To assess the impact of a dense understory of the bamboo Yushania microphylla Munro on tree regeneration in monospecific Abies densa Griff. stands of the central Bhutan Himalayas, the age-class distribution of fir regeneration, the microsite preferences, and height growth as well as the relationship between height of the bamboo, gap fraction, and tree seedling density were studied. Seedling densities were much lower on sites with bamboo. Recruitment was more or less continuous, and there was no indication of overall synchronized single-cohort regeneration in bamboo plots. On sites with bamboo understory, the light regime at the forest floor is strongly influenced by the height of the bamboo. A large portion of the variance of tree seedling density could be explained by the height of the bamboo. The mortality of fir seedlings is considerably reduced at elevated microsites. Fir establishment on the forest floor is restricted to sites where bamboo density is low and light levels are higher. On sites with dense, unbrowsed bamboo, light levels are too low for long-term survival of fir seedlings, resulting in a lack of suppressed regeneration with minimal height growth. Because of the absence of this fraction, the average height increment of fir seedlings is higher on sites with bamboo.Résumé : Dans le but d'évaluer l'impact d'un sous-étage dense du bambou Yushania microphylla Munro sur la régénération des arbres, dans les peuplements monospécifiques d'Abies densa Griff. de l'Himalaya du Bhûtân central, les auteurs ont examiné la distribution des classes d'âge de la régénération en sapin, les microsites préférés et la croissance en hauteur, ainsi que la relation entre la hauteur du bambou, la proportion d'ouvertures et la densité des semis d'arbres. La densité des semis était beaucoup plus faible dans les sites avec bambou. Le recrutement, lui, était plus ou moins continu et il n'y avait pas d'indication d'une régénération synchronisée sous forme d'une cohorte unique dans les parcelles de bambou. Dans les sites avec sous-étage de bambou, le régime de lumière sur le parterre de la forêt est fortement influencé par la hauteur du bambou. Une grande proportion de la variance de la densité des semis des arbres peut être expliquée par la hauteur du bambou. La mortalité des semis de sapin est réduite considérablement sur les microsites surélevés. L'établissement du sapin sur le parterre de la forêt est limité aux sites où la densité du bambou est faible et les niveaux de lumière élevés. Sur les sites avec une couverture dense et non broutée du bambou, la lumière est trop faible pour permettre une survie à long terme des semis du sapin et aboutit au manque d'une régénération supprimée dotée d'une croissance en hauteur minimale. En l'absence de cette composante, l'accroissement moyen en hauteur des semis de sapin est plus élevé sur les sites avec le bambou.[Traduit par la Rédaction] Gratzer et al. 1527

Mahalanobis D2 statistics was used to study the genetic diversity among 36 genotypes of sesame grown in the Kharif season of 2001. Observations recorded on ten characters revealed the wide genetic diversity of 36 genotypes. By applying Tocher's method, 36 genotypes were grouped into 7 clusters. The clustering pattern indicated that there was no relationship between genetic diversity and geographic diversity. Maximum intercluster distance was observed between clusters VI and VII (D-84.48). Genotypes having their divergence in between m+s and m-s were selected as parent which are supposed to give rise to higher frequency of heterotic crosses.

Genetic analysis of seed yield and five yield components as well as oil yield per plant through 10 X 10 diallel excluding reciprocal revealed that all the characters were governed by both additive as well as dominance gene effects, with preponderance of additive gene effect for days to flower; equal importance of both gene effects for days to maturity and with greater magnitude of dominance gene effect for plant height,seeds per capsule, 500 seeds weight, seed yield per plant and oil yield per plant. Asymetrical distribution of increasing and decreasing alleles was noticed for all the traits except seeds per capsule, seed yield and oil yield. More number of dominant genes were present (K/K >1) for days to flower, days to maturity and plant height. The population improvement through reciprocal recurrent selection or biparental mating is suggested for increasing seed and oil yield.

An experiment on biofertilizers alongwith different nitrogen (N) levels in pearlmillet was conducted during kharif seasons of 2 years at the Dry Farming Research Station, Solapur. The data pooled over two seasons indicated that the seed inoculation with Azotobacter, Azospirillum and their mixture increased grain and stover yield irrespective of N levels over no biofertilizer inoculation and no N application. Dual inoculation of Azotobacter and Azospirillum + 50 kg N/ha produced the highest grain yield (14.91 g/ha), however, it was at par with the grain yield (13:13 g/ha) obtained with dual inoculation of Azotobacter and Azospirillum + 37.5 kg N/ha. This indicates the possibility of N economy in pearlmillet by the use of biofertilizers.

Genetic analysis of components of variation for seed yield, oil yield and yield components revealed the importance of both additive and non additive type of gene action in the inheritance of all the characters studied. However, preponderance of additive components was observed for phenological traits, viz. days to flower and days to maturity, equal importance of both additive and dominance components for plant height, primary branches per plant, 500-seeds weight and seed oil content, whereas preponderance of dominance component was revealed for number of capsules per plant, seeds per capsule, seed yield per plant, biological yield per plant, harvest index and oil yield per plant. The biparental mating or diallel selective mating is suggested to exploit the genetic components for improvement of the characters studied.