months, namely July and August. At this time the leaves showed some symptoms of yellowing and tip burns, which vanished in the autumn. Despite these difficulties, development at Qetura is satisfactory (Fig. 11). At Besor the fastest growth occurred in May-August, and damage to leaves was not observed.
Many cultivars are known in India of which two, 'Gola' and 'Seb', were introduced by us to Israel. They were grafted onto Z. spina-cristi (native to our region) and onto Z. abysscinica. Development at the various sites on each of the two rootstocks is successful; a one-year-old plant at Qetura is shown in Fig. 12.
There is no way of predicting the success of the various species at each locations. Both marula and mongongo were introduced from Botswana (a semiarid zone), yet there are considerable differences in performance between the two species. Mongongo failed at Neot Hakikar, probably due to NaCl salinity. Marula is growing well in all locations despite some inhibition of growth at Neot Hakikar. In the latter orchard only a few species have survived and are still growing. These include ber (which was introduced from India) and various cacti including pitahaya agria but excluding Hylocereus species, which suffered both from the extreme light and from the extreme salinity. Ciruelo is also growing very well at this location. The sulfate salinity at Qetura is less harmful to the new plant introductions than the NaCl salinity characteristic of Neot Hakikar. Mango and pummelo on a proper rootstock (13-1 and sour orange, respectively) are grown commercially at Qetura, but are unable to survive at Neot Hakikar. White sapota grows well at Besor. It seems to tolerate cold weather but not very high temperatures. Given special care and proper selection of rootstocks and cultivars, the plant might also be grown at Qetura. To draw definite conclusions about the performance of a species at a particular location it is obligatory to test in situ. Aside from simple survival, successful economic performance, which depends on yields and product quality, requires evaluation.
Selection of rootstocks and scion cultivars will have to be performed for promising species in the future. Correspondingly, proper vegetative techniques will have to be developed for each of the plant species that grows successfully. These rare and wild fruit trees deserve much more attention from the scientific community than they have so far received.
|Botanical name||Common name||Family|
|Casimiroa edulis||White sapota||Rutaceae|
|Diospyros digyna||Black sapota||Ebenaceae|
|Dovyalis caffra||Kei apple||Flacourtiaceae|
|Inga vera||Ice cream bean||Mimosaceae|
|Opuntia ficus-indica||Prickly pear||Cactaceae|
|Sclerocarya birrea subsp. caffra||Morula (Marula)||Anacardiaceae|
|Stenocereus gummosus||Pitahaya agria||Cactaceae|
|Stenocereus thurberi||Pitahaya dulce||Cactaceae|
|Strychnos cocculoides||Monkey orange||Loganiaceae|
|Ziziphus mauritiana||Ber (Indian jujube)||Rha.mnaceae|
|Ricinodendron rautanenii||Mongongo (Manketti)||Euphorbiaceae|
|Parameter||Qetura||Neot Hakikar||Besor||Ramat Negev|
|Mean daily temperature (°C)|
|Hottest month (August)||30-32||32-34||26-28||26-28|
|Coldest month (January)||14-16||14-16||12-14||8-10|
|Annual number of days with temperature of:|
|35°C or more||125-150||126-150||0-10||11-25|
|10°C or less||1-25||1-25||76-100||126-150|
|Average pan evaporation rate (mm/day)|
|Annual rainfall (mm)||<40||<40||200||90|
|Parameter||Qetura||Neot Hakikar||Besor||Fresh water||Brackish|
|ion content (mg/1)|
|Parameterz||Qetura||Neot Hakikar||Besor||Ramat Negev|
|Texture||sandy loam||sandy loam||sandy loam||loam|
|Conductivity (dS/m at 25°C)||0.63-3.39||1.34-6.13||0.6-2.1||0.7-2.3|
|Total CaCO3 (%)||6-10||14-32||2-12||8-27|
|Fig. 1. Site of experimental orchards established in the Negev desert.|
|Fig. 2. Surviving yehib plant at Qetura (3 years old) (October 1988).|
|Fig. 3. Growth of individual yehib plants at Qetura during 1987. Seedlings were planted in 1985. Plants died at all other locations.|
|Fig. 4. Growth of mongongo plants at three locations during 1987. Seedlings were planted in 1986. After initial growth at Neot Hakikar, all plants showed leaf yellowing followed by leaf burns from NaCl salinity and died. No. of plants: 29 (Qetura), 13 (Neot-Hakikar), 27 (Besor).|
Fig. 5. Well-developed 3-year-old mongongo tree at Besor (October 1988).
|Fig. 6. Growth of marula plants at three locations during 1987. Seedlings were planted in 1986. No. of plants: 30 (Qetura), 29 (Neot Hakikar) and 30 (Besor).|
|Fig. 7. Fast-development 3-year-old marula tree at Qetura (October 1988).|
|Fig. 8. Growth of pitahaya agria plants at three locations during 1987. Seedlings at Neot-Hakikar and Besor were planted in 1986. Since seedlings at Qetura were planted one year earlier, growth in 1986 is included. No. of plants: 30 (Qetura), 20 (Neot-Hakikar), 30 (Besor).|
|Fig. 9. Pitahaya agria cactus (3 years old) at Qetura (October 1988).|
|Fig. 10. Growth of white sapota plants at two locations during 1987. Seedlings were planted in 1986. No. of plants: 14 (Qetura), 30 (Besor). All the white sapota plants died at Neot Hakikar after showing symptoms of severe leaf bum from NaCl salinity. At Qetura some plants showed leaf yellowing, especially during midsummer months.|
|Fig. 11. White sapota (3 years old) at Qetura (October 1988).|
Fig. 12. One-year-old ber tree, 'Gola' cultivar, grafted on Ziziphus spina-cristi at Qetura (October 1988).