Low-yielding Varieties Research Articles

Leaf senescence and physiological characters in different adzuki bean (Vigna angularis) cultivars (lines)

The aim of the study is to examine the relation of leaf senescence and its physiological characters at different flower internodes from flowering to maturing, to explore the aging mechanisms of adzuki bean leaf, to find out the intrinsic yield-forming mechanisms and to provide a theoretical basis for high-yield breeding and production of adzuki beans. A field experiment was conducted, the high-yielding (2000-75 and JiHong 9218) and the low-yield varieties (HongBao1 and WanXuan1), all adopted in the summer planting ecological region of China, were grown in 2008 and 2009, and their leaf physiological characters, such as chlorophyll contents, net photosynthetic rates (Pn), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) activities and malondialdehyde (MDA) contents were determined. The results indicated that the chlorophyll contents, Pn, SOD and CAT activities gradually decreased from 15 days after the varieties flowered to maturing, but their POD activities and MDA contents gradually increased when leaves senescence started. Leaf senescence initiated from the low internodes and gradually moved toward to the upper internodes after the plants flowered. Compared with low-yielding varieties, high-yielding varieties maintained higher contents of chlorophyll contents,Pn and SOD, CAT in the late stages, and thus resulting significantly higher grain yields. The overall data indicated that yield is positively correlated with leaf chlorophyll and Pn, as well as SOD and CAT activities and negatively associated with POD activities and MDA accumulations at the late growth stage. Therefore, effective inhibition of leaf senescence or prolonging the functional period of leaves at the late growing stage plays an important role in raising yield. Key words: Adzuki bean, leaf senescence, chlorophyll content, seed yield.

Differential response of potatoes (Solanum tuberosum L.) to salinity in an arid environment and field performance of the seed tubers grown with fresh water in the following season

Ten potato varieties, commonly grown in the Mediterranean region, were grown on sandy soil in an arid desert area of Israel. The potatoes were drip-irrigated with three water sources: fresh water (control – ENV1), saline water from a local well (intermediate salinity – ENV2) and the local well water enriched with NaCl (high salinity – ENV3). The average salinity levels expressed as the electrical conductivity (EC) measured in the soil extracts from the root zone were 2.35, 5.1 and 8.5dSm−1 for the ENV1, ENV2 and ENV3 treatments, respectively. Salinity stress decreased fresh tuber yields, increased tuber dry matter and soluble solids, increased tuber electrolyte content and lowered osmotic potential (OP) of the tuber sap in all varieties. ANOVA and Fisher's LSD pair-comparisons revealed highly significant differences among the varieties in all traits. Correlation analyses showed negative associations between tuber yield and tuber traits (dry matter, DM; total soluble solids, TSS, EC and OP). Positive associations were found between tuber DM and TSS, EC and OP. There was no positive association between early maturation or yielding capacity and tolerance to salinity. Vivaldi, a high-yielding variety and Almera, a low-yielding variety were found significantly less susceptible to salinity than Mondial, a late-maturing and high-yielding variety, and Charlotte, an early-maturing and low-yielding variety. The significant differences in the response to salinity stress indicated genotypic variation in the response to salinity and support the potential of breeding for tolerance to salinity in potatoes.When seed tubers of the three irrigation treatments were grown with fresh water irrigation during the following season, there were no significant differences in plant growth or tuber yields from the three seed sources in most varieties indicating the possibility of using saline water for the production of potato seed tubers.

Leaf Senescence and Reactive Oxygen Metabolism in Different Adzuki Bean Cultivars (Lines)

To examine the relation of leaf senescence and its reactive oxygen metabolites from different nodes of various adzuki bean cultivars, to explore the aging mechanisms of adzuki bean leaf, to find out the intrinsic yield-forming mechanisms and to pro-vide a theoretical basis for high-yield breeding and production of adzuki beans. We conducted a field experiment, two high-yielding cultivars, 2000-75 and Jihong 9218, and two low-yielding cultivars, Hongbao 1 and Wanxuan 1, all adopted in the summer planting ecological region of China, were grown in 2008 and their leaf physiological indices, such as chlorophyll content, soluble-protein content, SOD, CAT and POD activities and MDA accumulations, were measured from flowering to ripening stages. The results showed that after flowering of the cultivars, their functional leaves aged gradually from bottom nodes to top nodes, and showed de-creased chlorophyll and soluble-protein contents, decreased SOD and CAT activities and increased POD activities and MDA accumulations in the proceed of senescence, for which there were significant differences among cultivars. Compared with the low-yielding varieties, the leaves of the high-yielding cultivars aged slower, showing relatively higher contents of chlorophyll and soluble-protein, higher activities of SOD and CAT at the late growth stage, and thus resulting significantly higher grain yields. The overall data indicated that yield is positively correlated with leaf chlorophyll and soluble-protein contents, as well as SOD and CAT activities and negatively associated with POD activities and MDA accumulations at the late growth stage. Therefore, effective inhibi-tion of leaf senescence or prolonging the functional period of leaves at the late growing stage plays an important role in raising yield.

The relationship between the yields of eight varieties of Nigerian maize and content of nitrogen, phosphorus and potassium in the leaf at flowering stage

SUMMARYStudies of the relationship between yield and content of N, P and K in the ear leaf of eight varieties of Nigerian maize, tested for three growing seasons, indicated that the varieties have different critical nutrient levels, although the values obtained for individual varieties were not significantly different from the pooled average critical level for any of the nutrients. The critical levels ranged from 2·85 to 3·19% N, 0·20 to 0·27% P and 2·06 to 2·60% K, while their pooled averages were 3·10% N, 0·23% P and 2·44% K.High ear leaf nutrient content was not a guarantee of high grain yield, and ear leaf nutrient values of low-yielding varieties were similar to those of the high-yielding varieties.

Chemical investigation of wheat

The extent and the mechanism of phytic acid decomposition in germinating wheat grain of a low-yielding and a high-yielding wheat variety have been investigated. While in the high-yielding variety this decomposition was most important on the first, fifth, and seventh day of germination, in the low-yielding variety extensive decomposition began only on the second day and reached its maximum value on the fifth day of germination. If one accepts the criterion of Mellanby for the rate of phytic acid decomposition, it appears that phytic acid is completely decomposed within seven days in the high-yielding variety and within six days in the low-yielding variety. The increase of free orthophosphate was not equivalent to the decrease of phytic acid, the difference representing the amount of orthophosphate phosphorus uptake in oxidative and photosynthetic phosphorylation. It was found that enzymatic hydrolysis of phytic acid in germinating wheat grain occurred stepwise, by the successive liberation of phosphoric acid and through the intermediate formation of penta-, tetra-, tri-, di-, and monophosphates of inositol, the final products being inositol and phosphoric acid. In ripe wheat grain before germination, only inositol hexaphosphate (phytic acid) was present.

THE INFLUENCE OF SEED SIZE ON RESULTS OF BARLEY YIELD TRIALS

Two series of tests were conducted to determine the influence of seed size on barley yield trials. In the first series, four varieties and four seed categories were studied in seven tests over a period of 3 years. It was shown that large seed produced more tillers and greater yields on the average than small, medium, or bulk seed. It was also illustrated that the yield ranking of varieties can depend on the size of seed used. For example, the large seed of Olli, a low-yielding variety, outyielded the small seed of Husky, a highly productive variety, in these tests. Only in one of the seven tests was emergence reduced by use of small seed.Yields from large seed were compared with those from a combination of large and medium-sized kernels in the second series. In 20 tests with four varieties, over a 2-year period, large seed was more productive on the average than the combination. Striking differences were obtained in some tests. These results serve to emphasize the necessity of using seed of comparable quality in yield trials.

Experimental studies on the significance of selection in plant breeding. 2. Studies on the effect of neighboring plants on the performance of space-planted one in paddy-rice.

Plants of two varieties of rice which were quite different in plant colour and yielding ability were planted in the same plots after the manner of mixing each other as shown in Fig. 1. These plots were replicated six times (Fig. 2). The width between rows was 10 inches and the plants spaced five inches apart within rows. From these plots, plants surrounded by those of the same variety (AS), plants in rows adjacent to another variety (ND), plants grown between two of another variety in 10 inches (LD) or in 5 inches apart (SD), and plants surrounded by those of another variety (AD) were individually harvested. The grain yield in grams, the number of spikes and the average weight of a panicle were recorded on plant basis in each plot (Tab. 1). The analysisses of variance were calculated from the nonweighted plant values (Tabs. 2∼4). From Tab. 2, it is seen that the mean square for varieties, and varieties x treatments, compared with error mean square, exceeded the 1% point and those for treatments the 5% point. It is plain, therefore, that there were significant differences in average yielding ability and that these varieties reacted in a differential manner at some treatments. These differential response of the varieties to some treatments was shown to result from the changes in the weight of a spike under different treatments (Tab. 4) and not the number of spikes per plant (Tab. 3). Average grain yields in Tab. 1 sbowed that those of the low-yielding variety became lower by the influence of neighboring high-yielder, and vice versa. It was concluded that the yield of spaced single plants in a population would be variably affected by the surrounding plants, and it would, therefore, be illegitimate to make plant selections on a basis of the yield of single plants in segregating generations.

The breeding of two-row winter-hardy barley

It has been shown in these breeding investigations that it is possible to combine the winter hardiness of low-yielding varieties possessing characters unsuited for cultivation in this country, with many of the desirable features of the best two-row spring varieties at present grown for malting purposes. Although, with the production of the new hybrid variety Pioneer, a definite advance has been made in the production of a two-row winter barley for malting, there is no reason to suppose that further improvements cannot be made, and work is proceeding with this object in view. But in addition to the special problem of malting barley, the results so far obtained indicate that there is considerable scope in this hybridization of winter and spring varieties for the production of forms suitable for growing as feeding barleys. The hybridization of varieties differing so widely in their morphological and physiological characters, and also in their ecological adaptation, gives a wide basis for the selection of a great range of forms. On the other hand, distant hybridization of this type is liable to result in the production of a very high proportion of worthless material, involving the loss of the highest expression of the very specialized characters necessary in a barley possessing the attributes of a high-yielding malting variety with satisfactory field characters.