ITEMS FROM PAKISTAN
Agronomic Research Station
Bahawalpur, Pakistan.
Muhammad S. Cheema.
Seeding wheat in a standing cotton crop.
Cotton and wheat are the most important crops of Pakistan. Cotton is an important cash crop, whereas wheat is a food. It is essential that both of these crops grow in suitable environments so that per acre yield of both can be increased. Wheat, mostly sown in January, follows cotton in the field. The wheat yield is affected by late planting. Several experiments have shown that wheat yields may decline by 16 kg/acre per day after the 30 November. If the cotton is harvested earlier so that wheat can be planted in time, one has to sacrifice the production of the last picking of cotton, which is 5 to 6 times more valuable than wheat production. Hence, no farmer will sacrifice his cotton production for the timely planting of wheat and will wait for the opening of bolls for complete harvesting. Keeping in view the above facts, there is an earnest need to develop a technology that enables the timely planting of wheat without losing the cotton production. For the cotton growing area, a new technique of planting wheat in a standing cotton crop (relay cropping) has been developed by the Directorate of Agronomy, Ayub Agricultural Research Institute, Faisalabad, on the basis of several years of experimenting. It is an economical and easily adaptable method, which is described briefly below:
1. Time and method of planting. Wheat is planted in no-till fields during mid November by first flooding cotton fields with irrigation. If the cotton field has ridges, it is irrigated till the ridges are submerged. After standing in water 8-l2 hours, soaked seed is broadcast at 60 kg/acre, followed by a light irrigation after 7-10 days. The rest of the irrigations are applied according to needs of the wheat crop. At the complete opening of cotton bolls, the cotton sticks are cut to be used as a fuel.
2. Use of fertilizer. Phosphorus (40 kg) and potash (20 kg) one third of the nitrogen (60 kg) are applied with the second irrigation in standing cotton. The remaining 40 kg of nitrogen is applied in January after harvesting and removal of the cotton sticks.
3. Weed control. The most important factor in this method is the control of weeds at the right time through the use of herbicides. Buctril M is used for controlling broad leaf weeds, and Dicuran MA 60 WP and Arelon 75 WP are recommended herbicides for narrow and broad leafed weeds. These herbicides are easily mixed with sand and broadcast following irrigation when the weeds are at the 2- to 4-leaf stage in the standing cotton.
Wild oat (Avena fatua) in competition with wheat.
Wild oat infestation in the wheat crop in Pakistan has increased much beyond the economic threshold and intensifies at a faster rate as the seeds shatter in infested fields before maturity and harvesting of the wheat crop. Studies on wild oat interference, nutrient competition, and the economic threshold level in wheat were conducted during the years 1989-90 and 1990-91, as a Ph.D study in Agronomy at the University of Agriculture, Faisalabad. The following conclusions were drawn from the experiments:
Determination of the critical period. There is a definite minimum period of time during which the wheat crop must be kept free of this weed to reduce yield losses. The experiment was comprised of two sets of treatments. The first set included wild oat-wheat competition for the first 2,3,4,5, and 6 weeks after crop emergence, as well as a full-season weedy check. In the second set of treatments, the wheat crop was kept weed free for first 2,3,4,5, and 6 weeks after crop emergence, and the check was maintained weed-free for the full season. Weed-free duration was maintained by hoeing and subsequent hand-pulling of wild oat and all other weeds. The results revealed that wild oat interference persisted for 4-6 weeks after crop emergence; was very critical; and resulted in a considerable reduction in grain yield, fertile tillers, 1,000 grain weight, and an ultimately poor harvest index. However, a crop free of wild oats 4-6 weeks after crop emergence gave significantly higher grain yield, fertile tillers, higher l,000 grain weight, and rich harvest index.
Wild oat in competition with wheat for nitrogen. The second experiment was conducted to determine the effect of different nitrogen levels in competitive behavior of wild oat densities and to measure reduction in wheat yield. Nitrogen levels of 50, 100, and 150 kg/ha, along with the check (no nitrogen application), were randomized in the main plots. Wild oat densities of 10, 20, 30, 40, and 50 wild oat plants/m^-2, along with a weed-free check, were randomized in subplots. The desired density of wild oats was maintained by manually thinning the natural stand of wild oats.
In competition with wheat, wild oat was better able to utilize the added nitrogen and gained a competitive advantage over the wheat at a low nitrogen rate. The competition decreased with an enhanced rate of N-application. This phenomenon was particularly notable at a weed density of 40 to 50 plants/sq. meter, where 150 kg nitrogen per hectare was applied. The reduction in wheat yield ranged from 27.1 to 33.5 %, compared with 40.3 to 50.4 % in the unfertilized plots. An increase in wild oat density caused a significant reduction in the number of grains per spike, 1,000 grain weight, and grain yield per hectare. Harvest index was highest in the weed-free check.
Graminon 500 Ec, a postemergent herbicide, significantly increased the number of grains per spike and kg grain yield per hectare, whereas different wild oat densities significantly reduced the number of grains per spike and grain yield per hectare. Application of Graminon at 2.5 l/ha significantly reduced the wild oat biomass as compared with the untreated plots. Its application resulted in a 80-90 % mortality of wild oats. The economic threshold level for Graminon 500 Ec, applied as a postemergent at 2.5 l/ha, was 28 wild oat plants per square meter.
ITEMS FROM ROMANIA
ICCPT Research Institute for Cereals and Industrial Crops
Fundulea, 8264, jud. Calarasi, Romania.
Winter killing during an unusual winter.
P. Mustatea, N.N. Saulescu, and Gh. Ittu.
We experienced very unusual weather conditions during winter. The first 10 days of November were relatively warm (maximum temperatures from 10.4-16.7 C and minimum temperatures from -2.5 to 12.2 C). Then, on November 11, the minimum temperatures dropped to -8.9 C and reached -11.6 and -11.9 C for the next 2 days, without snow and with very little hardening of the plants. The next 20 days were cold, with minimum temperatures reaching -12.4 C on November 19 and -14.2 C on November 28, but with 6-13 cm of snow protecting the crops. December 1993, January, and the first half of February 1994, were warmer than usual, with maximum temperatures positive all along (reaching 13.0 C in December) and negative temperatures around freezing, but on February 16, minimum temperatures were again down to -11.3 C.
Although the minimum temperatures were not as low as usual in our region, the early and sudden frost killed most winter barley crops and produced differential winter killing in wheat, only partially correlated with usual winter hardiness. Old, locally adapted, wheat cultivars were more affected than most new Rumanian cultivars, among which Dropia, Flamura 85, and Lovrin 41 were the best, although they are not the best in freezing tests of hardened plants. The best survival was recorded in the Great Plains cultivars (Karl, Parker, and Centurk; and also in TAM 105, and TAM 107, which are not outstanding in freezing tests on hardened plants). Several Bulgarian cultivars (Jasen, Priaspa, Katia, and Sadovo 1) were affected badly, as were most Italian (e.g., Libellula, Pandas, and Centauro) and French (e.g., Soissons and Thesee) cultivars.
Leaf rust resistance gene transferred from Aegilops variabilis.
Mariana Ittu, A. Giura, Gh. Ittu, and N.N. Saulescu.
A line, G516, obtained by crossing wheat with Aegilops variabilis (Ae. peregrina) showed seedling resistance to the most virulent leaf rust races present in Romania. Susceptible segregates were observed following artificial inoculation of F₂ seedlings from crosses between G516 and lines carrying Lr9, Lr19, and Lr24. The only known seedling with the leaf rust resistance gene transferred from Ae. variabilis is not allelic with Lr9, Lr19 or Lr24, previously transferred from Aegilops or Agropyron species. The new leaf rust resistance gene was provisionally designated Lrv.
Segregation ratios in crosses of Lrv with Lr19 and Lr24 agree with the hypothesis of two dominant genes. For the cross `Lrv x Lr9', there was an excess of susceptible seedlings, which might be due to abnormal transmission of the introgressed gene(s).
Tests are under way to check the allelic relationship of Lrv to the genes recently transferred to wheat from Ae. squarrosa by the Kansas State University team.
Partial sterility caused by low nonfreezing pre-anthesis temperatures.
N.N. Saulescu, Gh. Ittu, and P. Mustatea.
Our efforts to breed for earliness, beyond that found in presently grown cultivars, have been hampered by an unusual lack of yield stability in most of the very early genotypes. We noticed that significant yield decreases often are associated with observable sterility, resulting in incomplete seed set. Sterility levels often are correlated with earliness and are higher in years when cool, although not freezing, temperatures are recorded even for a few days during April and/or first days of May. However, important differences in sterility levels can be seen among genotypes of the same earliness in sterility-inducing environments. The phenomenon might be quite common, because we not only observed sterility in early genotypes several times at several locations in Romania, but also in 1993 at Corvallis, Oregon. Sterility of early genotypes was particularly severe at Fundulea in 1993, with estimated yield reductions of 60-70 % in some Chinese cultivars.
Chances of breeding very early cultivars with improved yield stability would be increased if we could select for less sterility in a reproducible sterility-inducing environment. Unfortunately, we know very little about this environment.
Qian et al. (Crop Sci 26:43-46, 1986) induced high levels of sterility by growing wheat in growth chambers at 11 C/6 C for long periods and found that such temperatures affected microspore development and anther dehiscence. However, their data do not allow any speculation about the most critical period and about the minimum duration of low temperatures that can induce sterility.
Last year we noticed very high levels of sterility in many Great Plains cultivars, especially Karl, in some Chinese, and some of our own early lines. (It is interesting that Qian et al. also found the highest sterility in some Great Plains cultivars.) Analysis of weather data revealed three short periods of lower temperatures that might have affected microspore development:
- April 7, 8, 9, with temperatures of 13.1/5.6 C, 11.7/4.4 C, and 9.4/2.8 C, respectively;
- April 14 and 15, with temperatures of 20.2/5.0 C and 23.2/5.7 C; and
- May 3, 4, 5, with temperatures of 16.4/6.6 C, 14.3/7.1 C, and 20.0/3.5 C, respectively.
The first cool period might have corresponded with meiosis, whereas the last one was at late booting.
Additional information came from an experiment where plants grown in the greenhouse were moved outdoors at different dates in April. The highest sterility was observed in plants that were past meiosis when moved outdoors on April 4. These plants were exposed to the first cool period just a few days later. Sterility varied in these plants from 98 % in line 6420 to about 40 % in lines AF92-1 and Tianshui 871, although all these genotypes were of approximately the same earliness. Further information is necessary to establish an efficient screening procedure for tolerance to low pre-anthesis temperatures.
S.C.A. Agricultural Research Station
Turda, ju. Cluj, Romania.
V. Botezan, V. Moldovan, and Maria Moldovan.
Apullum, a new winter wheat cultivar.
The cultivar Apullum, obtained by individual selection from the combination `Odesskaia 75/Bezostaia 1' was certified in 1992. Apullum is a high-yielding cultivar with good adaptation ability to diverse pedologic, climatic, and technological conditions. It also has an excellent resistance to frost, superior even to the resistant control cultivar, Odesskaia 51, and the capacity to form a large number of ears per unit area in most environmental conditions. This cultivar is resistant to yellow rust and stem rust and shows a high level of partial resistance to Septoria leaf blotch.
The regression coefficients of Apullum yields, calculated both in relation with other varieties and with the environment indices, were subunitary, thus, expressing its tendency to better tolerate unfavorable environmental conditions.
Apullum represents a step forward in combining high productivity with certain essential agronomic traits for stability and quality of wheat crops.
Triticale breeding program at the Agricultural Research Station, Turda.
This program was started in 1975. In the beginning, the main objectives were the study and diversification of germplasm; the improvement of cytologic stability; the creation of normal grains for structure and weight; the improvement of earliness; resistance to lodging, diseases, and pests; tolerance to water excess and soil toxicity; and the possibilities for use of the production.
The researchers have been directed especially towards breeding the spring and winter hexaploid Triticales. Since 1986, two winter triticale cultivars (Vladeasa and Ulpia) and one spring triticale cultivar (Tebea) have been released and certified.
Ulpia, certified in 1993, was created as a high-yielding winter triticale cultivar. Ulpia was selected from the cross `TF6/Tt 118-78'. It is a medium-tall cultivar, with good winter hardiness and resistance to sprouting. It is also resistant to leaf, yellow, and stem rusts; powdery mildew; and Helminthosporium sp. and of medium resistance to Septoria and Fusarium spp. It has a good TKW value of 49 g, and also a high protein content (13.92 %). For a 3-year average in 10 locations, it outyielded the previously released triticales, Vladeasa and TF2, by 26% and 13 %, respectively.
Tebea is a spring triticale cultivar certified in 1991. It was selected from the cross `HT 77-777/Panda R x L21'. It is a medium-tall cultivar resistant to lodging and low temperatures in early spring. It is also more resistant to sprouting than winter triticales. This cultivar has a good tolerance to soil aluminum toxicity. It has good resistance to rusts, powdery mildew, and Septoria sp. and medium resistance to Fusarium head blight. For a 3-year average in four locations, it outyielded Speranta (the control cultivar, spring wheat) by 29 %. The protein content of 17.2 % is also good.
Investigation of the genetics of the harvest index in winter wheat.
The harvest index heredity mechanisms were studied within a 6-hybrid combination system, including the parents, P₁ and P₂; hybrids, F₁ and F₂; and backcrosses, BC₁ and BC₂; for each hybrid combination. The results indicated that the harvest index heredity is ruled by additive, dominate, and epistatic genetic effects that are functions of each specific hybrid combination.
The narrow sense heritability coefficients were scored high, ranging between 0.47-0.83, except in one combination where the two parents exhibited close harvest index values. The positive transgression rates for the harvest index scored between 3 % and 271.3 %, depending on the genotype.
A significant correlation was established between the harvest index and individual plant yield, main wheat ear yield, and TKW. The correlation with biological production was poor, indicating in some cases that high harvest indices do not necessarily mean high grain yields and that they might be the result of low biological production.
The alternative suggested here for improving practical breeding involves the application of selection for harvest index in the early generations with all ensuing advantages and continued selection performed on more advanced generations for harvest index combined with production.