Preliminary Yield Trials Research Articles

No-Pesticide Preliminary Yield Trials in Peanut1

Abstract Pest-resistant peanut (Arachis hypogaea L.) cultivars are critically important to reduce the increasing cost of production. Current pesticides used in the U.S. are effective but very expensive. The objective of this study was to evaluate several advanced Georgia breeding lines when grown without nematicides, fungicides, or insecticides. Preliminary yield trials without pesticides were conducted for 3 yr (1996-98) at the Univ. of Georgia, Coastal Plain Exp. Sta. under irrigation. However, preplant and occasionally post-applied herbicides were used for weed control. Thrips damage was noticeably uniform and severe early in the growing season each year, but plants seemingly recovered by midseason. Probably the most endemic diseases in the Southeast are both early and late leaf spots [Cercospora arachidicola Hori and Cercosporidium personatum (Berk. & Curt.) Deighton, respectively] and tomato spotted wilt virus (TSWV). Results from replicated field tests strongly suggest that it would be economically feasible to significantly reduce pesticide cost by growing multiple pest-resistant advanced Georgia breeding lines as compared to the five check cultivars Florunner, GK-7, Southern Runner, Florida MDR 98, and Georgia Browne. However, dollar values were variable and low with no pesticides because of the overall reduction in yield. An alternative approach for greater net returns possibly may be achieved by only reducing currently recommended input costs rather than eliminating pesticides with pest resistant cultivars.

Development of TGMS lines for developing two-line rice hybrids for the tropics

A breeding program was initiated at the International Rice Research Institute (IRRI) in 1990 to develop thermosensitive genic male sterile (TGMS) rice lines for developing two-line rice hybrids for the tropics. The TGMS trait was transferred from a temperate japonica TGMS mutant, Norin PL 12, to indica and tropical japonica rice varieties using the pedigree selection procedure. Six new TGMS rice lines adapted to tropical conditions were developed which showed complete pollen and spikelet sterility when maximum temperature was higher than 30 °C 1–2 week after panicle initiation. However, up to 85.5% spikelet fertility was observed when these lines were exposed to 26–29 °C during the critical stage. Using two of these TGMS lines, some heterotic rice hybrids showing 1–1.6 t/ha higher grain yield than the inbred check varieties were identified in unreplicated observational yield trial conducted at IRRI. Two of the six two-line hybrids yielded significantly higher than the check variety in a replicated preliminary yield trial.

Co. 1 GUINEA GRASS (PANICUM MAXIMUM JACG.)

The germplasm types of Guine sagrass in the Tamil Nadu Agricultural University. Coimbatore were evaluated for green fodder yield during 1980-82 along with the local variety. Six selections were found promising in 1982-83 and preliminary yield trials were conducted from 1985 to 1988. The selection TNGG 2 was found to be best recording a maximum green fodder yield potential of 250 t/ha/yr with mean yield of 160 t/ha/yr. The selection TNGG-2 recorded 172 cm height, 20-35 tillers, 26.64% crude fibre, 24.4 TDDM and 67.6% IVDMD. It is drought and shade tolerant. This selection was released as Co.1 Guinea grass in 1992 by Tamil Nadu Agricultural University. Coimbatore.

Selection of sites for preliminary maize yield trials in the rainforest zone of South-Western Nigeria

Grain-yield data obtained from 49 varieties of maize (Zea mays L.), grown at each of five sites for two years, were analyzed with the objective of identifying two or three sites where mean performance adequately predicted the mean performance of all five sites combined. Regression of overall varietal mean on site or site-combination means was done and the predictive potential of a site or combination of sites was judged by four criteria: (i) r2≥0.9, (ii) b≥1.0, (iii) high yield (i.e., yield greater than or equal to overall mean yield) and (iv) consistent yield (i.e., yield did not fall below the mean yield by more than 10%). In addition, a trial differentiation index, D, was used to compare the site combinations selected on the basis of the above criteria with the differentiation potential of all five sites combined. None of the five individual sites and the ten two-site combinations satisfactorily predicted overall mean yield. However, five three-sites combinations had values of D similar to that of all the five sites. Rank-correlation coefficients of the three-site combinations with all five sites ranged from 0.90 to 0.79. It was concluded that certain three-site combinations could be satisfactorily used for preliminary maize yield trials in the rainforest ecological zone of S.W. Nigeria.

Breeding for Disease and Insect Resistances in Keng Rice

Tainung 67 was crossed with Tetep, Carreon, Dawn and other donor parents followed by 3 to 4 consecutive backcrossings to Tainung 67 for improving its blast resistance. A genetic study on the BC1F1's revealed that Tetep was most numerous in the genes resistant to 4 races of the blast fungus tested. An upland blast nursery with corn border lines facilitated the screen-testing of breeding lines. Many new selections from this breeding program were resistant to the blast disease and outyielded Tainung 67. Tainung 67 was also crossed with yellow dwarf resistant Firooz, followed by 2 consecutive backcrossings to Tainung 67. From the segregating progenies of these backcross hybrids, 11 new strains resistant to yellow dwarf were selected. The yields of 2 strains surpassed that of Tainung 67. The brown planthopper resistance of a Oryza rufipogon was tranes-ferred to Ponlai by 2 consecutive breeding programs. TNGY8849, a final selection that was resistant to blast and brown planthoppers, is being recommended for registration. Various other varieties possessing Bph 1, bph 2, Bph 3 and bph 4 were also crossed with Tainung 67, followed by 2 consecutive backcrossings. The resistant strains selected from the segregating materials of these hybrids are being tested in the preliminary yield trial. Several japonica cultivars showed resistance in a test for white-backed planthopper resistance, including moderately resistant Tainung 67. A breeding program and the genetic study related with the resistance are in progress. Twenty-one double cross F1's between the lines selected mostly from the above mentioned backcross breeding programs were subjected to anther culture cooperated with tissue culturists. A total of 1,567 green AC, plants derived from the anther culture gave only 230 diploid AC1S, lines for screen-testing. The rate of this diploid recovery was greatly improved later. Segregation patterns of blast, planthopper resistances and shattering habit of rice grains among the AC1S1 lines showed that the combination of different desirable traits by double crossing followed by anther culture will he successful and readily useful.

Predicting yield and processing quality of potato breeding selections

The linear relationship between “site mean” and potato cultivar performance was used to develop predictive models for total yield, yield of US No 1 grade, per cent US No 1 grade, specific gravity and fried chip color. The best fitting linear expression for each of the traits was determined by linear regression for specific cultivars. Common limits for “site means” could then be substituted into the expressions for predictive purposes. Application of this method to large and small data sets demonstrated its use for interpreting preliminary yield trial information for the identification of superior breeding selections.

GRAM WEIGHT IN RELATION TO POD AND SHOOT WEIGHTS IN BENGAL GRAM

In preliminary yield trials of crops the plant breeder has often to handle a large number of types although only a few of these can be carried forward. It is a practical consideration that the methods adopted at such a stage allow examination of as wide a range of material as possible with the minimum of labour and with- out loss of efficiency. Each crop sets its own problem in this connection. In Bengal gram (Cicer arietinum) for instance, the actual determina- tion of the yield requires the stripping and threshing of the pods and will take time and labour when the number of plants is large. Any method which will do away with much of this labour will be an improvement. Towards this end, other more easily determinable characters indicative of yield were investigated. The results of such a study are presented in this paper, from work done at the Nandyal Agricultural Research Station during the year 1932-33.