Productivity of Acacia angustissima accessions at two sites in the subtropics

Low leaf biomass yields coupled with small land sizes are some of the major constraints faced by smallholder farmers that grow protein-rich fodder trees and shrubs. Given these challenges, availability of highly productive seed sources would be important to enable farmers to produce leaf fodder in sufficient quantities. 14 accessions of Acacia angustissima were evaluated for leaf, wood and total biomass production at two subtropical sites with uni-modal rainfall in Zimbabwe, with the objective of identifying high leaf biomass yielding accessions. There were up to fourfold difference in biomass yield between the accessions. Leaf dry matter yield ranged from 1.65 to 8.81 Mg ha-1 and 3.7 to 12.4 Mg ha-1 for wood biomass at the higher altitude site (1530 m a.s.l.) but were much lower at 1272 m a.s.l. where they ranged between 0.37 and 4.88 Mg ha-1 for leaf and 0.4 and 7.2 Mg ha-1 for wood. The most productive accessions for leaf biomass were 16231 and 18579 at the higher altitude site, while 18586 and 18501 had the highest yields at the lower altitude. Although no one accession was consistently high yielding across the two sites, the least productive accessions were consistently poor at both sites. The advantage of using selected superior accessions over the unselect bulk seed was up to 85%. These findings underscore the need to promote the use of only high yielding accessions rather than unselect bulk seed. This study identified new, more productive accessions of A. angustissima that potentially widens the genetic base of the germplasm assembled in Zimbabwe.Key words: Leaf biomass, accession, accession × site interaction, Acacia angustissima

Phenology of Sclerocarya birrea (A. Rich.) Hochst. Provenances

Phenology study was conducted to assess 22 genotypes of Sclerocarya birrea (A. Rich.) Hochst, collected from West, Eastern and Southern Africa. Assessments were done on time for bud onset, flower opening, leaf flush, fruit set, fruit maturity period and fruit production.  Highly significant (P< 0.001) variations between provenances were obtained in all the phenological traits assessed including variations between sexes in time from flower bud set to anthesis. There was flowering overlaps and synchrony between provenances and sexes with males flowering earlier than females. So far two subpopulations have emerged within the trial referred to as early and late flowering genotypes. The early flowering included provenances from Mozambique, and Swaziland while the late flowering encompassed provenances from Malawi, Zimbabwe, Namibia, Tanzania and Zambia. Fruit maturity period ranged from 76±2 to 192±15days. The early flowering genotypes flowered, fruited and matured between August and January while the late genotypes flowered and fruited from September to May. There were highly significant (P≤0.001) variations in fruit yield of S. birrea provenances between 2016/2017 and 2017/2018 seasons with the former being more productive than the later confirming that S. birrea fruit yield is not constant across seasons due to seed mating effects. There were very strong positive relationship ranging r=0.81 to r=0.78 between leaf flush, bud set, flower opening and fruit set significant at (P<0.001). Some trees classified as females in the first year as based on flowers were found have male flowers which calls for more detailed investigations into this sex change behaviour

Foliage pests of Marula (Sclerocarya birrea) in Malawi: susceptibility of different provenances

Knowledge of insects’ damage to Agroforestry species is prerequisite prior to promotion of domestication of the species. The study was conducted to assess foliage insect pests in 21 Sclerocarya birrea provenances. Assessment parameters included tolerance levels, tree canopy position of attack, mode of leaf defoliation and type of insect pests responsible for the damage. The results revealed that highly tolerant provenances to leaf defoliation included Kalanga, Magunde, Moamba, and Marracuene. Highly susceptible provenances comprised of Chikwawa, Rumphi, Ntcheu, Missira and Mangochi. Highly significant (P < 0.001) variations existed in tree damage basing on crown position. The top canopy was the most affected followed by the middle and bottom canopies. Leaf damage was found to be significantly (X2 = 4.989, P = 0.026) associated with fruit production, and leaf damaged trees were found to produce three times (Odds Ratio = 3.2) less fruits compared to undamaged tree leaves. The most dominate form of leaf damage was defoliation (43%), followed by skeletonizing (18%). The least leaf damage trees were 37%. Leaf defoliators comprised of two orders namely Coleoptera (beetle) and Lepidoptera (caterpillar). Ceratitis (Pterandrus) capitata (fruit flies) were the most destructive to mature fruits. Although not the primary objective of the study, Ceratitis (Pterandrus) capitata (fruit flies) was identified as the major pest of Marula fruits. Future provenance or progeny trials should be replicated across different ecological areas in order to assess genotype-by-environment interaction effects resulting from differences in leaf flushing period

Tree Seed and Seedling Supply Systems: A Review of the Asia, Africa and Latin America Models

The paper reviews tree seed and seedling supply systems in sub-Saharan Africa, Asia and Latin America. Across these regions, the review found that some of the germplasm supply systems do not efficiently meet farmers’ demands and environmental expectations in terms of productivity, species and genetic diversity. In some countries, germplasm used is mostly sourced from undocumented sources and often untested. Germplasm quality control systems are only found in a few countries. Appreciation of the value of tree germplasm of high genetic quality is low. Non-government organisations (NGOs) in many African countries play a prominent role in the supply of germplasm which is usually given to farmers without charge. The practice of giving farmers free germplasm by NGOs in many African countries and also government participation in germplasm supply in some Asian countries has been blamed for crowding out private entrepreneurs, although this is not substantiated by any evidence to suggest that the smallholder farmers are willing and able to pay for the germplasm. In some Latin American countries, private companies, government and NGOs provide farmers tree germplasm in a partnership in which farmers provide land and labour in return. Overall, tree germplasm markets are large in Asia, due in part to large afforestation programs, intermediate in Latin America and small in Africa where smallholder farmers constitute the market. In countries where germplasm quality control is practiced, it is either through a legal framework or voluntary. A few countries in Africa, Asia and Latin America have developed protocols for certification of tree seeds based on the OECD. Some germplasm suppliers use branding as a way of differentiating their germplasm as having superior quality. To enhance the use of high quality germplasm, there is a need to demonstrate the value of using such germplasm and raise awareness of germplasm quality among the farmers and policy-makers